Intramyocardial Injection of siRNAs Can Efficiently Establish Myocardial Tissue-Specific Renalase Knockdown Mouse Model

Mitochondrial aspartate/glutamate carrier AGC1 regulates cardiac function via Drp1-mediated mitochondrial fission in doxorubicin-induced cardiomyopathy

Mitochondrial fission has been noted in the pathogenesis of dilated cardiomyopathy (DCM), but the underlying specific regulatory mechanism, especially in the development of doxorubicin (DOX)-induced cardiomyopathy remains unclear. In the present study, we explore whether the aspartate-glutamate carrier1 (AGC1) interacts with the fission protein dynamin-related protein 1 (Drp1) and reveal the functional and molecular mechanisms contributing to DOX-induced cardiomyopathy. Results of co-immunoprecipitation mass spectrometry (CO-IP MS) analysis based on heart tissue of DCM patients revealed that AGC1 expression was significantly upregulated in DCM-induced injury and AGC1 level was closely correlated with mitochondrial morphogenesis and function. We showed that AGC1 knockdown protected mice from DOX-induced cardiomyopathy by preventing mitochondrial fission, while the overexpression of AGC1 in the mouse heart led to impairment of cardiac function. Mechanistically, AGC1 overexpression could upregulate Drp1 expression and contribute to subsequent excessive mitochondrial fission. Specifically, AGC1 knockdown or the use of Drp1-specific inhibitor Mdivi-1 alleviated cardiomyocyte apoptosis and inhibited impairment of mitochondrial function induced by DOX exposure. In summary, our data illustrate that AGC1, as a novel contributor to DCM, regulates cardiac function via Drp1-mediated mitochondrial fission, indicating that targeting AGC1-Drp1 axis could be a potential therapeutic strategy for DOX-induced cardiomyopathy.

Adeno-associated virus 9-mediated RNA interference targeting SOCS3 alleviates diastolic heart failure in rats

OBJECTIVE

To explore the effect of adeno-associated virus 9-mediated RNA interference targeting SOCS3 (AAV9-SOCS3 siRNA) on the treatment of diastolic heart failure (DHF).

METHOD

A rat DHF model was established, and cardiac function and hemodynamic changes were measured. HE, Sirius red and TUNEL staining were applied to observe the pathological changes in the myocardium. Immunoblotting and immunohistochemical staining were utilized to detect SOCS3 expression. The expression levels of various factors, including fibrosis-related factors (collagen I, collagen II, α-SMA and TGF-β), inflammatory-related factors (IL-1β, IL-6, TNF-α, p-p65 and ICAM-1) and factors related to the JAK/STAT signal pathway were analyzed by immunoblotting and/or qPCR. The serum levels of IL-1β, IL-6, and TNF-α were measured using ELISA.

RESULTS

SOCS3 expression was significantly downregulated in the DHF rat model by SOCS3 siRNA delivery. In the successfully established DHF rat model, cardiac function was clearly decreased, and cardiomyocyte apoptosis and myocardial fibrosis were significantly increased. These changes were ameliorated by treatment with AAV9-SOCS3 siRNA. The expression levels of p-JAK2 and p-STAT3 were significantly upregulated in the AAV9-SOCS3 siRNA group compared with the sham and AAV9-siRNA control groups, indicating that SOCS3 is a negative regulator of this signaling pathway. The expression levels of collagen I/III, α-SMA and TGF-β were also decreased at both the mRNA and protein levels. In addition, the serum and myocardial tissue expression levels of inflammatory-related factors, such as IL-6, IL-1β, and TNF-α, were also reduced by the administration of AAV9-SOCS3 siRNA compared with the AAV9-siRNA control.

CONCLUSIONS

SOCS3 gene silencing by AAV9-SOCS3 siRNA administration in a DHF rat model significantly reduced myocardial fibrosis and the inflammatory response and improved heart function. Therefore, this treatment is a potential therapeutic method for treating DHF.

Endostatin Stimulates Proliferation and Migration of Myofibroblasts Isolated from Myocardial Infarction Model Rats

Myofibroblasts contribute to the healing of infarcted areas after myocardial infarction through proliferation, migration, and production of extracellular matrix (ECM). Expression of endostatin, a cleaved fragment of type XVIII collagen, increases in the heart tissue of an experimental myocardial infarction model. In the present study, we examined the effect of endostatin on the function of myofibroblasts derived from an infarcted area. The myocardial infarction model was created by ligating the left anterior descending artery in rats. Two weeks after the operation, α-smooth muscle actin (α-SMA)-positive myofibroblasts were isolated from the infarcted area. Endostatin significantly increased the proliferation and migration of myofibroblasts in vitro. On the other hand, endostatin had no effect on the production of type I collagen, a major ECM protein produced by myofibroblasts. Endostatin activated Akt and extracellular signal-regulated kinase (ERK), and the pharmacological inhibition of these signaling pathways suppressed the endostatin-induced proliferation and migration. A knockdown of the COL18A1 gene in the myocardial infarction model rats using small interference RNA (siRNA) worsened the cardiac function concomitant with wall thinning and decreased the α-SMA-positive myofibroblasts and scar formation compared with that of control siRNA-injected rats. In summary, we demonstrated for the first time that endostatin might be an important factor in the healing process after myocardial infarction through the activation of myofibroblasts.