Anales RANF

P10. P URINERGIC S IGNALING IN R ENAL , G ASTROINTESTINAL AND M USCULOSKELETAL S YSTEM P.92 ADP-INDUCED P2Y 1 -MEDIATED OSTEOGENESIS IS DOWNREGULATED BY OVEREXPRESSED P2Y 12 AND P2Y 13 RECEPTORS IN POSTMENOPAUSAL MESENCHYMAL STEM CELLS C. Bessa-Andrês 1,2 , R. Pinto-Cardoso 1,2 , M.A. Costa 1,2,3 , J. Marinhas 4 , R. Freitas 4 , C. Vieira 1,2 , J.B. Noronha-Matos 1,2 , P. Correia-de-Sá 1,2 1 Lab. Farmacologia e Neurobiologia, 2 Center for Drug Discovery and Innovative Medicines (MedInUP), 3 Dept. Química, ICBAS - Univ. Porto, and 4 Serv. Ortopedia e Traumatologia, Centro Hospitalar de Gaia - Espinho, Portugal. While ATP is a known promoter of the osteogenic differentiation of human bone marrow mesenchymal stem cells (BM-MSCs), the osteogenic role of ADP-sensitive P2Y 1 , P2Y 12 and P2Y 13 receptors has been a matter of debate. The P2Y 1 R sensitizes human BM-MSCs to parathormone, while the P2Y 13 R has been associated to bone remodelling only in rodents. Blockage of P2Y 12 R with the anti-thrombotic drug, clopidogrel, causes a dual role on bone homeostasis depending on dosage. To clarify the role of ADP-sensitive P2Y receptors in human osteogenesis, BM-MSCs were isolated from young females and postmenopausal (Pm) women, which were cultured for 35 days with an osteogenic-inducing medium. Cells growth (MTT assay), osteogenic commitment (alkaline phosphatase activity, ALP), and bone nodule formation (Alizarin red assay) were significantly decreased in BM-MSC cultures from Pm women compared to younger females. Selective activation of P2Y 1 R with MRS 2365 (0.1 µM) significantly increased proliferation of BM-MSCs from young females by 64±6% and 35±4% at culture days 7 and 14, respectively; increases were also observed on ALP activity (1073±368%, at day 21) and on culture mineralization (185±28%, at day 35). The P2Y 1 R agonist was devoid of effect on Pm BM-MSCs unless P2Y 12 and P2Y 13 receptors activity were blocked with AR-C66096 (0.1 µM) and MRS 2211 (10 µM), respectively. Readmission of P2Y 1 R-induced osteogenesis by these blockers is more likely in Pm BM-MSCs overexpressing P2Y 12 R and P2Y 13 R vis a vis P2Y 1 R. Data suggest that co-activation of P2Y 12 R and/or P2Y 13 R downregulates ADP-induced P2Y 1 - mediated osteogenic differentiation of BM-MSCs in Pm women. This leads us to propose that P2Y 1 R agonists used in combination with P2Y 12 R and/or P2Y 13 R antagonists may be a useful strategy for the treatment of bone defects in Pm women. Work supported by FCT (UID/BIM/04308/2019 and PTDC/MED-FAR/29398/2017) and FEDER (POCI- 01-0145-FEDER-029398). RPC is in receipt of a PhD fellowship by FCT (SFRH/BD/135942/2018).