Study on the mechanism of OSM participating in myocardial fibrosis by inhibiting TGFβ-induced EndMT of cardiac microvascular endothelial cells through SPARC/SMAD signaling.

Cardiac fibrosis constitutes a crucial element in the progression of diverse chronic cardiac conditions. Notably, a significant correlation has been observed between the endothelial-to-mesenchymal transition (EndMT) and the emergence of cardiac fibrosis. To investigate mechanisms, we employed immunofluorescence for α-SMA and CD31 analysis, Western blotting for CD34, vimentin, and SPARC overexpression. CCK8, wound healing, and transwell assay-assessed cell viability, invasion, and migration. SPARC overexpression plasmid was constructed and validated by Western blotting. Fibrosis levels were quantified via Masson staining, and collagen 1 and 3 expressions were measured using ELISA assays. Notably, in TGF-β-induced H5V cells, the downregulation of CD31 and CD34 expression, along with the upregulation of α-SMA and vimentin, suggests the induction of EndMT in cardiac fibrosis. Interestingly, OSM treatment mitigated EndMT progression, cell invasion, migration, and the expression of p-SMAD2, p-SMAD3, and SPARC in TGF-β-treated H5V cells. Further analysis revealed that OSM alleviated TGFβ-induced EndMT, invasion, and migration of cardiac microvascular endothelial cells by suppressing SPARC/SMAD signaling. Moreover, OSM therapy notably mitigated myocardial tissue fibrosis, along with a reduction in the expression of collagen 1, collagen 3, α-SMA, and CD34, while augmenting CD31 and vimentin expression in ISO-induced myocardial tissue. Additionally, OSM exhibited the ability to suppress myocardial tissue fibrosis and the expression of EndMT markers as well as SPARC/SMAD signals in ISO-induced myocardial tissue. Our comprehensive analysis unveiled that OSM contributes significantly to myocardial fibrosis modulation by inhibiting TGFβ-mediated EndMT in myocardial microvascular endothelial cells via SPARC/SMAD signaling.