Limbal lymphangiogenesis after corneal injury: an autoradiographic study

Blood and lymphatic vessel proliferation into the cornea occurs after severe trauma. Whilst the events early in blood vessel growth are reasonably understood, little is known of the early events in lymphangiogenesis. In this study, a model for proliferating lymphatic vessels using tritiated-thymidine autoradiography and light microscopy is described. A two-hour labeling index of 0.59% occurred in the lymphatic endothelium of the normal unstimulated limbus. After thermal cautery of the peripheral cornea, labeling of the limbal lymphatic vessels increased significantly at 36 hours, rose to a maximum of 6.8% four days after injury and thereafter returned to normal levels. Blood capillaries with a background level of 0.83% showed an increase in labeling at 17 hours, with high levels occurring at 36 hours (13.6%) and again from 61 to 84 hours (12.6%). Venular cells increased labeling at 25 hours from a control level of 0.58%, with a sharp peak of activity around 36 hours (13.2%). Synthesis of DNA similarly returned to normal levels in the blood vessels after four days. The staggered onset and differing durations of significantly increased labeling suggest either that various stimuli or arrays of stimuli are involved, or each cell type responds differently to the same stimulus for proliferation.