Integrin alpha 9 blockade suppresses lymphatic valve formation and promotes transplant survival

Abstract

PURPOSE. The lymphatic pathway mediates transplant rejection. We recently reported that lymphatic vessels develop luminal valves in the cornea during lymphangiogenesis, and these valves express integrin alpha 9 (Itga-9) and play a critical role in directing lymph flow. In this study, we used an allogeneic corneal transplantation model to investigate whether Itga-9 blockade could suppress valvulogenesis after transplantation, and how this effect would influence the outcomes of the transplants. METHODS. Orthotopic corneal transplantation was performed between fully mismatched C57BL/ 6 (donor) and BALB/c (recipient) mice. The recipients were randomized to receive subconjunctival injections of either Itga-9 blocking antibody or isotype control twice a week for 8 weeks. Corneal grafts were assessed in vivo by ophthalmic slit-lamp biomicroscopy and analyzed using Kaplan-Meier survival curves. Additionally, whole-mount full-thickness corneas were evaluated ex vivo by immunofluorescentmicroscopy on both lymphatic vessels and valves. RESULTS. Anti–Itga-9 treatment suppressed lymphatic valvulogenesis after transplantation. Our treatment did not affect lymphatic vessel formation or their nasal polarized distribution in the cornea. More importantly, Itga-9 blockade led to a significant promotion of graft survival. CONCLUSIONS. Lymphatic valvulogenesis is critically involved in transplant rejection. Itga-9 targeting may offer a new and effective strategy to interfere with the immune responses and promote graft survival.