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J.A. Rada, L. Shelton; The Effect of Equibiaxial Stretch on Scleral Extracellular Matrix Remodeling . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1011.
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Purpose: In order to understand the effect of mechanical strain on scleral extracellular matrix metabolism, scleral fibroblasts were subjected to equibiaxial stretch and extracellular matrix synthesis and degradation were evaluated. Methods: Isolated human scleral fibroblasts were seeded onto flexible bottom culture plates, and subjected to a cyclic stretch regimen of 15% equibiaxial stretch for 45seconds followed by 15 sec rest over a 48 period in the presence of 35SO4. Following in vitro stretch, the cells and the conditioned medium were harvested. Newly synthesized proteoglycans, pro–MMP–2 and active MMP–2 were measured in the medium by western blot and gel zymogramography, while steady state levels of TIMP–2 mRNA and MT1–MMP (MMP–14) mRNA were measured in the cell layer using real time reverse transcription PCR. Results: The predominant gelatinolytic enzyme secreted by scleral fibroblasts was MMP–2 (gelatinase A). Mechanical stretch resulted in a significant increase in the active form of MMP–2 (+86%, p = 0.0022), decreased amounts of the proenzyme form of MMP–2 ( –55%, p = 0.181), and decreased levels of TIMP–2 mRNA (–38%, p = 0.0087). The rate of scleral proteoglycan synthesis and levels of steady state MMP–14 mRNA were not significantly affected by equibiaxial stretch. Conclusions: These results suggest that mechanical stretch stimulates the activation of pro–MMP–2 by scleral fibroblasts, possibly through lowered levels of TIMP–2. Increased levels of active MMP–2 in the sclera would be expected to contribute to active extracellular matrix turnover and scleral remodeling.
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