Oxygen control of stem cell niches and cell fates

Did you know that physiological normoxia generally falls in the 2-9% O₂ (14.4-64.8 mm Hg) range for most adult cells in vivo? 3 remarkable exceptions are thymus, kidney medulla and most importantly bone marrow which can exist at 1% O2 (7.2 mm Hg). On the other hand, stem and progenitor cells are frequent residents of hypoxic niches and low O₂ regulates their differentiation. Conclusion?

Although most cells are maintained in culture conditions at 21% O₂, this is unlikely to be optimal for maintaining their normal proliferative or developmental state. The derivation of novel stem and undifferentiated cell populations should therefore be enhanced by culture in the range of 3–5% O₂.

More on this very important and usually neglected oxyphsiological angle on stem cells, development and culture in the very uptodate review: The role of oxygen availability in embryonic development and stem cell function by Simon@Keith in Nat Rev Mol Cell Biol. 2008 Apr;9(4):285-96.

Some stem cells (such as those in the endosteal bone marrow compartment) occupy extremely low O2 microenvironments (<0.5% O2)

“What is the meaning of life?” for a life extensionist

In No kidding, I am a cum laude philosopher, and so can you! it turned out that finally I got a philosophy diploma. That said, from now on I am officially qualified to think on the big questions of life. For instance, I can find out new arguments and concepts and I can answer (or at least fine-tune) questions like: ‘what is the meaning of life?’. (The best analysis of this question for me was Robert Nozick’s Philosophy and the Meaning of Life in the last chapter of his book Philosophical Explanations, for an official intro see Stanford Encyclopedia of Philosophy)

So here is a short analysis and an answer of mine to this most important philosophical question from the point of view of a life extension supporter:

1. premise: this question could be answered only if it not about the general meaning of all life, but the particular meaning of individual human lives.

2. analysis: let’s fill the question up to show the variables in it: ‘what is the meaning of an individual human life (x) for somebody individual (y)?’