Injured Cardiac Tissue-Targeted Delivery of TGFβ1 siRNA by FAP Aptamer-Functionalized Extracellular Vesicles Promotes Cardiac Repair.

Purpose: Small-interfering RNA (siRNA) therapy holds significant potential for treating cardiac injury; however, its clinical application is constrained by poor blood stability and insufficient cellular uptake. Extracellular vesicles (EVs) have emerged as an effective delivery system for siRNA in vivo; but their lack of specific cell or tissue-targeting ability remains a major challenge. Thus, we aimed to develop an EV-based delivery system capable of targeted delivery of therapeutic siRNA to injured cardiac tissue for cardiac repair.

Methods: To identify fibroblast activation protein (FAP) as a potential target for delivery to injured cardiac tissue, we analyzed cardiac tissues from patients with heart failure and angiotensin II (Ang II)-treated mice. Injured cardiac tissue-targeting EVs were developed by embedding a cholesterol-conjugated FAP aptamer, which specifically targets FAP, onto human serum-derived EVs (hEV).

Results: Our findings revealed that FAP is upregulated after cardiac injury, highlighting its potential as a target for siRNA delivery to injured cardiac tissues. We successfully developed FAP aptamer-functionalized hEV (hEV@FAP) and confirmed their typical EV characteristics, including morphology, size distribution, zeta potential, and marker protein expression. In addition, hEV@FAP demonstrated high targeting selectivity to FAP-positive regions both in vitro and in vivo. To treat cardiac injury, hEV@FAP were loaded with TGFβ1 siRNA (siTGFβ1), identified as a molecular target for cardiac repair. In Ang II-treated mice, intravenous administration of hEV@FAP-siTGFβ1 effectively reduced Ang II-induced TGFβ1 expression in cardiac tissues, attributed to the protective and targeting capabilities of hEV@FAP. Consequently, hEV@FAP-siTGFβ1 significantly improved cardiac function, reduced myocardial fibrosis, and decreased cardiomyocyte cross-sectional area (P < 0.05) without inducing systemic toxicity.

Conclusion: hEV@FAP represents a novel approach for targeted delivery of therapeutic siRNA to injured cardiac tissues, providing a promising nanomedicine for cardiac repair.