NMDA receptors are involved in the regulation of BMP4-mediated survival in rat cochlear epithelial cells.

Bone morphogenic protein (BMP4) and the N-methyl-d-aspartic acid (NMDA) receptor both participate in the regulation of cochlear sensory epithelial cell survival. However, whether the NMDA receptor is involved in the BMP4 pathway has not been fully elucidated in rat cochlear sensory epithelial cells. Here, we show that after 3 days of culture with exogenous BMP4, the number of surviving cells in the treated group was less than that in the control group. The apoptosis rate was higher and the percentage of cells in S-phase was lower in the experimental group than in other control group. When the cells were cultured with noggin for 3 days, the results were opposite of those observed with BMP4. When BMP4-treated cells were supplemented with APV for 3 days, the number of viable cells and the percentage of those in S-phase were greater compared to the BMP4-only group. Additionally, the apoptosis rate was lower in the BMP4+APV cells than in the cells cultured with BMP4 only. Meanwhile, the number of NR2B-positive cells, as revealed by the NR2B mRNA and protein levels, was greater in the BMP4 group than in the control group. These results suggest that BMP4 may affect the expression of NR2B, thus playing a role in regulating the survival of cochlear epithelial cells.