Physical Frailty is Modifiable in Young Cardiac Rehabilitation Patients.

Frailty is a standardized, quantitative metric used to assess multisystem physiologic reserve and vulnerability to poor health outcomes. Cardiac rehabilitation (CR) positively impacts patient outcomes, including frailty, in adult cardiovascular disease (CVD); however, both the frailty paradigm and CR are understudied in pediatric CVD. This retrospective, single-center cohort study aimed to determine baseline composite frailty for pediatric-onset CVD patients and examine its change throughout CR using a proposed frailty assessment tool. Youth with pediatric-onset CVD participating in CR were stratified into five CVD diagnostic groups: post-heart transplant (HTx) (n = 34), post-ventricular assist device (VAD) (n = 12), single ventricle (n = 20) and biventricular (n = 29) congenital heart disease, and cardiomyopathy (n = 25), and frailty was assessed at baseline and every 30 days during CR. Post-HTx and post-VAD groups had significantly higher median frailty scores at baseline (6/10 and 5.75/10, respectively) driven by reduced strength, gait speed, and functional status. All groups except post-VAD displayed a significant absolute reduction in frailty from baseline to 120 days (HTx: - 3.5; VAD: - 3; SV CHD: - 1; BV CHD: - 1; CM: - 1.5), with similar median post-CR scores (1-3/10 in all groups). These improvements did not significantly correlate with number of CR sessions attended. This study established that frailty exhibits discriminatory utility across pediatric-onset CVD groups at baseline and is significantly modifiable over time. Improvements in frailty and other fitness metrics are likely due to a combination of post-operative recovery, post-diagnosis pharmacological and lifestyle changes, and CR. Further study of this frailty tool is needed to explore its prognostic utility.

Epigenetic Priming of Human Pluripotent Stem Cell-Derived Cardiac Progenitor Cells Accelerates Cardiomyocyte Maturation.

Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) exhibit a fetal phenotype that limits in vitro and therapeutic applications. Strategies to promote cardiomyocyte maturation have focused interventions on differentiated hPSC-CMs, but this study tests priming of early cardiac progenitor cells (CPCs) with polyinosinic-polycytidylic acid (pIC) to accelerate cardiomyocyte maturation. CPCs were differentiated from hPSCs using a monolayer differentiation protocol with defined small molecule Wnt temporal modulation, and pIC was added during the formation of early CPCs. pIC priming did not alter the expression of cell surface markers for CPCs (>80% KDR+/PDGFRα+), expression of common cardiac transcription factors, or final purity of differentiated hPSC-CMs (∼90%). However, CPC differentiation in basal medium revealed that pIC priming resulted in hPSC-CMs with enhanced maturity manifested by increased cell size, greater contractility, faster electrical upstrokes, increased oxidative metabolism, and more mature sarcomeric structure and composition. To investigate the mechanisms of CPC priming, RNAseq revealed that cardiac progenitor-stage pIC modulated early Notch signaling and cardiomyogenic transcriptional programs. Chromatin immunoprecipitation of CPCs showed that pIC treatment increased deposition of the H3K9ac activating epigenetic mark at core promoters of cardiac myofilament genes and the Notch ligand, JAG1. Inhibition of Notch signaling blocked the effects of pIC on differentiation and cardiomyocyte maturation. Furthermore, primed CPCs showed more robust formation of hPSC-CMs grafts when transplanted to the NSGW mouse kidney capsule. Overall, epigenetic modulation of CPCs with pIC accelerates cardiomyocyte maturation enabling basic research applications and potential therapeutic uses. Stem Cells 2019;37:910-923.

The Coagulopathy of Acute Promyelocytic Leukemia: An Updated Review of Pathophysiology, Risk Stratification, and Clinical Management.

Acute promyelocytic leukemia (APL) has a well-established mechanism and a long-term prognosis that exceeds that of any other acute leukemia. These improving outcomes are due, in part, to all-trans retinoic acid (ATRA) and arsenic trioxide (ATO), two targeted and highly active agents in this disease. However, there remains a considerable morbidity and mortality risk in APL secondary to clinically significant hemorrhagic and/or thrombotic events. Prevention and treatment of these coagulopathic complications remain significant impediments to further progress in optimizing outcomes for patients with APL. Moreover, the relative rarity of APL hinders adequately powered randomized controlled trials for evaluating APL coagulopathy management strategies. This review draws from peer-reviewed works falling between initial descriptions of APL in 1957 and work published prior to January 2023 and provides an updated overview of the pathophysiology of hemorrhagic and thrombotic complications in APL, outlines risk stratification parameters, and compiles current clinical best practices. An improved understanding of the pathophysiologic mechanisms driving hemorrhage and thrombosis along with the completion of well-designed trials of management strategies will assist clinicians in developing interventions that mitigate these devastating complications in an otherwise largely curable disease.

Humanized Mouse Models for Evaluation of PSC Immunogenicity.

New human pluripotent stem cell (hPSC)-derived therapies are advancing to clinical trials at an increasingly rapid pace. In addition to ensuring that the therapies function properly, there is a critical need to investigate the human immune response to these cell products. A robust allogeneic (or autologous) immune response could swiftly eliminate an otherwise promising cell therapy, even in immunosuppressed patients. In coming years, researchers in the regenerative medicine field will need to utilize a number of in vitro and in vivo assays and models to evaluate and better understand hPSC immunogenicity. Humanized mouse models-mice engrafted with functional human immune cell types-are an important research tool for investigating the mechanisms of the adaptive immune response to hPSC therapies. This article provides an overview of humanized mouse models relevant to the study of hPSC immunogenicity and explores central considerations for investigators seeking to utilize these powerful models in their research. © 2020 Wiley Periodicals LLC.