Researchers here demonstrate extended life spans in rats as a result of life-long regular transplantation of stem cells. The specific mechanisms are unknown, but the researchers suggest that the proximate causes involve altered levels of various signal molecules leading to better operation and maintenance of native cells and tissues. Given that one study can't measure everything of interest, this should probably be taken as a preliminary set of suppositions, though reasonable given what is known of stem cell therapies at this point. Following on from this work it is definitely the case that more life span studies should take place for stem cell treatments.
Aging brings about the progressive decline in cognitive function and physical activity, along with losses of stem cell population and function. Although transplantation of muscle-derived stem/progenitor cells extended the health span and life span of progeria mice, such effects in normal animals were not confirmed.
Human amniotic membrane-derived mesenchymal stem cells (AMMSCs) or adipose tissue-derived mesenchymal stem cells (ADMSCs) were intravenously transplanted to 10-month-old male F344 rats once a month throughout their lives. Transplantation of AMMSCs and ADMSCs improved cognitive and physical functions of naturally aging rats, extending life span by 23.4% and 31.3%, respectively. The stem cell therapy increased the concentration of acetylcholine and recovered neurotrophic factors in the brain and muscles, leading to restoration of microtubule-associated protein 2, cholinergic and dopaminergic nervous systems, microvessels, muscle mass, and antioxidative capacity.
The results indicate that repeated transplantation of AMMSCs and ADMSCs elongate both health span and life span, which could be a starting point for antiaging or rejuvenation effects of allogeneic or autologous stem cells with minimum immune rejection.