Background: Heart failure with preserved ejection fraction (HFpEF) is a major health concern. Pathological stimuli and interactions between cardiac fibroblasts (CFs) and other cell types may lead to cardiac fibrosis and diastolic dysfunction, which are hallmarks of HFpEF. Interstitial and perivascular cardiac fibrosis correlates with poor prognosis in HFpEF; however, mechanisms of fibrosis remain poorly elucidated, and targeted therapies are lacking. Cardiac reprogramming is a promising therapeutic approach for myocardial infarction that facilitates cardiac regeneration and antifibrosis action through Mef2c/Gata4/Tbx5/Hand2 (MGTH) overexpression in resident CFs. However, the efficacy of this approach on HFpEF is yet to be established.
Methods: Herein, we examined the effects of cardiac reprogramming in HFpEF using Tcf21iCre/Tomato/MGTH2A transgenic mice, which expressed both MGTH and reporter expression in CFs for cardiac reprogramming and lineage tracing upon tamoxifen administration. To establish HFpEF model mice, we used a combination of a high-fat diet and nitric oxide synthase inhibition. Bulk RNA-sequencing, single-cell RNA-sequencing, and spatial transcriptomics were conducted to determine fibrotic mechanisms and the efficacy of cardiac reprogramming in HFpEF. We generated new tamoxifen-inducible transgenic mice overexpressing each reprogramming factor in CFs to investigate the effect of single factors. Last, we analyzed the effect of reprogramming factors in human CFs.
Results: Cardiac reprogramming with MGTH overexpression improved diastolic dysfunction, cardiac hypertrophy, fibrosis, inflammation, and capillary loss in HFpEF. Cardiac reprogramming converted approximately 1% of resident CFs into induced cardiomyocytes. Bulk RNA-seq indicated that MGTH overexpression upregulated genes related to heart contraction and suppressed the fetal gene program (Nppa and Nppb) and proinflammatory and fibrotic signatures. Single-cell RNA-sequencing and spatial transcriptomics revealed that multiple CF clusters upregulated fibrotic genes to induce diffuse interstitial fibrosis, whereas distinct CF clusters generated focal perivascular fibrosis in HFpEF. MGTH overexpression reversed these profibrotic changes. Among 4 reprogramming factors, only Gata4 overexpression in CFs reduced fibrosis and improved diastolic dysfunction in HFpEF by suppressing CF activation without generating new induced cardiomyocytes. Gata4 overexpression also suppressed profibrotic signatures in human CFs.
Conclusions: Overexpressing Gata4 in CFs may be a promising therapeutic approach for HFpEF by suppressing fibrosis and improving diastolic dysfunction.
Keywords: cardiac fibroblasts; fibrosis; heart failure; single-cell RNA-sequencing; spatial transcriptomics.