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Elevated levels of vascular endothelial growth factor (VEGF) A are thought to cause glomerular endothelial cell (GEnC) dysfunction and albuminuria in diabetic nephropathy. We hypothesized that VEGFC could counteract these effects of VEGFA to protect the glomerular filtration barrier and reduce albuminuria. Isolated glomeruli were stimulated ex vivo with VEGFC, which reduced VEGFA- and type 2 diabetes-induced glomerular albumin solute permeability (Ps'alb). VEGFC had no detrimental effect on glomerular function in vivo when overexpression was induced locally in podocytes (podVEGFC) in otherwise healthy mice. Further, these mice had reduced glomerular VEGFA mRNA expression, yet increased glomerular VEGF receptor heterodimerization, indicating differential signaling by VEGFC. In a model of type 1 diabetes, the induction of podVEGFC overexpression reduced the development of hypertrophy, albuminuria, loss of GEnC fenestrations and protected against altered VEGF receptor expression. In addition, VEGFC protected against raised Ps'alb by endothelial glycocalyx disruption in glomeruli. In summary, VEGFC reduced the development of diabetic nephropathy, prevented VEGF receptor alterations in the diabetic glomerulus, and promoted both glomerular protection and endothelial barrier function. These important findings highlight a novel pathway for future investigation in the treatment of diabetic nephropathy. [ABSTRACT FROM AUTHOR]

Endothelial cells form the inner lining of all blood vessels and play a vital role in regulating vascular permeability. This applies to the circulation in general and also to specific capillary beds including the renal glomerular capillaries. Endothelial dysfunction, including increased permeability, is a key component of diabetes-induced organ damage. Endothelial cells together with their glycocalyx, grown on porous membranes, provide an excellent model to study endothelial permeability properties. Here we describe the measurement of two characteristics of glomerular endothelial cell (GEnC) monolayers: electrical resistance and macromolecular passage. Trans-endothelial electrical resistance provides a measure of small-pore pathways across the endothelium and provides an index of monolayer confluence and cell-cell junction integrity. Measurement of macromolecular passage provides an index of large-pore pathways and use of labeled albumin provides direct relevance to the clinically important parameter of albuminuria. The combination of the two approaches provides a fantastic tool to elucidate endothelial barrier function in vitro including in response to cytokines, pathological stimuli, and potential therapeutic agents.