Recently she has discovered a “partial pathway,” previously undescribed in the blood system, that is involved in the process of repair. “The reason we thought the factor that awakens muscle stem cells might be in the blood,” she explains, “is that organ systems decline globally with age, which implies that any signal has to reach many different locations.” A good place to look for a universal signal such as that, she reasoned, is in the blood.
In fact, her work has already shown that exposing an old animal to the blood of a young animal restores function to progenitor cells in a variety of tissues, not only in skeletal muscle. She is now collaborating with other Harvard laboratories to study such effects in the pancreas, liver, brain, and heart. “This might be a more broadly applicable mechanism,” she says, “an inroad for discovering pathways that can enhance repair activity.” In some cases, Wagers thinks, induced repair mechanisms that fail with age might overlap with genetic disorders, so that studying these pathways could advance research on cures for certain diseases. At the very least, she suspects that the “kinds of molecules we discover that enhance endogenous repair activity” could someday play an important role in readying tissues for cell therapy, once that field is mature. Adds Melton, “This has gotten us thinking more about not just fixing the human body when it is broken, but about how to harness the natural activity of stem cells for homeostatic repair to keep us healthy. We’re not there yet, but I think that is where we are headed.”