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J Chen, BJ Tripathi, RC Tripathi; Aqueous Humor Growth Factors Decrease mRNA Expression of Decorin by Trabecular Cells . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1046.
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Purpose: To determine the effect of growth factors (GFs) present in primary and secondary aqueous humor on the expression of decorin mRNA by trabecular cells. Methods: First-passage porcine trabecular cells were maintained in serum-free medium (SFM) for 48 hrs prior to incubation in SFM that contained a mixture of GFs at concentrations either present in primary aqueous humor (1.36 ng/ml bFGF, 1.74 ng/ml IGF-1, 14.2 mg/ml transferrin; 0.57 ng/ml TGF-ß1 and 2.47 ng/ml TGF-ß2) or those present in secondary aqueous humor (0.91 ng/ml bFGF, 79.4 ng/ml IGF-1, 23.1 mg/ml transferrin, 3.86 ng/ml TGF-ß1, and 3.46 ng/ml TGF-ß2), or in SFM alone for 48 hrs or for 7 days. After extraction of total RNA, we performed RT-PCR using primer pairs specific for porcine decorin. We quantified and normalized the products to mRNA expression of GAPDH as the internal control. Results: Using primer pairs specific for decorin, a single PCR-amplified product with the expected size of 253 bp was obtained from trabecular cells. Compared to cells maintained in SFM, the expression of decorin mRNA was down-regulated by 20% after 48 hrs and 50% after 7 days of incubation in primary aqueous humor GFs. After 48 hrs and 7 days of incubation in secondary aqueous humor GFs, the expression of decorin mRNA by trabecular cells was decreased 50% and 80%, respectively. Conclusion: Because proteoglycans, such as decorin, imbibe fluids, these molecules have the capacity to influence resistance to aqueous outflow in the trabecular meshwork. The combination and concentration of GFs in aqueous humor, especially the increased amount of TGF-ßs in secondary aqueous humor, probably down-regulated the mRNA expression of decorin by trabecular cells and thus, are implicated in suppressing excessive production of this proteoglycan in the trabecular meshwork of the aqueous outflow pathway.
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