A quantitative study of the interstitial expression of alpha-smooth muscle actin (alpha-SMA) in idiopathic membranous glomerulonephritis and minimal change disease in adults.

Twelve adult patients with early stages of idiopathic membranous glomerulonephritis (MGN) and 10 with minimal change disease (MCD) for whom both light and electron microscopy as well as immunofluorescence microscopy and full clinical data were available were examined quantitatively. Morphometric investigations were performed by means of a computer image analysis system to evaluate whether morphometric analysis could reveal differences between interstitial expression of alpha-smooth muscle actin (alpha-SMA) in early cases of MGN and MCD in adults, and, in particular, to examine the relationship between alpha-SMA expression and interstitial infiltrates in these glomerulopathies. The morphometric study revealed that mean values of the interstitial expression of alpha-SMA, interstitial volume, CD45RB+, CD43+, CD20+ and CD68+ cells were in MGN patients increased in comparison with normal controls, and MCD group, most of them significantly. The correlations between interstitial expression of alpha-SMA and interstitial volume, CD45RB+, CD43+, CD20+ as well as CD68+, cells were in MCD patients weak and not significant. In MGN group significant positive correlations were found between interstitial expression of alpha-SMA and interstitial volume as well as CD68+ cells. In conclusion, our study demonstrated that in adults, interstitial expression of alpha-SMA in early cases of membranous glomerulonephritis, was significantly stronger than that in minimal change disease. It is noteworthy that in MCD interstitial alpha-SMA staining was similar to that in normal kidney. The significant positive correlation between interstitial expression of alpha-SMA and interstitial CD68+ cells needs further investigations to elucidate whether monocytes/macrophages play a role in the process of inducing the myofibroblast phenotype in resting fibroblasts.