MicroRNA-124 Controls the Proliferative, Migratory, and Inflammatory Phenotype of Pulmonary Vascular Fibroblasts
Rationale: Pulmonary hypertensive remodeling is characterized by excessive proliferation, migration, and pro-inflammatory activation of adventitial fibroblasts. In culture, fibroblasts maintain a similar "activated" phenotype. The mechanisms responsible for generation/maintenance of this phenotype remain unknown.
Objective: We hypothesized that aberrant expression of miR-124 regulates this activated fibroblast phenotype, and sought to determine the signaling pathways through which miR-124 exerts effects.
Methods and Results: We detected significant decreases in miR-124 expression in fibroblasts isolated from calves and humans with severe pulmonary hypertension. Overexpression of miR-124 by mimic transfection significantly attenuated proliferation, migration, and MCP-1 expression of hypertensive fibroblasts, while anti-miR-124 treatment of control fibroblasts resulted in their increased proliferation, migration, and MCP-1 expression. Furthermore, the alternative splicing factor, polypyrimidine tract-binding protein 1 (PTBP1), was shown to be a direct target of miR-124 and to be upregulated both in vivo and in vitro in bovine and human pulmonary hypertensive fibroblasts. miR-124 effects on fibroblast proliferation were mediated via direct binding to the 3'UTR of PTBP1 and subsequent regulation of Notch1/PTEN/FOXO3/p21Cip1 and p27Kip1 signaling. We showed that miR-124 directly regulates MCP-1 expression in PH-/IPAH-Fibs. Further, we demonstrated that miR-124 expression is suppressed by histone deacetylases (HDACs), and that treatment of hypertensive fibroblasts with HDAC inhibitors increased miR-124 expression and decreased proliferation and MCP-1 production.
Conclusions: Stable decreases in miR-124 expression contribute to an epigenetically reprogrammed, highly proliferative, migratory, and inflammatory phenotype of hypertensive pulmonary adventitial fibroblasts. Thus therapies directed at restoring miR-124 function, including HDAC inhibitors, should be investigated.
- splicing factors
- pulmonary hypertension
- vascular remodeling
- Received April 19, 2013.
- Revision received October 10, 2013.
- Accepted October 11, 2013.