The expression of cytoskeletal proteins (alpha-SMA, vimentin, desmin) in kidney tissue: a comparison of fetal, normal kidneys, and glomerulonephritis

The aim of the study is a comparison of the expression of cytoskeletal proteins, alpha smooth muscle actin (alpha-SMA), vimentin, and desmin in fetal, normal kidney and proliferative (diffuse proliferative and membranoproliferative glomerulonephritis) and nonproliferative (membranous glomerulonephritis) glomerulonephritis. We have studied the expression of cytoskeletal proteins (alpha-SMA, vimentin, desmin) in the paraffin embedded tissue sections from the kidneys of 10 normal kidney (adults and infants), 13 fetal kidney, 12 membranous glomerulonephritis (MGN), 8 membranoproliferative glomerulonephritis (MPGN), 8 diffuse proliferative glomerulonephritis (DPGN). Interstitial and glomerular positive stainings were evaluated. Vimentin expression was similar in normal infant and adult kidneys with positive staining in glomeruli and negative staining in interstitium. In fetal kidneys, glomerular mesangial and epithelial cells and blastematous areas showed positive reactivity with vimentin. Alpha-SMA staining was different among the groups. In fetal kidney, alpha-SMA expression was found in glomerular mesangial cells and blastematous areas. Alpha-SMA staining was positive in peritubular area and glomerular mesangial cells in infant kidney. In adult kidneys, glomerular staining with alpha-SMA disappeared but peritubular positivity continued. Interstitial staining with alpha-SMA was positive in fibrotic areas of proliferative (MPGN, DPGN) and non-proliferative (MGN) glomerulonephritis, but positive glomerular staining with alpha-SMA was found only proliferative glomerulonephritis. Desmin expression was negative in all groups. Desmin is not expressed in early stages of kidney growth, infant and adult kidneys, and proliferative and nonproliferative glomerulonephritis. Interstitial staining of vimentin in the diseased kidney tissues revealed increased fibrosis. Alpha-SMA revealed important differences in different stages of nephrogenesis. Glomerular mesangial staining with alpha-SMA in developing (fetal and infant kidneys) and proliferative glomerulonephritis suggest that it may be a marker of proliferation. In addition, it shows myofibroblastic differentiation in interstitium in diseased kidneys.