How did you come up with the parabiosis experiment—an old and young mouse sharing circulation?
For some time, I’d thought that the “aging environment” might be contained in the blood circulation. Earlier reports in the 1980s on muscle transplantation took pieces of young muscle and transplanted it to old animals and vice versa. In every situation, it was the age of the host that determined how successful or unsuccessful regeneration was. That implied to me that perhaps the responses of muscle stem cells are regulated by their niche much more than by the age of the cell itself. But, I didn’t know how I would explore this hypothesis until my husband had this idea at journal club. We were discussing a paper from Weissman’s laboratory where they did parabiosis of animals the same age. My husband said, “What if we connect young and old mice together?” I immediately met with Irv—he was one of my thesis committee members and he always at least pretended that he was glad to talk to me. And before I even finished my first sentence, he had already started nodding and said, “The people in
