ObjectiveTo explore the preparation method and performance characteristics of a new double-network hydrogel based on carboxymethyl chitosan （CMCS）/silk fibroin （SF）/copper-doped bioactive glass （CuBG）. MethodsPolyethylene glycol diphenyldehyde （PEGDE） was used as a cross-linking agent to cross-link CMCS， which was then blended with enzymatically cross-linked SF and CuBG nanoparticles to prepare a double-network hydrogel. The optimal ratio of CMCS/SF/CuBG double-network hydrogels was determined by gelation time and rheological analysis. The injectability of each group of gel was evaluated through injectability testing and rheological viscosity analysis. The swelling properties of the hydrogels were measured using the gravimetric method. The cytocompatibility of the hydrogels was evaluated using cell counting kit-8 （CCK-8） assay and live/dead cell staining. ResultsThe gelation time of the CMCS single-network hydrogel exceeded 4 minutes， and its mechanical strength was poor. With the addition of SF and CuBG， the gelation time of the hydrogel was shortened， the mechanical strength was enhanced， and the swelling index decreased. Hydrogel injection could form clear and continuous patterns. The CCK-8 and cell live/dead staining results showed that the survival rate of HUVECs cultured in leaching solution of each group of hydrogels was greater than 90%， with complete cell morphology and good proliferation status. ConclusionThe CMCS/SF/CuBG double-network hydrogel exhibits a suitable gelation time， stable mechanical properties， excellent swelling rate， and exhibits no cytotoxicity. These findings indicate that the hydrogel has considerable potential for biomedical applications.

Pathological cardiac hypertrophy serves as a significant foundation for cardiac dysfunction and heart failure. Recently, growing evidence has revealed that microRNAs (miRNAs) play multiple roles in biological processes and participate in cardiovascular diseases. In the present research, we investigate the impact of miRNA-34c-5p on cardiac hypertrophy and the mechanism involved. The expression of miR-34c-5p was proved to be elevated in heart tissues from isoprenaline (ISO)-infused mice. ISO also promoted miR-34c-5p level in primary cultures of neonatal rat cardiomyocytes (NRCMs). Transfection with miR-34c-5p mimic enhanced cell surface area and expression levels of foetal-type genes atrial natriuretic factor (Anf) and β-myosin heavy chain (β-Mhc) in NRCMs. In contrast, treatment with miR-34c-5p inhibitor attenuated ISO-induced hypertrophic responses. Enforced expression of miR-34c-5p by tail intravenous injection of its agomir led to cardiac dysfunction and hypertrophy in mice, whereas inhibiting miR-34c-5p by specific antagomir could protect the animals against ISO-triggered hypertrophic abnormalities. Mechanistically, miR-34c-5p suppressed autophagic flux in cardiomyocytes, which contributed to the development of hypertrophy. Furthermore, the autophagy-related gene 4B (ATG4B) was identified as a direct target of miR-34c-5p, and miR-34c-5p was certified to interact with 3' untranslated region of Atg4b mRNA by dual-luciferase reporter assay. miR-34c-5p reduced the expression of ATG4B, thereby resulting in decreased autophagy activity and induction of hypertrophy. Inhibition of miR-34c-5p abolished the detrimental effects of ISO by restoring ATG4B and increasing autophagy. In conclusion, our findings illuminate that miR-34c-5p participates in ISO-induced cardiac hypertrophy, at least partly through suppressing ATG4B and autophagy. It suggests that regulation of miR-34c-5p may offer a new way for handling hypertrophy-related cardiac dysfunction.