The role of stem cells in aging, as well as the changes in stem cell populations and capacities that come with aging, would seem to be the topic of the day. I've touched on it before; the presently ongoing research is fascinating to watch. For example, the debate over whether, how and how much changes in the surrounding environment and signaling of other cells is responsible for the decline in stem cell activity with age. Or is it that stem cell populations become worn out and decline in numbers? It's an important difference for those seeking to safely repair this age-related degeneration.
One hypothesis is that aging directly affects stem cells as a consequence of exhaustive proliferation. Alternatively, it is also possible that aging indirectly affects stem cells by acting on their microenvironment.
On this topic, a good post from Ouroboros today:
A good deal of recent work suggests that the environment in which a stem cell resides (the "niche") is at least as important to regenerative capacity as any property of the stem cell itself. A recent paper by Carlson and Conboy expands our knowledge of the deleterious effect of old niches on young cells; provides some tantalizing evidence of a mechanism, involving regulation of gene expression in the stem cells; and underscores the fundamental importance of studying the interaction between cells and their microenvironment.
Scientists on the "microenvironment matters and here's why" side of the debate look to be presenting their case ever more convincingly in the past year. As Chris Patil points out:
The most straightforward implication of Morgan and Conboy's findings is that we will need to address the tissue microenvironment/niche/cell-cell signaling issues in order to optimize the therapeutic potential of [human embryonic stem cells (hESCs)] introduced into an aged patient.
An obvious corollary is that identifying, targeting and inhibiting the "dominant" factors that decrease hESC pluripotency and proliferative capacity should be a major priority for scientists interested in developing stem-cell based solutions to the treatment of age-related disease.
You can't just drop stem cells into a patient and expect quality results if their local tissue is actively suppressing and sabotaging the rescuers.
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