STEM CELL DIFFERENTIATION AND RELEASE OF PARACRINE FACTORS INDUCED BY HYDROXYLAPATITE/COLLAGEN COMPOSITE SCAFFOLD

Bone homeostasis is maintained by the fine orchestration of osteoblast dependent bone formation and osteoclast mediated bone resorption. Extensive studies reported a cross talk between immune and skeletal systems, by which several immune cells and cytokines regulate bone metabolism. In bone tissue engineering, inflammation is an important factor that should be considered to develop successful biomaterial based therapeutics. In this study, the effects of a Hydroxylapatite/Collagen composite biomaterial, employed in maxillo-facial surgery, were evaluated using human bone marrow mesenchymal stem cells (BM-MSCs), as in vitro model. A profiler PCR array was employed to evaluate the expression of genes involved in BM-MSC osteogenic/chondrogenic differentiation, at 7 days. The expression of the osteoblast protein marker (Osteocalcin, OCN) was also evaluated by immunofluorescence . Proteins released into BM-MSCs supernatants were measured using Bio Plex in BM MSCs, at days 3 and 7. At day 3, BM-MSCs produce IFN-γ to promote their own osteogenic differentiation. At day 7, several genes involved in BM-MSC osteogenic/chondrogenic signalling pathways tested upregulated in BM-MSCs grown on biomaterial, compared to control. Moreover, immunofluorescence showed a significant increase of the OCN protein expression in cells grown on biomaterial. Subsequently, BM-MSCs released anti-inflammatory cytokines, such as IL4, and other cytokine involved in stem cell recruitment and angiogenesis, including IP10 and VEGF. In conclusion, our investigation indicates that our model of study can successfully be translated in maxillo-facial surgery for bone repair. Our data demonstrate that the scaffold investigated herein has immunomodulatory potential and is capable of directing anti-inflammatory innate immune mediated responses associated to tissue regeneration.