Characterization of a stabilized form of microplasmin for the induction of posterior vitreous detachment.
OBJECTIVE
To investigate the stability and safety of a diluted acidified form of microplasmin and its ability to induce a posterior vitreous detachment (PVD) following intravitreal injection in post-mortem porcine eyes.


METHODS
Microplasmin diluted in normal saline (NS) and balanced salt solution (BSS+) was assayed for residual activity by hydrolysis of the chromogenic substrate Glu-Phe-Lys-pNA. Residual activity on vitreous was determined by injecting aliquots of microplasmin reconstituted in balanced salt solution (BSS+) or normal saline (NS) kept at room temperature (RT) for up to 1 hr, then injected in aliquots of porcine vitreous and incubated for 2 hr at 37°C. The breakdown products were submitted to SDS Page electrophoresis and compared to determine the level of enzymatic activity. Pig eyes were incubated with graded concentrations of microplasmin 0.625, 1.25, or 2.50 mg/mL reconstituted in BBS+ or NS. Morphologic alterations and the ability to induce a PVD was assessed by light and electron microscopy.


RESULTS
Microplasmin's enzymatic activity in an in vitro assay in BSS+ was 70% of its baseline value after 30 min, and about 50% after 60 min at RT. The corresponding effect on degradation of vitreous gel was 60 and 40% baseline at 30 and 60 min. There was no loss of activity in the microplasmin diluted in normal saline over this time period. Dilution of acidified microplasmin in normal saline did not lead to structural changes within the retina. A dose dependent PVD was observed in eyes treated with microplasmin diluted in NS.


CONCLUSIONS
Acidified (stabilized) microplasmin has the same intraocular activity profile as microplasmin at a neutral pH. Better retention of activity at room temperature makes it a better candidate for use in clinical practice.
Gad Elkareem
Ashraf M
AM
Department of Ophthalmology, Academic Medical Center, University of Amsterdam, The Netherlands.
Willekens
Ben
B
Vanhove
Marc
M
Noppen
Bernard
B
Stassen
Jean Marie
JM
de Smet
Marc D
MD
D000143:Acids; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004591:Electrophoresis, Polyacrylamide Gel; D005341:Fibrinolysin / Q000008:administration & dosage* / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D056965:Injections, Intraocular; D008854:Microscopy, Electron; D009994:Osmolar Concentration; D010446:Peptide Fragments / Q000008:administration & dosage* / Q000737:chemistry; D012965:Sodium Chloride; D012996:Solutions; D013552:Swine; D013696:Temperature; D013997:Time Factors; D014822:Vitreous Body / Q000187:drug effects / Q000473:pathology; D020255:Vitreous Detachment / Q000139:chemically induced* / Q000473:pathology
D000143:Acids; D010446:Peptide Fragments; D012996:Solutions; D012965:Sodium Chloride; C054561:microplasmin; D005341:Fibrinolysin