Possible modulation of process extension by N-methyl-D-aspartate receptor expressed in osteocytic MLO-Y4 cells

In contrast to osteoblasts, little attention has been paid to expression profiles of different glutamatergic signaling machineries in osteocytes, which are the most abundant cells with a possible role as a mechanical sensor in bone. Here, we show that N-methyl-D-aspartate receptor (NMDAR) is expressed by osteocytic cells in five-weeks-old mouse tibiae in vivo as well as by osteocytic MLO-Y4 cells in vitro. Sustained exposure to the NMDAR antagonist dizocilpine significantly increased the number of cells with processes in cultured MLO-Y4 cells. These results suggest that NMDAR would be expressed by osteocytes with an unidentified role in the process extension.