Quantification of platelet-derived growth factor A, factor B and receptor beta in human renal biopsy tissue using competitive reverse transcriptase polymecase chain reaction: comparison between immunoglobulin A nephropathy and thin membrane nephropathy

Platelet-derived growth factor (PDGF) is a pleiotropic cytokine synthesized by various resident renal cells and infiltrating cells. Its best-studied r ole in the kidney is in the mediation of glomerular mesangial cell prolifer ation. The relationship between expression of PDGFA, PDGFB and the receptor beta (PDGFR beta) in human renal biopsies of immunoglobulin A nephropathy (IgAN), a disease characterized by mesangial cell proliferation, and thin m embrane nephropathy (TMN), a non-proliferative glomerulopathy, was studied. Using competitive reverse transcriptase-polymerase chain reaction (RT-PCR) , the quantity of mRNA molecules of each growth factor and the receptor was determined in renal biopsies from 20 patients with IgAN and 16 with TMN. I n addition, eight nephrectomy samples with paired cortical and medullary sa mples were studied. There was no significant difference between the disease groups for PDGFA (TMN, 1409 +/- 475 copy number/microgram RNA; IgAN, 691 /- 133, P = 0.35), PDGFB (TMN, 2280 +/- 467; IgAN, 1465 +/- 197, P = 0.10) or PDGFR beta (TMN, 1387 +/- 273; IgAN, 1402 +/- 344, P = 0.68). Analysis o f nephrectomy samples showed higher constitutive expression of PDGFA and PD FGB in the medulla as compared with the cortex. However, further analysis o f cortical samples in the IgAN group again failed to show a significant dif ference compared with TMN. We conclude that whole tissue analysis may have masked upregulation at glomerular level although it should reflect mRNA exp ression in the tubulointerstitial compartment.