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J. Li, B.J. Tripathi, R.C. Tripathi, K.V. Chalam; Trabecular Cell Expression of Fibronectin and MMP–3 is Modulated by Aqueous Humor Growth Factors . Invest. Ophthalmol. Vis. Sci. 2004;45(13):4421.
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Purpose: To investigate the mRNA and protein expression of fibronectin and matrix metalloproteinase (MMP)–3 by trabecular cells that were treated with growth factors present in primary and secondary aqueous humor. Methods: Serum–deprived porcine trabecular cells were incubated for 48 hrs or 7 days in medium containing either primary or secondary aqueous humor growth factors or in serum–free medium as controls. We extracted total RNA, performed RT–PCR using primer pairs specific for fibronectin, MMP–3 and GAPDH, and quantified the products. We utilized Western blot analysis to detect and quantify fibronectin and MMP–3 protein levels in the cellular extracts of total protein samples. Results: Compared with controls, expression of fibronectin mRNA by trabecular cells was increased by 50 and 100% after incubation in primary aqueous humor growth factors for 48 hrs or 7 days, respectively, and 50 and 130% after incubation in secondary aqueous humor growth factors. MMP–3 mRNA expression was decreased by 25 and 50% after incubation in primary aqueous humor growth factors for 48 hrs or 7 days, respectively, and 80 and 85% after incubation for 48 hrs or 7 days, respectively, in secondary aqueous humor growth factors. Fibronectin protein increased 3.5–fold and 6–fold after incubation for 48 hrs with primary or secondary aqueous humor growth factors, respectively; after 7 days, the level increased 4– and 7–folds, respectively. MMP–3 protein was not detectable by Western blotting. Conclusions: The up–regulation of fibronectin mRNA by trabecular cells exposed to growth factors present in secondary aqueous humor augmented by the down–regulation of MMP–3 mRNA contributed to the accumulation of fibronectin. Our findings open the possibility that induction of MMP–3 gene expression in the trabecular meshwork of glaucomatous eyes could effectively reduce the buildup of fibronectin in the aqueous outflow pathway to decrease outflow resistance in glaucomatous states of the eye.
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