INTERSTITIAL MYOFIBROBLASTS IN IGA GLOMERULONEPHRITIS

We examined renal biopsy specimens from patients with mesangial IgA gl omerulonephritis (n = 25; plasma creatinine 0.05-0.30 mmol/l) to ascer tain whether the myofibroblast has a role in progressive renal interst itial fibrosis. Myofibroblasts were identified by morphology and alpha smooth muscle actin (a-SMA) immunostaining at the light and electron microscope level. Results were related to staining for interstitial le ukocytes and collagen III. A control group consisted of 6 normal renal transplant donors from whom biopsy specimens were taken at the time o f vascular anastomosis. The fractional volume of interstitial alpha-SM A staining was greater in patients with mesangial IgA glomerulonephrit is than in the control group (17.2 vs. 1.3%; p<0.001). alpha-SMA stain ing was increased in areas of interstitial fibrosis with prominent per iglomerular and peritubular distribution. Ultrastructural studies esta blished that alpha-SMA staining in the renal interstitium was intracel lular, cytoplasmic, and confined to myofibroblast-like cells and proce sses. The a-SMA expression correlated with fractional volume of tubula r atrophy/dilation (r = 0.79, p < 0.001), interstitial connective tiss ue (r = 0.66, p<0.001), leucocytes (r = 0.72, p<0.005), and collagen I II (r = 0.71, p<0.001). Staining correlated with renal function at the time of biopsy (r = 0.64, p<0.005) and after 2 years of followup (r = 0.77, p<0.01). In conclusion, cells with a myofibroblast-like phenoty pe have a significant role in the progression of tubulointerstitial in jury.