Rosmarinic Acid‐Treated Exosomes Modulate <scp>TGF</scp> ‐β1/Smad3 Signaling to Alleviate Cardiac Fibrosis in an In Vitro/In Vivo Model

Cardiac fibrosis (CF) is a major complication of myocardial infarction (MI), impairing myocardial function and leading to heart failure. Rosmarinic acid (RA) exhibits cardioprotective and antifibrotic properties, representing a promising therapeutic strategy for CF. This study evaluated the efficacy of exosomes derived from RA-primed adipose-derived stem cells (ADSCs), focusing on how RA-priming enhances their antioxidant and antifibrotic capacity against CF. An Isoproterenol (ISO)-induced myocardial injury model was established in vitro and in vivo. In vitro, H9C2 cardiomyoblasts were first injured with ISO and then treated with either exosomes (Exo) or RA-primed exosomes (RA-MSC-Exo) to assess cell viability and apoptosis. In vivo, 48 Wistar rats were divided into six groups: Control, Exo, RA-MSC-Exo, ISO, ISO + Exo, and ISO + RA-MSC-Exo. We assessed cardiac biomarkers (CK-MB and troponin I), reactive oxygen species (ROS), and total antioxidant capacity (TAC). We performed echocardiographic, molecular (real-time PCR and Western blotting), and histological analyses (Masson's trichrome staining) to evaluate cardiac function, fibrosis signaling pathways (NF-κB, TGF-β1, SMAD3), and collagen deposition. In vitro, both Exo and RA-MSC-Exo treatments significantly restored cell viability and reduced apoptosis in ISO-injured H9C2 cells. In vivo, both treatments significantly mitigated ISO-induced cardiac injury by reducing cardiac biomarkers, decreasing ROS production, and enhancing TAC levels. These interventions downregulated the expression of NF-κB, TGF-β1, Smad3, and Collagen I, leading to attenuated collagen deposition and improved cardiac function. Our study demonstrates that RA-primed exosomes effectively mitigate CF and improve cardiac function in an ISO-induced myocardial ischemia model. This targeted approach offers a promising therapeutic strategy for managing myocardial injury and its fibrotic complications.