Effect of plasmin on laminin and fibronectin during plasmin-assisted vitrectomy.

OBJECTIVE To determine whether plasmin will cleave the laminin and fibronectin located at the vitreoretinal junction during plasmin-assisted vitrectomy. METHODS Western blot analyses were performed with antilaminin or anti-fibronectin antibodies on the internal limiting membranes collected from patients with macular holes or cystoid macular edema who underwent vitrectomy with or without plasmin. The results were compared with the results of in vitro experiments in which commercially available laminin and fibronectin were exposed to commercially available plasmin. RESULTS In all eyes treated with plasmin, a posterior vitreous detachment was not present before surgery but was created easily with a minimal suction of less than 100 mm Hg during vitrectomy. Western blot analyses showed that the laminin and fibronectin in the internal limiting membrane exposed to plasmin during vitrectomy were degraded to several fragments of lower molecular weights, including a fragment of approximately 13,000 Da for laminin and a fragment of approximately 30,000 Da for fibronectin. These lower-molecular-weight fragments also appeared in the in vitro experiments. CONCLUSION The laminin and fibronectin at the vitreoretinal junction are degraded during plasmin-assisted vitrectomy. CLINICAL RELEVANCE These findings provide evidence for the efficacy of using plasmin to create a posterior vitreous detachment during vitreoretinal surgery.