Tubular phenotypic change in progressive tubulointerstitial fibrosis in human glomerulonephritis.
There is much debate over the origins of fibroblast-type cells that accumulate in interstitial fibrosis. A controversial hypothesis, supported by data from animal and cell-culture studies, is that fibroblast-type cells can derive from tubular epithelial cells by a process of epithelial-mesenchymal transdifferentiation. However, to date, no evidence supports this postulate in human glomerulonephritis. This study sought to provide evidence that tubular epithelial cells can undergo phenotypic change toward a fibroblast-like cell in human glomerulonephritis. One hundred twenty-seven open renal biopsy specimens from patients with minimal change disease (MCD), immunoglobulin A (IgA) nephropathy, and rapidly progressive glomerulonephritis (RPGN) were examined for tubular phenotypic change by two-color immunohistochemistry using the criteria of de novo expression of alpha-smooth muscle actin (alpha-SMA), a myofibroblast marker; loss of the epithelial marker cytokeratin; and collagen production. In normal human kidney and MCD, tubular epithelial cells expressed cytokeratin with no evidence of alpha-SMA staining. However, in 36 of 90 cases of IgA nephropathy and 9 of 18 cases of RPGN, small numbers of tubular epithelial cells in areas of fibrosis showed de novo alpha-SMA expression, accounting for 0.4% +/- 0.2% (IgA nephropathy) and 3.8% +/- 1.5% (RPGN) of cortical tubules. An intermediate stage of phenotypic change was observed in some cuboidal epithelial cells that expressed both cytokeratin and alpha-SMA. Tubules containing alpha-SMA-positive (alpha-SMA(+)) cells also stained for collagen types I and III, suggesting that tubular cells undergoing phenotypic change have an active role in the fibrotic process. There also was a marked increase in transforming growth factor-beta1 (TGF-beta1) tubular expression in areas with interstitial fibrosis, including tubules with phenotypic change. There was a highly significant correlation between tubular alpha-SMA expression and interstitial fibrosis, interstitial alpha-SMA(+) myofibroblast accumulation, deposition of collagen types I and III, tubular TGF-beta1 expression, and renal dysfunction. In conclusion, this study provides evidence that tubular epithelial cells can undergo phenotypic change toward a myofibroblast-like phenotype on the basis of de novo alpha-SMA expression, loss of cytokeratin, and de novo collagen staining. These data, although not conclusive, provide the first support for the hypothesis that transdifferentiation of tubular epithelial cells has a role in progressive renal fibrosis in human glomerulonephritis.
Jinde
K
K
Department of Nephrology, Tokai University School of Medicine, Isehara, Japan.
Nikolic-Paterson
D J
DJ
Huang
X R
XR
Sakai
H
H
Kurokawa
K
K
Atkins
R C
RC
Lan
H Y
HY
D000199:Actins / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism / Q000473:pathology*; D005921:Glomerulonephritis / Q000378:metabolism / Q000473:pathology*; D005922:Glomerulonephritis, IGA / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D007684:Kidney Tubules / Q000378:metabolism / Q000473:pathology*; D009402:Nephrosis, Lipoid / Q000378:metabolism / Q000473:pathology*; D010641:Phenotype
D000199:Actins