Résumé :
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Communication n° 450. The used of stem cells from cell-based tissue-engineering strategies represents a promising alternative for the repair of adult tissue diseases. Like bone marrow, adipose tissue is derived from the mesenchyme and contains stromal cells that can be separated from adipocytes. This stromal fraction AT-SC (adipose tissue-derived stem cells) has been shown to differentiate in vitro in adipogenic, osteogenic, chondrogenic and myogenic lineages. Moreover, in vivo, transplantation of AT-SC was described to increase mass and functional capacity of rabbit damaged muscle, as well as to participate in the re-vascularization of the ischemic hind limb in nude mice. The aim of our study was to sort population of putative progenitors or stem cells in human AT-SC using surface protein characterization by flow cytometry. Our data showed that the large majority of AT-SC expressed CD90 (Thy-1) and the hematopoietic stem cells marker CD34 (86±4 and 72±6 % of positive cells, respectively), these markers were maintained, in same levels, in 7 days culture-expanded cells (D7). Monocyte/macrophage CD11b and hematopoietic CD45 positive cells (13±1 and 14±2 % respectively) were detected on fresh AT-SC but expression disappear after D7. Interestingly, a minor population expressing stem-cells markers was present and characterized by CD56+/CD45-; CD13, FLK-1 (VEGF-R2) and Abcg2 positive cells in fresh isolated AT-SC. Abcg2 is a determinant of the side population (SP) cell phenotype. SP, that is enriched in repopulating activity, was recently identified in several tissues as bone marrow, skeletal muscle and skin. Accordingly to the dual-wavelength flow cytometry method using vital dye Hoechst 33342, SP representing 0.6±0.07% of the cells was isolated from human AT-SC fraction. All together, these data strongly suggest the presence of stem cells within the stromal fraction of human adipose tissue that could be an easily accessible source of cells for tissue repair strategies. We are currently sorting these cells to evaluate their pluripotency properties and particularly their myogenic potentiality.
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