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Janice Vranka, Kate Keller, Ted Acott; Extracellular Matrix Gene Expression Profiling of High and Low Flow Areas of Human Trabecular Meshwork. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3566.
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Several studies have shown that aqueous humor outflow is segmental, rather than uniform, around the circumference of the trabecular meshwork (TM). Extracellular matrix (ECM) composition is thought to not only vary in localized areas of high or low outflow, but also to respond differently to external stimuli thus affecting relative outflow rates. The purpose of this work was to identify ECM genes that display segmental differences in expression levels and which change in response to increased pressure in both low and high flow areas of the TM.
Human donor eyes were perfused at 1x and 2x pressure in vitro using anterior segment perfusion organ culture. Fluorescent amine-modified microspheres (200nm diameter) were injected into anterior segments during perfusion. Relative intensity of fluorescence was used to visualize and separate low and high flow areas of the TM. RNA was isolated and quantitative PCR arrays were used to identify ECM and adhesion gene differences in high and low flow areas of the TM from respective regions of perfused eyes.
Differences in fold regulation of ECM genes, including MMPs, proteoglycans, integrins, and cell adhesion molecules were seen when comparing low and high flow areas of the TM both at physiological and elevated pressures. MMPs and SPARC were among the genes that were up-regulated in high flow regions under physiological conditions. At 2x pressure versican was one of the major genes up-regulated in high flow regions, in comparison with low flow regions at the same pressure conditions. A variety of genes were down-regulated in high flow regions in comparison with low flow regions at both 1x and 2x pressures, including integrins, cell adhesion molecules and collagens. Among the multiple genes that changed in strictly low or strictly high flow regions in response to elevated pressures were versican and SPARC, whose expression levels were inversely correlated to each other. This suggests a differential response to increased pressure in low and high flow regions of the TM.
Here we have shown differences in mRNA levels of several ECM genes in low and high flow areas of the TM at physiological and elevated pressures. These results provide further evidence for segmental differences in ECM composition that may in turn influence aqueous outflow resistance in the TM.
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