“…Many tissues, such as skin (Blanpain and Fuchs, 2009), intestine (Clevers, 2013), muscle (Shadrach and Wagers, 2011), lung (Green et al, 2013; and the hematopoietic system (Orkin and Zon, 2008), are endowed with stem cells that ensure repair from damage induced by wear and tear, cellular turnover and injury. In contrast to PSCs, adult stem cells are generally difficult to maintain, grow and expand in vitro.…”