Stem cells: progress in research and edging towards the clinical setting

Mouse embryonic stem cells have been shown to differentiate into a variety of tissues in vitro and in transplantation experiments can produce many dif ferent cell types. Multipotent stem cells in adult humans have also shown a high degree of plasticity: haemopoietic stem cells, for example, have been shown to contribute to several other tissues, such as liver. From these si mple observations there has been considerable extrapolation into the use of such putative totipotent stem cells in the clinical setting, with the deve lopment of 'designer' tissue engineering, whose aim is to create large tiss ues or even whole organs for clinical use. In practical terms, however, the re are many limitations and difficulties and clinical use has been restrict ed to a very few settings, eg the use of fetal cells in Parkinson's disease . Nonetheless, there is enormous potential in this area, and also in the ap plication of embryonic or adult stem cells as carriers for gene therapy; bu t the limitations of such treatment, in particular the stability of manipul ated cells, and the problems of ageing and Ooncogenicity, not to mention a host of ethical and regulatory issues, all need to be considered.