Targeting CCR2+ macrophages and SPP1 in HFpEF: the promise of vagus nerve stimulation

Abstract Background Heart failure with preserved ejection fraction (HFpEF) affects around 50% of heart failure patients, and is associated with high morbidity and limited therapeutic options. Immune and inflammatory mechanisms, particularly cardiac resident macrophages (CRM), have been implicated in HFpEF pathology, though their specific contribution remains unclear. Prior studies indicate that transcutaneous vagus nerve stimulation (tVNS) may reduce fibrosis and inflammation in HFpEF, suggesting a potential for immune modulation treatment. Osteopontin (SPP1), a pro-inflammatory cytokine, may critically influence these immune pathways. Purpose This study aims to elucidate the role of CCR2+ CRM in HFpEF and evaluate the effect of tVNS on modulating their inflammatory behavior. Additionally, it investigates the expression of SPP1 within the HFpEF immune environment, and its impact on cardiac fibrosis and inflammation. Methods HFpEF was induced in male C57BL/6 CCR2-RFP mice using a high-fat diet and L-NAME, a nitric oxide synthase inhibitor. Mice received either tVNS or sham treatment for four weeks. Cardiac function was assessed via echocardiography, and single-cell RNA sequencing (scRNAseq) was employed to characterize CRM subsets. SPP1 expression levels were analyzed across control, HFpEF, and HFpEF + tVNS groups to assess its involvement in inflammation and fibrosis. In parallel, an SPP1 knockout (SPP1-KO) HFpEF model evaluated the effects of SPP1 deletion on the HFpEF phenotype. Results Induction of HFpEF led to diastolic dysfunction, cardiac hypertrophy, and fibrosis, confirmed through echocardiographic and histological assessments. scRNAseq analysis identified four CRM subtypes: TLF+, MHC2+, CCR2+, and IFNγ-responsive, with HFpEF specifically increasing CCR2+ CRM (Figure 1). tVNS significantlyimproved HFpEF phenotype and fibrosis, reduced CCR2+ CRM percentage and reversed their transcriptional profile towards baseline, particularly affecting pro-inflammatory and fibrotic genes, including SPP1. Notably, SPP1 levels were elevated in HFpEF, especially within CCR2+ CRM, but were substantially decreased following tVNS (Figure 2). The SPP1-KO model showed reduced fibrosis and improved diastolic function in HFpEF, further confirming SPP1’s role in driving cardiac inflammation and fibrosis. Conclusions CCR2+ CRM may play a central pathogenic role in HFpEF through the promotion of inflammation, fibrosis, and monocyte recruitment. Both tVNS and SPP1 deletion ameliorated the HFpEF phenotype, with tVNS modulating CCR2+ CRM and reducing SPP1 expression, linking both to inflammatory and fibrotic responses in disease progression. These findings highlight the potential of targeting CCR2+ CRM and SPP1 as therapeutic approaches for HFpEF and underscore the promise of tVNS as a non-invasive treatment strategy to mitigate HFpEF-related cardiac remodeling.Figure 1 Figure 2