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Guadalupe Villarreal, Jr., Dong-Jin Oh, Min Hyung Kang, Douglas J. Rhee; Coordinated Regulation of Extracellular Matrix Synthesis by the MicroRNA-29 Family in the Trabecular Meshwork. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4650.
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The microRNA-29 (miR-29) family has emerged, in various tissues, as a key modulator of extracellular matrix (ECM) homeostasis. In this study, we investigate the role of the miR-29 family in the regulation of ECM accumulation in the trabecular meshwork (TM) under basal and TGF-β2 stimulatory conditions.
Human TM cells were incubated with 2.5 ng/mL activated, recombinant human TGF-β2 for 24, 48, and 72 h. A specific pharmacologic inhibitor, SIS3, was used to block SMAD3 function in the context of TGF-β2 stimulation. Changes in the expression of the miR-29 family were assessed by real-time PCR. The effect of miR-29 molecules and inhibitors on ECM levels was determined by immunoblot analysis.
All three members of the miR-29 family were expressed in cultured TM cells. Incubation of TM cells with TGF-β2 induced miR-29a and suppressed miR-29b levels, with no significant effect on miR-29c. Additional studies revealed that SMAD3 inhibition upregulates miR-29a, miR-29b, and miR-29c expression under basal conditions. Under TGF-β2 stimulatory conditions, miR-29b expression was significantly reduced by SMAD3 inhibition, while miR-29a and miR-29c levels were not significantly affected. Gain and loss-of-function experiments demonstrated that the miR-29 family functions as a critical suppressor of various ECM proteins in the TM under basal and TGF-β2 stimulatory conditions.
The findings derived from this study identify the miR-29 family as an important regulator of ECM expression in the TM and suggest that its modulation by TGF-β2 may be important in controlling ECM accumulation. Together, these data provide further insights into the complex molecular mechanisms governing ECM homeostasis in the TM.
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