HFpEF: serum oxylipin analyses and myocardial biopsy-based transcriptomics indicate distinct signatures of pulmonary vascular remodeling

Background

In early stages of heart failure with preserved ejection fraction (HFpEF), isolated post-capillary pulmonary hypertension (Ipc-PH) occurs. As pulmonary vasculature remodels with disease progression, PH evolves into combined pre- and post-capillary PH (Cpc-PH), quantified with elevated pulmonary vascular resistance (PVR, >2 Woods unit). CpcPH is assosciated with worsening right ventricular function and multiorgan failure. The goal of this study is to define serum and myocardial biopsy characteristics of disease progression from Ipc- to Cpc-PH in PH-HFpEF.

Methods

Our two-step study analyzed: 1. serum oxylipins of 40 patients (20 Ipc- and 20 Cpc-PH), and 2. within that cohort, we performed endomyocardial biopsy of 10 patients (5 Ipc- and 5 Cpc-PH) with long-read RNA sequencing analyses focused on transcript usage of titin protein (primary determinant of myocardial stiffness in HFpEF).

Results

Among Ipc- vs Cpc-PH patients (mean±SD), age was 65±9 vs 69±10 years, female sex 50% vs 45%, mean pulmonary artery pressure 31±8 vs 33±10 mmHg, pulmonary artery wedge pressure (rest/exercise) 18±3/30±4 vs 17±4/32±6 mmHg, and PVR 1.2±0.6 vs 5.7±2.4 Woods unit.

Oxylipins capture signals of worsening vascular stiffness and inflammation as PH-HFpEF worsens. Oxylipins derived from omega-6 fatty acids are signaling lipids that increase immune cell infiltration, vascular stiffness, and increased cytokine production (Figure 1A). Using LC/MS based lipidomics we are able to quantify 121 oxylipins in human plasma (Figure 1B), and observed signatures distinguished Ipc-PH from Cpc-PH. Both IpcPH and CpcPH had elevated prostaglandin signaling including prostaglandin E2 (PGE2), PGH2, PGG2, and PGF2 (Figure 1C&D). However, the distinguishing feature is the observation that CpcPH also had elevated leukotrienes, including LTB4 and LTD4, which are associated with increased vascular stiffness.

From myocardial biopsies, we performed long-read RNA-seq analysis in 10 patients (Fig. 2A). Critically, sufficient RNA was extracted from all biopsies and long-read RNA-seq was successfully carried out. Analysis of the resulting data identified 5536 transcripts that were differentially expressed (adjusted p<0.05 and |log2fc|>1) with 3212 and 2324 up- and down-regulated in the high- versus low-risk subgroups (Fig. 11B). Notably, titin transcripts were among those exhibiting distinct transcript usage profiles in high- (Cpc-PH) versus low-risk (Ipc-PH) PH-HFpEF (Fig. 2B-D). This provides critical evidence of differences in titin-transcript usage with worsening myocardial stiffness and disease progression (early vs advanced stage PH-HFpEF), which may translate to stiffer titin protein and consequent pulmonary remodeling in PH-HFpEF.

Conclusion

As pulmonary vascular remodeling worsens in PH-HFpEF, serum oxylipin analyses captures signals of increased inflammation and Titin protein expression changes on myocardial biopsy investigation.Figure 1Figure 2