Cross-talk between miR-29 and transforming growth factor-betas in trabecular meshwork cells

To investigate the interactions between microRNA-29 (miR-29), a negative regulator of extracellular matrix (ECM), and transforming growth factors (TGF)β-1 and TGFβ-2.

Changes in expression of the miR-29 family were analyzed by quantitative-PCR (Q-PCR) after treatment with TGFβ1 and TGFβ2 (1 ng/mL). TGFβ1 and TGFβ2 were evaluated at gene expression and protein levels by Q-PCR and ELISA, respectively, in human trabecular meshwork (HTM) cells transfected with miR-29b or scramble control. TGFβ1 promoter activity was analyzed using an adenovirus with the reporter SEAP. The effects of miR-29b and TGFβ2 on ECM gene expression were evaluated in cells transfected with miR-29b or scramble control and treated with TGFβ2, and the expression of ECM genes was analyzed by Q-PCR.

TGFβ2 but not TGFβ1, downregulated the three members of the miR-29 family. Overexpression of miR-29b antagonized the effects of TGFβ2 on the expression of several ECM components. MiR-29b decreased the expression of TGFβ1 at the promoter, transcript, and protein levels but had only a minor effect on the expression of active TGFβ2. The inhibition of TGFβ1 by miR-29b was partially recovered after co-transfection with a plasmid-expressing bone morphogenetic protein 1.

Results showed some level of crosstalk between TGFβs and miR-29. Specifically, the downregulation of miR-29 by TGFβ2 contributed to the induction of several ECM components by this cytokine in TM cells. This observation, together with the inhibitory effects of miR-29b on the expression of TGFβ1, suggests that the miR-29 family could play an important role in modulating TGFβs on the outflow pathway.