I have written about cancer stem cells several times in this blog, but many oncologists and cancer researchers still see cancer stem cells mainly as hypothetical entities whose relevance if not very-existence is questionable.  A recent article in Gen points out that a number of pharmaceutical companies are betting big on cancer therapies based on going after cancer stem cells.

As I wrote in my July 2009 post On cancer stem cells, most cancer therapies are based on killing cancer cells – as many cells as possible.  But cancers frequently and persistently recur after bouts of radiation or chemotherapy.  The culprit is thought to be cancer stem cells, where any surviving ones simply go about making new cancer cells.  A new therapeutic concept is therefore to focus on killing the cancer stem cells.  “While normal stem cells are essential for development, play a key role in tissue maintenance, and aid in repair, cancer stem cells are believed responsible for tumorigenesis, metastases, and cancer recurrence(ref).”  I reported further research regarding cancer stem cells in my August 2009 blog post Update on cancer stem cells.

It turns out the way to do this is to target the same signaling pathways involved in the proliferation and differentiation of normal stem cells, pathways I have discussed previously in this blog. 

Notch is one such pathway which I discussed in the post On cancer stem cells.  As reported in Gen: “Different points in the (Notch) pathway have been targeted for drug development. OncoMed Pharmaceuticals’ OMP-21M18 is an antibody that blocks signals by binding to Delta-like ligand. The drug, which is in a clinical trial involving patients with advanced solid tumors, is part of a $1.4 billion collaboration with GlaxoSmithKline.  Merck and Roche have inhibitors to γ-secretase that cleaves the Notch receptor releasing the Notch intracellular domain, a transcription factor. Both companies’ drugs are in early testing against solid tumors. Finally, Trojantec is targeting the Notch pathway with a truncated version of Mastermind, a coactivator involved in chromatin-specific transcription. The drug may prove useful against tumors that overexpress Notch signaling components(ref).”  The role of Notch signaling in stem cell proliferation and differentiation was touched on in my blog post Niche, Notch and nudge.

PI3K/Akt is another pathway being targeted.  “The PI3K/Akt pathway’s importance in cancer is partly attributable to PI3K’s (phosphatidylinositol 3-kinase’s) association with oncogenic growth factor receptors, notably for epidermal growth factor, platelet-derived growth factor, and mesenchymal transition factor. The pathway is also prone to mutations associated with oncogenesis, including changes in the catalytic subunit of PI3K that occur in prostate, breast, endometrium, urinary tract, and colon cancers. — Similarly, mutations of the lipid phosphatase PTEN that normally serves to deactivate the PI3K/Akt pathway are found in cancers of the endometrium, brain, skin, and prostate, while mutations in the protein kinase Akt, which is downstream of PI3K, are overexpressed in head and neck squamous cell carcinoma, and in pancreatic and ovarian cancers. Eight drugs targeting the PI3K/Akt pathway are in clinical trials(ref).”  I have mentioned the P13K/Akt/mTOR and its relationship to stem cells in several posts including More mTOR links to aging theories.

The Hedgehog signaling pathway is another one being targeted by new drugs in the pipeline.   “The Hedgehog pathway provides an intercellular regulatory mechanism that serves essential functions in the normal proliferation and differentiation of stem cells. Mutations in this pathway figure in basal cell carcinoma, medulloblastoma, and other malignancies. Three drugs that interfere with hedgehog signaling are in clinical trials—two, Infinity Pharmaceuticals’ IPI-926 and Genentech/Curis’ GDC-0449, are derivatives of cyclopamine, which has been studied extensively(ref).”

Heavy players in the pharma industry are betting big on new therapies for going after cancer stem cells.  Perhaps more cancer researchers should start watching where the “smart money” is flowing.

This post reviews some key research findings regarding liver regeneration and discusses what is known about the mechanisms involved.   It turns out that a bunch of my favorite blog topics are involved: telomerase, stem/progenitor cells, mTOR signaling, MAPK signaling, NOTCH signaling and NF-kappaB activation. 

“The liver is the largest and most metabolically complex organ in humans(ref),”  it has a complex internal structure(ref), and it performs many diverse tasks required for the health of other body systems(ref).  Further, the human liver has a remarkable capacity for self-regeneration when damaged or when even up to 80% of it is removed by surgery(ref).  Unlike almost any other organ in humans, it can simply grow back.  If a section of the liver is removed, as part of regeneration “normally quiescent hepatocytes undergo one or two rounds of replication to restore the liver mass by a process of compensatory hyperplasia(ref).”   Hepatocytes are the central cells involved in normal liver functioning making up 70% to 80% of the mass of the liver.  Compensatory hyperplasia simply means extra fast proliferation of cells to replace a lost part of the liver.  The amazing thing is how fast this happens.  In a study of regeneration in pig livers, maximum regenerative response occurred three days after up to 70% partial hepatectomy(ref).  “The timing and events of the regenerative response in the pig compared favorably with other animal models and the maximum regenerative response occurred on the third postoperative day, irrespective of the size of the partial hepatectomy.” 

Liver regeneration is not always possible depending on the nature and extent of damage, and the age of the patient involved.   According to the American Liver Foundation, around 17,000 Americans are currently on a waiting list for a liver transplant.  Understanding of what is involved in liver regeneration might assist in facilitating regeneration beyond that normally possible and possibly in developing regeneration strategies for other human organs.

·        Telomerase activation is centrally involved in liver regeneration

Since telomere shortening has long been known to limit organ regeneration(ref), it can be concluded a-priori that liver regeneration must involve the expression of telomerase.  The publication Regeneration in pig livers by compensatory hyperplasia induces high levels of telomerase activity tells an important part of the story.  In simple language, liver regeneration is accompanied by a burst of telomerase activation.  “Quiescent human hepatocytes exhibit very low or undetectable levels of telomerase activity. However, hepatocytes display a remarkable proliferative capability following liver injury. To investigate whether liver regeneration by compensatory hyperplasia is associated with telomerase activation, we measured telomerase activity in pig livers after 70 to 80% partial hepatectomy using a fully quantitative real-time telomeric repeat amplification protocol. In contrast to commonly studied inbred laboratory mouse strains, telomere length and telomerase activity in porcine tissues are comparable to humans. RESULTS: Following partial hepatectomy, histology revealed mitotic hepatocytes as marker for compensatory hyperplasia. As expected, there was no induction of inflammation. Telomerase activity increased significantly showing the highest levels (5-fold upregulation) in pigs treated with partial hepatectomy and hepatic decompression. Moreover, telomerase activity significantly correlated to the number of mitotic hepatocytes. CONCLUSION: Our data demonstrate telomerase activation in liver regeneration by compensatory hyperplasia in a large animal model with telomere biology comparable to humans. Telomerase activation may constitute a mechanism to protect proliferating liver cells against telomere shortening and oxidative stress.”  [Some of the research reported here is based on working with pig livers, good models of human livers. “Moreover, pig telomeres are comparable to those of humans regarding length and shortening during aging (ref)(ref). Because of these similarities, pigs have been utilized as model system to investigate telomerase regulation and telomere dynamics in mammalians(ref)(ref).”]

