Intrinsic dynamics of the fat graft: in vitro interactions between the main cell actors.

Background: Successful soft-tissue reconstruction requires autologous tissue transfer in respect to the increasingly important "replace like-with-like" principle. Autologous lipoaspirate material for fat grafting can easily be obtained in large amounts without substantial donor-site morbidity. The exact nature and fate of the different cells in the transplanted fat graft and their contribution to tissue reconstruction, however, remain largely unknown.
Methods: Adipose tissue was harvested from healthy female patients. CD34+ adipose-derived stem cells were isolated through magnetic-activated cell sorting and brought into co-culture with mature adipocytes in various culture medium conditions. Proliferation and differentiation of the adipose-derived stem cells were examined through histology, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays, and polymerase chain reaction assays.
Results: This study demonstrates that adipose-derived stem cells from fresh adipose tissue can be isolated within a few hours via magnetic-activated cell sorting with selection for CD34+ cells. All unpassaged adipose-derived stem cells in fresh adipose tissue are CD34+. Subsets include CD34+ CD31+ and CD34+ CD271+. No CD34+ CD45+ cells were present. Histological staining, polymerase chain reaction, and MTT assays confirm that purified mature adipose cells incite adipose-derived stem cells proliferation and adipose differentiation in vitro.
Conclusions: This in vitro study demonstrates important interactions between the main actors in the adipose graft, the adipose-derived stem cells and the mature adipocytes. Although the eventual fate of these cells in a clinically implemented fat graft is still largely unknown, the results of this study support the theory that lipofilling can be conceived as an in vivo tissue engineering approach in which the mature adipocytes within fat grafts support proliferation and differentiation in the co-grafted stromal cell population.