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N. Comes, T. Borras; Individual Response to Pressure and Relative Abundance of Relevant Genes in Human Trabecular Meshwork. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3288.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate whether the individual clinical response to pressure could be elucidated at the molecular level by differential gene expression of relevant genes of the human trabecular meshwork (TM). A panel of 21 genes was selected on the basis of their linkage, association with glaucomatous conditions and/or involved in mechanisms relevant for TM function. Our goal was to study the individual molecular response to pressure by determining their relative expression pattern under normal and elevated IOP.
Paired anterior segments from non-glaucomatous post-mortem individuals (n=5) were perfused for 24h to baseline (C=0.24±0.03 µl/min/mmHg). The perfusion was then set up at constant pressure, with one eye maintained at its physiological pressure and the contralateral raised ~35 mmHg over its own baseline. At 3d, TMs were dissected and total RNA was extracted. Differential expression of each individual’s 21 selected genes was determined simultaneously and in triplicates by RT-TaqMan PCR using 18S as a control. The individual relative abundance of each gene was calculated comparing its average expression to that of its own 18S under the same condition. The individual response to pressure was evaluated by calculating fold changes of high vs. normal pressure samples using the formula 2-deltadeltaCt (Ct=cycle at threshold).
Under normal pressure, the relative abundance of most of the 21 genes (81%) was similar in all individuals. Matrix GLA (MGP) and αB-crystallin showed the highest level of expression while ELAM1, thrombomodulin, cochlin, IGF1 and osteoglycin (OGN) were the least expressed. ANGPTL7 (CDT6)’s relative abundance was individual-dependent. In contrast, only 3 of the 21 genes, CDT6, MYOC and MGP (14%), responded to pressure (up or down more than 1.5-fold) in all individuals (general responder genes). Of the three, only CDT6 was an up-responder in all of them. With the exception of transgelin, all remaining selected genes, such as connective tissue growth factor, IL-6, or superoxide dismutase1 were up or down regulated in only 1-3 of the five individuals (individual responder genes). The rank of response of all genes (based in fold-change) was different in each individual.
Although the relative abundance of relevant genes appeared to be mostly general, the molecular response to pressure had a more significant individual response component. The elucidation of pressure-responding genes with an individual component might help understanding the different responses to pressure observed in the clinic, and perhaps reveal compensatory mechanisms for the regulation of IOP.
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