PATTERNS OF MATRIX SYNTHESIS IN GLOMERULAR SCLEROSIS

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Influenced by the enthusiasm of his eventual sponsors, the applicant developed an increasing interest in the molecular biologic aspects of glomerular disease during his two-year clinical nephrology fellowship. At the conclusion of this clinical training, the applicant started research training with the hope of developing a productive academic career. With the sponsors' guidance and supervision, the applicant devoted the first two years of his laboratory training towards developing an immunohistochemical method that permits the localization of RNA transcripts to a single cell, a level of resolution previously unobtainable. Subsequently, we used this new technique to identify specific glomerular cell types expressing glomerular matrix (ECM) and basement membrane (GBM) protein mRNAs, thus, defining the cellular origins for these proteins and demonstrating, in contrast to previously held concepts, that glomerular basement membrane synthesis is asymmetric and the cellular origins of its individual components are diverse. This new information provides the framework for further studies comparing normal basement membrane metabolism to processes involved in disease models. Our preliminary studies on the rat 5/6 nephrectomy (NTX) model of glomerular sclerosis reveal that the cellular synthetic patterns which occur soon after NTX appear similar to cellular events seen during glomerular embryogenesis. These findings provide the basis for the following hypotheses: 1) that the initial glomerular adaptive response to 5/6 NTX represents a coordinated return to fetal patterns of ECM/GBM synthesis; 2) that the later or sclerotic phase of the 5/6 NTX model represents a maladaptive, discoordinate pattern of ECM/GBM synthesis; and 3) this involves changes in cellular patterns of types of ECM/GBM protein synthesis or their corresponding degradative enzymes. The long-term research objectives of the applicant during and after the award period relate to an improved understanding of the mechanisms that govern the progression of glomerular disease. Understanding the metabolic changes within individual glomerular cell types and their relation to matrix alterations is, therefore, an important goal. The specific short-term objectives of this proposal address these issues in the specific context of the sclerotic process and result from this recent work accomplished by the applicant and his sponsors. Specifically, we propose to study the cellular patterns of glomerular matrix, degradative enzyme, and cytokine expression after 5/6 nephrectomy during both the hypertrophic (early) and sclerotic (late) stages of this model. Using ISRT and complimentary techniques that quantitate RNA transcripts, the amount and cellular location of these proteins will be assessed, providing new insights into the role of each glomerular cell types in the pathogenesis of glomerular sclerosis. All equipment and resources required for the completion of this project are already available at the applicant's facility. Arrangements have also been made to insure his protected, uninterrupted research time. This, in addition to the sponsors' continued support of the applicant, will provide the environment necessary for the applicant's further scientific progress and for the successful completion of this project.