Role of Xanthine Oxidoreductase from Mesenchymal Cells in Retinal Inflammation after Pericyte Breakdown

Glycemic control is important for diabetic retinopathy (DR), but not sufficient for the inhibition after proliferative DR (PDR). Uric acid in the vitreous is reportedly increased in patients with DR, especially in the PDR. Here, the involvement of xanthine oxidoreductase (XO), responsible for uric acid production, in worsening DR was examined in both mouse model and co-cultured angiogenesis model. First, retinal pericytes were abolished by anti-PDGFRβ antibody injection to C57/Bl6 neonatal mouse at P1. Pericyte dropout from endothelial cells is reportedly early histological change in DR, and induces bleeding, abnormal angiogenesis, inflammation, and retinal detachment with rapid progression at P9-11. The expression of XO level in retina was increasing after pericyte breakdown, and was proportional to VEGF, and preceding the increase of TNFalpha. When 3.6mg/kg Febuxostat (Fbx), an XO inhibitor was injected at P7, widespread edema and retinal detachment/funnel-like deformation were dramatically improved by Fbx treatment at P11. ICAM-1+ cells surrounding edema and CD11b+ cells were reduced. Next, we performed a 3D culture sprouting assay using HUVEC spheroids in collagen gel co-cultured with human lung fibroblast (hLF) in fibrin gel. By Fbx treatment within the physiological concentration, the branch sprouting, cellular migration to the distal side and mitosis in branch stems were inhibited. ICAM-1 increase in HUVEC was observed with hLF co-culture but was suppressed by Fbx treatment. Finally, these effects of Fbx were not shown on HUVEC in planar culture. On the other hand, dissolution of fibrin by hLF was delayed directly due to Fbx. VEGF and PAI-1 expression from hLF and MMP-9 activity in medium were decreased by Fbx treatment. In summary, XO inhibition improved retinal inflammation and injury after pericyte loss. These results suggest the role of humoral inflammatory factors from mesenchymal cells surrounding retinal vessels in the hyperpermeable state such as DR. Disclosure A. Kushiyama: Research Support; Self; Teijin Pharma Limited, Sanwa Kagaku Kenkyusho Co., Ltd., Kowa Pharmaceutical Co., Ltd, StaGen. Consultant; Self; RIZAP. T. Kikuchi: None. H. Yamazaki: None. T. Yamamotoya: None. H. Sakoda: None. M. Fujishiro: Research Support; Self; Johnson & Johnson Services, Inc.. Y. Nakatsu: None. A. Uemura: Research Support; Self; Daiichi Sankyo Company, Limited, Boehringer Ingelheim GmbH, KAN Research Institute, Inc. T. Shirakura: Employee; Self; Teijin Pharma Limited. T. Asano: Research Support; Self; Teijin Pharma Limited, Sanwa Kagaku Kenkyusho Co., Ltd., Sanofi K.K. Y. Iwamoto: Board Member; Self; Japan Diabetes Foundation.