Renal expression of alpha-smooth muscle actin and c-Met in children with Henoch–Schönlein purpura nephritis

Alpha-smooth muscle actin (α-SMA) is the actin isoform that predominates within vascular smooth-muscle cells and plays an important role in fibrogenesis. On the other hand, c-Met is the receptor for hepatocyte growth factor (HGF), which plays a role in protection from injury and has anti-fibrogenetic effects. To clarify whether α-SMA and HGF are associated with the progression of renal injury in Henoch–Schönlein purpura nephritis (HSPN), we evaluated the renal expression of α-SMA and c-Met in HSPN patients. Patients were divided into three groups. Group 1 consisted of eight patients (male:female 4:4) with stage II or less in the classification of the International Study of Kidney Disease in Children (ISKDC), Group 2 consisted of 20 patients (male:female 11:9) with ISKDC stage III or greater and a good prognosis, and group 3 consisted of seven patients (male:female 3:4) with ISKDC stage III or greater and poor prognosis. Renal biopsy findings, including c-Met and α-SMA staining, were investigated for each group. At first biopsy, the mean scores for renal α-SMA and glomerular c-Met in groups 2 and 3 were higher than those in group 1, while mean scores for neither renal α-SMA nor glomerular c-Met differed between groups 2 and 3. At second biopsy, the mean scores for renal α-SMA staining in group 3 were higher than those in group 2, and mean score for glomerular c-Met staining in group 3 was lower than that in group 2. In groups 2 and 3, the mean scores for glomerular and interstitial α-SMA staining at first biopsy were correlated with the chronicity index (CI) at second biopsy, but the mean score for glomerular c-Met staining at first biopsy correlated with neither the activity index (AI) nor CI in the first or second biopsies in all groups. Our findings suggest that the expression of renal α-SMA may be associated with progression of renal injury in HSPN.