β-Glycerophosphate accelerates RANKL-induced osteoclast formation in the presence of ascorbic acid

Despite numerous reports of the synergistic effects of -glycerophosphate and ascorbic acid in inducing the differentiation of osteoblasts, little is known about their roles in osteoclastic differentiation. Therefore, we investigated the effect of -glycerophosphate on osteoclastogenesis in the presence of ascorbic acid using primary mouse bone marrow cultures treated with macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor (NF)- B ligand (RANKL). -Glycerophosphate dose-dependently increased RANKL-induced osteoclast formation in the presence of ascorbic acid. This stimulatory effect was apparent when -glycerophosphate and ascorbic acid were only added during the late stages of the culture period, indicating that they influence later events in osteoclastic differentiation. While the combination of -glycerophosphate and ascorbic acid inhibited RANKL-stimulated activation of ERK and p38, and degradation of I B, it increased the induction of c-Fos and NFATc1. In addition, -glycerophosphate and ascorbic acid together enhanced the induction of COX-2 following RANKL stimulation. Taken together, our data suggest that -glycerophosphate and ascorbic acid have synergistic effects on osteoclast formation, increasing RANKL-mediated induction of c-Fos, NFATc1 and COX-2 in osteoclast precursors.