Injectable graft substitute active on bone tissue regeneration

With the aim to obtain an injectable bioactive scaffold that can accelerate bone formation in sinus lift augmentation, in bony void and in fracture repair, we have developed a three-dimensional (3D) jelly collagen containing Lysophosphatidic acid (LPA) and 1α,25-Dihydroxyvitamin D3 (1,25D3). Using an in vitro 3D culture model of bone fracture we show that the contraction of the collagen gel is mediated by Rho-kinase activation in osteoblasts. This contraction was cell concentration dependent and was increased by LPA which favored apposition and fastening of bone fragments approach. LPA was shown to act through actin cytoskeleton reorganization and myosin light chain phosphorylation of human primary osteoblasts (hOB). Moreover LPA conferred osteoconductive properties as evidenced by the induction of proliferation, differentiation and migration of hOB. The addition of 1,25D3 did not enhance cell mediated gel contraction but stimulated the maturation of hOB in vitro through the production of extra cellular matrix of higher quality. On the basis of these observations, the collagen gel enriched with LPA and 1,25D3 described herein can be considered as an injectable natural scaffold that allows the migration of cells from the side of bone defect and as a promising candidate to accelerate bone growth and fracture healing.