[Differentiation potential of human stem cells--approaches to tissue engineering and to cell transplantation]

The prospect of future clinical applications of human stem cells is one of the major arguments for the use of embryonic stem cells. Scientists are currently developing methods to culture and isolate different somatic cell types. The enormous capacity for proliferation of embryonic and certain adult stem cells combined with suitable protocols to differentiate these cells may allow the production of sufficient amounts even of those cell types which cannot be expanded in the terminal differentiated state. The ability to generate large quantities of certain somatic cells in vitro has led to the first cell transplantation-based therapeutic concepts and clinical studies. Even today comparatively simply structured in vitro-engineered tissues are applied clinically. However, to grow larger and more complex structures, a variety of problems including their vascularisation and the development of suitable matrices have to be resolved. In the long term, tissue engineering offers an as yet incalculable potential for future medical applications and may finally allow the development and clinical transplantation of complex tissues or even whole organs.