Vitamin D inhibits proliferation and profibrotic marker expression in hepatic stellate cells and decreases thioacetamide-induced liver fibrosis in rats

Background and aim Hepatic stellate cells (HSCs) are key participants in liver fibrosis development. 1,25 (OH) D-2(3), the active form of vitamin D, has antiproliferative properties and antifibrotic potential, as well as a role in extracellular matrix and matrix metalloproteinase (MMP) regulation in renal and lung fibrosis. Little is known about the role of 1,25(OH)(2)D-3 in liver and its involvement in liver fibrosis. Therefore, we investigated the antiproliferative and antifibrotic effects of 1,25(OH)(2)D-3 in primary cultured HSCs and in a rat model of liver fibrosis induced by thioacetamide (TAA). Methods Primary HSCs were isolated from rats' livers and treated with 1,25(OH)(2)D-3. Proliferation was examined by bromodeoxyuridine. Vitamin D receptor (VDR) expression and several fibrotic markers were detected by western blot analysis and real-time PCR. Collagen I alpha 1 and MMP-9 promoter activity were measured by luciferase assay. MMP-9 enzymatic activity was investigated by zymography. VDR silencing was performed by sh-RNA. An in vivo study was performed on TAA-induced liver fibrosis model in rats treated with or without 1,25 (OH)(2)D-3. The fibrotic score and collagen deposition were determined by Masson and by Sirius red staining. Results While VDR was highly expressed in quiescent HSCs, its expression decreased up to 40% during activation. Addition of 1,25(OH)(2)D-3 to activated HSCs stimulated VDR expression. 1,25(OH)(2)D-3 suppressed HSC proliferation and cyclin D1 expression by similar to 50% and tissue inhibitor of metalloproteinase 1 (TIMP-1) by 60% and led to a 40% downregulation of collagen I alpha 1 expression. Moreover, 1,25(OH)(2)D-3 increased MMP-9 activity by 30%. Silencing VDR by sh-RNA demonstrated that suppression of cyclin D1 and collagen Ia1 protein expression was VDR dependent. Treatment with 1,25 (OH)(2)D-3 significantly reduced extracellular matrix deposition and lowered the fibrotic score in TAA-induced liver fibrosis. Conclusion 1,25(OH)(2)D-3 has antiproliferative and antifibrotic effects on liver fibrosis in in vitro and in vivo models and may be considered as having potential therapeutic value.