BACKGROUND: Osteoinduction and subsequent bone formation rely on efficient mesenchymal stem cell (MSC) recruitment. It is also known that migration is induced by gradients of growth factors and cytokines. Degradation of Ca-containing biomaterials mimics the bone remodeling compartment producing a localized calcium-rich osteoinductive microenvironment. The aim of our study was to determine the effect of calcium sulfate (CaSO) on MSC migration. In addition, to evaluate the influence of CaSOon MSC differentiation and the potential molecular mechanisms involved. 2+ 4 4
METHODS: A circular calvarial bone defect (5 mm diameter) was created in the parietal bone of 35 Balb-C mice. We prepared and implanted a cell-free agarose/gelatin scaffold alone or in combination with different CaSOconcentrations into the bone defects. After 7 weeks, we determined the new bone regenerated by micro-CT and histological analysis. In vitro, we evaluated the CaSOeffects on MSC migration by both wound healing and agarose spot assays. Osteoblastic gene expression after BMP-2 and CaSOtreatment was also evaluated by qPCR. 4 4 4
RESULTS: CaSOincreased MSC migration and bone formation in a concentration-dependent manner. Micro-CT analysis showed that the addition of CaSOsignificantly enhanced bone regeneration compared to the scaffold alone. The histological evaluation confirmed an increased number of endogenous cells recruited into the cell-free CaSO-containing scaffolds. Furthermore, MSC migration in vitro and active AKT levels were attenuated when CaSOand BMP-2 were in combination. Addition of LY294002 and Wortmannin abrogated the CaSOeffects on MSC migration. 4 4 4 4 4
CONCLUSIONS: Specific CaSOconcentrations induce bone regeneration of calvarial defects in part by acting on the host's undifferentiated MSCs and promoting their migration. Progenitor cell recruitment is followed by a gradual increment in osteoblast gene expression. Moreover, CaSOregulates BMP-2-induced MSC migration by differentially activating the PI3K/AKT pathway. Altogether, these results suggest that CaSOscaffolds could have potential applications for bone regeneration. 4 4 4
