The Max-Planck-Institute for Heart and Lung Research in Bad Nauheim focusses on research on the processes being responsible for regeneration and repair of organs such as the heart. Previous studies had shown that stem cells might play an important role. In one of their projects scientists therefore investigated the potential of adult and embryonal stem cells to differentiate into completely developed tissue cells such as skeletal muscle or heart muscle cells. Data show that the use of specific differention factors indeed induces cell programmes which lead to the expression of typical muscle-cell specific factors. However, stem cells could not completely be transfered into muscle cells. In contrast, researchers observed in vitro experiments the fusion of stem cells and differentiated muscle cells, which could point towards a potential repair mechanism: Muscle repair may not be mediated by transdifferentiation of stem cells into muscle cells, but rather by fusion of stem and muscle cell. Doing so, vitality of the “sick” cell might be improved. In a second study, Max-Planck researchers investigated whether stem cells might contribute to the repair of heart tissue after myocardial infarction. They showed that after injection of stem cells isolated from skeletal muscles or of heart muscle cells which had be risen from embryonic stem cells, that at least in an animal model heart function can be improved. The positive effect most likely is based on a mechanism, in which growth stimulating substances are released into the damaged heart tissue by the injected cells.