Effects of Substrate Mechanics on Contractility of Cardiomyocytes Generated from Human Pluripotent Stem Cells

Human pluripotent stem cell (hPSC-) derived cardiomyocytes have potential applications in drug discovery, toxicity testing, developmental studies, and regenerative medicine. Before these cells can be reliably utilized, characterization of their functionality is required to establish their similarity to native cardiomyocytes. We tracked fluorescent beads embedded in 4.4–99.7 kPa polyacrylamide hydrogels beneath contracting neonatal rat cardiomyocytes and cardiomyocytes generated from hPSCs via growth-factor-induced directed differentiation to measure contractile output in response to changes in substrate mechanics. Contraction stress was determined using traction force microscopy, and morphology was characterized by immunocytochemistry for α-actinin and subsequent image analysis. We found that contraction stress of all types of cardiomyocytes increased with substrate stiffness. This effect was not linked to beating rate or morphology. We demonstrated that hPSC-derived cardiomyocyte contractility responded appropriately to isoprenaline and remained stable in culture over a period of 2 months. This study demonstrates that hPSC-derived cardiomyocytes have appropriate functional responses to substrate stiffness and to a pharmaceutical agent, which motivates their use in further applications such as drug evaluation and cardiac therapies

YAP1 withdrawal in hepatoblastoma drives therapeutic differentiation of tumor cells to functional hepatocyte-like cells

BACKGROUND and AIMS: Despite surgical and chemotherapeutic advances, the five-year survival rate for Stage IV Hepatoblastoma (HB), the predominant pediatric liver tumor, remains at 27%. YAP1 and beta-Catenin co-activation occurs in 80% of children\u27s HB; however, a lack of conditional genetic models precludes tumor maintenance exploration. Thus, the need for a targeted therapy remains unmet. Given the predominance of YAP1 and beta-Catenin activation in HB, we sought to evaluate YAP1 as a therapeutic target in HB. APPROACH and RESULTS: We engineered the first conditional HB murine model using hydrodynamic injection to deliver transposon plasmids encoding inducible YAP1(S127A) , constitutive beta-Catenin(DelN90) , and a luciferase reporter to murine liver. Tumor regression was evaluated using bioluminescent imaging, and tumor landscape characterized using RNA and ATAC sequencing, and DNA foot-printing. Here we show that YAP1(S127A) withdrawal mediates \u3e90% tumor regression with survival for 230+ days in mice. YAP1 (S127A) withdrawal promotes apoptosis in a subset of tumor cells and in remaining cells induces a cell fate switch driving therapeutic differentiation of HB tumors into Ki-67 negative hbHep cells with hepatocyte-like morphology and mature hepatocyte gene expression. YAP1 (S127A) withdrawal drives formation of hbHeps by modulating liver differentiation transcription factor (TF) occupancy. Indeed, tumor-derived hbHeps, consistent with their reprogrammed transcriptional landscape, regain partial hepatocyte function and rescue liver damage in mice. CONCLUSIONS: YAP1(S127A) withdrawal, without silencing oncogenic beta-Catenin, significantly regresses hepatoblastoma, providing the first in vivo data to support YAP1 as a therapeutic target for HB. YAP1(S127A) withdrawal alone sufficiently drives long-term regression in hepatoblastoma because it promotes cell death in a subset of tumor cells and modulates transcription factor occupancy to reverse the fate of residual tumor cells to mimic functional hepatocytes

Impact of Weekend Versus Weekday Admission on Pediatric Trauma Patient Morbidity and Mortality

Background Injuries are the leading cause of death in the United States for children between the ages of 1 and 19 years. Weekend hospital admission has been associated with poor outcomes and higher mortality rates for a variety of diseases. We examined the impact of weekend versus weekday admission on in-hospital morbidity and case-fatality rates for pediatric trauma patients. Methods We performed a cross-sectional analysis on the 2016 Kids’ Inpatient Database. The study population included pediatric trauma patients under the age of 19 years which were stratified by weekend vs weekday admission. Weightings were used to produce national estimates. Multiple logistic regression analyses were performed to assess the odds of in-hospital complications and death after adjusting for a variety of potentially confounding demographic and clinical factors. Results Patients admitted on a weekend were older, more frequently male, White, and privately insured. Weekend admissions had a higher Injury Severity Score (6.7 vs 5.4, p\u3c0.001), as well as higher rate of intensive care unit (ICU) admission (8.5% vs 7.1%, p\u3c0.001) and in-hospital case-fatality rate (1.3% vs 1.1%, p=0.003), but lower rate of in-hospital complications (6.1% vs 6.8%, p\u3c0.001). Unadjusted logistic regression demonstrated that weekend admission was associated with higher odds of in-hospital death as compared to weekday admission (odds ratio 1.20, 95% confidence interval [CI] 1.07 – 1.35), but in the multivariable adjusted model this was no longer statistically significant (adjusted odds ratio [aOR] 1.06, 95% CI 0.94 – 1.20). Weekend admission was associated with lower odds of in-hospital complications (aOR 0.90, 95% CI 0.86 - 0.95), but higher odds of ICU admission (aOR 1.12, 95% CI 1.06 – 1.18). Conclusions Weekend admission in pediatric trauma is associated with higher odds of ICU admission. There does not appear to be an association between weekend admission and odds of in-hospital death, however it may be associated with lower odds of in-hospital complications

