A couple of years ago, Chinese researchers demonstrated modestly extended longevity in mice through transplantation of mesenchymal stem cells. This sort of thing is a very brute-force approach to enhanced regeneration: it's more or less the least and first possible action that can be taken after developing the technology to extract, purify, and culture stem cells outside the body. Researchers are still in the midst of gathering a full understanding of what exactly goes on under the hood in the variety of circumstances and methodologies whereby tissue is flooded with additional stem cells. But as is demonstrated by the trials and stem cell clinics around the world, there is ample evidence that benefits are possible given the right approach.
Here is a more recent open access paper by a different research group that also shows extended longevity in mice with transplantation of stem cells; in this case cells from young donor mice given to old recipient mice:
Increasing evidence suggests that the loss of functional stem cells may be important in the aging process. Our experiments were originally aimed at testing the idea that, in the specific case of age-related osteoporosis, declining function of osteogenic precursor cells might be at least partially responsible.
To test this, aging female mice were transplanted with mesenchymal stem cells from aged or young male donors. We find that transplantation of young mesenchymal stem cells significantly slows the loss of bone density and, surprisingly, prolongs the life span of old mice. These observations lend further support to the idea that age-related diminution of stem cell number or function may play a critical role in age-related loss of bone density in aging animals and may be one determinant of overall longevity.
The mean life span of control mice was 765 days However, the mean life span for mice that received young BMSCs transplants was 890 days ... Overall, these results suggest that transplantation of BMSCs derived from young animals extends life span. However, it is not clear whether the prolonged lifespan may be associated with improved tissue regeneration.
The connection between attempting therapy for osteoporosis and resulting increases in longevity have shown up in other contexts - such as that bisphosphonate study that was reported a year ago or so - enough to make it a possible point of interest, and something to keep an eye out for in future research results. There's certainly no shortage of research groups working on osteoporosis or other bone issues with the use of mesenchymal stem cells. For example: