INTERSTITIAL MYOFIBROBLASTS - PREDICTORS OF PROGRESSION IN MEMBRANOUSNEPHROPATHY

Aims-To determine the role of interstitial myofibroblasts in the progr ession of membranous nephropathy; and to assess the predictive value o f quantifying myofibroblasts in determining long term renal outcome. M ethods-All cases of membranous nephropathy, diagnosed by renal biopsy at University Hospital of South Manchester between 1984 and 1987, were studied retrospectively. The biopsy specimens (n = 26) were reviewed and analysed morphometrically to measure interstitial volume as a prop ortion of the total volume of renal cortex, and numbers of interstitia l myofibroblasts (cells positive for a-smooth muscle actin within the interstitium). Clinical data, with a follow up of seven to eight years , was available for 24 patients, and renal outcome was correlated with pathological changes in the initial diagnostic biopsy specimen. Resul ts-The number of myofibroblasts and interstitial volume were inversely correlated with creatinine clearance at the initial biopsy, and at th e end of follow up. Percentage sclerosed glomeruli or stage of glomeru lar disease, assessed by electron microscopy, did not correlate with r enal function at initial biopsy or during follow up. The number of myo fibroblasts, but not interstitial volume, correlated with severity of proteinuria at initial biopsy. Of 15 biopsy specimens showing no or mi ld interstitial fibrosis, four showed a notable increase in the number of interstitial myofibroblasts. All of these patients developed chron ic renal failure, compared with three of 11 patients whose specimens s howed no or a mild increase in myofibroblast numbers. Conclusions-Inte rstitial myofibroblasts play a role in the development of interstitial fibrosis and progressive renal failure in membranous nephropathy. Inc reased numbers of myofibroblasts in biopsy specimens showing only mild fibrosis may predict subsequent chronic renal failure.