|Programm||"Degeneration und Regeneration– Grundlagen, Diagnostik und Therapie"|
Angiogenesis and Lymphangiogenesis in the Cornea: Implications for Immune Rejection after Keratoplasty and Novel Therapeutic Options
The normal human cornea is free of blood and lymphatic vessels. This requires the presence of antiangiogenic and antilymphangiogenic factors in the cornea. New findings on both types of inhibitors are outlined. Nonetheless, corneal inflammatory diseases and surgical manipulations can induce corneal neovascularization. This neovascularization usually consists of a parallel induction of angiogenesis (outgrowth of new blood vessels) and lymphangiogenesis (outgrowth of lymphatic vessels) into the cornea. Mechanisms of corneal hem- and lymphangiogenesis as well as their dependency on growth factors of the VEGF family are demonstrated. The parallel induction of hem- and lymphangiogenesis not only reduces corneal transparency but also renders such a cornea high-risk in case of subsequent grafting procedures. Corneal lymphatics improve delivery of antigenic material and antigen presenting cells to the regional lymph nodes. The importance of pre-existing corneal blood and lymphatic vessels as well as their postoperative ingrowth in relation to immune rejection are discussed as are novel antiangiogenic strategies to improve graft survival.