Article révisé par les pairs
Résumé : Accumulating evidence indicates that extracellular nucleotides, signaling through purinergic receptors, play a significant role in bone remodeling. Mesenchymal stem cells (MSC) express functional P2Y receptors whose expression level is regulated during osteoblast or adipocyte differentiation. P2Y13- deficient mice were previously shown to exhibit a decreased bone turnover associated with a reduction in the number of both osteoblasts and osteoclasts on the bone surfaces. We therefore examined whether P2Y13 R activation was involved in the osteogenic differentiation of MSC. Our study demonstrated that ADP stimulation of P2Y13 R(+/+) (but not P2Y13 R(-/-) ) adherent bone marrow stromal cells (BMSC) increased significantly the formation of alkaline phosphatase-colony forming units (CFU-ALP), as well as the expression of osteoblastic markers (Osterix, Alkaline Phosphatase, Collagen I) involved in the maturation of pre-osteoblasts into osteoblasts. The number of CFU-ALP obtained from P2Y13 R(-/-) BMSC and the level of osteoblastic gene expression after osteogenic stimulation were strongly reduced compared to those obtained in wild-type cell cultures. In contrast, when P2Y13 R(-/-) BMSC were incubated in an adipogenic medium, the number of adipocytes generated and the level of adipogenic gene expression (PPARγ2 and Adipsin) were higher than those obtained in P2Y13 R(+/+) MSC. Interestingly we observed a significant increase of the number of bone marrow adipocytes in tibia of P2Y13 R(-/-) mice. In conclusion, our findings indicate that the P2Y13 R plays an important role in the balance of osteoblast and adipocyte terminal differentiation of bone marrow progenitors. Therefore, the P2Y13 receptor can be considered as a new pharmacological target for the treatment of bone diseases like osteoporosis.

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