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Microplasmin: ex vivo characterization of its activity in porcine vitreous
Marc D de Smet1, Christophe Valmaggia, Javier Zarranz-Ventura
1Department of Ophthalmology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. mddesmet1@mac.com
Purpose:
Microplasmin is a recombinant protein limited to the enzymatic moiety of plasmin without any of its cringle domains. Its enzymatic activity is similar to that of plasmin enzyme. The present study characterizes in a porcine eye model the vitreolytic ability of microplasmin.
Method:
Freshly harvested porcine eyes were used in these trials. Eyes were injected with escalating doses of microplasmin (62.5, 125, 250, 400 microg) for 1 hour or with 125 microg microplasmin with increasing time exposures (15, 30, 60, 120 minutes). Eyes were fixed by a very slow dehydration process to preserve the integrity of the vitreous retinal interface. They were examined by light microscopy to determine the degree of posterior vitreous detachment and by scanning electron microscopy (SEM) to study structural changes.
Results:
Effective separation of the posterior hyaloid appeared to be dose dependent. After 1 hour, the posterior pole was detached in 100% of porcine eyes exposed to 125 microg microplasmin and in the midperiphery to 250 microg microplasmin. Vitreous at the ora did not detach. At 120 minutes of exposure, midperipheral detachment was observed with 125 microg microplasmin. A smooth retinal surface was seen where the enzyme caused posterior vitreous detachment. There was also significant change to the integrity of the vitreous without any obvious structural alterations to the retina by histology or scanning electron microscopy.
Conclusions:
Microplasmin caused vitreolysis and posterior vitreous separation in an ex vivo porcine eye model in an apparent dose- and time-dependent fashion. In this model system, the minimal effective dose appeared to be 125 microg.
Insights
Microplasmin effectively separates the posterior vitreous in a porcine eye model. This vitreolysis is dose- and time-dependent, with 125 micrograms being the minimum effective dose for posterior vitreous detachment.
Area of Science:
- Ophthalmology
- Biochemistry
- Enzymology
Background:
- Microplasmin is a recombinant protein containing only the enzymatic part of plasmin.
- It exhibits enzymatic activity comparable to native plasmin.
- Understanding its vitreolytic potential is crucial for potential therapeutic applications.
Purpose of the Study:
- To characterize the vitreolytic ability of microplasmin.
- To evaluate microplasmin's efficacy in inducing posterior vitreous detachment (PVD) in a porcine eye model.
- To determine the dose and time dependency of microplasmin's vitreolytic action.
Main Methods:
- Fresh porcine eyes were used for ex vivo experiments.
- Eyes were treated with varying doses of microplasmin (62.5–400 µg) for 1 hour or with 125 µg microplasmin for extended durations (15–120 minutes).
- Vitreous structural integrity and posterior vitreous detachment were assessed using light microscopy and scanning electron microscopy (SEM) after careful dehydration.
Main Results:
- Posterior hyaloid separation was dose-dependent, with 125 µg achieving 100% detachment at the posterior pole after 1 hour.
- Higher doses (250 µg) led to midperipheral detachment within 1 hour.
- Significant changes in vitreous structure were observed without apparent retinal damage on histology or SEM.
Conclusions:
- Microplasmin induces vitreolysis and posterior vitreous separation in an ex vivo porcine model.
- The effect is dependent on both the dose and duration of exposure.
- The minimal effective dose for inducing PVD in this model was determined to be 125 µg.
