Soluble guanylate cyclase stimulator reduced the gastrointestinal fibrosis in bleomycin-induced mouse model of systemic sclerosis

Background: Systemic sclerosis (SSc) is a chronic autoimmune-mediated connective tissue disorder. Although the etiology of the disease remains undetermined, SSc is characterized by fibrosis and proliferative vascular lesions of the skin and internal organs. SSc involves the gastrointestinal tract in more than 90 % of patients. Soluble guanylate cyclase (sGC) stimulator is used to treat pulmonary artery hypertension (PAH) and has been shown to inhibit experimental skin fibrosis.

Methods: Female C57BL/6J mice were treated with BLM or normal saline by subcutaneous implantation of osmotic minipump. These mice were sacrificed on day 28 or day 42. Gastrointestinal pathologies were examined by Masson Trichrome staining. The expression of fibrosis-related genes in gastrointestinal tract was analyzed by real-time PCR, and the levels of collagen in the tissue were measured by Sircol collagen assay. To evaluate peristaltic movement, the small intestinal transport (ITR%) was calculated as [dyeing distance × (duodenum - appendix)] - 1 × 100 (%). We treated BLM-treated mice with sGC stimulator or DMSO orally and analyzed them on day 42.

Results: Histological examination revealed that fibrosis from lamina propria to muscularis mucosa in the esophagus was significantly increased in BLM-treated mice, suggesting that BLM induces esophageal hyperproliferative and prefibrotic response in C57BL/6J mice. In addition, the gene expression levels of Col3a1, CCN2, MMP-2, MMP-9, TIMP-1, and TIMP-2 in the esophagus were significantly increased in BLM-treated mice. More severe hyperproliferative and prefibrotic response was observed in the mice sacrificed on day 42 than the mice sacrificed on day 28. The ITR% was found to be significantly lower in BLM-treated mice, suggesting that gastrointestinal peristaltic movement was reduced in BLM-treated mice. Furthermore, we demonstrated that sGC stimulator treatment significantly reduced hyperproliferative and prefibrotic response of esophagus and intestine in BLM-treated mice, by histological examination and Sircol collagen assay.

Conclusions: These findings suggest that BLM induces gastrointestinal hyperproliferative and prefibrotic response in C57BL/6J mice, and treatment with sGC stimulator improves the BLM-induced gastrointestinal lesion.