·        Telomerase activation possibly allows extensive mitosis (cell division) of hepatocytes

The publication Telomerase reconstitution immortalizes human fetal hepatocytes without disrupting their differentiation potential provides data with respect to fetal hepatocytes that may or may not apply to the mature working hepatocytes that remain in the working part of a partially destroyed liver.  The study was of fetal hepatocytes in-vitro.  “Telomerase-reconstituted cells were capable of preserving elongated telomeres, propagated in culture beyond replicative senescence for more than 300 cell doublings (to date), and maintained their liver-specific nature, as analyzed by a panel of hepatic growth factors, growth factor receptors, and transcription factors as well as albumin, glucose-6-phosphatase, glycogen synthesis, cytochrome P450 (CYP) expression profiles, and urea production. Moreover, the immortalized cells exhibited no oncogenicity, and no up-regulation of c-Myc was detected. The cells engrafted and survived in the liver of immunodeficient mice with hepatocellular gene expression.”  The extent to which this finding applies to mature hepatocytes in-vivo subject to niche signaling is unknown.

·        The differentiation of hepatic progenitor cells is involved.

An important question is “where do the new hepatocytes come from?  There are two possibilities: mitosis (cell division) of the hepatocytes already in the liver, and differentiation of hepatic progenitor cells to make new hepatocytes.  “Hepatic progenitor cells are immature epithelial cells that reside in the smallest ramifications of the biliary tree in human liver. These cells are capable of differentiating toward the biliary and the hepatocytic lineages. — an increased number of progenitor cells (referred to as “activation”) and differentiation of the same toward hepatocytes or bile duct epithelial cells, or both, is a component of virtually all human liver diseases. The extent of progenitor cell activation and the direction of differentiation are correlated with the severity of the disease and the type of mature epithelial cell (hepatocyte or bile duct epithelial cell), respectively, that is damaged(ref).”

These findings are interesting but raised my thirst for answers to several other questions:  1.  What cells are making the telomerase (e.g. hepatic progenitor cells or hepatocytes)? 2.  What is the role of the telomerase in liver regeneration? 3.  To what extent is the liver regeneration due to mitosis of existing hepatocytes and to what extent is it due to differentiation of hepatic progenitor cells? 4.  What other stem cells might be involved, such as for renewing the supply of hepatic progenitor cells?  5. What kind of signaling is articulating the whole regeneration process?  6. What hope does all this offer for longevity?  So, I went on a literature quest for a couple of days.  I found a number of research papers that cast slivers and rays of light on some of the questions.

·        Normally by themselves, hepatocytes do not express telomerase

In fact the publication In vitro expansion of human hepatocytes is restricted by telomere-dependent replicative aging says  “As expected, untransduced PHH (proliferating human hepatocytes ) progressively lost telomeric repeats and arrested after 30-35 cell divisions with telomeres of less than 5 kilo bases. In comparison, telomerase-reconstituted PHH maintained elongated telomeres and continued to proliferate as shown by colorimetric assays and cell counts. In this study, telomere stabilization extended the proliferative capacity of in vitro proliferating human neonatal hepatocytes. Therefore, telomere attrition needs to be addressed when developing techniques to expand human hepatocytes.”

·        Liver regeneration capability declines with the age of the animal or person

An explanation is given in a publication entitled Aging Reduces Proliferative Capacities of Liver by Switching Pathways of C/EBPα Growth Arrest.  “The liver is capable of completely regenerating itself in response to injury and after partial hepatectomy. In liver of old animals, the proliferative response is dramatically reduced, the mechanism for which is unknown. The liver specific protein, C/EBPα, normally arrests proliferation of hepatocytes through inhibiting cyclin dependent kinases (cdks). We present evidence that aging switches the liver-specific pathway of C/EBPα growth arrest to repression of E2F transcription. We identified an age-specific C/EBPα-Rb-E2F4 complex that binds to E2F-dependent promoters and represses these genes. The C/EBPα-Rb-E2F4 complex occupies the c-myc promoter and blocks induction of c-myc in livers of old animals after partial hepatectomy. Our results show that the age-dependent switch from cdk inhibition to repression of E2F transcription causes a loss of proliferative response in the liver because of an inability to induce E2F target genes after partial hepatectomy providing a possible mechanism for the age-dependent loss of liver regenerative capacity.” No surprise since many studies show that c-myc plays critical roles in cell proliferation and differentiation.  

·        Liver regeneration involves complex signaling

This signaling has been studied for some time.  I have already mentioned the roles of E2F transcription and c-myc.  A 1998 paper Signal transduction during liver regeneration states “Following partial hepatectomy (PH), there is a rapid and highly orchestrated series of biochemical events which occur prior to cellular proliferation. Some of these events are presumably intimately linked with the eventual regeneration of the liver, whereas others are likely to be stress related or required for the continued differentiated function of the liver while regeneration is occurring.  The regulation of the AP-1 transcription factor c-Jun during hepatic regeneration has been studied here. — It is concluded that the stimulation of one-third or two-thirds PH (partial hepatectomy) activates JNK through a mechanism that requires TNFalpha, which phosphorylates the c-Jun activation domain in hepatocytes, resulting in enhanced transcription of AP-1-dependent genes. — the induction of NFkappaB during liver regeneration following PH appears to be a required event to prevent apoptosis and to allow for normal cell cycle progression.”  I comment that the induction of NF-kappaB is not surprising since such translocation of NF-kappaB into the cell nucleus is required to activate the expression of a number of growth-related genes.

·        MAPK, mTOR  and Notch pathways are involved in liver regeneration, suggesting that stem/progenitor cell differentiation plays an important role.

The publication PI3K-FRAP/mTOR pathway is critical for hepatocyte proliferation whereas MEK/ERK supports both proliferation and survival suggests intimate involvement in liver regeneration of two pathways that have been discussed in this blog: mTOR and MAPK/ERK, and lends further weight to the argument that differentiation of stem/progenitor cells may be critically involved.  The blog post More mTOR links to aging theories links mTOR expression to the quiescence and proliferation of hematopoietic stem cells. I made the point “Effective mTORC1 negative regulation is essential for keeping the stem cell supply chain working well, at least insofar as hematopoietic stem cells are concerned.” That is, the negative regulation is needed to keep rate of differentiation of hematopoietic stem cells under control so as not to exhaust the pools of such cells.  When the body’s task is regenerating a liver, on the other hand the need is for increased differentiation of stem/progenitor cells to create new hepatocytes, that is activation of the P13K-FRAP/mTOR pathway as described in the above-mentioned publication.  At least, that is my conjecture. 

The same publication mentions activation of the MAPK/ERK pathway.  “–partial hepatectomy induces a rapid but transient activation of mitogenic signal transduction pathways, in particular phosphoinositide 3-kinase and mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK)(ref).”  The role of the MAPK/ERK and Notch pathways in the stem cell supply chain are discussed in my recent blog post Niche, Notch and Nudge. MAPK/ERK appears to be very important regulator of Notch activity, and Notch activity in turn is essential for the inter-cellular communication required to form a complete organ.  You can’t get a complicated highly-structured organ like the liver without the cells doing a lot of talking to each other. 

