Abstract 15650: MicroRNA-21 Integrates Pathobiological Signaling in Pulmonary Vascular Endothelial Cells: Implications for Pulmonary Arterial Hypertension
Background: Pulmonary arterial hypertension (PAH) is a complex constellation of disorders with characteristic vascular histopathology that, in part, results from dysregulated endothelial cell (HPAEC) survival and proliferation. MicroRNA-21 (miR-21) is a pleiotropic regulatory factor that is induced by hypoxia and predicted to target the type 2 bone morphogenetic protein receptor (BMPRII), both of which mediate PAH pathology. We propose that miR-21 integrates BMPRII and hypoxia-dependent signaling in order to control HPAEC phenotypes observed in PAH.
Methods and Results: As assayed by quantitative polymerase chain reaction, miR-21 is increased in monocrotaline-treated rat lung tissue, an in vivo model of PAH [5.2 ± 0.57 (fold change ± SEM)]. Under hypoxia, both mature (1.8 ± 0.11-fold) and primary transcripts of miR-21 (2.2 ± 0.17-fold) are increased in cultured HPAECs. The master transcriptional regulator in hypoxia, Hypoxia Inducible Factor-1α (HIF-1α), actively regulates this process, as miR-21 is increased both in HPAECs transduced with stabilized HIF-1α (1.5 ± 0.13-fold), and in mouse lung constitutively expressing HIF proteins [Von Hippel Lindau null tissue (3.5 ± 0.40-fold)]. To determine whether miR-21, in turn, regulates BMPRII expression, we altered miR-21 expression in HPAECs by forced expression with oligonucleotide mimics. This treatment decreased BMPRII protein expression by 35% [2.4 ± 0.37 (miR-21); 3.7±0.26 (control) arbitrary gel densitometry units, p < 0.02]. Finally, corresponding with the known effects of BMPRII mutations on HPAEC survival and apoptosis, miR-21 reduced proliferation as assayed by BrdU uptake [6.9 ± 0.25 (miR-21) vs. 9.1± 0.37 (control) RFU/cell, p<0.001], as well as increased apoptotic signaling as assayed by caspase-3/7 activity [4.3 ± 0.45 (miR-21); 2.4 ± 0.19 (control) arbitrary luminescence units/cell, p<0.01].
Conclusions: The regulation and function of miR-21 in pulmonary vascular endothelial cells are tightly linked to hypoxia and BMPRII signaling, suggesting an important role for this microRNA in the progression of PAH.
- © 2010 by American Heart Association, Inc.