Enzymatic vitreolysis with recombinant microplasminogen and tissue plasminogen activator

To generate microplasmin (microPlm) using recombinant microplasminogen (microPlg) and recombinant tissue plasminogen activator (rt-PA) before intravitreous injection and to investigate the efficacy of microPlm in inducing posterior vitreous detachment (PVD).

Forty-eight female or male New Zealand white rabbits were randomized into three groups. Recombinant human microPlg was incubated with rt-PA with a 200:1 molar ratio at 37 degrees C for 40 min. The right eyes of groups 1, 2, and 3, were injected with 0.5, 1.0, and 1.5 U microPlm in 0.1 ml respectively, and 0.1 ml balanced salt solution (BSS) was injected into the left eye as controls. Scanning electron microscopy (SEM), gross specimen examination, B-ultrasonography and optical coherence tomography (OCT) were performed to detect vitreoretinal interface.

Over eighty percent of recombinant human microPlg could be activated to active microPlm by rt-PA after 40 min incubation. Complete PVD was found at vitreous posterior pole of microPlm-treated eyes without morphological change of retina. Complete PVD of 25, 75, and 87.5% rabbit eyes was induced by 0.5, 1.0 and 1.5 U recombinant microPlm respectively on day 1. The remnants of vitreous cortex at the posterior pole were dependent on the concentration of microPlm. Among the four approaches for detecting PVD, SEM, gross specimen examination, and B-ultrasonography were more effective methods than OCT.

Intravitreous injection of 1.5 U microPlm can effectively induce complete PVD in rabbit eyes on day 1 without morphological change of retina.