Functional transient receptor potential channels in human cardiac c-kit cells

Abstract

Background and objective: Human adult c-kit+ cardiac stem cell are characterized by the expression of c-kit in the absence of lineage markers such as kx2.5. They are self-renewing, clonogenic, and multipotent, giving rise to a minimum of three differentiated cell types: myocytes, smooth muscle, and endothelial vascular cells. These cells, although not specifically programmed for myocardial differentiation, have been shown to improve cardiac function in a myocardial injury/reconstitution assay. However, cell biology is not understood. The present study was to investigate the expression of transient receptor potential (TRP) channels in human cardiac c-kit+ cells, and their role in regulating migration and proliferation. Methods: Whole-cell patch voltage-clamp, RT-PCR, and Western blot approaches were used to determine functional expression of TRP channels in cultured human cardiac c-kit+ cells. ShRNA targeting TRP channels were constructed to silence the related TRP channels. Wound healing and transwell assay were applied to observe the effect of the TRP channels on cell migration. Cell proliferation assay was made with MTT and 3H-thymidine incorporation approaches. Results: A small background current was inhibited by the TRPC channel blocker La3+. Removal of Mg2+ of pipette solution or bath solution induced a Mg2+-sensitive TRPM7 current, and the current was suppressed by the TRP channel blocker 2-aminoethoxydiphenyl borate. RT-PCR revealed significant mRNA expression of TRPC1, TRPC3, TRPC4, TRPV2, TRPV4, and TRPM7 channels in human preadipocytes. Western blot analysis confirmed the protein expression of these TRP channels. ShRNAs targeting TRPV2, TRPV4 and TRPM7 suppressed the corresponding gene and protein expression. Interestingly, TRPV2-shRNA and TRPM7-shRNA significantly reduced proliferation of human cardiac c-kit+ cells. Migration of human cardiac c-kit+ cells was reduced by TRPV2-shRNA, TRPV4-shRNA. Conclusion: Our results demonstrate for the first time that multiple TRP channels, TPC1/3/4, TRPV1/2/4, and TRPM7, are present in human cardiac c-kit+ cells. TRPV2, TRPV4 and TRPM7 channels participate in regulating migration and proliferation in human cardiac c-kit+ progenitor cells.