Abstract
Purpose :
Diabetic retinopathy (DR) is a leading cause of blindness. DR may cause diabetic macular edema (DME), which compromises central vision in 25% of DR patients. Anti-Vascular Endothelial Growth Factor (VEGF) drugs represent the standard of care for DME. However, lack of response occurs in approximately 50% of DME treated patients, with 20% of them showing signs of progression to proliferative DR. Thus, a better understanding of DR pathogenesis is required to develop new drugs.
Methods :
Drug responder (RES)/non-RES patients were defined based on the effect of anti-VEGF drugs on edema reduction. The angio-inflammatory potential of non-RES/RES vitreous samples was evaluated in vitroon endothelial cells (ECs). To mimic the structural and molecular changes that occur in DR retinae, non-RES or heat-inactivated (HI) vitreous were injected intravitreally in mice. Spheroid sprouting assay was exploited to assess the efficacy of anti-VEGF drugs versusmulti-target anti-heparin-binding protein (anti-HBP) compounds (i.e.the biotechnological heparin-like molecule K5-N,OS(H) and BOC2) on non-RES vitreous sample activity.
Results :
Orthotopic eye injection of non-RES vitreous promoted the upregulation of the EC marker Cd31and of the glial activation marker Gfap, which were paralleled by the reduction of the junction protein Occludinand smooth muscle cell marker αSmalevels. Moreover, non-RES vitreous induced monocyte/M2 macrophage infiltration and the overexpression of growth factors and cytokines, including Vegfand interleukins. Notably, HI vitreous was ineffective, pointing to a proteinaceous nature of the non-RES vitreal mediators acting on mouse retinae. In this frame, the blockade of vitreal HBPs mediated by K5-N,OS(H) completely abrogated the activity of non-Res samples. It is worth noticing that the potency of K5-N,OS(H) was significantly higher than the anti-VEGF ranibizumab, which was only partially effective at the clinically relevant, saturating concentration of 10 µM, with no further improvement at a double dose. Similar results were obtained with the anti-HBP BOC2, thus confirming the pivotal role played by HBPs in DR progression.
Conclusions :
Our data show that VEGF is only part of a complex machinery regulating angiogenesis, inflammation and edema formation during DR and that drug resistance is due to the activation of compensatory mechanisms mediated by HBPs besides VEGF.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.