How old cells can regain youth

Old cells may regain a youthful phenotype when exposed to a young cell environment, say researchers in Nature this week. The results, say the authors, indicate that aged satellite cells have an intrinsic ability to regenerate.

"We know old tissue repairs poorly, but it's not because there aren't stem cells ready to do the repair," coauthor Thomas Rando told The Scientist. "The problem is, with age, the environment the stem cells hit changes, [and] it makes them less responsive."

To study how systemic factors affect satellite cell regeneration, researchers from Stanford University and VA Palo Alto Health Care System in California created fusions of the circulatory systems of old mice and young mice—a technique known as parabiosis. The young mice were transgenic, expressing either green florescent protein or a distinct CD45 allele.

Five days after injuring the mice's hindlimbs, researchers found nucleated embryonic myosin heavy chain, a specific marker seen ...