·        Progenitor cell rejuvenation can reverse age-related decline in liver renewal by restoring Notch signaling

The “letter to nature” Rejuvenation of aged progenitor cells by exposure to a young systemic environment discusses the role of Notch signaling with respect to liver progenitor cells.  “The decline in hepatic progenitor cell proliferation owing to the formation of a complex involving cEBP-a and the chromatin remodeling factor brahma (Brm) inhibits the regenerative capacity of aged liver. — The exposure of satellite cells from old mice to young serum enhanced the expression of the Notch ligand (Delta), increased Notch activation, and enhanced proliferation in vitro.  Furthermore, heterochronic parabiosis (a fancy term for pairing up old mice with young mice) increased aged hepatocyte proliferation and restored the cEBPa complex to levels seen in young animals. These results suggest that the age-related decline of progenitor cell activity can be modulated by systemic factors that change with age.” Further, similar pairing of old mice did not result in comparable cell rejuvenation.  “The cEBP- α–Brm protein complex was detected in liver extracts from old isochronic parabionts but not in young isochronic parabionts. Notably, the formation of the cEBP- α –Brm complex was diminished in liver extracts from old heterochronic parabionts. The complex was present at elevated levels in young heterochronic parabionts as compared to young controls. This was also consistent with the modest inhibition of hepatocyte proliferation in young heterochronic parabionts. A young systemic environment restores a young molecular signaling profile to aged progenitor cells in the liver and also appears to enhance their proliferation(ref).”

·        The research that I read leaves me unclear as to the primary actions and locations of telomerase activation and the relationship of telomerase activation to hepatocyte proliferation.   I hypothesize  that one important role of the increased telomerase expression is to accelerate the differentiation of hepatic progenitor cells into new hepatocytes.

The pig-liver researchers stated  “Based on our results, we propose that telomerase activation in proliferating hepatocytes is the main cause for increased telomerase activity in regenerative liver nodules. This conclusion is supported by the significant correlation of telomerase activity to the number of mitotic hepatocytes in our study(ref).” However this statement does not say whether telomerase activation is a cause of the proliferation or a byproduct of it.  And, if there is a causal relationship it does not say what it is. Telomerase activation could possibly a) increase proliferation by promoting the rate of differentiation of hepatic progenitor cells into hepatocytes or b) by the rate of mitosis of such progenitor cells or c) by the rate of mitosis of hepatocytes or by c) delay of senescence of hepatocytes, or by d) any combination of these factors.  To my knowledge telomerase activation is not normally associated with increased mitosis of cells but is known to be able to significantly delay cell senescence and to promote differentiation of stem and progenitor cells, so my guess is that of the above choices all are likely to apply. 

·        Research in liver-related stem cells is recent and partial

The 2005 article Which stem cells for adult liver? demonstrated a lack of concrete knowledge about liver stem cells.  “While hepatocytes can be considered conceptually as unipotent stem cells, the presence of true stem or progenitor cells within adult livers has been largely debated.”  The article goes on to discuss a number of possibilities that might be used for stem cell therapy in livers. Some earlier reports suggested evidence for the presence of hematopoietic stem cells in adult livers(ref).   A November 2008 research report indicates some progress.  “A novel protein marker has been found that identifies rare adult liver stem cells, whose ability to regenerate injured liver tissue has the potential for cell-replacement therapy. For the first time, researchers at the University of Pennsylvania School of Medicine led by Linda Greenbaum, MD, Assistant Professor of Medicine in the Division of Gastroenterology, have demonstrated that cells expressing the marker can differentiate into both liver cells and cells that line the bile duct.”  The marker is the protein Foxl1.

·        Hepatic progenitor and stem cells are possibly implicated in liver cancers

The understanding of cancer stem cells is fairly new and the existence of liver cancer stem cells is an area being investigated actively.  According to a 2009 review paper Liver stem cells and hepatocellular carcinoma.   “Constant proliferation of stem cells is a vital component in liver tissues. In these renewing tissues, mutations will most likely result in expansion of the altered stem cells, perpetuating and increasing the chances of additional mutations and tumor progression. However, many details about hepatocellular cancer stem cells that are important for early detection remain poorly understood”  A September 2009 article reports the isolation of liver cancer stem cells that appear before tumor formation.

·        Telomerase activity may telegraph the possibility of liver cancer

Again, this has been known for a relatively long time.  The 1998 publication Telomerase activity in precancerous hepatic nodules states “These findings suggest that telomerase activation is an early event in large nodule formation in cirrhosis, which may facilitate the action of other factors in the process of carcinogenesis. Telomerase activity in large hepatic nodules is not always indicative of malignant transformation.”  Another publication comes to the conclusions “These results suggest that the induction of hTERT mRNA is an important early event and that its measurement by real-time quantitative RT-PCR is a useful tool to detect premalignant/malignant tendencies in hepatic nodules. However, hTERT gene dosage and c-myc expression are not the main mechanisms regulating hTERT expression in hepatocarcinogenesis.”  And a third 2002 study states “This study shows that hTERT re-expression takes place both in hepatic regeneration occurring in cirrhosis and in the early steps of hepatocarcinogenesis, and involves mainly the beta-splice variant of this molecule. Additional regulatory mechanisms may be required for the expression of the full-length hTERT transcript.” 

The ambivalent attitude to telomerase activation that has been widespread among cancer researchers for many years applies also to some of those concerned with liver regeneration.  The 2007 publication Telomerase activation in liver regeneration and hepatocarcinogenesis: Dr. Jekyll or Mr. Hyde? concludes “At present, it is unclear, whether telomerase activation preserves the non-malignant phenotype and replicative longevity of liver cells or constitutes an early alteration obligatory for an unlimited proliferation and malignant transformation.”  I wonder why this is posed as an either-or choice instead of accepting the overwhelming evidence that both are the case and which one is present depends on circumstances.

·        Progress is being made in decoding the signaling leading to liver cancers

The 2008 paper Hepatocellular cancer arises from loss of transforming growth factor beta signaling adaptor protein embryonic liver fodrin through abnormal angiogenesis suggests a specific mechanism.  “Loss of ELF (embryonic liver fodrin) in the liver leads the cancer formation by deregulated hepatocyte proliferation and stimulation of angiogenesis in early cancers.”  This paper builds on the argument in a 2007 paper Disruption of transforming growth factor-beta signaling through beta-spectrin ELF leads to hepatocellular cancer through cyclin D1 activation.  “Thus, we show that TGF-beta signaling and Smad adaptor ELF suppress human hepatocarcinogenesis, potentially through cyclin D1 deregulation. Loss of ELF could serve as a primary event in progression toward a fully transformed phenotype and could hold promise for new therapeutic approaches in human HCCs.” 

Another 2008 publication CpG island methylator phenotype association with upregulated telomerase activity in hepatocellular carcinoma looks at cancer gene activation in terms of DNA methylation:  “CpG island methylator phenotype (CIMP) involves the targeting of multiple genes by promoter hypermethylation. — We examined the promoter methylation status of 9 genes associated with telomerase activity in 120 HCC, 120 cirrhosis tissues and 10 normal liver tissues by methylation-specific PCR. — CIMP lead to high levels of expression of telomerase activity through the simultaneous inactivation of multiple genes associated with telomerase activity by concordant methylation.” Another interesting study concludes “The results of this study suggest that HBx expression may play a role in hepatocellular carcinogenesis by interfering with telomerase activity during hepatocyte proliferation.”

So, in the light of all of the above the bottom-line guesses to answer my questions are:

1.     What cells are making the telomerase?   I found no direct answers.  I presume both hepatic progenitor cells and hepatocytes are doing so in response to chain of distress signaling present in damaged livers that is only partially understood.

2.     What is the role of the telomerase in liver regeneration?  I hypothesize that there are two important roles: a) enhancing the proliferation potential of hepatocytes and hepatic progenitor cells by allowing a large number of additional population doublings before cell senescence sets in and b) is promoting the health and differentiation of hepatic progenitor cells into hepatocytes.

