Autosomal dominant polycystic disease (ADPKD), third as a cause of renal failure and accounts for about 10% of individuals in end-stage renal disease. ADPKD presents as progressive, segmental tubular expansion with compression and atrophy of renal tissue resulting in loss of function. Tubular cell proliferation and chemical and structural changes of the tubular basement membrane may have key roles in the pathogenesis of ADPKD, however, its exact pathogenesis remains unknown. In two experimental models of PKD progressive cyst growth occurred apparently in the absence of a detectable increased rate of tubular cell proliferation and, in vitro, ADPKD cells compared to normal renal epithelial cells did not exhibit accelerated growth. However, basement membranes lining cysts in a drug- induced model of PKD and in ADPKD demonstrated structural alterations and a decreased content of heparin sulfate proteoglycan. Basement membranes elaborated by cyst-derived cells from ADPKD exhibit these changes in vitro. This suggests that the gene product(s) related t proteoglycan synthesis/degradation are defective in ADPKD and that this in vitro system may be a useful model to elucidate the biochemical/molecular basis of the disease. The research plan will test the hypothesis that ADPKD is due to a defect in the synthesis/degradation of basement membrane heparin sulfate proteoglycan resulting in tubular dysmorphogenesis. Studies will be done on monolayers in culture of ADPKD cells and normal human tubular epithelial cells (NK). For this purpose several rat HS-PG core protein cDNA clones have been isolated by immunologic screening of lambda gt11 expression vector libraries with a polyclonal anti-HS-PG core protein antibody.
The specific aims of the project are to 1) characterize proteoglycans (PGs) and core proteins synthesized de novo by ADPKD and NK cells, 2) characterize glycosaminoglycans (GAGs) synthesized de novo by ADPKD and NK cells and determine the status of their sulfation, 3) determine the kinetics of PG synthesis/degradation to include the metabolism of PG core protein, the metabolism and sulfation of GAGs and transport kinetics (cellular to extracellular) of PGs and GAGs, 4) determine levels of transcription and translation of HS-PG core protein and 5) determine levels of mRNA expression for PGs in tubular cells and renal interstitial cells in ADPKD and normal human kidney sections by in situ hybridization. The long-term aim of this proposal is to elucidate the biochemical/molecular basis of ADPKD. This may allow therapeutic approaches to control or reverse the disease process.
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