Isolierung und Transplantation mesenchymaler Stammzellen aus Nabelschnurblut

Purpose: There is evidence that mesenchymal somatic stem cells isolated from cord blood have the capability to differentiate into different tissues. Strategies to isolate, cryopreserve and differentiate mesenchymal stem cells are of high interest. We examined survival, proliferation and transdifferentiation of human mesenchymal stem cells transplanted into healthy mouse livers. Methods: Mesenchymal stem cells isolated from human cord blood were transplanted into the livers of 12 SCID mice. Liver tissue was stained for stem cells with the fluorescent dye PKH26 7 and 21 days after transplantation. Expression of human albumin, α1-antitrypsin, GATA4, α-fetoprotein, β2 microglobulin and β-actin in stem cells was studied before and after transplantation with immunohistochemistry and RT-PCR. Results: PKH-positive, fluorescent, intact cells were identified in the livers of all 12 transplanted mice. More PKH26-positive cells were seen after 21 than after 7 days. Expression of human albumin in mouse liver tissue was demonstrated immunohisto-chemically with a specific monoclonal antibody and confirmed with RT-PCR. Conclusion: Human mesenchymal stem cells isolated from cord blood can survive, proliferate and transdifferentiate after transplantation into mouse liver tissue. This may have therapeutic applications in the future. It appears that gene expression by the transplanted stem cells adapts to the host tissue. The transplanted stem cells express some, but not all genes typically expressed in liver (for instance albumin but not GATA4). It is not clear whether this is due to an inherent limitation of these stem cells to transdifferentiate or to interspecies incompatibilities between humans and mice.