Résumé :
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Communication n° 242. Introduction : Process of skeletal muscle regeneration depends on the presence of satellite cells. It is postulated that stem cells from different tissues, such as bone marrow, can be involved in this process. Yet, the fate of human umbilical cord blood (HUCB) cells after implantation into damaged muscle has not been examined. Since, the SCID (severe combined immunodefficient) mice have ability to accept xenogenic grafts, we choose them for transplantation experiments in order to avoid rejection of the human cells. Here we present first detailed description of the fate of intramuscularly implanted HUCB cells. Objectives : In this report we demonstrate the participation of the HUCB cells in the short-term skeletal muscle regeneration of SCID mouse. Methods : The HUCB cells, labeled with PKH26 (red fluorescent dye) were implanted directly into damaged gastrocnemius muscle. The mouse was euthanized, the muscles were dissected, cryosectioned and analyzed for presence of PKH26 fluorescence. Next, the muscles were dissagregated by pronase treatment. Human antigenes present on isolated cells were detected with anti-HLA-ABC-Cy5 antibody and analyzed by flow cytometry and confocal microscopy. Results : We compared time-course of regeneration process of gastrocnemius muscle immunodefficient and BALB/c mice. In cryosections produced from muscles during the first 3 days of regeneration the fluorescently labelled HUCB were detected as a separate population. On sixth and seventh day of regeneration we noticed new PKH26 labeled myofibers. The parallel flow cytometric analyses revealed the presence of strongly fluorescent cells during the first 3 days of regeneration. During the following period of 4 days we observed small number of PKH26 marked cells. The PKH26 labeled cells from regenerating muscles expressed HLA-ABC antigens as was detected by specific antibodies. Conclusions : We show, that HUCB cells can fuse with satellite cells during muscle regeneration and form multinucleate myotubes. Therefore, HUCB stem cells participate in mouse muscle regeneration.
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