Background: Long-term treatment of inflammatory bowel disease (IBD) remains an ongoing challenge and intestinal stenosis or fibrosis are common complications during the course of Crohn's disease (CD). Anti-inflammatory strategies, such as anti-tumor necrosis factor (TNF) antibodies or immunosuppressants, are only partially effective in preventing fibrosis and surgery often does not provide a definite solution. Thus, anti-fibrotic therapy approaches are still an unmet clinical need. Oxysterols are oxidized derivatives of cholesterol which play an important role in a spectrum of biological activities. Cholesterol 25-hydroxylase (CH25H) mediates enzymatic conversion of cholesterol to 25-hydroxycholesterol (25-HC), which modulates immune responses and oxidative stress. In vitro analysis of human fetal lung fibroblasts demonstrated 25-HC to promote alpha-smooth muscle actin (alpha-SMA) expression and collagen production, to augment the release of matrix metallopeptidases and stimulate transforming growth factor (TGF)-beta release. We characterized the role of CH25H in the development of intestinal fibrosis.
Methods: Sections of small intestine from a donor mouse, either wildtype or CH25H knockout, were transplanted subcutaneously into the neck of a recipient mouse of the same genotype. Seven days after surgery the intestinal grafts were isolated and examined for collagen layer thickness and mRNA expression of fibrosis mediators.
Results: In our in vivo fibrosis model, mice deficient for the CH25H enzyme developed a thinner collagen layer compared to wildtype controls. Reduced collagen deposition in CH25H knockout animals was confirmed by automated image analysis. Furthermore, concentration of the collagen metabolite hydroxyproline was significantly decreased in CH25H knockout intestinal transplants. mRNA expression of fibrosis mediators including lysyl oxidase-like 2, collagen type 1 and type 3 was decreased in CH25H knockout mice compared to wildtype controls as confirmed by qPCR.
Conclusions: Our findings indicate an involvement of CH25H in the pathogenesis of intestinal fibrosis. CH25H deficiency partially prevented collagen deposition, pointing to oxysterols as a potential new treatment option for CD associated fibrosis. Further mechanistic and therapeutic studies will be necessary.