Circulating immune cell signature analysis in HFpEF across species [scRNA-Seq - mouse]

Background: HFpEF is a heterogeneous clinical picture that is closely related to extracardiac comorbidities such as obesity, hypertension and diabetes and is associated with chronic, low-grade systemic inflammation. Previous studies on myocardial biopsies of HFpEF patients showed intramyocardial inflammatory activity, suggesting that the inflammatory processes in HFpEF are predominantly systemic and exhibit compartment specific-patterns. Methods: We performed single cell RNA sequencing (scRNA-seq) of peripheral blood mononuclear cells (PBMCs) of HFpEF patients (n=6), HFrEF patients (n=8) and healthy controls (n=7) taking obesity status into account. For validation, bulk RNA sequencing was performed on whole blood samples. In parallel, the systemic immune cell response was investigated in a HFpEF mouse model (induced by a high-fat diet plus L-NAME), with one group additionally administered the anti-inflammatory agent nitro-oleic acid (NO₂-OA). Results: Analysis of human PBMCs revealed a HFpEF-specific inflammatory fingerprint, which manifested in obesity-related increased expression of cytokine signaling genes (e.g. CCL2, TNF) and obesity-independent increases in mitochondrial-associated activity. In the mouse model, HFpEF animals showed a comparable increase in inflammatory markers, with treatment with NO₂-OA leading to a partial normalization of immunological signatures and a significant improvement in diastolic function. Conclusion: Our results demonstrate that the immune cells of patients with HFpEF are characterized by a distinct transcriptional immune signature that differs from that of patients with HFrEF. The conserved immunological signatures between humans and mice, and the beneficial effect of NO₂-OA in a preclinical model, provide important translational insights and generate hypotheses for personalized interventions in HFpEF.