Regulatory T cell augmentation by a long noncoding RNA: mechanisms and therapeutic applications in myocarditis - PROJECT SUMMARY/ABSTRACT Myocarditis is an inflammatory disease of the myocardium which is often triggered by a viral infection. Despite the use of supportive measures and guideline-directed medical therapy for heart failure, mortality still exceeds 10% at one year, and lasting complications in survivors (e.g., persistent dilated cardiomyopathy) are not uncommon. No specific treatment for acute myocarditis has been validated. Immunosuppressive drugs have had anecdotal success, but overall survival is not improved. Myocarditis is characterized by robust innate and adaptive immune responses that increase proinflammatory cytokines and recruit activated immune cells (e.g., neutrophils, macrophages, dendritic cells and T cells) to the myocardium. But not all immune cells are harmful: regulatory T cells (Tregs) favor tissue repair and functional recovery. In particular, the subset of CD4+Foxp3+ Tregs has the potential to mitigate injury via release of inhibitory cytokines (e.g., IL-10), growth factors (e.g. TGFβ), or contact-dependent effects. Such a conjecture is bolstered by several early phase clinical trials showing that autologous Treg cell infusion is safe and promising, in diseases ranging from Type 1 diabetes to solid organ transplant rejection. However, the very long processing times (weeks to months) required for ex vivo expansion render autologous Treg cell therapy implausible for acute myocarditis. For all these reasons, a therapy which can selectively and quickly expand Tregs in vivo is highly desirable. Our previous studies demonstrated that extracellular vesicles secreted by human cardiosphere-derived cells (CDC-EVs) increase proliferation of mouse Tregs and augment their production of IL-10, which, in turn, induces cardioprotection in vivo. We have also found that CDC-EVs increase Tregs, and improve heart function, in rodent models of myocarditis. However, the mechanism underlying CDC-EV-enhanced proliferation and activation of Treg cells is unknown. In preliminary data, we show that a CDC-EV-enriched long noncoding RNA (lncRNA), BCYRN1, upregulates Treg cells in vitro: proliferation and migration are enhanced, and the Tregs become activated to secrete IL-10. Here we propose to dissect the mechanism whereby BCYRN1 upregulates Tregs, and to characterize the disease-modifying bioactivity of BCYRN1 in experimental myocarditis. The overarching goal of this proposal is to advance the development of a novel RNA-based approach targeting regulatory T cell function as an effective therapy for acute myocarditis. Using multiple in vitro and in vivo approaches, this goal will be achieved in 3 specific Aims: (Aim 1): Explore the molecular mechanism(s) underlying BCYRN1-mediated human Treg cell proliferation, migration, and IL-10 production. (Aim 2): Synthesize the functional miR-binding sequences of BCYRN1, and test their effects on Treg cell proliferation, migration, and IL-10 production in vitro. (Aim 3): Test in vivo the therapeutic potential of BCYRN1 and BDSS in a mouse model of acute myocarditis. Thus, we will address both mechanistic and translationally-motivated questions, using state-of-the-art scientific methods and preclinical disease models.
