Platelet-derived growth factor receptors in the kidney--upregulated expression in inflammation

Major features of a long-standing inflammation in the kidney are vascular proliferation, glomerulosclerosis, interstitial fibrosis and tubular atrophy, leading to a gradual deterioration of the renal function. In this study we have investigated the expression of B-type receptors for platelet-derived growth factor (PDGF) in frozen sections from normal and inflamed kidneys. Immunohistochemical techniques, employing two monoclonal antibodies specific for PDGF B-type receptors, were used. The specimens investigated were 15 kidneys removed by transplantectomy because of chronic rejection, 20 cases of glomerulonephritis with crescent formation, mesangial proliferation or non-proliferative glomerulonephritis, and six normal kidneys. In parallel we characterized cellular infiltrates and class II transplantation antigen expression in the inflamed kidneys. An enhanced PDGF receptor expression was found on intimal cells and on smooth muscle cells of the proliferating vessels, on glomerular cells in glomeruli with mesangial proliferation, and on fibroblast-like cells in the proximity of clusters of infiltrating macrophages and T-lymphocytes of the interstitial tissue. Induction of PDGF receptor expression may render cells responsive to stimulation by PDGF, released from PDGF-producing cells, such as activated macrophages and from platelets. Our data suggest that PDGF is involved in the proliferation of mesenchymal cells that is seen in rejected kidney transplants and glomerulonephritis.