Anales RANF

P.15 P2X7 RECEPTOR MODULATES THE OSTEOGENIC DIFFERENTIATION OF STROMAL STEM CELLS FROM HUMAN ADIPOSE TISSUE M. Carluccio 1,2 , M. Zuccarini 1 , S. Ziberi 1,2 , P. Giuliani 1 , C. Morabito 1,2 , M. Mariggiò 1,2 , E. Adinolfi 3 , E. Orioli 3 , P. Di Iorio 1 , F. Caciagli 1 , R. Ciccarelli 1,2 . 1 University of Chieti-Pescara, Chieti, Italy. 2 StemTeCh Group, Chieti, Italy. 3 University of Ferrara, Ferrara, Italy. Since the role of P2X7 receptors (P2X7Rs) is still controversial in cell osteogenic differentiation, we investigated their expression and effects in mesenchymal/stromal stem cells derived from human subcutaneous adipose tissue (S-ASCs), which are of potential interest in bone regenerative medicine. Undifferentiated S-ASCs expressed higher mRNA levels for the P2X7AR full-length isoform, equipped with a ionic channel and a macropore, than for the truncated P2X7BR variant, lacking the pore. P2X7R stimulation by the agonist BzATP increased cell [Ca 2+ ]i and migration without impairing proliferation or causing pore opening. The antagonist A438079 reversed these effects. In contrast, BzATP, added to the osteogenic medium, decreased extracellular matrix mineralization and expression of osteogenic transcription factors (Runx2, alkaline phosphatase, osteocalcin) and of P2X7R A and B subunits. BzATP-induced effects were not due to a reduction in cell proliferation or to an increase in apoptotic/necrotic events, but rather to a decrease in P2X7R expression. Noteworthy, A438079, administered alone during cells differentiation, first restrained this process, enhancing it later. Accordingly, A438079 reversed Bz-ATP effects only in the second phase of S-ASCs osteogenic differentiation. Apyrase, an ATP diphosphohydrolase, had a similar behavior. These effects were confirmed by experiments of titanium scaffold colonization by S-ASCs. Our findings suggest that adenosine derived from purine metabolism contributes to a pro-osteogenic activity of endogenous ATP, in turn related to a prevalent P2X7RB expression. Conversely, P2X7R pharmacological stimulation by BzATP, like that induced by high ATP levels occurring during tissue injury, would compromise osteogenic differentiation of local/exogenous stem cells and thereby bone repair.