Background and Aims: Pulmonary hypertension (PH) is characterized by progressive pulmonary vascular remodeling and increased right ventricular afterload, ultimately leading to right heart failure. Mitochondria are key regulators of cardiac energy metabolism, redox balance, and cellular survival under hemodynamic stress. The impact of sex on PH incidence and outcome is well recognized but the molecular mechanisms underlying sex-specific cardiac metabolic adaptation and therapeutic responses remain incompletely understood.
This study aimed to evaluate functional, morphological, and mitochondrial alterations in the myocardium of monocrotaline (MCT)-induced PH mice, with special regard to sex differences and the effects of the dual endothelin receptor antagonist macitentan (MAC).
Methods: Male (♂n=19) and female (♀n=25) C57BL/6 mice were divided into three groups: untreated controls (Ctrl.), MCT-induced PH (MCT) animals, and PH-mice treated with MAC treatment (MCT_MAC). Hemodynamic (RVPsys) and echocardiographic parameters (TAPSE, RAarea, FAC) were recorded to validate successful disease induction. Histological analyses, based on Hematoxylin–Eosin (H&E) and Sirius Red (SI) stainings, were evaluated by using a semiquantitative sum-score system. To assess sex- and treatment-dependent transcriptional patterns in cardiac tissue of PH mice, a pathway focused RT-PCR based gene expression analysis including 84 genes related to oxidative phosphorylation (OXPHOS), fatty acid metabolism, and mitochondrial biogenesis was used.
Results: Hemodynamic measurements validated successful PH induction with partial improvement under MAC therapy.
Of the 84 mitochondrial genes analyzed, 19 showed (>±2.5fold) expression changes after PH induction, with 8 genes upregulated in males and 11 in females. Males showed a pronounced upregulation of OXPHOS-associated genes, including Cox8c (+11.12fold) and Cox11 (+6.65fold) whereas females exhibited only mild induction of these genes (Cox11 +1.43-fold, Cox8c +1.57fold). Conversely, females showed a higher upregulation of mitochondrial quality-control and lysosomal genes, particularly Atp6v1g3 (+44.11fold) compared to males Atp6v1g3 (+5.25fold).
Under MAC treatment, males maintained elevated expression of OXPHOS genes whereas females showed normalization of mitochondrial quality-control genes and stable OXPHOS expression.
These treatment-dependent transcriptional profiles aligned with the functional and structural findings, showing sustained OXPHOS activation in males but enhanced mitochondrial recovery in females under MAC therapy.
Conclusions: MCT-induced PH triggered sex-dependent mitochondrial changes. Males displayed strong and sustained activation of OXPHOS genes consistent with elevated metabolic stress, while females upregulated mitochondrial quality-control pathways reflecting adaptive protection. Under MAC therapy, females demonstrated greater transcriptional normalization, suggesting improved mitochondrial recovery and resilience compared to males. These findings underline the importance of sex-specific differences in mitochondrial transcriptional dysregulation when developing targeted metabolic therapies for pulmonary hypertension.
