[Current state of establishing and maintaining human embryonic stem cell lines and key problems in these studies]

Derivation of human embryonic stem cell and embryonic germ cell lines has widespread and far-reaching significance on human basic research and transplantation therapies. Human pluripotential stem cells provide an exciting new model for studying early human embryogenesis, understanding normal human development and abnormal development, provide a powerful system for discovering human novel genes and testing their function, offer new strategies for discovering of novel growth factors and medicines and promise a renewable source of cells for tissue transplantation, cell replacement and gene therapies. Research history of establishment of human ES and EG cell lines is reviewed. Several methods of establishment of these cell lines involving in the protocol, route, significance and possibility are discussed. Selection of the feeder layer, medium, and supplemental cytokines and their roles in establishing and maintaining human ES and EG cell lines at present are illustrated in detail systematically. Effects and used methods of several kinds of digestive en-zyme in propagations are prepared. Several methods for identifying human ES and EG cells are summarized. At the end, some key problems which are urgent to resolve in these studies at present are put forward and analyzed.