Integrin alpha 11 in the regulation of the myofibroblast phenotype: implications for fibrotic diseases

Tissue fibrosis, characterized by excessive accumulation of aberrant extracellular matrix (ECM) produced by myofibroblasts, is a growing cause of mortality worldwide. Understanding the factors that induce myofibroblastic differentiation is paramount to prevent or reverse the fibrogenic process. Integrin-mediated interaction between the ECM and cytoskeleton promotes myofibroblast differentiation. In the present study, we explored the significance of integrin alpha 11 (ITGA11), the integrin alpha subunit that selectively binds to type I collagen during tissue fibrosis in the liver, lungs and kidneys. We showed that ITGA11 was co-localized with α-smooth muscle actin-positive myofibroblasts and was correlatively induced with increasing fibrogenesis in mouse models and human fibrotic organs. Furthermore, transcriptome and protein expression analysis revealed that ITGA11 knockdown in hepatic stellate cells (liver-specific myofibroblasts) markedly reduced transforming growth factor β-induced differentiation and fibrotic parameters. Moreover, ITGA11 knockdown dramatically altered the myofibroblast phenotype, as indicated by the loss of protrusions, attenuated adhesion and migration, and impaired contractility of collagen I matrices. Furthermore, we demonstrated that ITGA11 was regulated by the hedgehog signaling pathway, and inhibition of the hedgehog pathway reduced ITGA11 expression and fibrotic parameters in human hepatic stellate cells in vitro, in liver fibrosis mouse model in vivo and in human liver slices ex vivo. Therefore, we speculated that ITGA11 might be involved in fibrogenic signaling and might act downstream of the hedgehog signaling pathway. These findings highlight the significance of the ITGA11 receptor as a highly promising therapeutic target in organ fibrosis.

Polymorphism of ornithine decarboxylase antizyme inhibitor 1 gene is associated with liver cirrhosis in Chinese hepatitis B patients / 中华肝脏病杂志

A cirrhosis risk score (CRS) comprised of single nucleotide polymorphisms (SNPs) in seven genes that predicts the risk of cirrhosis in Caucasian hepatitis C has been reported. The present study was to evaluate the association of 11 separate but related SNPs and the CRS with cirrhosis risk in Chinese hepatitis B patients. A total of 563 Chinese subjects with persistent HBV infection (349 with evident liver cirrhosis and 214 without cirrhosis clinically or pathologically) were studied. The candidate SNPs were detected with a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) method. The allele frequency and genotype distribution of each polymorphism as well as the CRS value within the cirrhosis and non-cirrhosis subjects were compared. The rs2679757 polymorphism of the antizyme inhibitor 1 (AZIN1) gene was associated with the risk of cirrhosis (x2 = 6.79, P = 0.03, odds ratio for GG+AG versus AA = 1.63, 95% confidence interval = 1.13-2.35). A gene variant (rs886277) in the transient receptor potential cation channel subfamily M, member 5 gene (TRPM5) was associated with liver cirrhosis, but did not reach statistical significance (x2 = 5.77, P = 0.06). Two SNPs (rs4986791, rs62522600) are not polymorphic in Chinese. Genotype frequencies of other SNPs were not different between the cirrhosis and non-cirrhosis groups. The overall CRS values were not different between the cirrhotic and non-cirrhotic groups (median value 0.57 versus 0.62, Z = -1.05, P = 0.29). SNP rs2679757 in the AZIN1 gene is associated with the risk of HBV-related liver cirrhosis in Chinese. The CRS for Caucasian population has limited applicability for predicting liver cirrhosis in Chinese hepatitis B patients. SNPs associated with cirrhosis prognosis in hepatitis B patients and liver diseases with other etiologies warrant further clinical validation.