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W. Xue, V. Sarthy, M. Hernandez; Microarray Analysis of Gene Expression Changes in MüLler Cells in Response to Hydrostatic Pressure. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5476. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Müller cells are the principal glial cells of the retina that form the outer and inner limiting membranes; at the inner limiting membrane, Müller cells are in direct contact with ganglion cells. Recent cell biological and microarray studies in animal models of glaucoma have shown that retinal Müller cells in situ upregulate the expression of certain genes in response to increased intraocular pressure. Whether pressure has a direct effect on Müller cells or the observed changes are due to Müller cell response to neuronal changes is not known. To address this question directly, we have examined gene expression changes in Müller cells grown in a pressure chamber.
Rat Müller cells (rMC-1) were exposed to elevated (60 mmHg) hydrostatic pressure (HP) or were maintained at ambient pressure (CP) for 6h and 24h. RNA was extracted and Affymetrix GeneChip microarrays were used to identify HP-responsive genes. Statistical analysis followed the MIAMI guideline of microarray data analysis, and ANOVA model was corrected by an empirical Bayesian method using LIMMA for small sample size. Pathways were identified by Ingenuity Pathways Analysis software. Realtime RT-PCR (qPCR) was used to validate several candidate genes.
At 6h, a total 208 genes showed > 1.5-fold change with p<0.01. 43 genes were upregulated while 35 genes down regulated. By qPCR, Amphiregulin (AREG) increased 2.88±0.07-fold, S100a1-fold increased 1.75±0.28, while Bone Morphogenic Protein Receptor, type II (serine/threonine kinase) (BMPR2) was downregulated 3.90±0.46-fold. Ingenuity canonical pathway analysis showed that ERK/MAPK, SAPK/JNK, TGF-beta, WNT/β-catenin, and actin cytoskeleton were significantly changed in Müller cells under high pressure.
Among the upregulated genes, BMP4 and GPNMB are known to be involved in anterior segment dysgenesis associated glaucoma or development of pigmentary glaucoma in mice. BMP4 and BMPR2 are part of the TGF-beta pathway known to be neuroprotective in the CNS. AREG is related to EGF and TGF-α, both of which are elevated in glaucomatous eyes. Finally, ERK/MAPK, SAPK/JNK, TGF-beta, WNT/β-catenin, and actin cytoskeleton pathways maybe part of Müller cell activation in glaucoma. These data show that Müller cells can directly respond to elevated pressure and HP-responsive genes may be important in the maintenance and survival of the retinal ganglion cells in glaucoma.
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