3.     To what extent is the liver regeneration due to mitosis of existing hepatocytes and to what extent is it due to differentiation of hepatic progenitor cells?   Again I found no direct answer but there seems to be strong evidence that both division of existing cells and differentiation of hepatic progenitor cells play critical roles.

4.     What other stem cells might be involved, such as for renewing the supply of hepatic progenitor cells?  Again there is no simple answer based on experiment.  Several kinds of multipotent stem cells are capable of transforming into hepatocytes and possibly into hepatic progenitor cells.  I conjecture that when liver regeneration is taking place several levels of the stem cell supply chain may be activated.

5.     What kind of signaling is articulating the whole regeneration process?   A number of kinds of signaling are identified in various papers.  Among those of importance that I have discussed before are mTOR, MAPK, and Notch.

6.     What hope does all this offer for longevity?  A great deal, I would say.  First, it appears that the age-related decline in liver regeneration capability can be reversed and that the “heterochronic parabiosis” techniques mentioned above might possibly be adopted so they work in clinical practice.  If they can be made to work they would apply to stem cell proliferation and differentiation in general and could be broadly applied across other organ systems for life extension.  Second, knowledge of the biochemical and genetic pathways active in liver regeneration will probably be  of high relevance in other areas of regenerative medicine.

A research report that appeared a few days ago suggests that birth control pills are having a profound effect on our programmed biological mechanisms for selecting sex partners and for the evolutionary selection of sex and perhaps other human characteristics.

Little stories tell the tale:

·        Before or without the pill it was “Me Tarzan, tough and a good fighter who grabbed you from the other wimpy guys.  You Jane, soft and cuddly strange creature, irresistible to me.  Let’s go have sex again.”  Although Tarzan is a strange animal for her, Jane loves the way he smells and she melts into his arms. Both are responding to biological urges that have kept our species going for millions of years

·        With the pill it is more like “Me Alfred, an insurance lawyer.  You Bridget, a designer of webs for auto dealers.  I found you on Facebook where I liked your little sketches.  We are a lot alike.  Let’s cook a seafood risotto for dinner together and then we can watch Masterpiece Theatre.”  Bridget does not notice anything in particular about how Alfred smells.   They don’t have sex very often but that seems quite fine.  The biological urge is blunted.

·        There is more.  Unbeknownst to Bridget, Alfred has been having a torrid affair with Jennifer, a perky Brazilian pizza-delivery girl who is not on the pill.  There is something about the way that Alfred smells that drives Jennifer to jump into bed with him.  And Alfred cannot resist Jennifer’s allure.  At the moment, Jennifer is pregnant with Alfred’s kid and he is working up courage to tell Bridget about that. The biological urge was working again and has done its thing.

The study which appeared October 6 2009 in the journal Trends in Ecology & Evolution is entitled Does the contraceptive pill alter mate choice in humans?  Basically, birth control pills disrupt the menstrual cycle.  However, the events in the menstrual cycle profoundly affect attractiveness of men for women and women for men and dictate when the sexual urge is mutually maximized.  “Female and male mate choice preferences in humans both vary according to the menstrual cycle. Women prefer more masculine, symmetrical and genetically unrelated men during ovulation compared with other phases of their cycle, and recent evidence suggests that men prefer ovulating women to others.  Such monthly shifts in mate preference have been suggested to bring evolutionary benefits in terms of reproductive success. New evidence is now emerging that taking the oral contraceptive pill might significantly alter both female and male mate choice by removing the mid-cycle change in preferences(ref).”   

The coverage of this study in an October 8 2009 Science Daily article summarizes the situation well.  The study shows “emerging evidence suggesting that contraceptive methods which alter a woman’s natural hormonal cycles may have an underappreciated impact on choice of partners for both women and men and, possibly, reproductive success — – Ovulating women exhibit a preference for more masculine male features, are particularly attracted to men showing dominance and male-male competitiveness and prefer partners that are genetically dissimilar to themselves. This is significant because there is evidence suggesting that genetic similarity between couples might be linked with infertility. Further, some studies have suggested that men detect women’s fertility status, preferring ovulating women in situations where they can compare the attractiveness of different women.” – –  “Dr. Alverne and colleague Dr. Virpi Lumma reviewed and discussed new research supporting the conclusion that use of the pill by women disrupted their variation in mate preferences across their menstrual cycle.

The authors also speculate that the use of oral contraceptives may influence a woman’s ability to attract a mate by reducing attractiveness to men, thereby disrupting her ability to compete with normally cycling women for access to mate.  — Of particular interest is the fact that women taking the pill do not exhibit the ovulation-specific attraction to genetically dissimilar partners(ref).” 

Another study reported last year raises similar issues.  “The contraceptive pill may disrupt women’s natural ability to choose a partner genetically dissimilar to themselves(ref).   ”This study was based on body odors. “Humans choose partners through their body odour and tend to be attracted to those with a dissimilar genetic make-up to themselves, maintaining genetic diversity. Genes in the Major Histocompatibility Complex (MHC), which helps build the proteins involved in the body’s immune response, also play a prominent role in odour through interaction with skin bacteria. In this way these genes also help determine which individuals find us attractive(ref).” 

But those body odors are not fully perceived by women who are on the pill.  “The research team analyzed how the contraceptive pill affects odour preferences. One hundred women were asked to indicate their preferences on six male body odour samples, drawn from 97 volunteer samples, before and after initiating contraceptive pill use. – “The results showed that the preferences of women who began using the contraceptive pill shifted towards men with genetically similar odours(ref).” 

This could be bad news for the stability of a relationship.  “Not only could MHC-similarity in couples lead to fertility problems but it could ultimately lead to the breakdown of relationships when women stop using the contraceptive pill, as odour perception plays a significant role in maintaining attraction to partners(ref).”  (Continuing the little story: When Bridget was finally told about Jennifer being pregnant she stopped having any sex with Alfred and stopped taking the pill.  She soon started experiencing Alfred as disgusting and, despite seeing a marriage counselor and the fact that their relationship had been working exceedingly well, she separated from him after two months.) 

An interesting question is what the implications of contraceptive pill usage might be for offspring and their evolutionary descendents.  Tarzan’s child with Jane and Alfred’s child with Jennifer would seem to continue with the established biological pattern – mating for diversity with male offspring having classical male characteristics and female offspring having classical female ones.  Stereotypical!  (Jane and Tarzan’s daughter got pregnant the first time when she was in high school.)  But what about a child born of Alfred and Bridget or any other couple where the woman is usually on the pill?   Would the lack of selection-for-diversity show up as genetic defects?  “Disturbing a woman’s instinctive attraction to genetically different men could result in difficulties when trying to conceive, an increased risk of miscarriage and long intervals between pregnancies. Passing on a lack of diverse genes to a child could also weaken their immune system(ref).”   

Another interesting question is whether evolutionary selection due to widespread use of the pill will favor people in which traditional male-female odor signaling plays a lesser part in mating and child conception.  That could be a partial explanation for why middle-class people in most advanced countries are getting married and having children much later in life.   Or, is evolutionary selection happening in which Tarzan is getting to be more Jane-like and Jane more Tarzan-like?  Good social arguments can be made that this is happening.  As we go now into the third and fourth generations of women on the pill, these questions could become more relevant. 

And finally, what about decline and blunting of sexual lust, the great traditional builder of populations?  Birth rates are declining in advanced countries where religious norms do not dictate having unlimited numbers of children.  Is the pill a major contributor to stabilization of the world’s population not only by cutting down the number of pregnancies but also by blunting natural sexual attractiveness? 

