Chitinase-3-like protein 1 (CHI3L1) is a myokine involving tissue remodeling and inflammatory processes. CHI3L1 and its receptor protease-activated receptor 2 (PAR2) are induced by exercise in skeletal muscles. However, it remains unknown if CHI3L1/PAR2 signaling also mediates exercise-induced cardioprotection after myocardial infarction. Twenty-four adult male rats were divided into three groups (n = 8/group), receiving: (1) a sham operation; (2) permanent ligation of left anterior descending coronary artery; and (3) post-MI exercise training with one-week adaptive treadmill exercise for seven days followed by four weeks of aerobic exercise. Left ventricular systolic and end-diastolic pressure indices were measured and cardiac fibrosis, and angiogenesis were examined. Furthermore, HUVEC cells were treated in vitro with AMPK agonist—AICAR (a putative pharmacological memetic of exercise), recombinant human CHI3L1, PAR2 receptor blocker (AZ3451), and PI3K inhibitor (LY294002), respectively. We found that post-MI exercise significantly upregulated CHI3L1, PAR2, pPI3K/PI3K, pAKT/AKT, pERK/ERK, improved cardiac function, and diminished fibrosis. AICAR increased HUVEC tubules formation and upregulated CHI3L1 and PAR2 and these changes were attenuated by PAR2 blocker. In conclusion, post-MI exercise training can effectively activate CHI3L1/PAR2 signaling, which led to the improved myocardial function and enhanced cardiac angiogenesis in the infarcted heart.

Therapeutic activation of endogenous utrophin, a homolog of dystrophin, represents a mutation-agnostic therapeutic strategy with considerable potential for treating Duchenne muscular dystrophy (DMD). However, the large size of current dCas9-based activation systems hinders efficient adeno-associated virus (AAV) delivery, and the long-term feasibility and therapeutic durability of such treatments remain uncertain. To overcome these limitations, we developed a muscle-targeted utrophin activation platform based on small activating RNA (saRNA), termed MyoAAV-saRNA. Screening of a panel of saRNAs targeting the Utrn promoter identified Utrophin-257 as the most effective variant, capable of inducing more than a 3.7-fold increase in dystrophin mRNA expression in vitro. This candidate was subsequently packaged into AAV vectors for systemic administration. Following intravenous delivery of MyoAAV 2A-saRNA-257 in mdx mouse models, significant upregulation of utrophin mRNA was observed. This activation led to functional improvements, including partial restoration of the sarcolemma, histopathological amelioration (reduced centronucleation, inflammation, and fibrosis), and enhanced muscle strength. Collectively, these preclinical findings establish MyoAAV-saRNA as a promising and translatable platform for utrophin induction, highlighting its therapeutic potential for DMD.

Duchenne muscular dystrophy (DMD) is a fatal rare disease caused by dystrophin deficiency, with no effective clinical treatments available to date. Using mdx mice as a model, this study investigated the therapeutic efficacy and interaction of mini utrophin (a truncated utrophin) and Yes-associated protein (YAP) delivered via recombinant adeno-associated virus (rAAV). Results showed that mini utrophin was efficiently expressed in mdx mouse skeletal muscle, significantly increased phosphorylated YAP (p-YAP) levels, restored the expression of dystrophin–glycoprotein complex (DGC) components (α/γ-sarcoglycans), reduced serum creatine kinase (CK) leakage, alleviated pathological damages such as central nucleation and inflammatory infiltration, and comprehensively improved grip strength, treadmill endurance, and pole climbing ability in mice. However, the co-overexpression of YAP completely antagonized these therapeutic effects, resulting in no improvement in pathological phenotypes or motor function of mdx mice. This study confirms that mini utrophin can effectively reverse DMD-related phenotypes, while excessive YAP activation abrogates its therapeutic efficacy, suggesting that precise regulation of YAP activity is required in DMD treatment and providing experimental basis for optimizing gene therapy strategies.