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J.G. Flanagan, S.A. Culp–Stewart, A.H. W. Ching, C.R. Ethier; The Differential Effect of Cyclic and Static Stretch on MMP–2 Activity in Rat Astrocytes . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1543.
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© ARVO (1962-2015); The Authors (2016-present)
Mechanical stretch of optic nerve tissues, and particularly glial cells, has been hypothesized to play a role in glaucomatous optic neuropathy, a central feature of which is extracellular matrix remodelling. Here we investigate how MMP–2 activity is affected by cyclic and static stretch in rat astrocytes.
Rat cortical astrocytes (DITNC1; PNAS 89:6467,1992) were grown in modified DMEM (with 4 mM L–Glutamine; 4500 g/L Glucose; 1.5 g/L sodium bicarbonate; supplemented with 10 % FBS) at 37°C in a 5 % CO2 humidified incubator. Cells were seeded onto collagen I coated BioFlex culture plates with peripheral guard rings at a density of 100,000 cells/well, and grown for 6 days. On day 6, cells were rinsed with DPBS and incubated for 24 hours with serum–free media. The cells were then subjected to 1, 3 or 15 % static (one–time stretch and hold) or cyclic (1 Hz, sinusoid) equi–biaxial stretch for 2 or 24 hours using the Flexercell FX–4000 Tension Plus System. Controls cells were serum–deprived and incubated without stretch for the experimental duration. Gelatin zymography was performed using conditioned media. MMP–2 activity was quantified by densitometry of bands under equilibrated loading conditions.
There was a consistent and repeatable up–regulation of MMP–2 for all 24 and 2 hour cyclic stretch conditions and a down–regulation of MMP–2 for all static stretch conditions. 1, 3 and 15% cyclic stretch for 24 hours gave an 75, 44 and 25% increase in normalized relative band density when compared to controls, and a 188% increase following 3% cyclic stretch for 2 hours. Static stretch of 1, 3 and 15% for 24 hours gave a 36, 42 and 57% decrease, and a 34% decrease following 3% cyclic stretch for 2 hours.
Cyclic and static stretches have different effects on MMP–2 activity in rat astrocytes. This is consistent with the idea that astrocytes can adapt to a static (one–time) stretch without altering MMP activity, while cyclic stretch induces MMP activity as the cell attempts to remodel its extracellular matrix environment.
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