Background and aim Hepatic stellate cells (HSCs) are key participants in liver fibrosis development. 1,25(OH)2D3, 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)2D3 in liver and its involvement in liver fibrosis. Therefore, we investigated the antiproliferative and antifibrotic effects of 1,25(OH)2D3 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)2D3. 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 Iα1 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)2D3. 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)2D3 to activated HSCs stimulated VDR expression. 1,25(OH)2D3 suppressed HSC proliferation and cyclin D1 expression by ∼50% and tissue inhibitor of metalloproteinase 1 (TIMP-1) by 60% and led to a 40% downregulation of collagen Iα1 expression. Moreover, 1,25(OH)2D3 increased MMP-9 activity by 30%. Silencing VDR by sh-RNA demonstrated that suppression of cyclin D1 and collagen Iα1 protein expression was VDR dependent. Treatment with 1,25(OH)2D3 significantly reduced extracellular matrix deposition and lowered the fibrotic score in TAA-induced liver fibrosis.
Conclusion 1,25(OH)2D3 has antiproliferative and antifibrotic effects on liver fibrosis in in vitro and in vivo models and may be considered as having potential therapeutic value.
- Liver fibrosis
- hepatic fibrosis
- hepatic stellate cell
- matrix metalloproteinase
- vitamin D receptor gene
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Shirley Abramovitch and Liora Dahan-Bachar contributed equally to the work and should be considered ‘first authors’.
Funding This study was supported by grant no. 3000-4894 from the Chief Scientist of the Ministry of Health, Israel.
Competing interests None to declare.
Provenance and peer review Not commissioned; externally peer reviewed.