As a personal note, I have had 5 natural children by 4 wives and have raised an additional 3 as my own.  I fully played ball with the natural biological imperative to reproduce and loved doing so.  However, of those eight children I raised, four have not had their own children so far despite the fact that all are over 30.

The stream of stem cell research seems to be turning into a river with cascades, waterfalls, whirlpools and even stem-cell treatment resorts.  I comment here on just one small part of the river, which is research on generating induced pluripotent stem cells (iPSCs) that are safe to use in human tissues. I also include a “crazy” idea at the end on how to close the loop in the stem cell supply chain, possibly enabling very very long lives.

Three of the key issues being worked on are 1.  making sure that the final iPSC products are free of viral genes or oncogenes or gene translocations, 2. Making sure the iPSCs are free of viral DNA introduced by the process of making them and 3.  raising the efficiency of iPSC production.  I discussed the first two of these issues before.  See June 2009 blog post Update on induced pluripotent stem cells. The original approach to iPSC production was to use a viral vector to insert four genes into the cell to be reverted to iPSC status: Oct4, Sox2, cMyc, and Klf4.  The blog post Rebooting cells and longevity mentions the approach and the alternatives that appeared to be visible back in March 2009, but that is a long time ago as far as iPSC stem cell knowledge is concerned. 

One of the central problems with the original approach was that the DNA of these genes unpredictably integrates itself into the DNA of the iPSCs and cMyc is known to be a potential oncogene. “When Myc is mutated, or overexpressed, the protein doesn’t bind correctly, and often causes cancer(ref).”  If the cells are to be used on humans, traces of those genes are unacceptable.  There is a growing perception that “– residual transgene expression in virus-carrying hiPSCs can affect their molecular characteristics and that factor-free hiPSCs therefore represent a more suitable source of cells for modeling of human disease(ref).” Virus vectors used for gene insertion for gene insertion are also suspect.  DNA from virus vectors can integrate into the DNA of the iPSC cells, possibly affecting their transcriptional profiles or sometimes even inducing cell death or tumors. What is desired is iPSC cells that are completely free of “footprints” due to how they were created.

One approach to the issue of foreign DNA in iPSC cells is to eliminate insertion of some of the four genes or eliminate their use altogether.  A June 2008 news story tells of four different approaches towards this end being pursued at that time.  Here are some more-recent publications, including one that appeared the day-before-yesterday.

The September 2009 paper Tgfβ Signal Inhibition Cooperates in the Induction of iPSCs and Replaces Sox2 and cMyc offers hope for eliminating use of two of the genes and also addresses the productivity issue.  “iPSC derivation is highly inefficient, and the underlying mechanisms are largely unknown. This low efficiency suggests the existence of additional cooperative factors whose identification is critical for understanding reprogramming. –]. Thus, the identification of compounds that enhance rather than solely replace the function of the reprogramming factors will be of great use. Here, we demonstrate that inhibition of Tgfbβ signaling cooperates in the reprogramming of murine fibroblasts by enabling faster, more efficient induction of iPSCs, whereas activation of Tgfβ signaling blocks reprogramming. In addition to exhibiting a strong cooperative effect, the Tgfβ receptor inhibitor bypasses the requirement for exogenous cMyc or Sox2, highlighting its dual role as a cooperative and replacement factor.”

In a recent blog post I mentioned another September 2009 publication relating to an approach to iPSC induction without introducing any genes into cells at all.  Induction of Stem Cell Gene Expression in Adult Human Fibroblasts without Transgenes.  “Because forced expression of these genes by viral transduction results in transgene integration with unknown and unpredictable potential mutagenic effects, identification of cell culture conditions that can induce endogenous expression of these genes is desirable. — Manipulation of oxygen concentration and FGF2 supplementation can modulate expression of some pluripotency related genes at the transcriptional, translational, and cellular localization level. Changing cell culture condition parameters led to expression of REX1, potentiation of expression of LIN28, translation of OCT4, SOX2, and NANOG, and translocation of these transcription factors to the cell nucleus. We also show that culture conditions affect the in vitro lifespan of dermal fibroblasts, nearly doubling the number of population doublings before the cells reach replicative senescence. Our results suggest that it is possible to induce and manipulate endogenous expression of stem cell genes in somatic cells without genetic manipulation, but this short-term induction may not be sufficient for acquisition of true pluripotency.”  This is work-in-progress but the idea of inducing pluripotency purely through manipulating culture conditions is intriguing.

Another approach to getting rid of the cancer genes from iPSCs was described in my recent blog post Toward a genetic cure for Parkinson’s disease which cites the March 2009 report Breakthrough produces Parkinson’s patient-specific stem cells free of harmful reprogramming genes.  As I said in that post, The approach used by the  researchers is a good example of gene editing.  “In the current method, Whitehead researchers used viruses to transfer the four reprogramming genes and a gene coding for the enzyme Cre into skin cells from Parkinson’s disease patients. The reprogramming genes were bracketed by short DNA sequences, called loxP, which are recognized by the enzyme Cre.  After the skin cells were reprogrammed to iPS cells, the researchers introduced the Cre enzyme into the cells, which removed the DNA between the two loxP sites, thereby deleting the reprogramming genes from the cells. The result is a collection of iPS cells with genomes virtually identical to those of the Parkinson’s disease patients from whom original skin cells came.” 

Yet-another chemical approach for increasing the efficiency of iPSC production is described in the year-old news report Technique for Rapidly Reprogramming Adult Cells Into Stem Cells Published in PLoS Biology.

In September2009, researchers from the University of California, San Diego School of Medicine and the Salk Institute for Biological Studies in La Jolla reported developing “ a safe strategy for reprogramming cells to a pluripotent state without use of viral vectors or genomic insertions.”  The cells produced were pluripotent but-not-quite virgin iPSCs.  “– these induced pluripotent stem cells (iPSCs) are very similar to human embryonic stem cells, yet maintain a “transcriptional signature.” In essence, these cells retain some memory of the donor cells they once were.  “”Working with neural stem cells, we discovered that a single factor can be used to re-program a human cell into a pluripotent state, one with the ability to differentiate into any type of cell in the body” said Muotri (the lead researcher). — “While most of the original genetic memory was erased when the cells were reprogrammed, some were retained,” said Muotri. He added that, in the past, it wasn’t known if this was caused by the use of viral vectors. “By using a footprint-free methodology, we have shown a safe way to generate human iPSCs for clinical purposes and basic research. We’ve also raised an interesting question about what, if any, effect the ‘memory retention’ of these cells might have(ref) .”

Then there is the RepSox approach revealed two days ago.  Of course it was Boston-based researchers (from the Harvard Stem Cell Institute) who come up with that name.  RepSox is a small-molecule compound the researchers discovered that replaces use of the gene Sox2 (thus the name RepSox) when reprogramming cells to iPSC status.  It turns out that RepSox also makes use of the gene c-Myc unnecessary. “– many scientists think the safest approach is to replace the genes altogether with so-called small molecules. In a study published online today in the journal Cell Stem Cell entitled A Small-Molecule Inhibitor of Tgf-β Signaling Replaces Sox2 in Reprogramming by Inducing Nanog, researchers from the Harvard Stem Cell Institute report that a single compound they dubbed RepSox can replace two of the four key reprogramming genes. – “We’re halfway home, and remarkably we got halfway home with just one chemical,” senior author Kevin Eggan, a professor in Harvard’s department of stem cell and regenerative biology, said in a statement. — Now the group will turn its attention to finding other small molecules that could replace the remaining genes – Oct4 and Klf4 – as well, “opening a route to purely chemical programming,” they write(ref).”

