A MODEL FOR BASEMENT MEMBRANE THICKENING IN DIABETES

糖尿病的进行性继发性并发症涉及病理

Progressive secondary complications of diabetes mellitus involve pathology of the kidney, retina, and general vasculature system. A common feature of these secondary complications is abnormalities of cell basement membranes (BM). These abnormalities are characterized in numerous tissues as a general thickening of basement membrane somehow resulting from the hyperglycemic conditions existing in individuals with diabetes. The structural alterations associated with the basement membranes of diabetics has been implicated as the basic defect leading to kidney malfunction, retinal lesions associated with blindness, and general vascular disorders associated with infection and tissue necrosis. The cellular and molecular basis for basement membrane alterations in diabetes is not understood, but current explanations include: 1) altered synthesis of basement membrane molecules, 2) altered turnover of basement membrane components, and 3) altered assembly and disassembly of the basement membrane lattice due to altered structure of individual components resulting from such chemical modifications as non-enzymatic glycation. Experimental approaches to evaluate these hypotheses are hampered by a lack of in vitro and in vivo cellular models. In order to approach this problem we have developed an in vivo cellular model in which basement membrane formation can be experimentally induced for subsequent analysis of the cellular mechanisms involved in the process. This model is comprised of an epithelial bilayer with an intervening basement membrane (i.e. a model reduced to the essential elements of interest in the hypotheses). In addition, we have determined that this in vivo model responds to hyperglycemic conditions by thickening its basement membrane as observed in diabetics. As opposed to vertebrate animal models of diabetes currently available however, the cell system we utilize develops a basement membrane within 96 hr and doubles the thickness of this basement membrane within this same time frame when exposed to elevated levels of glucose.This model was developed using the Cnidarian, Hydra vulgaris. The proposed project will utilize this in vivo model to determine if glucose-mediated basement membrane thickening results from cellular abnormalities in the synthesis of basement membrane components. Using expertise developed in the Dr. Bode's laboratory (host laboratory) related to the molecular biology of Hydra, the P.I. will use cDNA, synthetic oligonucleotides, and polymerase chain reaction (PCR) technology to screen existing Hydra cDNA libraries to develop Hydraspecific probes for use in studies designed to test hypotheses regarding the effect of elevated glucose levels on the synthesis of basement membrane components.