Vagal Stimulation Rescues HFpEF by Altering Cardiac Resident Macrophage Function

BACKGROUND: We previously showed in a rat model of heart failure with preserved ejection fraction (HFpEF) that transcutaneous vagus nerve stimulation (tVNS) reduced cardiac fibrosis and inflammation. However, macrophage-mediated mechanisms through which tVNS rescues cardiac function remain poorly understood. METHODS: We induced HFpEF in 8-week-old mice by a combination of a high-fat diet and l -NG-nitro arginine methyl ester for 5 weeks, followed by 4 weeks of tVNS or sham stimulation. At this time, we analyzed cardiac function by echocardiography and immune cell numbers by single-cell RNA sequencing and flow cytometry. RESULTS: Our data demonstrate that HFpEF mice exhibited diastolic dysfunction, left ventricular hypertrophy, and fibrosis, consistent with HFpEF, and that tVNS significantly improved HFpEF severity. Analysis of merged single-cell RNA sequencing data from control, HFpEF+sham, and HFpEF+tVNS mice showed that HFpEF was associated with the accumulation of Spp1 -expressing CCR2 (C-C chemokine receptor type 2) + cardiac resident macrophages (CRM). Furthermore, treatment with tVNS reduced the number of CCR2 + CRM and the expression of Spp1 while also inducing the expression of Igf1 in TLF + (Timd4 + [T-cell immunoglobulin and mucin domain containing 4 + ]/Lyve1 + [Lymphatic vessel endothelial hyaluronan receptor 1 + ]/Folr2 + [Folate receptor 2 + ]) and MHC2 + (Major histocompatibility complex 2 + ) CRM. Global deletion of Spp1 or blockade of CCR2 + CRM recruitment improved HFpEF, whereas TLF + /MHC2 + specific deletion of Igf1 reversed the protective effect of tVNS on HFpEF. The benefits of tVNS were also abolished in the setting of disrupted acetylcholine/α7nAChR (α7 nicotinic acetylcholine receptor) signaling, either via pharmacological inhibition of α7nAChR or choline acetyltransferase deletion in CD4 + (cluster of differentiation) T cells. CONCLUSIONS: Collectively, our data indicate that tVNS improves HFpEF by reducing Spp1 expressing CCR2 + CRM and inducing expression of proreparative Igf1 in TLF + /MHC2 + CRM. These effects are mediated through cholinergic signaling, highlighting a neuroimmune pathway in HFpEF.