Abstract Rationale Pulmonary arterial hypertension (PAH) is a chronic lung disease of increased pulmonary artery (PA) pressure and remodeling leading to right ventricular (RV) failure and death. While originating in the lungs, PAH symptom severity and survival are linked to RV dysfunction. We hypothesized that a reverse approach of analyzing dysregulated genes in late stage failing RV may uncover new therapeutic targets in the lungs to attenuate PH progression in earlier disease stages. The incidence of PAH is much higher in female patients than males; a striking 4:1 ratio. Distressingly, knowledge on which sex-biasing factors underlie female predominance in PAH is scarce. Methods Online-available RNA sequencing datasets of RV from PAH patients and monocrotaline (MCT) PH rats were used. Human lung tissue was obtained from the Pulmonary Hypertension Breakthrough Initiative Biobank. In vitro experiments were performed in PA smooth muscle cells (SMC) and fibroblasts (FB) isolated from a female donor and PAH patient. Novel Sry-modified rats where chromosomal and gonadal sex are disentangled were employed. Gene silencing was performed in MCT rats by siRNA intratracheal instillation. Results We discovered that the gene coding for small leucine-rich proteoglycan Biglycan (BGN), is highly and significantly upregulated between PAH RV and control RV, which is shared between human and rat. BGN expression is also upregulated in lungs of PAH patients and PH rats versus their respective healthy controls. BGN is coded on the X chromosome and is an x-inactivation-escapee gene. Both in RV and lungs, BGN expression is upregulated to a higher extent in female PAH patients compared to male. Female MCT rats express significantly higher levels of BGN in lungs compared to male rats. Male Sry rats with XX chromosomes express significantly higher levels of BGN in their lungs vs male rats with XY chromosomes. Accordingly, XX male rats exhibit worse PH with higher RVSP and enhanced PA remodeling. Online single-cell atlases revealed that BGN is enriched in SMC and FB in the lungs. Indeed, BGN expression was upregulated in PAFB and PASMC isolated from PAH patients. Functionally, silencing BGN inhibited proliferation, collagen production, but promoted apoptosis in PAH-PAFB and PAH-PASMC. Lastly, intratracheal instillation of BGN siRNA reduced MCT- induced PH in female rats. Conclusion Higher BGN expression may underlie female susceptibility to PAH by promoting a proliferative, fibrotic and anti-apoptotic phenotype in PASMC and PAFB, leading to PA vascular remodeling. Silencing BGN in the lungs may be a novel therapeutic approach against PAH. This abstract is funded by: American Heart Association
Medzikovic et al. (Fri,) studied this question.