Vagal Stimulation Rescues HFpEF by Altering Cardiac Resident Macrophage Function.

Abstract

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. 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. 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 <i>Spp1</i>-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 <i>Spp1</i> while also inducing the expression of <i>Igf1</i> 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 <i>Spp1</i> or blockade of CCR2⁺ CRM recruitment improved HFpEF, whereas TLF⁺/MHC2⁺ specific deletion of <i>Igf1</i> 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. Collectively, our data indicate that tVNS improves HFpEF by reducing <i>Spp1</i> expressing CCR2⁺ CRM and inducing expression of proreparative <i>Igf1</i> in TLF⁺/MHC2⁺ CRM. These effects are mediated through cholinergic signaling, highlighting a neuroimmune pathway in HFpEF.