The Heart Failure-Induced Long Non-Coding RNA Heat4 Reduces the Inflammatory Response of Non-Classical Monocytes and Mediates Regeneration After Vascular Injury

Background and Purpose: Activation of the immune system correlates with the severity and the prognosis of patients with heart failure (HF). This study aims to identify and characterize long non-coding RNAs (lncRNAs) as a potential mechanistic link between the pathophysiology of HF and the activation of the immune system. Methods and Results: Using next-generation sequencing, we identified the lncRNA Heat4 to be 2-fold upregulated in the blood of patients with HF compared to controls (N=4; p<0.05). Heat4 induction was validated in an independent second patient cohort via qPCR (HF: N=63; Controls: N=38; p<0.05). Magnetic-activated cell sorting revealed non-classical monocytes as the primary cellular source of Heat4 (N=4; 3.37-fold compared to classical monocytes; p<0.05). This finding was verified by single-cell RNA sequencing. Overexpression of Heat4 in monocytes decreased inflammation, as indicated by a reduction of Interleukin 1β (IL1β) expression (N=6; 38.71% reduction). Accordingly, reduction of Heat4 caused upregulation of IL1β levels (N=5; 1.51-fold; p<0.05). In vivo , overexpression of Heat4 in human monocytes increased vascular regeneration after injury of the carotid artery in NOD-SCID mice (N=6; 1.85-fold compared to injection of control monocytes; p<0.05). Conclusion: The long non-coding RNA Heat4 is elevated in the blood of HF patients. Mechanistically, Heat4 limits the extent of the inflammatory response of non-classical monocytes and leads to a faster regeneration after vascular injury. Therefore, lncRNAs such as Heat4 may provide novel targets for future heart failure treatments.