[Embryonic stem cells: new possible therapy of degenerative diseases].

The capacity of embryonic stem (ES) cells for virtually unlimited self-renewal and differentiation has opened up the prospect of widespread applications in biomedical research and regenerative medicine. The use of these cells would allow to overcome the problems of donor tissue shortage and also implant rejection if the cells are made immunocompatible with the recipient. Since the derivation in 1998 of human ES cell lines from pre-implantation embryos, considerable research is centered on their biology, on how differentiation can be encouraged towards particular cell lineages and also on means to enrich and purify derivative cell types. In addition, ES cells may be used as an in vitro system not only to study cell differentiation but also to evaluate the effects of new drugs and the identification of genes as potential therapeutic targets. This review will summarize what is known about animal and human ES cells with particular emphasis on their application in four animal models of human diseases. Present studies of mouse ES cell transplantation reveal encouraging results but also technical barriers that have to be overcome before clinical trials can be considered.