Cloning of rodent megsin revealed its up-regulation in mesangioproliferative nephritis

Background. We recently cloned a new human mesangium-predominant gene. megs in. Megsin is a novel member of the: serine protease inhibitor (serpin) sup erfamily. To elucidate functional roles of this gene, we cloned megsin in r odents and investigated its role in a rat nephritis model. Methods. Megsin homologues were cloned from cultured rat and mouse mesangia l cDNAs utilizing polymerase chain reaction (PCR) with degenerative primers . Expression of meg sin in three different types of resident glomerular cel ls was investigated by PCR. Levels of megsin mRNA expression at various tim e points in the anti-Thy1 rat nephritis model were studied by semiquantitat ive PCR and Northern blotting analysis. In order to investigate megsin prot ein expression in anti-Thy1 nephritis rats, we raised antibody against rat megsin-specific synthetic peptide, with which immunohistochemical studies w ere performed. Results. Rat and mouse megsins were composed of 380 amino acids, which reve aled 75.3 and 73.9% identity, respectively, with human megsin at the amino acid level. Characteristic features as an inhibitory serpin were conserved in both rat and megsin megsins. PCR analysis revealed expression of megsin in cultured mesangial cells but not in glomerular epithelial or endothelial cells. In anti-Thy1 nephritis rats, semiquantitative PCR and Northern blot ting showed that expression of megsin mRNA was up-regulated in glomeruli at day 8. Immunohistochemical studies demonstrated the prominent accumulation of megsin in glomeruli at the same time point. Megsin was mainly localized in mesangial area. The megsin expression level returned to the basal level at day 28. Conclusion. Sequences of megsin were well conserved among different species . Rat megsin was also predominantly expressed in mesangial cells. Expressio n of megsin was up-regulated at the peak of hypercellularity and matrix acc umulation in the mesangioproliferative glomerulonephritis model, suggesting that megsin may participate in the process of glomerulosclerosis by modula ting extracellular matrix deposition or cell survival.