Introduction

Tight regulation of paracrine VEGF signaling between podocytes and glomerular endothelial cells (GEC) is required for maintenance of the glomerular filtration barrier (GFB) structure and function. Disruption of VEGF homeostasis has been implicated in various types of glomerular diseases. However, current therapies neither specifically target the glomerulus nor the VEGF pathway but in addition present multiple side effects. Therefore, identification of new approaches aimed at restoring local VEGF remains a potential therapeutic target to treat glomerular disease. _x000D_ _x000D_ We previously showed that amniotic fluid stem cells (AFSC) are renoprotective in Alport Syndrome (AS), a model of CKD. They home within the diseased glomeruli and secrete extracellular vesicles (EVs). EVs play key role in stem cell mediated paracrine function, including the kidney. Herein, we demonstrate that AFSC derived EVs regulate VEGF/VEGFRs signaling balance in AS GEC via modulation of sFlt1, the soluble isoform of VEGFR1. _x000D_

Methods

We measured VEGF activity in AS glomeruli by WB. We assessed VEGF/VEGF-Rs activity in GEC, including the sFlt1. We characterized AFSC-EVs cargo by FACS and by miRs arrays and evaluated their potential to affect VEGF biology in GEC.

Results

Glomeruli from AS mice showed increased VEGF activity through increased phosphorylation of VEGFR-2 early on during progression accompanied by modulation of sFlt1. These observations were associated with GEC damage that showed altered VEGFR signaling. Importantly, EVs presented with VEGFRs and angiomodulatory microRNA. These EVs successfully integrated within GEC and modulated VEGF activity. EVs lacking both the full and soluble VEGFR-1 failed to rescue GEC from VEGF inflicted damage.

Conclusions

In conclusion, we demonstrated for the first time the aberration of VEGF signaling within AS glomeruli. We further showed that AFSC derived EVs play important role in maintaining glomerular homeostasis of VEGF signaling, presenting with a potential for new targeted therapies in CKD.

Funding

CIRM, Alport Syndrome Foundation