Transient receptor potential melastatin 4 channel is required for rat dental pulp stem cell proliferation and survival.

OBJECTIVES: Investigate the role of the transient receptor potential melastatin 4 (TRPM4) channel in rat dental pulp stem cell (DPSC) proliferation and survival. MATERIALS AND METHODS: Immunofluorescence and FACS analysis were used to detect the stem cell marker CD90. Alizarin Red S and Oil Red O staining were used to identify osteoblast and adipocyte differentiation, respectively. To characterize TRPM4, patch-clamp recordings were obtained from single cells in the whole-cell configuration mode. The significance of TRPM4 for proliferation and survival was examined with 9-phenanthrol, a TRPM4 inhibitor during a 96-hour period of culture. Real-time Ca2+ imaging analysis with Fura-2AM was used to investigate the impact of TRPM4 on intracellular Ca2+ signals. RESULTS: DPSCs were CD90-positive and differentiated into osteoblasts. Patch-clamp recordings revealed currents typical of TRPM4 that were Ca2+ -activated, voltage-dependent and Na+ -conducting. Inhibition of TRPM4 resulted in a significant reduction in the cell population after a 96-hr period of culture and transformed the biphasic pattern of intracellular Ca2+ signalling into sustained oscillations. CONCLUSIONS: Rat DPSCs have stem cell characteristics and functional TRPM4 channels that are required for proliferation and survival. These data suggest that the shape and frequency of intracellular Ca2+ signals may mediate stem cell proliferation and survival.