Abstract 13932: Lung-targeted Sin3a Gene Therapy as a Promising Strategy to Restore Bmpr2 Expression in Pulmonary Arterial Hypertension

Abstract

Background: Pulmonary arterial hypertension (PAH) is a fatal lung disease of multifactorial etiology, with no curative treatment. Several studies have previously suggested that hypermethylation of the BMPR2 promoter may be associated with gene repression and disease progression. However, the underlying mechanisms have yet to be discovered. Sin3A/B (Switch-Independent 3) plays a critical role in the transcriptional regulation of genes through various epigenetic mechanisms. Here, we investigated for the first time the role of SIN3a in the regulation of BMPR2 methylation and expression in PAH. Methods: Expression of SIN3a was analyzed by qRT-PCR and western blot in lung tissues from PAH patients and rodent models of PAH. Using a gain- and loss-of-function approach, we investigated the role of SIN3a on cell proliferation (BrdU assay) and migration (Boyden chamber assay), and BMPR2 levels in primary human pulmonary arterial smooth muscle cells (hPASMC) and endothelial cells (hPAEC). The methylation level was analyzed by MS-PCR. The therapeutic potential of SIN3a was tested in vivo in the Sugen/Hypoxia (SuHx) mouse and monocrotaline (MCT) rat models of PAH using an adeno-associated virus 1 encoding human SIN3a. Results: We found a significant downregulation of SIN3a expression in the lung samples from PAH patients, SuHx mice, and MCT rats. In hPASMC and hPAEC, our results showed that SIN3a inhibits cell proliferation, migration, and upregulates BMPR2 through two distinct pathways. In hPASMC, our data showed that SIN3a upregulates BMPR2 expression by inhibiting the methylation level of the BMPR2 promoter. In hPAEC, SIN3a restored BMPR2 expression independently of the methylation status by upregulating the FOXK2 transcription factor. In vivo , our results showed that restoring SIN3a expression by gene therapy significantly decreased MCT- and SuHx-induced PAH as illustrated by decreased vascular and RV remodeling, hypertrophy, PAP and RVSP. Conclusions: Altogether, our study revealed that SIN3a plays a critical role in the regulation of BMPR2 expression by modulating the lung epigenetic landscape. Additionally, our study identifies lung-targeted SIN3a gene therapy as a new promising therapeutic strategy for treating PAH patients.