Molecular Pathogenesis of Connective Tissue Disease-Associated Pulmonary Arterial Hypertension: A Narrative Review

Pulmonary arterial hypertension (PAH) is a lethal condition marked by the proliferation and remodeling of small pulmonary arteries, ultimately leading to right ventricular hypertrophy and right heart failure. PAH secondary to connective tissue diseases (CTDs) is a progressive complication with a complex pathogenesis that results in the reduced efficacy of vasodilation-based therapies and poor clinical outcomes. Systemic sclerosis is the most commonly associated CTD with PAH in Western countries and has been most extensively investigated. Systemic lupus erythematosus and other CTDs may also be associated with PAH; however, they are less studied. In this review, we explore the general pathobiology of PAH, with a particular emphasis on recent advances in the molecular pathogenesis of CTD-PAH, including endothelial cell dysfunction, dysregulated cell proliferation and vascular remodeling, extracellular matrix remodeling, in situ thrombosis, right ventricular dysfunction, genetic aberrations, and immune dysregulation. We also conduct a thorough investigation into the potential serum biomarkers and immune dysregulation associated with CTD-PAH, summarizing the associated autoantibodies, cytokines, and chemokines. Furthermore, relevant animal models that may help unravel the pathogenesis and contribute to the development of new treatments are also reviewed.