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A. El-Osta; Laser-Mediated Activation of Matrix Metalloproteases (MMPs) Leading to Increased Transport Across Ageing Bruch's Membrane: Implications for Treatment of ARMD. Invest. Ophthalmol. Vis. Sci. 2010;51(13):6196.
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© ARVO (1962-2015); The Authors (2016-present)
To assess the involvement of active MMP-9 in the proposed improvement of hydraulic transport across human Bruch’s membrane (BM) following laser mediated retinal rejuvenation therapy.
Isolated samples of human RPE-Bruch’s-choroid (n=54; age 23-92 yr) were mounted in Perspex tissue cassettes with a central 6mm aperture. One third of the samples (subset 1; n=18) were used to measure baseline hydraulic conductivity (HC) across BM following removal of RPE. The central 4mm portion of RPE of the second subset (n=18) was irradiated with 2RT laser (30 ‘burns’ each resulting from a train of 50 x 3ns pulses; TRE=31.8J.cm2). The third subset (n=18) was not irradiated to act as procedural control. The cassettes were incubated DMEM + 10% FCS for 21 days with medium changes every 3 days. The RPE monolayer from subsets 2 & 3 was then removed from underlying BM, washed with PBS and inserted into vertical Ussing chambers equipped with a hydrostatic pressure feed and associated digital manometers to follow fluid (movement through the preparation. An initial pressure head with PBS (corresponding to IOP) was applied to BM and the corresponding change in pressure profile as fluid traversed the preparation was used to calculate the basal HC of the preparation and following incubation period. At the end of the experiment, tissue samples were processed for zymography to determine the MMP profiles within the preparation.
Baseline HC of Bruch’s membrane in 54 donor samples (age-range 23-92 yr) showed an age-related exponential decline (HC = 85.1exp-0.065*age) with a half-life of 11 years, compatible with previous studies. Irradiated samples (Subset 2; n=18, age-range 23-92 yr) showed a marked improvement in HC (p<0.05), raising the transport curves upwards (HC = 121.2exp-0.03*age) with an improved half-life for the decay function of 16 years. The improvement was particularly marked in the younger subset of donors. No significant change in HC was found in procedural controls. Zymographic analysis of MMP content post-incubation showed greater availability of active MMP-9 in irradiated samples, reflecting reduced porosity in this subset.
Modulation of the MMP system in RPE cells that leads to the release of activated MMP-9 provides one mechanism for improving the transport characteristics of ageing human BM. This mechanism appears to operate during RPE wound healing following laser insult. These results will be discussed in relation to retinal rejuvenation therapy for the management of ARMD.
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