Introduction: The active form of vitamin D (1,25-dihydroxy-vitamin D3) is known to increase fast-type myosin heavy chain expression in differentiated myogenic cell lines. The mechanisms for this effect are not fully understood. The aim of this study was to determine the role of signals transmitted through the vitamin D receptor (VDR) during differentiation of myoblasts. Methods: Electroporation was used to introduce VDR siRNA molecules into C2C12 and G8 murine myoblast cell lines. Gene and protein expression profiles of VDR-gene silenced cells were analyzed in vitro. Results: Suppressing VDR expression by RNA interference resulted in inhibition of myogenic differentiation of C2C12 and G8 cell lines at both mRNA and protein levels. Conclusions: Our results suggest that myoblasts require signals transmitted through VDR for differentiation into myocytes and emphasize the importance of VDR expression in skeletal muscles for maintaining muscle volume in the elderly.
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