Cholecalciferol and calcitriol action on fibrogenesis in C2C12 myotubes-treated with angiotensin II

Angiotensin II (AII) is a potent inducer in a classical renin-angiotensin system (RAS) responsible for skeletal muscle fibrosis via angiotensin II type I receptor in chronic disease patients. Vitamin D 3 has been proposed on reduction of RAS components and amelioration of fibrosis in several aging tissues. Nevertheless, effect of vitamin D 3 and its bioactive metabolite on fibrogenesis in skeletal muscle cells challenged with AII is currently unknown. In this study, the effects of cholecalciferol (VD 3 ) and calcitriol (1,25VD 3 ) on fibrogenesis induced by AII were investigated in differentiated C2C12 mouse skeletal muscle cells. Myotubes were assigned into vehicle, AII, AII+VD 3 , and AII+1,25VD 3 groups. AII treatment resulted in a significant decrease in fusion index and increase protein expression of the alpha-smooth muscle actin (α-SMA) when compared with vehicle-treated group. Treatment of VD 3 , but not 1,25VD 3 , preserved AII-induced impairment of myotube differentiation. Protein expression of α-SMA and phospho-Smad2/3 was downregulated in combined treatments of AII with VD 3 and 1,25VD 3 compared with AII treated-alone group. Vitamin D receptor protein expression was significantly upregulated in myotubes-treated with AII+1,25VD 3 , but not AII+VD 3 compared to the vehicle-treated group. For the nonclassical RAS axis, it produced the opposite effects of AII through Mas receptor. After inhibition of Mas receptor with A779, anti-fibrotic effect of vitamin D 3 was abolished in myotubes-exposed to AII. Altogether, cholecalciferol and Mas receptor could be the possible therapeutic targets for muscular fibrosis induced by high levels of angiotensin II. This work was financially supported by the Faculty of Pharmacy, Srinakharinwirot University and Srinakharinwirot University 2024 (to M.H.). This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.