Transforming growth factor beta 1 (TGF-fl1) is necessary for preventing excessive cell proliferation that could otherwise lead to cancer and inflammation. As animals age, the concentration of TGF-fl1 increases, causing stem cells to deactivate and preventing them from adequately responding to tissue and organ injuries. Scientists are investigating how a new drug may lower levels of TGF-fl1 in older animals, allowing stem cells to reactivate and regenerate unhealthy tissues.