T-Type Ca2+ Channel Blockers Increase Smooth Muscle Progenitor Cells and Endothelial Progenitor Cells in Bone Marrow Stromal Cells in Culture by Suppression of Cell Death

Objective: To examine the expression patterns and roles of voltage-dependent Ca2+ channels in bone marrow stromal cells (BMSCs). Materials and Methods: Ca2+ currents of BMSCs were measured by the whole-cell patch clamp method. The number and percentage of deaths of BMSCs cultured for 14 days with or without Ca2+ channel blockers were evaluated using a MTT assay and an LDH assay, respectively. Results: T-type Ca2+ channel current was recorded in 0, 2, 10, and 4% of BMSCs on days 3, 10, 17, and 24 in culture, respectively. L-type Ca2+ channel current was first recorded on day 24 in 6% of BMSCs. Addition of the T-type Ca2+ channel blocker mibefradil but not the L-type Ca2+ channel blocker nifedipine significantly increased the cell count. Immunocytochemical analysis revealed increases in the counts of smooth muscle progenitor cells (SMPCs) and endothelial progenitor cells (EPCs). Mibefradil but not nifedipine significantly decreased the rate of cell death. Conclusion: T-type Ca2+ channel blockers increased the numbers of SMPCs and EPCs in cultured BMSCs, partly through suppression of cell death. Thus, T-type Ca2+ channel blockers may have the potential to provide an increased number of both BMSC-derived SMCs and ECs of potential use in cell and gene therapy.