Influence of glucose on murine metanephric development and proteoglycans: morphologic and biochemical studies

The offspring of severe juvenile diabetics suffer from a multitude of congenital anomalies, including genito-urinary defects. Whether these defects are related to hyperglycemic states remains to be determined. In this study, the effect of glucose on metanephric development and extracellular matrix proteoglycans (PG), the regulators of morphogenesis, was investigated. Metanephric explants, harvested at Day 13 of gestation, were exposed to 30 mM of D-glucose for 1 to 7 days in an organ culture system. Light microscopy revealed a significant reduction in the size of explants and the nephron population in metanephroi exposed to glucose. A marked dysmorphogenesis of the ureteric bud branches was also observed. They were swollen and had blunted tips. The latter are the site of nascent nephron formation. Electron microscopy revealed malformation of the S-shaped body nephrons, which had poorly formed clefts and lacked cells in their distal convolutions. The precapillary stage glomeruli showed effacement of the foot processes, attenuation of the glomerular basement membrane, decreased surface microvilli, and an increased number of intercellular junctions. Immunofluorescence microscopy indicated a decreased reactivity of antibody directed against basement membrane heparan sulfate-PG. By light microscopy-autoradiography, a generalized decrease in [35S] sulfate incorporation was observed, especially at the tips of the ureteric bud branches. Electron microscopy-autoradiography revealed a significant decrease in the silver grain density (concentration of radiation) in the matrix compartment of the nephrons, i.e., cleft of the S-shaped body and glomerular basement membrane of the precapillary-stage glomeruli. Biochemical studies revealed a decrease in the incorporated radioactivity associated with the fraction of PG. The newly synthesized PG had a reduction in their molecular weight and charge-density characteristics but had an increased proportion of chondroitin sulfate. These data suggest that D-glucose induces marked dysmorphogenesis of the embryonic kidney during in vitro metanephric development and that these alterations may be related to perturbations in the de novo synthesis of PG, one of the essential morphogenetic regulators of the extracellular matrix.