Association between screen time and depressive symptoms in a sample of Chinese medical students: Mediator role of empathy.

Medical students are at high risk of psychological subhealth under heavy stress with increasing screen time. This study aimed to explore the association between screen time and depressive symptoms and determine empathy as a mediating factor. In this cross-sectional study, a total of 945 medical students were surveyed, and 924 medical students were ultimately included after standard exclusion criteria. They reported their daily screen time and completed the Chinese version of the Jefferson Scale of Empathy-Student Version (JSE-S) and the Self-Rating Depression Scale (SDS). t tests and analysis of variance showed a significant difference in empathy and depressive symptoms by sex, stage, and screen time. The correlation analysis revealed that both affective and cognitive empathy have inverse associations with depressive symptoms. The mediation model confirmed that cognitive empathy played a positive mediating role between screen time and depressive symptoms, reducing the impact of screen time on depressive symptoms. Our study may add empirical evidence to prevent and intervene in depressive symptoms. These findings call for considering controlling screen time and enhancing cognitive empathy as interventions for medical students' depressive symptoms.

Engineering the viscoelasticity of gelatin methacryloyl (GelMA) hydrogels via small "dynamic bridges" to regulate BMSC behaviors for osteochondral regeneration.

The dynamic extracellular matrix (ECM) constantly affects the behaviors of cells. To mimic the dynamics of ECM with controllable stiffness and energy dissipation, this study proposes a strategy in which a small molecule, 3,4-dihydroxybenzaldehyde (DB), was used as fast "dynamic bridges'' to construct viscoelastic gelatin methacryloyl (GelMA)-based hydrogels. The storage modulus and loss modulus of hydrogels were independently adjusted by the covalent crosslinking density and by the number of dynamic bonds. The hydrogels exhibited self-healing property, injectability, excellent adhesion and mechanical properties. Moreover, the in vitro results revealed that the viscous dissipation of hydrogels favored the spreading, proliferation, osteogenesis and chondrogenesis of bone marrow mesenchymal stem cells (BMSCs), but suppressed their adipogenesis. RNA-sequencing and immunofluorescence suggested that the viscous dissipation of hydrogels activated Yes-associated protein (YAP) by stabilizing integrin ß1, and further promoted nuclear translocation of smad2/3 and ß-catenin to enhance chondrogenesis and osteogenesis. As a result, the viscoelastic GelMA hydrogels with highest loss modulus showed best effect in cartilage and subchondral bone repair. Taken together, findings from this study reveal an effective strategy to fabricate viscoelastic hydrogels for modulating the interactions between cells and dynamic ECM to promote tissue regeneration.