Whatever the approach that ultimately turns out to be most successful, researchers are tackling the oncogene, the viral DNA and the productivity problems involved with producing iPSCs that are safe to use with human cells.  These citations are just a small sample of those that already exist and those that can be expected.

A visionary note

A final note of a personal vision.  Suppose, just imagine, that following some of the lines of research described above, a set of small-molecule activators could be identified that selectively causes reversion of a small sub-population of multipotent adult stem cells in-vivo (e.g. hematopoietic stem cells or mesenchymal stem cells) in their niches to return to iPSC status.  Those iPSC cells would then likely respond to niche signaling and differentiate to produce fresh niche-specific multipotent adult stem cells, cells free of the age-related epigenetic burden carried by the older multipotent cells.  What I am imagining is a supplement that closes the loop in the stem cell supply chain which could have a profound longevity-extending effect.  See the blog post The stem cell supply chain – closing the loop for very long lives.  It may sound crazy but if anybody wants to take me on I would make a small even-money bet that we will hear about something like this within the next three years.

When I first learned about computers in 1950, there were probably less than a three dozen people in the world doing computer programming, and I soon joined their ranks.  At that time, to suggest that computer programming would become an occupation involving tens of millions of people would have gotten me labeled as a crazy visionary.  Yesterday I started to wonder about how many people are involved now with genetic reprogramming of body cells.  At first I guessed that the number is anywhere from a few hundred to a few thousand.  Then, later last night, I realized that the number is about 6.8 billion people, the world’s population.  Everybody is constantly involved in reprogramming their own genes. 

Gene reprogramming can involve two quite different things: modifying genes themselves or modifying the epigenomic information that determine what the genes do.  You are born with a set of genes, those same genes are in every cell of your body and, without an extraordinary intervention you will die with the same genes.  It is possible to change some of your genes in some of your cells using sophisticated gene splicing techniques, for example to correct a genetic disease-creating defect.  See the blog post Treating genetic diseases with corrected induced pluripotent stem cells.  However, changing genes is not something that can be done lightly and almost all of us will live our lives out with the same genes we started out with.

Gene reprogramming is mostly about is modification of epigenetic information in the DNA which affects gene expression. After all, the differences between all the different kinds of cells in our body are due to gene expression.  So, “gene reprogramming” usually involves altering epigenomic markers (e.g. DNA methylation, histone acetylation and protein folding) so as to affect gene expression in cells with some objective in mind, such as curing a disease created by a gene polymorphism.   (Why the “re” in reprogramming?  For two reasons: first because computer researchers have pre-empted the term “genetic programming” to describe a fundamentally different algorithmic approach to computing, one that is vaguely based on genetics but not necessarily useful for dealing with what goes on with the DNA in real biological cells.  The other reason is that the cells worked with in reprogramming are already behaving according to some kind of epigenetic program and the objective is to alter that program.)

The big enchilada of genetic reprogramming today is reverting cells to induced pluripotent stem cell (iPSC) status, a matter I have touched on in several previous posts, starting with the post Rebooting cells and longevity. In a matter of only months the tiny initial stream of research in this area is already growing into a river.  New ways are being discovered for turning stem cell genes off and on, for example, ones like manipulation of culture conditions that do not require virus vectors or transgenes(ref).    Here is a recently compiled list of articles related to deliberate cell reprogramming.

But deliberate gene reprogramming using sophisticated laboratory techniques is only a very tiny part of the picture.

Gene reprogramming goes on constantly in the process of aging and is a feature of many disease processes. For example, a 2003 publication, Growth Hormone, Acromegaly, and Heart Failure: The Gene Reprogramming Theory, states “When the myocardium hypertrophies to face an increased mechanical load, extensive gene reprogramming occurs in the cardiomyocytes. Some genes are downregulated, whereas others are upregulated. A distinct feature of this process is the re-emergence of an ensemble of fetal genes that are normally quiescent in the adult myocardium. It was theorized that the hypertrophic cardiomyocytes are sentenced to death, as an inherent consequence of the new gene programme (Katz, 1994)” The 1999 publication Adrenergic induction of bimodal myocardial protection: signal transduction and cardiac gene reprogramming states “The delayed adaptive response is associated with the expression of cardiac genes encoding fetal contractile proteins, and PKC-I may transduce the signal for reprogramming of cardiac gene expression.”  Another article related to gene reprogramming in heart tissues is Myocardial gene reprogramming associated with a cardiac cross-resistant state induced by LPS preconditioning.  Many other studies also relate to gene reprogramming in specific tissues and under particular disease conditions. 

Cancers do masterful jobs of gene reprogramming, sometimes changing the expression of hundreds of different genes. One of the central things most cancers do, for example, is to reprogram so as to inactivate expression of the p53 apoptosis gene.  According to a recently-suggested line of thought “–  cancer could begin when normal cells spontaneously reprogram themselves, for reasons yet unknown, beginning the process that results in a cancerous tumor(ref).”

Gene reprogramming can also occur due to environmental or stress conditions.  In May 2009 it was reported “Breathing polluted air for even a short period of time can cause some genes to undergo reprogramming, which may affect a person’s risk of developing cancer and other diseases, say Italian researchers. — Comparisons of blood DNA samples from healthy workers who were exposed to high levels of airborne particulates at a foundry near Milan revealed that after only three days of exposure, changes occurred in four genes that have been linked to tumor suppression.” – “This finding indicates “that environmental factors need little time to cause gene reprogramming, which is potentially associated with disease outcomes.”

The situation is not always simple.  For example, the reprogramming introduced by stress may be beneficial or harmful dependent on a cell’s capability to mobilize a response to the stress.  See the blog post Stress and Longevity.

What you eat reprograms your genes.  The blog post Recent research on the Mediterranean diet cites research indicating that the cell reprogramming resulting from following this diet results in multiple health and longevity benefits.  Cigarette smoking affects gene reprogramming, probably in several ways(ref) (ref).  So does exercise(ref)(ref). So does taking resveratrol(ref) and taking curcumin(ref)(ref).  In fact all of the dietary supplements in the combined anti-aging supplement firewall induce gene reprogramming to one extent or the other.  So what else can reprogram your genes? Just about everything you experience and do and your emotional and mental states.  See the post Optimism and epigenomic activation.  Simply put, research shows that optimism enhances longevity.  Your mental state can create epigenomic modifications, DNA methylation on your chromosomes and histone acetylation/deacetylation modifications, and therefore alter your gene expression pattern and therefore affect your longevity.The Anti-aging lifestyle Regimen section of my treatise contains numerous “conventional wisdom” suggestions for keeping yourself young.  All of these suggestions – every one of them – is a suggestion about how you can reprogram your genes so as to enhance the prospects for longevity. 

Eating a tripple-cheeseburger whopper with a double order of fries and a giant coke reprograms your genes one way.  Exercising 47 minutes a day (my target) reprograms your genes another way.  You are a gene-reprogrammer!