Caregiver-perceived neighborhood safety and pediatric asthma severity: 2017-2018 National Survey of Children\u27s Health

OBJECTIVE: To examine the association between caregiver-perceived neighborhood safety and pediatric asthma severity using a cross-sectional, nationally representative sample. STUDY DESIGN: Using data from the 2017-2018 National Survey of Children\u27s Health, children aged 6-17 years with primary caregiver report of a current asthma diagnosis were included (unweighted N = 3209; weighted N = 3,909,178). Perceived neighborhood safety, asthma severity (mild vs. moderate/severe), demographic, household, and health/behavioral covariate data were collected from primary caregiver report. Poisson regression with robust error variance was used to estimate the association between perceived neighborhood safety and caregiver-reported pediatric asthma severity. RESULTS: Approximately one-third of children studied had moderate/severe asthma. A total of 42% of children with mild asthma and 52% of children with moderate/severe asthma identified as Hispanic or non-Hispanic Black. Nearly 20% of children with mild asthma and 40% of children with moderate/severe asthma were from families living below the federal poverty level (FPL). Children living in neighborhoods perceived by their caregiver to be unsafe had higher prevalence of moderate/severe asthma compared to those in the safest neighborhoods (adjusted prevalence ratio: 1.34; 95% confidence interval: 1.04-1.74). This association was found to be independent of race/ethnicity, household FPL, household smoking, and child\u27s physical activity level after adjusting for covariates. CONCLUSIONS: Children living in neighborhoods perceived by their caregiver to be unsafe have higher prevalence of moderate or severe asthma. Further investigation of geographic context and neighborhood characteristics that influence childhood asthma severity may inform public health strategies to reduce asthma burden and improve disease outcomes

A multicenter evaluation of pediatric emergency department injury visits during the COVID-19 pandemic.

BACKGROUND: Injuries, the leading cause of death in children 1-17 years old, are often preventable. Injury patterns are impacted by changes in the childs environment, shifts in supervision, and caregiver stressors. The objective of this study was to evaluate the incidence and proportion of injuries, mechanisms, and severity seen in Pediatric Emergency Departments (PEDs) during the COVID-19 pandemic. METHODS: This multicenter, cross-sectional study from January 2019 through December 2020 examined visits to 40 PEDs for children < 18 years old. Injury was defined by at least one International Classification of Disease-10th revision (ICD-10) code for bodily injury (S00-T78). The main study outcomes were total and proportion of PED injury-related visits compared to all visits in March through December 2020 and to the same months in 2019. Weekly injury visits as a percentage of total PED visits were calculated for all weeks between January 2019 and December 2020. RESULTS: The study included 741,418 PED visits for injuries pre-COVID-19 pandemic (2019) and during the COVID-19 pandemic (2020). Overall PED visits from all causes decreased 27.4% in March to December 2020 compared to the same time frame in 2019; however, the proportion of injury-related PED visits in 2020 increased by 37.7%. In 2020, injured children were younger (median age 6.31 years vs 7.31 in 2019), more commonly White (54% vs 50%, p < 0.001), non-Hispanic (72% vs 69%, p < 0.001) and had private insurance (35% vs 32%, p < 0.001). Injury hospitalizations increased 2.2% (p < 0.001) and deaths increased 0.03% (p < 0.001) in 2020 compared to 2019. Mean injury severity score increased (2.2 to 2.4, p < 0.001) between 2019 and 2020. Injuries declined for struck by/against (- 4.9%) and overexertion (- 1.2%) mechanisms. Injuries proportionally increased for pedal cycles (2.8%), cut/pierce (1.5%), motor vehicle occupant (0.9%), other transportation (0.6%), fire/burn (0.5%) and firearms (0.3%) compared to all injuries in 2020 versus 2019. CONCLUSIONS: The proportion of PED injury-related visits in March through December 2020 increased compared to the same months in 2019. Racial and payor differences were noted. Mechanisms of injury seen in the PED during 2020 changed compared to 2019, and this can inform injury prevention initiatives