Diabetic nephropathy (DN) is the leading cause of end-stage renal disease (ESRD). DN is characterizedby glomerular extracellular matrix accumulation, mesangial expansion, basement membrane thickening, and renal interstitial fibrosis. To date, mounting evidence has shown that H2 relaxin possesses powerful antifibrosis properties; however, the mechanisms of H2 relaxin on diabetic nephropathy remain unknown. Here, we aimed to explore whether H2 relaxin can reduce production of extracellular matrix (ECM) secreted by human mesangial cells (HMC). HMC were exposed to 5.5 mM glucose (NG) or 30 mM glucose (HG) with or without H2 relaxin. Fibronectin (FN) and collagen type IV levels in the culture supernatants were examined by solid-phase enzyme-linked immunoadsorbent assay (ELISA). Western blot was used to detect the expression of α-smooth muscle actin (α-SMA) protein. Quantitative polymerase chain reaction (qPCR) method was employed to analyze transforming growth factor (TGF)-β1 mRNA expression. Compared with the normal glucose group, the levels of fibronectin and collagen type were markedly increased after being cultured in high glucose medium. Compared with the high glucose group, remarkable decreases of fibronectin, collagen type IV, α-smooth muscle actin, and TGF-β1 mRNA expression were observed in the H2 relaxin-treated group. The mechanism by which H2 relaxin reduced high glucose-induced overproduction of ECM may be associated with inhibition of TGF-β1 mRNA expression and mesangial cells' phenotypic transition. H2 relaxin is a potentially effective modality for the treatment of DN.Key words human mesangial cell (HMC); human H2 relaxin; extracellular matrix (ECM); transforming growth factor (TGF)-β1; diabetic nephropathy (DN) Diabetic nephropathy (DN) is one of the most common chronic complications of diabetes, and a major cause of end-stage renal disease (ESRD).1) Once the clinical diabetic nephropathy is diagnosed, most of the DN patients will inevitably develop ESRD after several years due to the lack of effective methods to delay its progression.2) Its pathology is characterized by glomerular extracellular matrix accumulation, mesangial expansion, basement membrane thickening, glomerulosclerosis and renal interstitial fibrosis.3) Laminin, fibronectin and type IV collagen are the main components of extracellular matrix, and the excessive extracellular matrix (ECM) plays a key role in the progression of diabetic nephropathy.
4)Previous in vitro studies 5,6) revealed that high glucose can stimulate the synthesis of ECM including fibronectin and type IV collagen through the activation of the transforming growth factor (TGF)-β dependent Smad signaling pathway, as well as upregulation of its receptor expression. Recently Liu et al. 7) reported that both 30 mM glucose (HG) and TGF-β1 can lead to over production of fibronectin. The underlying mechanism was thought to be mesangial cell caveolae has a role in regulating fibronectin production partly through caveolin-1 phosphorylation.TGF-β is recognized as a major mediat...