Poster T13 - Targeted gene silencing with small interfering RNA loaded lipid nanoparticles to treat cardiac fibrosis

Introduction: Clinical data indicate the strong association of myocardial infarction (MI) and myocardial fibrosis, while this fibrosis significantly induces adverse myocardial remodeling. Cardiac fibroblasts are a major cell type in the normal structure of myocardium. In response to injury, they differentiate into activated fibroblasts that express periostin (Postn). Sustained activation of fibroblasts increases tissue stiffness and reduces compliance, which results in deterioration of cardiac function. Nevertheless, few therapeutics directly target excessive fibrosis. Reversing activated fibroblasts into quiescent fibroblasts represents a promising strategy for fibrosis alleviation and cardiac repair.

Materials and

Methods: We employed small interfering RNA (siRNA) against BRD4 (siBRD4) to induce gene silencing and reverse activated fibroblasts. In specific, we loaded siBRD4 into lipid nanoparticles (LNPs), followed by further conjugation with anti-FAP antibodies (FAP-LNP-siBRD4) to enable specific targeting to activated fibroblasts. The therapeutic efficacy of FAP-LNP-siBRD4 was explored in mouse models of MI and cardiac fibrosis. Fibroblast deactivation and its-mediated microenvironment alteration were studied via single-nucleus RNA sequencing (snRNA-seq) and cytokine analysis. Moreover, preclinical toxicity was analyzed in nonhuman primates and mice.

Results, Conclusions, and Discussions: Systemic administration of this targeted therapy specifically inhibited fibroblast activation, reduced fibrosis, and improved cardiac functions in mouse models of myocardial infarction and cardiac fibrosis. Single-nucleus RNA sequencing and cytokine analysis further revealed the alleviation in fibrosis and inflammation after this therapy. The safety of this approach was also validated in nonhuman primates and mice, suggesting its potential for clinical translation.

Our findings offers a proof-of-concept for potentially treating cardiac disorders by targeting and deactivating fibroblasts using siBRD4-loaded LNPs in mouse models. As activated fibroblasts play a pivotal role in the progression of fibrosis, our LNP platform could also be used to deliver other genetic materials, such as a microRNA and mRNA, potentially exploring new targets or pathways in fibroblast activation. The use of conjugated anti-FAP antibodies within LNPs highlights a strategy that could be extended to other fibrotic disorders where activated fibroblasts are a key feature. The crosstalk of fibroblasts with other cell types further inspires exploration into how deactivated fibroblasts contribute to microenvironment modulation and cardiac repair, with the expectation of developing new anti-fibrosis strategies.

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