“…For the induction of specific cell lineages from ES cells, purified growth and/or differentiation factors or factorproducing feeder or stromal cells have been used (Chadwick et al, 2003;Cohen et al, 2007;Green et al, 2003;Kaufman et al, 2001;Kehat et al, 2001;Lavon et al, 2006;Levenberg et al, 2002;Mummery et al, 2003;Rambhatla et al, 2003;Sottile et al, 2003;Vodyanik and Slukvin, 2007;Zhang et al, 2001). In some cases, very complex culture strategies have been used, including the sequential addition and withdrawal of factors and purification of specific cell populations during the culture period (Fang et al, 2006;Wang et al, 2005).…”