SMOC2 plays a role in heart failure via regulating TGF-β1/Smad3 pathway-mediated autophagy

Abstract

Heart failure (HF) is a major global cause of morbidity and mortality. This study aimed to elucidate the role of secreted protein acidic and rich in cysteine-related modular calcium-binding protein 2 (SMOC2) in HF development and its underlying mechanism. Using a rat HF model, SMOC2 expression was examined and then knocked down via transfection to assess its impact on cardiac function and damage. The study also evaluated the effects of SMOC2 knockdown on autophagy-related molecules and the transforming growth factor beta 1 (TGF-β1)/SMAD family member 3 (Smad3) signaling pathway. Intraperitoneal injection of the TGF-β agonist (SRI-011381) into the HF rat model was performed to explore the SMOC2-TGF-β1/Smad3 pathway relationship. SMOC2 expression was elevated in HF rats, while its downregulation improved cardiac function and damage. SMOC2 knockdown reversed alterations in the LC3-II/I ratio, Beclin-1, and p62 levels in HF rats. Through transmission electron microscope, we observed that SMOC2 knockdown restored autophagosome levels. Furthermore, SMOC2 downregulation inhibited the TGF-β1/Smad3 signaling pathway, which was counteracted by SRI-011381. In conclusion, SMOC2 knockdown inhibits HF development by modulating TGF-β1/Smad3 signaling-mediated autophagy, suggesting its potential as a therapeutic target for HF.

Keywords: SMOC2; TGF-β1/Smad3 signaling pathway; autophagy; heart failure.

Figure 1

Downregulation of SMOC2 improved cardiac function and damage in HF rats. (a) qPCR and western blot assays showed SMOC2 expression in HF rats. (b) qPCR and western blot assays showed SMOC2 expression in HF rats after SMOC2 knockdown. (c) Echocardiographic parameters of HF rats after SMOC2 knockdown. LVESD: left ventricular end-systolic diameter; LVEDD: left ventricular end-diastolic diameter; EF: left ventricular ejection fraction; FS: left ventricular fractional shortening. (d) and (e) HE and Masson staining showed pathological changes in myocardial tissues of HF rats after SMOC2 knockdown (scale bar = 50 µm). CVF: collagen volume fraction. **P < 0.01 compared to sham group; ^# P < 0.05 and ^## P < 0.01 compared to HF + sh-NC group.

Figure 2

Downregulation of SMOC2 alleviated myocardial injury in HF rats. (a)–(c) ELISA showed the levels of serum NT-proBNP, cTnI, and cTnT in HF rats after SMOC2 knockdown. (d) qPCR showed Acta2 expression in HF rats after SMOC2 knockdown. **P < 0.01 compared to sham group; ^## P < 0.01 compared to HF + sh-NC group.

Figure 3

Downregulation of SMOC2 regulated autophagy in HF rats. (a) Western blotting showed the expression of autophagy-related markers (LC3 II/I, Beclin-1, and p62) in HF rats after SMOC2 knockdown. (b) TEM showed the state of autophagy in HF rats after SMOC2 knockdown (scale bar = 2 µm). **P < 0.01 compared to sham group; ^## P < 0.01 compared to HF + sh-NC group.

Figure 4

Downregulation of SMOC2 inhibiting TGF-β1/Smad3 signaling pathway. (a) qPCR showed TGF-β1 and Smad3 expression in HF rats after SMOC2 knockdown. (b) Western blot assay showed TGF-β1, Smad3, and p-Smad3 expression in HF rats after SMOC2 knockdown. **P < 0.01 compared to sham group; ^## P < 0.01 compared to HF + sh-NC group.

Figure 5

Downregulation of SMOC2 affected autophagy and mitigated cardiac damage in HF rats via inhibiting the TGF-β1/Smad3 signaling pathway. TGF-β agonist (SRI-011381, 30 mg/kg daily) was intraperitoneally injected into the HF rats that were transfected with sh-SMOC2. (a) qPCR showed SMOC2 expression in rats. (b) and (c) HE and Masson staining showed pathological changes in the myocardial tissues of rats (scale bar = 50 µm). CVF: collagen volume fraction. (d) Western blot assay showed the expression of autophagy- and TGF-β1/Smad3 signaling pathway-related proteins in rats. *P < 0.05 and **P < 0.01 compared to sham group; ^# P < 0.05 and ^## P < 0.01 compared to HF + sh-NC group; ^& P < 0.05 and ^&& P < 0.01 compared to HF + sh-SMOC2 group.