Biology subjects

Posnack, N.

Publications and source records attributed to Posnack, N..

7 recordsLinked to original sources

bioRxiv2026

Functional Assessment and Extended Culture of Human Pediatric Cardiac Tissue Slices for Preclinical Testing

Background: Living human myocardial slices preserve native tissue architecture, but their application to pediatric cardiac physiology or prolonged functional testing remains limited. We adapted a passive culture method for small surgical myocardial specimens obtained from patients with congenital heart disease (CHD). Methods: Atrial and ventricular specimens were obtained from 41 cardiac surgery patients (7.7{+/-}11.1 years; 1 day-49 years). Myocardial tissue was sectioned into slices and studied acutely, or maintained under free floating, rocking cell culture conditions without electrical or mechanical stimulation. Calcium transients were recorded in response to external pacing (0.2-2 Hz) at baseline, and after isoproterenol or norepinephrine exposure. Selected preparations underwent viability, histological, and gene expression analyses. Results: Pacing evoked calcium transients were recorded from all four cardiac chambers, exhibiting expected frequency-dependent shortening. Mean interslice and intraslice coefficients of variation were 11.1% and 7.6%. Viability was 85.8 {+/-} 5.6% post-slicing and 78.8 {+/-} 5.0% after 3-5 hours. Calcium transients remained detectable through 178 days in atrial and 119 days in ventricular slices. Calcium transient durations were relatively stable during extended culture. Beta-adrenergic agonists shortened calcium transient durations (isoproterenol: 32% atrial, 25% ventricular at 0.3 Hz); responses to isoproterenol persisted to approximately 120 days in selected atrial slices and 60 days in ventricular slices. Selected histological features were preserved, although some extracellular matrix and apoptosis related transcripts changed. Conclusions: Small surgical specimens support repeated physiological measurements and pharmacological testing during extended passive culture, providing a platform for human developmental and disease-specific cardiac research.

physiology↗

bioRxiv2026

Postnatal Development Shapes the Cardiac Response to Milrinone

Background: Milrinone, a phosphodiesterase-3 (PDE-3) inhibitor, is widely used to improve cardiac output in pediatric and adult patients. Yet, developmental differences in myocardial responsiveness to milrinone remain incompletely understood. In this study, we examined the impact of postnatal maturation on the acute cardiac effects of milrinone using an intact guinea pig heart model. Methods: Neonatal (0-2 days), juvenile (4-10 days), and adult (> 6 months) guinea pig hearts were excised, Langendorff-perfused, and cardiac metrics were evaluated under basal conditions and in response to acute milrinone treatment (15 minutes, 10 and 100 M sequential concentrations). Pseudo-electrocardiograms were recorded continuously and left ventricular pressure measurements were performed under sinus rhythm and in response to external pacing. Post-rest potentiation was used to assess contractile reserve, and optical action potentials and calcium transients were recorded. Results: Baseline left ventricular developed pressure (LVDP), action potential duration (APD), and calcium transient duration (CaD) increased with postnatal maturation, consistent with developmental cardiomyocyte remodeling and refinement of excitation-contraction coupling. Milrinone increased heart rate in all age groups, with the greatest chronotropic response at 100 M. Milrinone also increased ventricular contractility and relaxation across developmental stages, but the magnitude of the response varied with age and was attenuated during high frequency pacing. Adult hearts had the greatest increase in LVDP during sinus rhythm and robust post-rest potentiation, which were less pronounced in neonatal hearts. APD and CaD were shortened in neonatal and adult hearts, but were minimally affected in juveniles, indicating a non-linear developmental pattern. Conclusions: Milrinone exerts positive chronotropic, inotropic, and lusitropic effects throughout development, but the magnitude and frequency dependence of these responses vary with age. These findings suggest that postnatal maturation influences the cardiac response to PDE3 inhibition. These developmental differences highlight the importance of considering age as a biological factor in pediatric drug selection and dosing.

pharmacology and toxicology↗

bioRxiv2025

Chamber-Specific Transcriptomic Insight into Cardiac Development using Guinea Pig and Human Heart Tissue

The heart undergoes significant molecular and functional adaptations throughout postnatal development. However, to date, our understanding of these dynamic changes in the human heart is limited. Moreover, advances in pediatric cardiac research can be hindered by a lack of preclinical models that accurately reflect human heart maturation. Guinea pigs may serve as a useful model for human cardiac research, as the guinea pig and human myocardium have similar ion channel expression and cardiovascular drug responsiveness. Despite these similarities, gene expression patterns during postnatal heart development have not been comprehensively investigated. In this study, we first characterized transcriptional changes in neonatal, juvenile, and adult guinea pig hearts - identifying gene ontologies and pathways associated with cardiac maturation. Second, we compared the transcriptional profile of right atria and left ventricular tissue to highlight unique and shared chamber-specific patterns in guinea pigs over time. Finally, we conducted a cross-species comparison of the right atrial transcriptome between humans and guinea pigs to identify conserved maturation markers and gene expression patterns. Our findings provide a molecular framework for understanding age- and chamber-specific cardiac development, supporting the guinea pig as a promising preclinical model for studying human heart maturation. By identifying conserved gene programs and developmental markers across species, this study lays the groundwork for age-specific pharmacological strategies and computational models that can help to refine treatment decisions and outcomes for pediatric cardiology patients. New and NoteworthyExisting knowledge on postnatal heart development and cardiomyocyte maturation is limited. We investigated age-dependent transcriptional changes in neonatal, juvenile, and adult guinea pig hearts - and then conducted a cross-species comparison to identify age-specific patterns that are conserved in the guinea pig and human atria. Expanding our knowledge of chamber- and age-specific gene expression patterns can inform and guide the selection of cardiovascular therapies in the pediatric population, where developmental differences are understudied.

