Cardiac differentiation of embryonic stem cells (ESCs) can give rise to de novo chamber cardiomyocytes and nodal pacemaker cells. Compared with our understanding of direct differentiation toward atrial and ventricular myocytes, the mechanisms for nodal pacemaker cell commitment are not well understood. Taking a cue from the prominence of canonical Wnt signaling during cardiac pacemaker tissue development in chick embryos, we asked if modulations of Wnt signaling influence cardiac progenitors to bifurcate to either chamber cardiomyocytes or pacemaker cells. Omitting an exogenous Wnt inhibitor, which is routinely added to maximize cardiac myocyte yield during differentiation of mouse and human ESCs, led to increased yield of spontaneously beating cardiomyocytes with action potential properties similar to those of native sinoatrial node pacemaker cells. The pacemaker phenotype was accompanied by enhanced expression of genes and gene products that mark nodal pacemaker cells such as Hcn4, Tbx18, Tbx3, and Shox2. Addition of exogenous Wnt3a ligand, which activates canonical Wnt/β-catenin signaling, increased the yield of pacemaker-like myocytes while reducing cTNT-positive pan-cardiac differentiation. Conversely, addition of inhibitors of Wnt/β-catenin signaling led to increased chamber myocyte lineage development at the expense of pacemaker cell specification. The positive impact of canonical Wnt signaling on nodal pacemaker cell differentiation was evidenced in direct differentiation of two human ESC lines and human induced pluripotent stem cells. Our data identify the Wnt/β-catenin pathway as a critical determinant of cardiac myocyte subtype commitment during ESC differentiation: endogenous Wnt signaling favors the pacemaker lineage, whereas its suppression promotes the chamber cardiomyocyte lineage.

Introduction

Early reports highlighted racial/ethnic disparities in the severity of COVID-19 seen across the USA; the extent to which these disparities have persisted over time remains unclear. Our research objective was to understand temporal trends in racial/ethnic variation in severity of COVID-19 illness presenting over time.

Methods

We conducted a retrospective cohort analysis using longitudinal data from Cedars-Sinai Medical Center, a high-volume health system in Southern California. We studied patients admitted to the hospital with COVID-19 illness from 4 March 2020 through 5 December 2020. Our primary outcome was COVID-19 severity of illness among hospitalised patients, assessed by racial/ethnic group status. We defined overall illness severity as an ordinal outcome: hospitalisation but no intensive care unit (ICU) admission; admission to the ICU but no intubation; and intubation or death.

Results

A total of 1584 patients with COVID-19 with available demographic and clinical data were included. Hispanic/Latinx compared with non-Hispanic white patients had higher odds of experiencing more severe illness among hospitalised patients (OR 2.28, 95% CI 1.62 to 3.22) and this disparity persisted over time. During the initial 2 months of the pandemic, non-Hispanic blacks were more likely to suffer severe illness than non-Hispanic whites (OR 2.02, 95% CI 1.07 to 3.78); this disparity improved by May, only to return later in the pandemic.

Conclusion

In our patient sample, the severity of observed COVID-19 illness declined steadily over time, but these clinical improvements were not seen evenly across racial/ethnic groups; greater illness severity continues to be experienced among Hispanic/Latinx patients.

Importance

Certain individuals, when infected by SARS-CoV-2, tend to develop the more severe forms of Covid-19 illness for reasons that remain unclear.

Objective

To determine the demographic and clinical characteristics associated with increased severity of Covid-19 infection.

Design

Retrospective observational study. We curated data from the electronic health record, and used multivariable logistic regression to examine the association of pre-existing traits with a Covid-19 illness severity defined by level of required care: need for hospital admission, need for intensive care, and need for intubation.

Setting

A large, multihospital healthcare system in Southern California.

Participants

All patients with confirmed Covid-19 infection (N = 442).

Results

Of all patients studied, 48% required hospitalization, 17% required intensive care, and 12% required intubation. In multivariable-adjusted analyses, patients requiring a higher levels of care were more likely to be older (OR 1.5 per 10 years, P<0.001), male (OR 2.0, P = 0.001), African American (OR 2.1, P = 0.011), obese (OR 2.0, P = 0.021), with diabetes mellitus (OR 1.8, P = 0.037), and with a higher comorbidity index (OR 1.8 per SD, P<0.001). Several clinical associations were more pronounced in younger compared to older patients (Pinteraction<0.05). Of all hospitalized patients, males required higher levels of care (OR 2.5, P = 0.003) irrespective of age, race, or morbidity profile.

Conclusions and relevance

In our healthcare system, greater Covid-19 illness severity is seen in patients who are older, male, African American, obese, with diabetes, and with greater overall comorbidity burden. Certain comorbidities paradoxically augment risk to a greater extent in younger patients. In hospitalized patients, male sex is the main determinant of needing more intensive care. Further investigation is needed to understand the mechanisms underlying these findings.

Objective

We sought to determine the extent of SARS-CoV-2 seroprevalence and the factors associated with seroprevalence across a diverse cohort of healthcare workers.

Design

Observational cohort study of healthcare workers, including SARS-CoV-2 serology testing and participant questionnaires.

Settings

A multisite healthcare delivery system located in Los Angeles County.

Participants

A diverse and unselected population of adults (n=6062) employed in a multisite healthcare delivery system located in Los Angeles County, including individuals with direct patient contact and others with non-patient-oriented work functions.

Main outcomes

Using Bayesian and multivariate analyses, we estimated seroprevalence and factors associated with seropositivity and antibody levels, including pre-existing demographic and clinical characteristics; potential COVID-19 illness-related exposures; and symptoms consistent with COVID-19 infection.

Results

We observed a seroprevalence rate of 4.1%, with anosmia as the most prominently associated self-reported symptom (OR 11.04, p<0.001) in addition to fever (OR 2.02, p=0.002) and myalgias (OR 1.65, p=0.035). After adjusting for potential confounders, seroprevalence was also associated with Hispanic ethnicity (OR 1.98, p=0.001) and African-American race (OR 2.02, p=0.027) as well as contact with a COVID-19-diagnosed individual in the household (OR 5.73, p<0.001) or clinical work setting (OR 1.76, p=0.002). Importantly, African-American race and Hispanic ethnicity were associated with antibody positivity even after adjusting for personal COVID-19 diagnosis status, suggesting the contribution of unmeasured structural or societal factors.

Conclusion and relevance

The demographic factors associated with SARS-CoV-2 seroprevalence among our healthcare workers underscore the importance of exposure sources beyond the workplace. The size and diversity of our study population, combined with robust survey and modelling techniques, provide a vibrant picture of the demographic factors, exposures and symptoms that can identify individuals with susceptibility as well as potential to mount an immune response to COVID-19.