Promotion of graft survival by vascular endothelial growth factor A neutralization after high-risk corneal transplantation

Objective: To evaluate whether hemangiogenesis, lymphangiogenesis, and concomitant invasion of mononuclear phagocytes occurring after high-risk corneal transplantation in already vascularized high-risk recipient corneal beds increase the risk for subsequent immune rejection. Methods: Three intrastromal sutures were left in place for 6 weeks in the corneas of BALB/c mice, causing neovascularization. Three weeks after suture removal, keratoplasty was performed (donors C57BL/6 mice). The treatment group received a vascular endothelial growth factor A (VEGF-A)-neutralizing cytokine trap at 0, 4, 7, and 14 days postoperatively (Fc protein was used as the control treatment). Morphometry was performed in corneal flat mounts using lymphatic endothelial hyaluronan receptor-1 (a specific lymphatic endothelial marker), CD31 (a panendothelial marker), and F4/80 (a marker for mononuclear phagocytes). Results: After corneal transplantation, significant additional hemangiogenesis (mean area covered by vessels [SD], 68% [18%] postoperatively vs 40% [18%] preoperatively; P=.03) and lymphangiogenesis (12% [1.3%] postoperatively vs 9% [2.8%] preoperatively; P = .03) were observed. Postoperative neutralization of VEGF-A inhibited operation-induced hemangiogenesis (35% [8%]; P = .007) and lymphangiogenesis (6% [1.6%]; P = .03) and decreased the recruitment of mononuclear phagocytes into the graft (mean [SD], 501 cells/mm² [152] in treated mice vs 684 cells/mm² [35] in Fc controls; P = .03). After 8 weeks, 23% of the treated corneas were not rejected, whereas all control corneas were rejected after 21 days (P = .007). Conclusions: Neutralization of VEGF-A after high-risk corneal transplantation effectively inhibits postoperative hemangiogenesis, lymphangiogenesis, and recruitment of antigen-presenting cells and improves corneal graft survival. Clinical Relevance: Blocking of VEGF-A after high-risk corneal transplantation may be a novel approach to improve graft survival.