The relationship between exercise commitment and college students' exercise adherence: The chained mediating role of exercise atmosphere and exercise self-efficacy.

OBJECTIVE: This study aims to explore the mechanisms underlying exercise commitment, exercise atmosphere, exercise self-efficacy, and exercise adherence among college students, as well as the impact of gender differences on these mechanisms. METHODS: Using a stratified cluster sampling method, 984 college students (aged 19.74 ± 1.25 years) from six universities in Anhui, Shandong, and Shaanxi provinces were randomly selected, with 403 male students and 581 female students. They had completed the Exercise Commitment Scale (ECC), Physical Exercise Atmosphere Scale (PEAS), Exercise Self-Efficacy Scale (ESES), and Exercise Adherence Scale (EPS). The study variables were analyzed in sequence for reliability and validity, correlation analysis, regression analysis, structural equation model testing, and bias-corrected percentile Bootstrap testing using SPSS 23.0 software and Hayes' (2013) Process plug-in. RESULTS: Exercise commitment significantly positively predicted exercise adherence (ß = 0.796, p < 0.01), exercise commitment significantly positively predicted exercise environment and exercise self-efficacy (ß = 0.645, p < 0.01, ß = 0.356, p < 0.01), exercise environment significantly positively predicted exercise self-efficacy and exercise adherence (ß = 0.344, p < 0.01, ß = 0.144, p < 0.01), and exercise self-efficacy significantly positively predicted exercise adherence (ß = 0.934, p < 0.01). The mediating role of exercise environment in the relationship between exercise commitment and exercise adherence does not exist in male college students, while it exists in female college students. CONCLUSIONS: Exercise atmosphere and exercise self-efficacy play a mediating role between exercise commitment and exercise adherence, with a total mediating effect value of 0.796. This study indicates that exercise commitment not only directly predicts exercise adherence, but also indirectly predicts exercise adherence through the chained mediating effects of exercise atmosphere and exercise self-efficacy. The above-mentioned mediating effect exists in female college students, while some mediating effects do not exist in male college students, thus gender has a significant impact on this mediating effect.

Phospholamban as a crucial determinant of the inotropic response of human pluripotent stem cell-derived ventricular cardiomyocytes and engineered 3-dimensional tissue constructs.

BACKGROUND: Human (h) embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) serve as a potential unlimited ex vivo source of cardiomyocytes (CMs). However, a well-accepted roadblock has been their immature phenotype. hESC/iPSC-derived ventricular (v) CMs and their engineered cardiac microtissues (hvCMTs) similarly displayed positive chronotropic but null inotropic responses to ß-adrenergic stimulation. Given that phospholamban (PLB) is robustly present in adult but poorly expressed in hESC/iPSC-vCMs and its defined biological role in ß-adrenergic signaling, we investigated the functional consequences of PLB expression in hESC/iPSC-vCMs and hvCMTs. METHODS AND RESULTS: First, we confirmed that PLB protein was differentially expressed in hESC (HES2, H9)- and iPSC-derived and adult vCMs. We then transduced hES2-vCMs with the recombinant adenoviruses (Ad) Ad-PLB or Ad-S16E-PLB to overexpress wild-type PLB or the pseudophosphorylated point-mutated variant, respectively. As anticipated from the inhibitory effect of unphosphorylated PLB on sarco/endoplasmic reticulum Ca2+-ATPase, Ad-PLB transduction significantly attenuated electrically evoked Ca2+ transient amplitude and prolonged the 50% decay time. Importantly, Ad-PLB-transduced hES2-vCMs uniquely responded to isoproterenol. Ad-S16E-PLB-transduced hES2-vCMs displayed an intermediate phenotype. The same trends were observed with H9- and iPSC-vCMs. Directionally, similar results were also seen with Ad-PLB-transduced and Ad-S16E-transduced hvCMTs. However, Ad-PLB altered neither the global transcriptome nor ICa,L, implicating a PLB-specific effect. CONCLUSIONS: Engineered upregulation of PLB expression in hESC/iPSC-vCMs restores a positive inotropic response to ß-adrenergic stimulation. These results not only provide a better mechanistic understanding of the immaturity of hESC/iPSC-vCMs but will also lead to improved disease models and transplantable prototypes with adult-like physiological responses.

Calcium signalling of human pluripotent stem cell-derived cardiomyocytes.

Loss of cardiomyocytes (CMs), which lack the innate ability to regenerate, due to ageing or pathophysiological conditions (e.g. myocardial infarction or MI) is generally considered irreversible, and can lead to conditions from cardiac arrhythmias to heart failure. Human (h) pluripotent stem cells (PSCs), including embryonic stem cells (ESC) and induced pluripotent stem cells (iPSCs), can self-renew while maintaining their pluripotency to differentiate into all cell types, including CMs. Therefore, hPSCs provide a potential unlimited ex vivo source of human CMs for disease modelling, drug discovery, cardiotoxicity screening and cell-based heart therapies. As a fundamental property of working CMs, Ca(2+) signalling and its role in excitation-contraction coupling are well described. However, the biology of these processes in hPSC-CMs is just becoming understood. Here we review what is known about the immature Ca(2+)-handling properties of hPSC-CMs, at the levels of global transients and sparks, and the underlying molecular basis in relation to the development of various in vitro approaches to drive their maturation.

Effect of engineered anisotropy on the susceptibility of human pluripotent stem cell-derived ventricular cardiomyocytes to arrhythmias.

Human (h) pluripotent stem cells (PSC) such as embryonic stem cells (ESC) can be directed into cardiomyocytes (CMs), representing a potential unlimited cell source for disease modeling, cardiotoxicity screening and myocardial repair. Although the electrophysiology of single hESC-CMs is now better defined, their multi-cellular arrhythmogenicity has not been thoroughly assessed due to the lack of a suitable experimental platform. Indeed, the generation of ventricular (V) fibrillation requires single-cell triggers as well as sustained multi-cellular reentrant events. Although native VCMs are aligned in a highly organized fashion such that electrical conduction is anisotropic for coordinated contractions, hESC-derived CM (hESC-CM) clusters are heterogenous and randomly organized, and therefore not representative of native conditions. Here, we reported that engineered alignment of hESC-VCMs on biomimetic grooves uniquely led to physiologically relevant responses. Aligned but not isotropic control preparations showed distinct longitudinal (L) and transverse (T) conduction velocities (CV), resembling the native human V anisotropic ratio (AR = LCV/TCV = 1.8-2.0). Importantly, the total incidence of spontaneous and inducible arrhythmias significantly reduced from 57% in controls to 17-23% of aligned preparations, thereby providing a physiological baseline for assessing arrhythmogenicity. As such, promotion of pro-arrhythmic effect (e.g., spatial dispersion by ß adrenergic stimulation) could be better predicted. Mechanistically, such anisotropy-induced electrical stability was not due to maturation of the cellular properties of hESC-VCMs but their physical arrangement. In conclusion, not only do functional anisotropic hESC-VCMs engineered by multi-scale topography represent a more accurate model for efficacious drug discovery and development as well as arrhythmogenicity screening (of pharmacological and genetic factors), but our approach may also lead to future transplantable prototypes with improved efficacy and safety against arrhythmias.