Data on the Aging of Stem Cells From Supercentenarian Blood
Researchers may gain some insight into the aging of stem cells and the relevance (or irrelevance) of nuclear DNA damage to aging from the analysis of blood and tissue donated by a supercentenarian:
Our blood is continually replenished by hematopoietic stem cells that reside in the bone marrow and divide to generate different types of blood cells, including white blood cells. Cell division, however, is error-prone, and more frequently dividing cells, including the blood, are more likely to accumulate genetic mutations. Hundreds of mutations have been found in patients with blood cancers such as acute myeloid leukemia (AML), but it is unclear whether healthy white blood cells also harbor mutations.In this new study, the authors used whole genome sequencing of white blood cells from a supercentenarian woman to determine if, over a long lifetime, mutations accumulate in healthy white blood cells. The scientists identified over 400 mutations in the white blood cells that were not found in her brain, which rarely undergoes cell division after birth. These mutations, known as somatic mutations because they are not passed on to offspring, appear to be tolerated by the body and do not lead to disease. The mutations reside primarily in non-coding regions of the genome not previously associated with disease, and include sites that are especially mutation-prone such as methylated cytosine DNA bases and solvent-accessible stretches of DNA.
By examining the fraction of the white blood cells containing the mutations, the authors made a major discovery that may hint at the limits of human longevity. "To our great surprise we found that, at the time of her death, the peripheral blood was derived from only two active hematopoietic stem cells (in contrast to an estimated 1,300 simultaneously active stem cells), which were related to each other. Because these blood cells had extremely short telomeres, we speculate that most hematopoietic stem cells may have died from 'stem cell exhaustion,' reaching the upper limit of stem cell divisions." Whether stem cell exhaustion is likely to be a cause of death at extreme ages needs to be determined in future studies.
Link: http://www.eurekalert.org/pub_releases/2014-04/cshl-hog041814.php
So it looks like this pretty much destroys any hope of reverse-aging, doesn't it? The article mentions people saving their stem cells when they're infants, but fat lot of good that does to older people, huh? It looks like there are hard limits to how long humans can live. Sorry, but all you people hoping for indefinite lifespans are going to be sorely disappointed.
I've read so many SF books, with so many alternatives to aging and dying. I can't think of one that beats getting old and dying. I'm not looking forward to it but I can't find an alternative I think is better.
"So it looks like this pretty much destroys any hope of reverse-aging, doesn't it? The article mentions people saving their stem cells when they're infants, but fat lot of good that does to older people, huh? It looks like there are hard limits to how long humans can live."
The accumulation of a few hundred mutations with age, should be easily correctable by the genetic engineering from a few decades from now. Old cells can be easily corrected outside the body, and checked for accuracy of corrections. So there really would be no need for young cells in storage, if we actually had to use external cell sources in therapies.
Regardless most of these mutations appear neutral, many harmful mutations are dealt by either the immune system or apoptosis. Provided there was adequate telomere lengthening in place it is likely more of the stem cell pools would be preserved in a functioning state.