Enhancing cardiac reprogramming via synthetic RNA oligonucleotides

Abstract

Reprogramming scar fibroblasts into new heart muscle cells has the potential to restore function to the injured heart. However, the effectiveness of reprogramming is notably low. We have recently demonstrated that the effectiveness of reprogramming fibroblasts into heart muscle cells (cardiomyocytes) is increased by the addition of RNA-sensing receptor ligands. Clinical use of these ligands is problematic due to their ability to induce adverse inflammatory events. To overcome this issue, we sought to determine whether synthetic analogs of natural RNA-sensing receptor ligands, which avoid generating inflammatory insults and are nuclease resistant, would similarly enhance fibroblast reprogramming into cardiomyocytes. Indeed, one such stabilized RNA, ICR2, increased the expression of cardiomyocyte-specific mRNAs in reprogrammed fibroblasts. Moreover, ICR2 enhanced the ability of reprogramming factors to produce cardiomyocytes with mature sarcomeres. Knockdown assays indicated that the effects of ICR2 were mediated by the RNA-sensing receptors Rig-I and TLR3. In addition, ICR2 reduced the effective dose and number of reprogramming factors needed for efficient reprogramming. In summary, the synthetic RNA oligonucleotide ICR2 is a potential therapeutic agent to enhance cardiac reprogramming efficiency.

A novel Cbx1, PurB, and Sp3 complex mediates long-term silencing of tissue- and lineage-specific genes

“…Since our initial discovery, we have gone on to demonstrate that miR combo improves cardiac function in heart injury models ( 5 ). Moreover, we have also found that reprogramming via miR combo utilizes immunity and epigenetic pathways ( 6 , 7 ). In addition to reprogramming fibroblasts to cardiomyocytes, miRNAs have also been used to reprogram cells to pluripotency ( 8 ) as well as to neurons ( 9 ).…”

Basic and Translational Research in Cardiac Repair and Regeneration

“…Upon binding to their specific ligands, RNA-sensing receptors activate a common signaling pathway that includes the transcription factors activator protein 1, interferon regulatory factors 3/7, and nuclear factor kappa B (NFkB) ( 79 ), which is consistent with observations that pharmacological TLR3 activators strongly enhance, while inhibitors of the TLR3-NFkB pathway block, the maturity of miR-combo–reprogrammed CMs ( 80 ). Synthetic RNA agonists of Rig-1 also enhanced the yield of mature CMs in response to treatment with miR-combo ( 81 ). Interestingly, miR-133 enhanced MEF2C, GATA4, and TBX5-induced direct cardiac reprogramming in human fibroblasts via targeting immune-related genes ( 82 ), suggesting distinct mechanisms underlying mouse and human reprogramming.…”

Immune Regulator Retinoic Acid-Inducible Gene I (RIG-I) in the Pathogenesis of Cardiovascular Disease

“…Hu et al. observed that a stabilized RNA, ICR2, increased the level of cardiomyocyte-specific genes in reprogrammed “fibroblasts” and enhanced their ability to differentiate into cardiomyocytes via the RIG-I and TLR3 pathways ( 78 ). In addition to the discrepancy in the above findings, the role of RIG-I in cell senescence is also controversial.…”

“…This suggests the inflammatory function of RIG-I in the progression of dilated cardiomyopathy. Another study showed that ICR2 (a stabilized RNA) enhanced the ability of cardiac fibroblasts to reprogram into cardiomyocytes via the RIG-I pathway without inducing inflammatory events ( 78 ). These results reveal the controversial role of RIG-I in cardiac dysfunction caused by different stimuli and requires further research to validate the phenotypes and underlying mechanisms.…”