Effect of Small/Intermediate Conductance Ca2+ Activated K+ Channel Opener on Myogenic Differentiation in C2C12 myoblasts

Abstract

Skeletal muscle tissue contains unique stem cells called myoblasts or satellite cells, and they play a pivotal role in the repair and maintenance of skeletal muscle by differentiation into muscle cells. However, the regenerative ability declines with age, and invite reduction of skeletal muscle mass (sarcopenia). We are searching for a compound which enhance muscle regenerative activity. Since membrane hyperpolarization facilitates the differentiation in myoblasts, we hypothesized that a compound which hyperpolarizesthe myoblast membrane potential may enhance the myogenic differentiation. It has been reported that a major current component in myoblast is the small/intermediate conductance Ca2+ activated K+ (SKCa/IKCa) channel. In this study, we treated mouse C2C12 myoblasts with DCEBIO, a SKCa/IKCa channel opener. C2C12 myoblasts fuse each other to form myotube in 2% horse serum medium. Our image analysis revealed DCEBIO significantly increased the percentage of fusion in a concentration dependent manner, and this effect was partially attenuated by co‐application of SKCa/IKCa channel blockers, apamin (100 nM) and TRAM‐34(1 μM). Furthermore, DCEBIO (10 μM) treatment increased the protein expression level of myosin heavy chain type II, a muscle specific protein. Our realtime RT‐PCR analysis showed that DCEBIO (10 μM) significantly increased the expression level of myogenin but not of Myo D, two of the essential transcription factors for myogenic differentiation. These suggest that DCEBIO enhanced myogenic differentiation by opening of SKCa/IKCa channel, and activated myogenic regulatory factor. These findings show a novel possibility of potassium channel openers as a muscle differentiation enhancer.