Abstract 4370781: Membrane-Repairing LncRNA Masir Protects the Heart from Ischemic Injury

Background: Cardiomyocytes (CMs) undergo constant mechanical stress during contraction and are vulnerable to membrane damage. Impaired sarcolemmal integrity is a key factor of heart failure progression; hence, strengthening membrane repair represents a promising strategy for cardioprotection. While long non-coding RNAs (lncRNAs) are pivotal in cardiac function and disease, their direct involvement in membrane repair remains largely unexplored. Objective: To identify lncRNAs involved in membrane repair and evaluate their therapeutic potential in ischemic cardiac injury. Methods: Subcellular RNA fractionation (cytosolic, organellar, and plasma membrane) were isolated from heart tissues and sequenced to identify lncRNAs enriched at the plasma membrane (PM). Top candidate lncRNAs were assessed for their role in endocytosis, exocytosis and membrane repair using HL-1 cardiac muscle cells, neonatal CMs, and human induced pluripotent stem cell (iPSC)-differentiated CMs. Intramuscular delivery of lncRNAs was used to evaluate their therapeutic effect in a mouse model of myocardial infarction (MI). Results: Of the top 30 candidate lncRNAs, five PM-enriched lncRNAs were successfully cloned, synthesized, and purified, including Masir (MG53-associated sarcolemma injury repair lncRNA). Gfp RNA served as a control. Masir enhanced both endocytosis and exocytosis in HL-1 cardiac muscle cells. Importantly, rapid extracellular treatment of Masir significantly reduced laser-induced membrane injuries in HL-1 cells and wild-type neonatal CMs but had no effect in MG53-knockout CMs. In vivo, Masir -treated mice demonstrated improved cardiac function post-MI compared to Gfp -treated controls, with higher ejection fraction (34.29% ± 5.36, n=13 vs. Gfp : 21.53% ± 2.64, p =0.047) and significantly smaller scar size. Notably, mouse Masir RNA also attenuated laser-induced membrane injury in hiPSC-derived CMs, highlighting its translational relevance. Conclusion: Masir interacts with MG53, promotes sarcolemmal membrane repair, and confers protection against ischemic injury. These finding demonstrate a direct, functional role for lncRNAs in membrane repair and establish a foundation for RNA-based therapies targeting heart disease.