There is disagreement, however, about the mechanism on which repair processes are based. Scientists from the Max Planck Institute for Heart and Lung Research in Bad Nauheim, Germany, in co-operation with colleagues from Martin Luther University in Halle-Wittenberg, have now shown that skeletal muscle tissue can fuse with adult stem cells, via a mechanism based on the participation of mediators which are generally involved in immune cell activation. Although being unable to transdifferentiate into completely functional muscle cells, they are integrated into the tissue complex by fusing with differentiated tissue cells. In contrast, in the heart muscle tissue the mechanism seems to be different from this. The scientists in Bad Nauheim conclude from their study that adult stem cells are involved in tissue repair processes in a paracrine way by delivering mediating factors rather than by simply becoming components of the regenerating organ. (Genes & Development, August 2005).
Stem cells are fully unspecialised cells which can develop into all kinds of cell types. Embryonic stem cells provide the origin of a developing organ, during the growth of an embryo. For example, mesenchymal cells stem cells from embryonic connective tissue transform themselves during embryogenesis into muscle cells, under the influence of certain growth factors.
Other stem cells adult stem cells play an important role throughout an organism's life. For example, bone marrow stem cells provide for the replenishment of short-lived blood cells. Adult stem cells can be found locally in various tissues and organs, and we have presumed that they are participating in the repair and maintenance of organ functions.
The controversial idea is that adult stem cells have the potential for transdifferentiation; in other words, that they are able to transmutate from one type of organ cell to another. If that is the case, bone marrow cells would be able to change into lots of differenPage: 1 2 3 Related biology news :1
Contact: Prof. Dr. Thomas Braun
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