The long term goal of this proposal is to determine the role of growth factors in the proliferative and sclerotic process that accompanies progressive glomerular diseases. The central hypothesis is that platelet-derived growth factor released by activated mesangial cells or infiltrating inflammatory cells and platelets actively participate in glomerular hypercellularity. Moreover, we hypothesize that an interplay between the expression-of PDGF and transforming growth factor-beta (TGF-beta) determine the progression of proliferative and sclerotic processes. To correlate growth factor expression with morphologic and functional changes, we will quantify PDGF and TGF-beta mRNAs expression and their translated proteins as well as their receptors in mouse kidneys of experimental glomerulonephritis models using solution hybridization assays, in situ hybridization and immunohistochemical techniques. We will utilize two mouse models of IgA nephropathy and lupus nephritis. To determine the time course of onset and progression of renal fibrosis, we will determine the rates of collagen synthesis in vivo in experimental and control animals and determine if the changes in collagen synthetic rates are associated with a preferential increase in any of the collagen subtypes. Levels of mRNAs encoding for specific collagen chains, will be quantified by Northern blotting or solution hybridization, and in situ hybridization; transcription rates will be assessed by nuclear run on assays. We well determine the contribution of decreased collagen degradation to fibrosis by measuring the activity and distribution of collagenase(s) and inhibitor. To establish a role for growth factors in mediating the renal injury, we will assess the effect of therapeutic intervention on growth factor expression and progression of renal disease. In the in vitro studies, we will determine the contribution of transcriptional and posttranscriptional mechanisms to the changes in PDGF mRNAs levels in response to growth factors and cAMP. We will determine if the opposing actions of cAMP and phorbol esters on A chain gene transcription are mediated by the same DNA response element and characterize the protein DNA interaction by gel retardation and DNAase foot printing assays. To determine if intracellular or secreted PDGF acts in an autocrine manner to regulate DNA synthesis, we will first identify the PDGF isoform secreted by mesangial cells and the PDGF receptor subtype the cells express and then utilize specific anti-PDGF antibodies added exogenously or microinjected into mesangial cells to shut off DNA synthesis. In addition, we will study the effect of selective PDGF gene inhibition utilizing antisense RNA transfection strategy on DNA synthesis. These studies should help establish a role for PDGF and TGF-beta in glomerular injury and determine the molecular mechanisms involved in PDGF A chain regulation.
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