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Direct matrix metalloproteinase enhancement of transscleral permeability
James D Lindsey1, Jonathan G Crowston, Ailinh Tran
1Hamilton Glaucoma Center and Department of Ophthalmology, University of California San Diego, La Jolla, California 92093-0946, USA.
Purpose:
Previous studies have shown that increased trans-scleral permeability after exposure to certain prostaglandins is associated with increased intrascleral matrix metalloproteinases (MMPs). The present study was undertaken to determine whether these MMPs could directly alter transscleral permeability.
Methods:
Freshly enucleated mouse eyes were incubated with human MMP-1, -2, and -14 for 4 hours at 37 degrees C. The eyes then were incubated with 10 or 70 kDa dextran-tetramethylrhodamine-lysine for 16 to 32 minutes at 37 degrees C. Two methods of analysis were used. In the first, quickly isolated retinas were homogenized and centrifuged. Fluorescence in the supernatants was determined by microspectrofluorimetry. In the second, the eyes were fixed in 4% paraformaldehyde, and frozen sections were prepared. After the identity of the sections was masked, the intensity of fluorescence in anterior, middle, and posterior regions of the outer retina and inner retina was scored with a 7-point grading scheme.
Results:
The concentration of 10-kDa fluorescent dextran was 5.14 +/- 1.61 microg/mL (mean +/- SD, n = 33) in the control retinal supernatants, and 6.37 +/- 2.67 microg/mL (n = 40) in the retinal supernatants from the MMP-treated eyes. This increase was statistically significant (P < 0.02, t-test). The structural organization of the retina and other ocular tissues was maintained in all experimental conditions. Histologic scoring of fluorescence found significantly increased dextran in the outer retina of eyes treated with MMPs for 32 minutes (the score of control eyes was 2.5 +/- 0.4 and of MMP-treated eyes was 3.5 +/- 0.1, mean +/- SD; P = 0.02, n = 3). Analysis by region found greater scores in the third of the retina nearest to the optic nerve head.
Conclusions:
These results show that MMP-1, -2, and -14 can directly increase transscleral permeability and support the view that the increased MMP-1 and -2 observed after topical PG treatment could contribute to increased uveoscleral outflow.
Insights
Matrix metalloproteinases (MMPs) directly increase transscleral permeability. This finding supports the role of MMPs in prostaglandin-induced changes in ocular tissues, potentially affecting uveoscleral outflow.
Area of Science:
- Ophthalmology
- Biochemistry
- Cell Biology
Background:
- Previous research linked prostaglandin exposure to increased intrascleral matrix metalloproteinases (MMPs).
- The direct impact of these MMPs on transscleral permeability remained unclear.
Purpose of the Study:
- To investigate whether matrix metalloproteinases (MMPs) can directly alter transscleral permeability.
- To determine the role of MMP-1, MMP-2, and MMP-14 in modulating ocular tissue permeability.
Main Methods:
- Mouse eyes were incubated with MMP-1, -2, and -14.
- Dextran permeability was assessed using fluorescence microscopy and microspectrofluorimetry.
- Histological scoring evaluated dextran distribution in retinal layers.
Main Results:
- MMP treatment significantly increased dextran concentration in retinal supernatants.
- Histological analysis showed significantly increased dextran in the outer retina of MMP-treated eyes.
- Increased permeability was observed predominantly in the posterior retina.
Conclusions:
- Matrix metalloproteinases (MMPs) -1, -2, and -14 directly enhance transscleral permeability.
- These findings suggest MMPs contribute to prostaglandin-induced alterations in ocular permeability.
- This mechanism may influence uveoscleral outflow in the eye.
