Enzymatic vitreolysis with recombinant microplasminogen and tissue plasminogen activator

Abstract

Purpose To generate microplasmin (lPlm) using recombinant microplasminogen (lPlg) and recombinant tissue plasminogen activator (rt-PA) before intravitreous injection and to investigate the efficacy of lPlm in inducing posterior vitreous detachment (PVD). Methods Forty-eight female or male New Zealand white rabbits were randomized into three groups. Recombinant human lPlg was incubated with rt-PA with a 200:1 molar ratio at 371C for 40 min. The right eyes of groups 1, 2, and 3, were injected with 0.5, 1.0, and 1.5 U lPlm 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. Results Over eighty percent of recombinant human lPlg could be activated to active lPlm by rt-PA after 40 min incubation. Complete PVD was found at vitreous posterior pole of lPlm-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 lPlm respectively on day 1. The remnants of vitreous cortex at the posterior pole were dependent on the concentration of lPlm. Among the four approaches for detecting PVD, SEM, gross specimen examination, and B-ultrasonography were more effective methods than OCT. Conclusion Intravitreous injection of 1.5 U lPlm can effectively induce complete PVD in rabbit eyes on day 1 without morphological change of retina.

Direct fibrinolytic agents: biochemical attributes, preclinical foundation and clinical potential

“…The results suggest that microplasmin (5 mg kg )1 ) induced less intracranial hemorrhage than did t-PA, and perhaps decreased cerebral injury better than t-PA, but one study [64] suggested that a higher micro-plasmin dose (10 mg kg )1 ) offered no advantage and perhaps contributed to higher mortality. Micro-plasmin has also been assessed for vitreolytic effects in cat [65], rabbit [66] and pig [67] models, with microgram amounts being injected locally to induce detachment of vitreous cortex from retina.…”

Emerging nonsurgical methods for the treatment of vitreomacular adhesion: a review

“…The initial pre-clinical studies revealed achievement of complete PVD (eg, bare ILM) at doses ranging from 62.5–125.0 μg (equivalent to 1–2 U of plasmin) in enucleated human eyes with or without adjunctive intraocular gas 148. In-vivo studies similarly exhibited complete PVD following 7–21 day intravitreal microplasmin exposure with doses differing based on species; cat eyes achieved PVD at doses of 14.5–25.0 μg,148 while two separate studies in rabbits reported consistent PVD at doses of 125–250 μg 149,150. No histologic toxicity148–150 or functional toxicity149 was noted excepting persistent a- and b-wave depression on ERG testing in the 250 μg group only.…”

Pharmacologic Vitreolysis with Ocriplasmin: Rationale for Use and Therapeutic Potential in Vitreo-Retinal Disorders

“…In all treated eyes, there was a temporary reduction in the a-and b-wave amplitudes on electroretinography, which recovered by 14 days after injection in all except for the 250 lg group. Most recently, Chen et al [41] used immunofluorescent histochemistry to find that intravitreal ocriplasmin degraded fibronectin and laminin, not only at the vitreoretinal interface but also at the level of the photoreceptor layer in the outer retina of rats-a potentially untoward effect. MIVI-I (Intravitreal Microplasmin During Surgical Vitrectomy) was the first study to examine the safety and preliminary efficacy of a single ocriplasmin injection in humans, over a range of doses and exposure times.…”