Circadian Rhythms of Early Afterdepolarizations and Ventricular Arrhythmias in a Cardiomyocyte Model

Chronobiological Patterns and Risk of Acute Aortic Dissection: A Clinical Retrospective and Two-Sample Mendelian Randomisation Study

AIM

Acute aortic dissection (AAD) represents a cardiovascular ailment characterised by a notable mortality rate. Chronobiological patterns can offer a predictive framework for anticipating the onset of AAD.

METHOD

Data were gathered from 1,151 patients diagnosed with AAD at Changhai Hospital in Shanghai, China, spanning 2000-2023. The χ2 test was used to assess whether specific periods exhibited significantly different seasonal/weekly distributions compared with others. Fourier models were utilised for the analysis of rhythmicity in monthly/circadian distribution. Publicly available genome-wide association studies datasets were used to establish the causal relationship between chronotype and AAD. Two sets of genetics instruments were used for analysis, derived from publicly available genetic summary data: 75 single-nucleotide polymorphisms (SNPs) significantly associated with chronotype; and SNPs associated with AAD in the FinnGen consortium.

RESULTS

The mean age was 51.5±13.8 years, with 665 patients (57.8%) aged <55 years. Among the 1,151 patients, 80.9% were male. The distribution of DeBakey types was 73.2% (843) for DeBakey I, 21% (242) for DeBakey II, and 5.7% (66) for DeBakey III. Comorbidities included hypertension in 58.5% (673 cases) and diabetes in 7.8% (90 cases). A peak occurred during colder periods (winter/December), and a trough was noted in warmer periods (summer/June). Weekly distribution exhibited no significant variation. Fourier analysis revealed a statistically significant circadian variation (p<0.0001) with a trough between 23:00 and 00:00, a prominent peak from 07:00 to 08:00, and a minor peak between 20:00 and 21:00. Subgroup analyses identified circadian rhythmicity in all subgroups, except for the DeBakey III group and the female group. Using the 75 chronotype-related SNPs, evidence was found of a potential causal effect of chronotype on the risk of AAD, as the inverse-variance weighting analysis showed that self-report chronotype of morningness was associated with a decreased risk of AAD.

CONCLUSION

The findings substantiate that the initiation of AAD displays noteworthy seasonal, monthly, and circadian patterns. The Mendelian randomisation analysis also indicated that the onset of acute aortic dissection is related to circadian rhythm. These findings offer a fresh perspective, facilitating the identification of triggering factors for AAD and bolstering preventive measures for this catastrophic event.

In Vitro Models of Cardiovascular Disease: Embryoid Bodies, Organoids and Everything in Between

Cardiovascular disease comprises a group of disorders affecting or originating within tissues and organs of the cardiovascular system; most, if not all, will eventually result in cardiomyocyte dysfunction or death, negatively impacting cardiac function. Effective models of cardiac disease are thus important for understanding crucial aspects of disease progression, while recent advancements in stem cell biology have allowed for the use of stem cell populations to derive such models. These include three-dimensional (3D) models such as stem cell-based models of embryos (SCME) as well as organoids, many of which are frequently derived from embryoid bodies (EB). Not only can they recapitulate 3D form and function, but the developmental programs governing the self-organization of cell populations into more complex tissues as well. Many different organoids and SCME constructs have been generated in recent years to recreate cardiac tissue and the complex developmental programs that give rise to its cellular composition and unique tissue morphology. It is thus the purpose of this narrative literature review to describe and summarize many of the recently derived cardiac organoid models as well as their use for the recapitulation of genetic and acquired disease. Owing to the cellular composition of the models examined, this review will focus on disease and tissue injury associated with embryonic/fetal tissues.

Circadian regulation of sinoatrial nodal cell pacemaking function: Dissecting the roles of autonomic control, body temperature, and local circadian rhythmicity

Strong circadian (~24h) rhythms in heart rate (HR) are critical for flexible regulation of cardiac pacemaking function throughout the day. While this circadian flexibility in HR is sustained in diverse conditions, it declines with age, accompanied by reduced maximal HR performance. The intricate regulation of circadian HR involves the orchestration of the autonomic nervous system (ANS), circadian rhythms of body temperature (CRBT), and local circadian rhythmicity (LCR), which has not been fully understood. Here, we developed a mathematical model describing ANS, CRBT, and LCR in sinoatrial nodal cells (SANC) that accurately captures distinct circadian patterns in adult and aged mice. Our model underscores how the alliance among ANS, CRBT, and LCR achieves circadian flexibility to cover a wide range of firing rates in SANC, performance to achieve maximal firing rates, while preserving robustness to generate rhythmic firing patterns irrespective of external conditions. Specifically, while ANS dominates in promoting SANC flexibility and performance, CRBT and LCR act as primary and secondary boosters, respectively, to further enhance SANC flexibility and performance. Disruption of this alliance with age results in impaired SANC flexibility and performance, but not robustness. This unexpected outcome is primarily attributed to the age-related reduction in parasympathetic activities, which maintains SANC robustness while compromising flexibility. Our work sheds light on the critical alliance of ANS, CRBT, and LCR in regulating time-of-day cardiac pacemaking function and dysfunction, offering insights into novel therapeutic targets for the prevention and treatment of cardiac arrhythmias.