It is now official; telomerase is really for-real.  A Nobel Prize was just granted to Carol Greider, Elizabeth Blackburn and Jack Szostak, for discovery of the telomerase enzyme 25 years ago.  Greider was a 23-year-old first-year graduate student back then.  My impression was that very few scientists paid any attention to telomerase at that time.  Yet, the awesome potential of telomerase is what got me interested in anti-aging research back in 1994. 

Monday, the world’s press was full of reports on the anti-aging potential of telomerase and the use of telomerase inhibition to cure cancers.   There is a danger now that hype and irresponsible commercialization of telomerase activators will start to obscure what is actually known about telomerase – similar to what has happened in the last two years with respect to resveratrol.   Since I have written extensively on the telomere-shortening theory of aging and the possible anti-aging roles of telomerase, I thought this might be a good time to provide annotated links to what I have written.

·        The write-up in my treatise of the Telomere Shortening and Damage theory of aging is a complete and current introduction to telomeres, their roles in aging and the key properties and roles of telomerase.   Telomerase achieves a lot more than simply extending telomeres.

·        The Telomere Shortening and Damage Firewall  section of the treatise discusses the activation of telomerase as a possible anti-aging intervention, one I have been using personally.

·        On October 5, 2008 I added a note to the treatise On telomerase expression and nervous system cells.

·        My first blog entry with respect to telomerase was A January 28, 2009 item Geron in the news again.  Geron was and continues to be the biotech company most heavily invested in telomere technology.

·        In This week’s anti-aging news Jan 31, 2009, and related to the discovery of a new telomerase-related protein TCAB1.

·        The February 18, 2009 blog post You may be able to keep your telomeres long reports on a Swedish large-population study of telomere lengths.

·        The February 22, 2009 post Updated discussion of the Telomere shortening theory of aging covered changes up to that point due to what I learned about telomeres and telomerase since I first drafted the Anti-Aging Firewalls treatise about a year earlier.  These changes have been since embodied in the treatise.  

·        The March 1, 2009 blog entry More telomerase tidbits discusses telomere length as  a predictor of susceptibility to coronary artery disease and discusses birds who have long telomeres and who live a very long time for birds.

·        The March 13, 2009 post From the fringe to the center discusses earlier and lesser prizes received by Blackburn and Greider and the emerging acknowledged relevance of telomerase.

·        In the June 5, 2009 blog post Linking up the theories of aging, I discuss links between the Telomere shortening and damage, the Programmed epigenomic changes, the Susceptibility to cancers and the Stem Cell Supply Chain Breakdown theories of aging.

·        In my June 9, 2009 blog post How am I doing I said  ”So, on the whole I feel very good about my anti-aging program so far.  Telomerase activation was one of the big changes in the last year and I think it might largely be responsible for some of the effects including improved eyesight and hair growth.”  

·        A June 11, 2009 post deals with the question Do resveratrol, curcumin and EGCG from green tea really inhibit the expression of telomerase? 

·   The July15, 2009 blog post Telomerase activation – upside and downside relates to another major update of the telomerase discussion in my treatise and mentions a possible danger involved with telomerase activation, that being promotion of the differentiation of cancer stem cells.

·        The September 30 blog post Revisiting telomere shortening yet-again reports on finding a treasure trove of recent publications which shed light on three issues: the relationship between two of the theories of aging (Telomere Shortening and Damage, and Stem Cell Supply Chain Breakdown),  the role of telomere shortening in multiple disease processes, and the nature of telomere shortening. 

Although at the moment I am most excited by the newest theory of aging, the Stem Cell Supply Chain Breakdown theory, I see the Telomere Shortening and Damage to be a very important complementary theory.  And I plan to continue taking a telomerase-activating daily supplement.

A team at the Whitehead Institute has taken a step towards finding a cure for Parkinson’s disease (PD) following an approach similar to but falling short of the approach outlined in my blog post Treating genetic diseases with corrected induced pluripotent stem cells.  The report’s headline is Breakthrough produces Parkinson’s patient-specific stem cells free of harmful reprogramming genes.  “Deploying a method that removes potentially cancer-causing genes, Whitehead Institute researchers have “reprogrammed” human skin cells from Parkinson’s disease patients into an embryonic-stem-cell-like state. Whitehead scientists then used these so-called induced pluripotent stem (iPS) cells to create dopamine-producing neurons, the cell type that degenerates in Parkinson’s disease patients.” 

The main innovation in this work was removal of the genes used for induction of reprogramming from the DNA of the produced iPSCs.  The researchers used an approach employed “since August 2006 for reprogramming adult cells into iPS cells by using viruses to transfer four genes (Oct4, Sox2, c-Myc and Klf4) into the cells’ DNA. Although necessary for reprogramming cells, these genes, the known oncogene c-Myc in particular, also have the potential to cause cancer. In addition, the four genes interact with approximately 3000 other genes in the cell, which may change how the cell functions. Therefore, leaving the genes behind in successfully reprogrammed cells may cause unintended alterations that limit the cells’ applicability for therapeutic use, for drug screens or to study disease in cell culture.” In recent months, incidentally, several other approaches to creating iPSCs have been reported that do not require use of these genes, including approaches that do not require insertion of genes at all(ref).

The approach the Whitehead researchers used is a good example of gene editing.  “In the current method, Whitehead researchers used viruses to transfer the four reprogramming genes and a gene coding for the enzyme Cre into skin cells from Parkinson’s disease patients. The reprogramming genes were bracketed by short DNA sequences, called loxP, which are recognized by the enzyme Cre.  After the skin cells were reprogrammed to iPS cells, the researchers introduced the Cre enzyme into the cells, which removed the DNA between the two loxP sites, thereby deleting the reprogramming genes from the cells. The result is a collection of iPS cells with genomes virtually identical to those of the Parkinson’s disease patients from whom original skin cells came.”  Clever!

“After removing the reprogramming genes, the — researchers differentiated the cells from the Parkinson’s disease patients into dopamine-producing nerve cells. In Parkinson’s disease patients, these cells in the brain die or become impaired, causing such classic Parkinson’s symptoms as tremors, slowed movement, and balance problems.”

Those cells might be very useful for testing out various treatments for PD in-vitro but of course retain any genetic defects that may have led to PD in the first place.  These cells are therefore questionably suitable for stem-cell replacement therapy.  The next step in developing a stem cell therapy for PD would be to strip out faulty genes that lead to PD susceptibility and replace them with healthy ones, as suggested in my post.  There has been some progress in identifying genes related to PD susceptibility(ref)(ref), with several genes having been identified that, when mutated, have to do with forms of PD, genes like alpha-synuclein,  parkin, DJ1, PINK1, and LRRK2.  However, my impression is that not enough is known about these genes yet to allow such gene correction. 

This work exemplifies hundreds of studies demonstrating modest steps of progress but aimed ultimately at stem-cell cures for diseases.   An earlier blog post Gene therapy for fruit flies with Parkinson’s Disease  discusses a different possible therapeutic approach, re-introducing a gene that has been lost on the process of evolution.    For an approach that might be more immediately useful for prevention of PD, check out my blog entry Mitochondria and Parkinson’s Disease

Conventional wisdom says that you will live healthier as you reach an advanced age if you live with a partner. A Scandinavian study published in July 2009 confirms that wisdom with respect to cognitive capability. The study, Association between mid-life marital status and cognitive function in later life: population based cohort study, had the objective of looking at whether mid-life marital status is related to cognitive function in later life. The study looked at a previously-researched sample of 1449 individuals from the Kuopio and Joensuu regions in eastern Finland with an average follow-up period of 21 years.

