Abstract
In the present study, we evaluated the benefits of an adipogenic predifferentiation, the pathway most closely related to osteoblastogenesis, on the pro-osteogenic potential of human adult multipotent bone marrow stromal cells (hBMSCs), both in vitro and in vivo. Adipogenic differentiation of hBMSCs for 14 days resulted in a heterogeneous cell population from which the most adipogenic-committed cells were eliminated by their lack of readhesion ability. Our results provided evidence that the select adherent adipogenic differentiated hBMSCs (sAD+ cells) express a gene profile characteristic of both adipogenic and osteogenic lineages. In vitro, when cultured in osteogenic medium, sAD+ differentiated along the osteogenic lineage faster than undifferentiated hBMSCs. In vivo, in an ectopic mouse model, sAD+ exhibited a significantly higher bone formation capability compared with undifferentiated hBMSCs. We sought, then, to investigate the underlying mechanisms responsible for such beneficial effects of adipogenic predifferentiation on bone formation and found that this outcome was not linked to a better cell survival post-implantation. The secretome of sAD+ was both proangiogenic and chemoattractant, but its potential did not supersede the one of undifferentiated hBMSCs. However, using co-culture systems, we observed that the sAD+ paracrine factors were pro-osteogenic on undifferentiated hBMSCs. In conclusion, adipogenic priming endows hBMSCs with high osteogenic potential as well as pro-osteogenic paracrine-mediated activity. This preconditioning appears as a promising strategy for bone tissue engineering technology in order to improve the hBMSC osteogenic potency in vivo.