Abstract Body (Do not enter title and authors here): Background: Dysfunction of systemic vascular endothelial cells (ECs) is common in heart failure with preserved ejection fraction (HFpEF). We sought to determine if organ-specific EC translational heterogeneity is present in HFpEF. Using a transgenic mouse model (RiboTag^EC), we analyzed the translatome (the mRNAs bound with ribosomes) of organ-specific ECs in a mouse HFpEF model induced by hypertensive/metabolic stresses.

Methods: Six-month-old male RiboTag^EC (Cdh5^CreERT2+/Rpl22^HA/+) mice, expressing a hemagglutinin tag in EC ribosomal protein Rpl22, were fed a high-fat diet and L-NAME water (N=4) or a normal diet and water (N=5) for 7 weeks. Organs were collected for Translating Ribosome Affinity Purification, RNA isolation, and RNA-seq. RNA-seq data were visualized using uniform manifold approximation and projection (UMAP). Differentially expressed genes (DEGs; absolute fold change ≥ 2 and false discovery rate (FDR) adjusted p-value ≤ 0.05). Pathway enrichment analyses were conducted (Ingenuity Pathways Analysis (IPA)).

Results: In UMAP, the EC translatome clustered by organ (heart, lung, skeletal muscle, and liver) highlighting organ-specific EC heterogeneity and by disease (HFpEF) status with cardiac ECs showing the most dramatic changes with HFpEF (Fig A). Cardiac ECs in HFpEF (vs Control) had 283 downregulated and 23 upregulated DEG (Fig B) out of 14,923 genes identified. There were significant differences in 142 canonical pathways (16 upregulated, 126 downregulated), including LXR/RXR activation, DHCR 24 signaling, regulation of insulin-like growth factors, eNOS signaling, acute phrase response (all down regulated) and IL-1b-mediated inhibition of RXR and unfolded protein response (both up regulated) (Fig C).

Conclusion: HFpEF induction caused extensive translational changes in EC but particularly cardiac ECs. In cardiac ECs, metabolism, anti-inflammatory, vasodilation, tissue repair, and angiogenesis pathways were inhibited, while pro-inflammatory response, insulin resistance, and proteostasis pathways were activated.