“Results:  People cohabiting with a partner in mid-life (mean age 50.4) were less likely than all other categories (single, separated, or widowed) to show cognitive impairment later in life at ages 65-79. Those widowed or divorced in mid-life and still so at follow-up had three times the risk compared with married or cohabiting people. Those widowed both at mid-life and later life had an odds ratio of 7.67 (1.6 to 40.0) for Alzheimer’s disease compared with married or cohabiting people. The highest increased risk for Alzheimer’s disease was in carriers of the apolipoprotein E e4 allele who lost their partner before mid-life and were still widowed or divorced at follow-up. The progressive entering of several adjustment variables from mid-life did not alter these associations(ref).”

I find these statistics impressive; three times the risk is way beyond a marginal effect.  If  you are living successfully with a partner you probably have to exercise your mind more.  The report concludes “Living in a relationship with a partner might imply cognitive and social challenges that have a protective effect against cognitive impairment later in life, consistent with the brain reserve hypothesis. The specific increased risk for widowed and divorced people compared with single people indicates that other factors are needed to explain parts of the results. A sociogenetic disease model might explain the dramatic increase in risk of Alzheimer’s disease for widowed apolipoprotein E e4 carriers.”

It is Sunday evening now and I am going to stop writing so I can hang out with my wife. 

Regular readers of this blog are familiar with the crucial importance of signaling molecules and transcription factors in life-related biological processes.  However, traditional mass spectrometry may have difficulty detecting such molecules which are produced in low numbers.  Although mass spectrometry is a very important technique for determining the presence of proteins in cells, the observations it produces produced are averages, often over millions of cells in a culture.  Information related to important subpopulations of cells or what is going on in a single cell is lost.  “Mass spectrometry (MS) has become a preeminent methodology of proteomics since it provides rapid and quantitative identification of protein species with relatively low sample consumption. Yet with the trend toward biological analysis at increasingly smaller scales, ultimately down to the volume of an individual cell, MS with few-to-single molecule resolution will be required(ref).”

A typical laboratory mass spectrometry system is the size of a supermarket food freezer.  Recently-reported research indicates that it may be possible to mass-produce mass spectrometers on microchips, ones that can analyze the proteins in individual cells. “A prototype for a mass spectrometer with single-molecule sensitivity has prospects for single-cell proteomics.   – – With new work from Michael Roukes’s group at the California Institute of Technology, however, this could potentially all change. Roukes and his colleagues recently reported a nanoelectromechanical system (NEMS)-based method that can be used to detect molecular mass with single-molecule sensitivity. — NEMS sensors are nanoscale devices that resonate at frequencies close to the microwave range(ref).”  According to Roukes “We report the first realization of MS based on single-biological-molecule detection with nanoelectromechanical systems (NEMS). NEMS provide unparalleled mass resolution, now sufficient for detection of individual molecular species in real time. However, high sensitivity is only one of several components required for MS. We demonstrate a first complete prototype NEMS-MS system for single-molecule mass spectrometry providing proof-of-principle for this new technique(ref).”“

“The next question is, that’s a lot of molecules that you need to measure one by one, and how the heck are you going to do that?” says Roukes. He envisions an elaborate microfluidics-based front-end separation system, which would distribute the contents of a single cell to a chip consisting of thousands of individual NEMS sensors, each one a tiny mass spectrometer(ref).”  Proof-of-concept has been established but the engineering challenge of building such a device remains. “Roukes is collaborating with researchers at CEA (French Atomic Energy Commission) Leti in Grenoble, to make such chips with thousands or even millions of NEMS sensors. Another challenge they must tackle is pushing the mass resolution to below a single dalton; their current mass resolution is about 1,000 daltons. “This will require us to scale down [the size of] the individual NEMS resonators,” says Roukes(ref).”

This stream of development is another example of what I talked about in my blog post Factors that drive Giuliano’s Law. You may recall that Giuliano’s Law is:

·        Starting now, every seven years will see the emergence of practical age-extension interventions (ones that have a potential of leading to extraordinary longevity) that double the power of the interventions available at the start of the 7 year period.  That is, on an average basis, the practical anti-aging interventions available at the end of a seven-year period will enable twice the number of years of life extension than did the interventions available at the start of the period.  Life extension is measured in years of life expectancy beyond those actuarially predicted for a given population. 

In that post I said “This law is valid for the same reason Moore’s Law for integrated electronics is valid – the law that the number of transistor elements on a chip at a given price point doubles roughly every two years.  This law has held for 40 years and is responsible for the corresponding increase in cost-effectiveness of computers, cell phones and all other electronics.  This law was the result of a strong positive feedback relationship between societal need, market, economic contribution, market vehicles, user applications, marketing channels, changes in user expectations advancement in the relevant basic science, advancement of technology, advancement of manufacturing capability and an entrepreneurial environment.”  And there is yet-another factor I did not mention before, and that is massive government investment in health sciences research.  Advances in basic research technology like spectrometry is one of the key factors driving life extension, a factor that works in close interplay with the other factors mentioned. 

The first computer I worked on, the UDEC at Wayne State University in 1952, was some 60 feet long, weighed several tons and filled a gigantic room under the dome of the old Victorian-design main building.  The computer chip in my Blackberry phone is the size of a large dandruff  flake and is tens of thousands of times more powerful and useful.   And I remember when powerful computers got to be the size of supermarket freezers, in the early 80s.  I wonder if someday we will carry pen or pin-sized mass spectrometers as part of our personalized medicine health monitoring system.

I love reporting on research that supports my favorite theories, and also on research that challenges them.  In the post The anti-antioxidant side of the story I reported on research suggesting a couple of possible downsides to antioxidant supplementation.  A just-published research publication suggests another possible downside: Antioxidant and oncogene rescue of metabolic defects caused by loss of matrix attachment.  “Normal epithelial cells require matrix attachment for survival, and the ability of tumour cells to survive outside their natural extracellular matrix (ECM) niches is dependent on acquisition of anchorage independence. Although apoptosis is the most rapid mechanism for eliminating cells lacking appropriate ECM attachment, recent reports suggest that non-apoptotic death processes prevent survival when apoptosis is inhibited in matrix-deprived cells.”  Specifically “detachment of mammary epithelial cells from ECM causes an ATP deficiency owing to the loss of glucose transport.”  The ATP deficient cells being in a state of stress had high levels of ROS expression and eventually died off, a good thing.  This kind of cell death is important because many cancers suppress the expression of apoptotic genes.  However, exposing the detached cells to antioxidants tended to restore ATP production and rescue the rouge cells, a bad thing.  

Another report on the same research states “Can antioxidants also promote cell transformation? MCF-10A cells expressing oncogenes that promote proliferation and suppress apoptosis (either human papillomavirus E7 and BCL-2, or ERBB2) exhibit limited colony formation in soft agar, but antioxidant treatment increased both the number and the size of colonies.” – “–antioxidants may promote tumours by suppressing the ability of ROS to prevent outgrowth of cells that are displaced from their natural microenvironment.” I have no idea as to whether the concern is a valid one for the health of live organisms, and, if so, the dimensions of the problem.

Repeating what I said in my earlier post, I stress that taking antioxidants is only one component of what is likely to be an effective anti-aging program such as that identified in my treatise ANTI-AGING FIREWALLS –  THE SCIENCE AND TECHNOLOGY OF LONGEVITY.  Further, taking certain antioxidants in excess quantities could conceivably be dangerous to health or longevity.