Pericardial adipose tissue promotes transition to heart failure with reduced ejection fraction upon pressure-overload in mice

Aims: In humans, secretome of pericardial (PAT) and epicardial adipose tissue (EAT) contribute to establishment of heart failure (HF) with preserved ejection fraction (HFpEF) originating from pressure-overload due to metabolic disorder. We examined whether PAT affects also manifestation and progression of pressure-induced HF in the absence of metabolic burden in mice. Methods and results: Progressive remodelling was assessed in C57BL/6J males, aged 9 wks, randomly assigned to sham surgery or transverse aortic constriction (TAC) for 1 week (early pressure-overload), 8 (chronic pressure-overload), or 12 weeks (HFrEF) with or without concomitant PAT excision. PAT removal did not affect early (1 wk TAC), and chronic (8 wks) pressure-overload induced concentric remodelling. However, the initial PAT excision prevented TAC-induced expansion of pro-inflammatory macrophages during early pressure-overload and attenuated the persistent LV expression of pro-hypertrophic, pro-inflammatory and pro-fibrotic factors as well as the drastic LV dilation and progressive systolic dysfunction in the long-term and thereby protected against the transition to HFrEF. This protection was associated with significant reduction of microscar and perivascular fibrosis. The latter was, at least in part, attributed to reduced accumulation of pro-fibrotic CD206+ macrophages around the coronaries 12 wks post-surgery in the absence of PAT compared to mice with intact PAT. In addition, PAT bulk RNA sequencing revealed the initiation of an extracellular matrix deposition programme in the PAT early upon TAC surgery, which might trigger fibrotic responses in the underlying myocardium. Indeed, isolated naive adult cardiac fibroblasts exposed to PAT lysate from 12 wks TAC mice increased collagen production and cell viability/proliferation. Conclusion: Our data suggest PAT to play divergent roles in the chronically pressure overloaded heart versus HFrEF - while widely not affecting concentric hypertrophy, PAT removal counteracts manifestation of HFrEF in mice, at least in part, by preventing excessive fibrotic and macrophage responses. Overall design: To investigate the impact of pericardial adipose tissue (PAT) on pressure-overload induced heart failure progression, we subjected male wild-type mice to TAC or sham surgery for different time periods with or without additional surgical PAT removal and characterized the PAT-dependent phenotypes. Vice versa we examined the impact of TAC-mediated pressure-overload and duration of pressure-overload on the PAT itself. Herein, we excised PAT 1 wk after TAC/Sham and 12 wks post -TAC in n=6-7/group for subsequent bulk PAT RNA sequencing. Comparative gene expression analyses were performed ( 1wk Sham vs. 1 wk TAC; 1 wk TAC vs. 12 wks. TAC).