Angiopoietin-2 Blockade Promotes Survival of Corneal Transplants.

PURPOSE: Corneal transplantation remains the last hope for vision restoration, and lymphangiogenesis (LG) is a primary mediator of transplant rejection. This study was to investigate the specific role of angiopoietin-2 (Ang-2) in transplantation-associated LG and graft rejection.

METHODS: Orthotopic corneal transplantation was performed between fully mismatched C57BL/6 (donor) and BALB/c (recipient) mice to assess the effects of Ang-2 blockade via neutralizing antibody. Grafts were evaluated in vivo by ophthalmic slit-lamp biomicroscopy and anterior segment optical coherence tomography (OCT) up to 8 weeks after surgery. Additionally, whole-mount corneas were analyzed for lymphatic and blood vessels and macrophages by immunofluorescent microscopy, and draining lymph nodes were assessed for donor-derived cells by flow cytometry.

RESULTS: Anti-Ang-2 treatment significantly suppressed LG and graft rejection. In this study, we achieved 75% suppression of LG and 80% graft survival. Our approach also inhibited donor-derived cell trafficking to draining lymph nodes and affected macrophage morphologic phenotypes in the grafted corneas. Additionally, Ang-2 blockade also reduced central corneal thickening, a parameter strongly associated with graft rejection.

CONCLUSIONS: Ang-2 is critically involved in corneal transplant rejection and anti-Ang-2 treatment significantly improves the outcomes of corneal grafts. Moreover, we have shown that anterior segment OCT offers a new tool to monitor murine corneal grafts in vivo. This study not only reveals new mechanisms for transplant rejection, but also offers a novel strategy to treat it.