Crucial role of corneal lymphangiogenesis for allograft rejection in alkali‐burned cornea bed

BACKGROUND: To examine the time course of hemangiogenesis, lymphangiogenesis, inflammation after corneal alkaline burns and compare with the importance of corneal hemangiogenesis, lymphangiogenesis and inflammation in allograft rejection on alkali-burned cornea bed, respectively. METHODS: Rat corneal hemangiogenesis and lymphangiogenesis were examined by whole mount immunofluorescence and double enzyme-histochemistry, and the state of corneal inflammation was evaluated by inflammation index scoring and histopathology. Then, corneal transplantations were divided into six groups and performed before the burn (group A) and on day 3 (group B), 2 weeks (group C), 5 weeks (group D), 6 weeks (group E) and 8 weeks (group F) after alkaline burns, respectively. The immune rejection of grafts was evaluated by interferon-gamma, interleukin-2 enzyme-linked immunosorbent assay and slit-lamp examination. RESULTS: Both corneal lymphatic and blood vessels reached the top 2 weeks after the burn. Corneal lymphangiogenesis disappeared 5 weeks after the burn, and corneal hemangiogenesis regressed completely 3 weeks later. Corneal inflammation was strong on day 3, but resolved 6 weeks after the burn. Compared with other groups, the mean survival time of groups B (4.67 +/- 1.03 days) and C (5.00 +/- 0.63 days) was significantly shorter (P < 0.05). The difference of mean survival time of grafts between group D (9.50 +/- 1.05 days) and group E (9.83 +/- 0.75 days), between group D and group F (10.00 +/- 0.89 days) was not significant (P > 0.05). CONCLUSIONS: Corneal lymphangiogenesis presents for a shorter duration than corneal hemangiogenesis or corneal inflammation but plays a crucial role in allograft rejection on alkali-burned cornea bed.