Glomerular expression of α-smooth muscle actin (α-SMA) in idiopathic mesangiocapillary glomerulonephritis type I. A quantitative study

Eighteen renal biopsy specimens from patients with mesangiocapillary glomerulonephritis type I (MCGN-I) evaluated by both light and electron microscopy as well as immunofluorescence microscopy and whose full clinical data were available were examined quantitatively. As control 10 biopsy specimens of kidneys removed because of trauma were used. Morphometric investigations were performed by means of a computer image analysis system to evaluate the glomerular expression of α-SMA in MCGN-I, as well as to determine whether this parameter could correlate with quantitatively analysed glomerular cells and mesangial areas. Another purpose of this study was to verify if the expression of α-SMA correlated with the intensity of glomerular leukocyte infiltrates in this glomerulopathy. The morphometric study revealed that mean values of the expression of α-SMA, total glomerular cells per total glomerular area, mesangium (% of total glomerular area), CD 45RB+, CD 43+, CD 20+ and CD 68+ cells were in MCGN-I patients increased in comparison with normal controls. Moreover, in the MCGN-I group, but not in controls, significant positive correlation existed between the glomerular expression of α-SMA and total glomerular cells per total glomerular area, mesangium (% of total glomerular area), as well as CD 45RB+ cells and CD 68+ cells. Significant positive correlation between α-SMA staining and total glomerular cells and mesangial areas suggested that increased α-SMA expression might be in MCGN-I and indicator of mesangial cell activation and mesangial matrix production. The significant positive correlation between the glomerular expression of α-SMA and glomerular CD 68+ cells requires further investigations to elucidate whether monocytes/macrophages play a role in the process of inducing myofibroblast phenotype in mesangial cells.