Inhibition of Hemangiogenesis and Lymphangiogenesis after Normal–Risk Corneal Transplantation by Neutralizing VEGF Promotes Graft Survival

Abstract

Abstract: : Purpose:To document occurrence and time–course of hem– and lymphangiogenesis after normal–risk orthotopic corneal transplantation in mice, and to test whether pharmacological strategies inhibiting these processes can improve long–term corneal graft survival. Methods:Occurrence and time–course of hem– and lymphangiogenesis was observed using double immunofluorescence of corneal flat–mounts (with PECAM–1 as panendothelial–, and LYVE–1 as lymphatic vascular endothelial cell–specific marker) after normal–risk allogeneic (C57BL/6 ––> BALB/c) and syngeneic (BALB/c ––> BALB/c) corneal transplantation. A molecular trap designed to eliminate VEGF A (VEGF Trap_R1R2; 12.5 mg/kg/mouse) was administered i.p. at the time of surgery, and 7 and 14 days later. Results: Both in allogeneic as well as syngeneic low–risk eyes, blood and lymph vessels arose simultaneously from the limbus after transplantation, and both vessel types reached donor tissue at one week. VEGF Trap_R1R2 significantly suppressed both postoperative hem– and lymphangiogenesis, and significantly improved long–term allograft survival after low–risk transplantation (p<0.05). Conclusions: Keratoplasty itself (whether syngeneic or allogeneic) is an important cause of VEGF A–dependent hem– and lymphangiogenesis. Post–keratoplasty neovascularization is identified as novel risk factor for subsequent immune rejections. Since inhibition of surgery–induced hem– and lymphangiogenesis can significantly enhance graft survival, surgery and wound healing processes have strong influences on graft outcome.

Keywords: neovascularization • transplantation • cornea: basic science