MicroRNA-124 Controls the Proliferative, Migratory, and Inflammatory Phenotype of Pulmonary Vascular Fibroblasts

Abstract

Rationale Pulmonary hypertensive remodeling is characterized by excessive proliferation, migration, and proinflammatory 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 microRNA-124 (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 monocyte chemotactic protein-1 expression of hypertensive fibroblasts, whereas anti–miR-124 treatment of control fibroblasts resulted in their increased proliferation, migration, and monocyte chemotactic protein-1 expression. Furthermore, the alternative splicing factor, polypyrimidine tract–binding protein 1, 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. The effects of miR-124 on fibroblast proliferation were mediated via direct binding to the 3′ untranslated region of polypyrimidine tract–binding protein 1 and subsequent regulation of Notch1/phosphatase and tensin homolog/FOXO3/p21Cip1 and p27Kip1 signaling. We showed that miR-124 directly regulates monocyte chemotactic protein-1 expression in pulmonary hypertension/idiopathic pulmonary arterial hypertension fibroblasts. Furthermore, we demonstrated that miR-124 expression is suppressed by histone deacetylases and that treatment of hypertensive fibroblasts with histone deacetylase inhibitors increased miR-124 expression and decreased proliferation and monocyte chemotactic protein-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 histone deacetylase inhibitors, should be investigated.

Translational Advances in the Field of Pulmonary Hypertension.Translating MicroRNA Biology in Pulmonary Hypertension. It Will Take More Than “miR” Words

“…Elevated miR-145 expression was observed in primary PASMCs cultured from patients with PAH with loss-of-function BMPR2 mutations as well as in the lungs of BMPR2-deficient mice. Importantly, mice with genetic deletions of miR-145 exhibited protection against PH (28). Conversely, miR-140 has been implicated in the regulation of Smad ubiquitination regulatory factor 1 (SMURF1), an E3-ubiquitin protein ligase 1, that in turn modulates BMPR2 signaling and PAH in vivo (29).…”

“…In vitro gain-and loss-of-function experiments revealed that decreased miR-124 in PAAFs from patients with PAH led to increased proliferation and migration through modulating the polypyrimidine tract-binding protein 1 (PTPB1) and subsequent inhibition of the cell cycle (28). Separately, the miR-130/301 family has been found to modulate extracellular matrix stiffening in PAAFs (31) via interfacing with the transcriptional coactivators YAP (Yes-associated protein) and TAZ (transcriptional coactivator with PDZ-binding motif).…”

miR-29a-3p Attenuates Hypoxic Pulmonary Hypertension by Inhibiting Pulmonary Adventitial Fibroblast Activation

“…4,5 During the remodeling, pulmonary adventitial fibroblasts (PAFs) are highly activated and undergo phenotype switch characterized by excessive proliferation, migratory, and inflammatory activity. 6,7 Therefore, inhibition of the aberrant activation of PAFs may reverse the remodeling process of pulmonary vascular adventitia and have therapeutic potential for HPH. 8 Increasing evidence shows that miRNAs, especially miR-29 family members, participate in the development of organ fibrosis via regulating the activation of fibroblasts.…”

“…[9][10][11] Downregulation of miR-29 underlies transforming growth factor-β-mediated pulmonary fibrosis, and overexpression of miR-29 inhibits bleomycin-induced pulmonary fibrosis. 12 Although PAFs in HPH undergo the similar activated phenotype to that in lung fibrosis, 6 the role of miR-29 family member in the hypoxia-induced activation of PAFs and the development of HPH is not known. On the other hand, hypoxia-inducible factor-1α (HIF-1α), a key transcription factor mediating cellular response to hypoxia, and Smad3, which can inhibit miR-29 expression in organ fibrosis, are interdependent in hypoxia.…”

Emerging Roles for Histone Deacetylases in Pulmonary Hypertension and Right Ventricular Remodeling (2013 Grover Conference series)

“…82 More recently, the efficacy of HDAC inhibitors in PH fibroblasts was linked to induction of miR-124. 86 miR-124 had previously been shown to have antiproliferative action in glioblastoma cells. 87 In cultured PH fibroblasts (both human and bovine), miR-124 expression was found to be dramatically downregulated.…”