Endothelial Cell Transcriptomics Reveal Activation of Ribosomal-related Pathways in Chronic Thromboembolic Pulmonary...

Pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH) are rare, severe forms of pulmonary hypertension (PH) characterized by elevated mean pulmonary arterial pressure (mPAP) and ∼20% mortality at 3 years. PAH is defined by progressive obliterative vasculopathy, whereas CTEPH results from persistent pulmonary artery obstruction by fibrotic thrombotic material, leading to vascular remodelling, right ventricular hypertrophy, and heart failure.

Endothelial colony-forming cells (ECFCs) derived from PAH and CTEPH patients and healthy-controls were analysed to identify disease-specific molecular and functional alterations. Transcriptomic profiling was integrated with functional assays, including global protein synthesis, mitochondrial bioenergetics, intracellular Ca²⁺ dynamics, and cellular ultrastructural assessment by transmission electron microscopy (TEM). The effects of riociguat, the approved therapy for inoperable or persistent post-surgical CTEPH, were also evaluated.

Significant differences in gene expression profiles were observed among PAH-ECFCs, CTEPH-ECFCs, and control-ECFCs. CTEPH-ECFCs, exhibited a unique upregulation of ribosomal and translation-related genes, accompanied by increased global protein synthesis. Network analysis revealed a highly connected ribosomal-translational hub within CTEPH transcriptome signature. CTEPH-ECFCs also exhibited mitochondrial remodelling, increased endoplasmic reticulum-mitochondria contacts, altered intracellular Ca²⁺ handling, and reduced maximal respiratory capacity. Riociguat did not reverse these abnormalities.

Dysregulated protein biosynthesis is a characteristic feature of CTEPH, distinguishing them from PAH. Our findings highlight a coordinated translation-mitochondria-MAM axis potentially involved in endothelial dysfunction and vascular remodelling, supporting the need for therapies targeting disease-specific molecular pathways beyond soluble guanylate cyclase stimulation.