Abstract: TH-PO686

Diabetes-Induced Impairments in Robo Signalling Augment Glomerular Angiogenesis

Session Information

Category: Diabetes

  • 501 Diabetes Mellitus and Obesity: Basic - Experimental

Authors

  • Zhang, Johnny Y., Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada
  • Sidiqi, Ahmad Mohammad Omar, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada
  • He, Xiaolin, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada
  • Gao, Feng, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada
  • Yuen, Darren A., Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada
Background

Diabetic glomerular angiogenesis represents an early form of diabetic kidney injury, and is classically thought of as being driven by increased podocyte VEGF production. Robo1 and Robo4 are cell surface receptors that can regulate VEGF-mediated endothelial angiogenic activity. We have shown previously that glomerular endothelial Robo4 expression is downregulated by high glucose exposure, whereas Robo1 expression is unchanged, and that Robo1 is essential for VEGF-induced angiogenic activity. Our objective is to determine whether high glucose-induced alterations in Robo4 levels regulate VEGF-induced glomerular angiogenesis in diabetes.

Methods

Glomerular endothelial cell (GEC) responsiveness to VEGF in angiogenesis assays was examined in both normal glucose (NG) and high glucose (HG) conditions, and following Robo4 knockdown. Using Robo4 knockout (KO) mice, the effect of Robo4 deficiency on diabetic glomerular angiogenesis was also analyzed using fluorescence microangiography (FMA) and PECAM-1 immunohistochemistry, while kidney functional output was measured by creatinine clearance.

Results

As compared to GEC grown in NG medium, GEC grown in HG medium expressed lower levels of the anti-angiogenic Robo4 receptor, but not the pro-angiogenic Robo1 receptor, and exhibited greater VEGF responsiveness. Robo4 deficiency was associated with augmented migration in vitro and increased PECAM-1 density, glomerular capillary length, and creatinine clearance in Robo4 KO mice (compared to their WT littermates) after 5 weeks of STZ-induced diabetes.

Conclusion

Our observations suggest that diabetic glomerular angiogenesis is driven not only by enhanced VEGF production, but also by enhanced glomerular endothelial VEGF responsiveness. This increased responsiveness appears to be promoted by a shift in glomerular endothelial Robo signalling, favouring more pro-angiogenic Robo1, and less anti-angiogenic Robo4 activity.