Insulin-producing cells derived from human embryonic stem cells: comparison of definitive endoderm- and nestin-positive progenitor-based differentiation strategies. oleh Rui Wei, Jin Yang, Wenfang Hou, Guoqiang Liu, Meijuan Gao, Lin Zhang, Haining Wang, Genhong Mao, Hongwei Gao, Guian Chen, Tianpei Hong