genomics↗

bioRxiv2024

Validation of a Demography-Based Adaptive QTc Formula using Pediatric and Adult Datasets Acquired from Humans and Guinea Pigs

IntroductionA variety of QT rate-correction (QTc) formulae have been utilized for both clinical and research purposes. However, these formulae are not universally effective, likely due to significant influences of demographic diversity on the QT-HR relationship. To address this limitation, we proposed an adaptive QTc (QTcAd) formula that adjusts to subject demographics (i.e., age). Further, we compared the efficacy and accuracy of the QTcAd formula to other widely used alternatives. MethodUsing age as a demographic parameter, we tested the QTcAd formula across diverse age groups with different heart rates (HR) in both humans and guinea pigs. Utilizing retrospective human (n=1360) and guinea pig electrocardiogram (ECG) data from in-vivo (n=55) and ex-vivo (n=66) settings, we evaluated the formulas effectiveness. Linear regression fit parameters of HR-QTc (slope and R{superscript 2}) were utilized for performance assessment. To evaluate the accuracy of the predicted QTc, we acquired epicardial electrical and optical voltage data from Langendorff-perfused guinea pig hearts. ResultsIn both human subjects and guinea pigs, the QTcAd formula consistently outperformed other formulae across all age groups. For instance, in a 20-year-old human group (n=300), the QTcAd formula successfully nullified the inverse HR-QT relationship (R{superscript 2}=5.1E-09, slope=-3.5E-05), while the Bazett formula (QTcB) failed to achieve comparable effectiveness (R{superscript 2}= 0.20, slope=0.91). Moreover, the QTcAd formula exhibited better accuracy than the age-specific Benatar formula (QTcBe), which overcorrected QTc (1-week human QT: 263.8{+/-}14.8 ms, QTcAd: 263.8{+/-}7.3 ms, p=0.62; QTcBe: 422.5{+/-}7.3 ms, p<0.0001). The optically measured pseudo-QT interval (143{+/-}22.5 ms, n=44) was better approximated by QTcAd (180.6{+/-}17.0 ms) compared to all other formulae. Furthermore, we demonstrated that the QTcAd formula was not inferior to individual-specific QTc formulae. ConclusionThe demography-based QTcAd formula showed superior performance across human and guinea pig age groups, which may enhance the efficacy of QTc for cardiovascular disease diagnosis, risk stratification, and drug safety testing. What is knownCorrected QT (QTc) is a well-known ECG biomarker for cardiovascular disease risk stratification and drug safety testing. Various QT rate-correction formulae have been developed, but these formulae do not perform consistently across diverse datasets (e.g., sex, age, disease, species). What the study addsWe introduce a novel QTc formula (QTcAd) that adapts to demographic variability, as the parameters can be modified based on the characteristics of the study population. The formula (QTcAd = QT + (|m|*(HR-HRmean)) - includes the absolute slope (m) of the linear regression of QT and heart rate (HR) and the mean HR of the population (HRmean) as population characteristics parametersUsing datasets from both pediatric and adult human subjects and an animal model, we demonstrate that the QTcAd formula is more effective at eliminating the QT-HR inverse relationship, as compared to other commonly used correction formulae.

physiology↗

bioRxiv2023

hiPSC-CM Electrophysiology: Impact of Temporal Changes and Study Parameters on Experimental Reproducibility

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are frequently used for preclinical cardiotoxicity testing and remain an important tool for confirming model-based predictions of drug effects in accordance with the Comprehensive in Vitro Proarrhythmia Assay (CiPA) initiative. Despite the considerable benefits hiPSC-CMs provide, concerns surrounding experimental reproducibility have emerged. Our study aimed to investigate the effects of temporal changes and experimental parameters on hiPSC-CM electrophysiology. hiPSC-CMs (iCell cardiomyocyte2) were cultured for 14 days and biosignals were acquired using a microelectrode array (MEA) system. Continuous recordings revealed a 22.6% increase in the beating rate and 7.7% decrease in the field potential duration (FPD) during a 20-minute equilibration period. Location specific differences across a multiwell plate were also observed, with hiPSC-CMs in the outer rows beating 8.8 beats per minute (BPM) faster than the inner rows. Cardiac endpoints were also impacted by cell culture duration; from 2-14 days the beating rate decreased (-12.7 BPM), FPD lengthened (+257 ms), and spike amplitude increased (+3.3 mV). Cell culture duration (4-10 days) also impacted hiPSC-CM drug responsiveness (E-4031, nifedipine, isoproterenol). Our study highlights multiple sources of variability that should be considered and addressed when performing hiPSC-CM MEA studies. To improve reproducibility and data interpretation, MEA-based studies should establish a standardized protocol and report key experimental conditions (e.g., culture time, equilibration time, electrical stimulation settings, report raw data values). New & NoteworthyWe demonstrate that hiPSC-CM electrophysiology measurements are significantly impacted by slight deviations in experimental techniques including electrical stimulation protocols, equilibration time, well-to-well variability, and length of hiPSC-CM culture. Furthermore, our results indicate that hiPSC-CM drug responsiveness changes within the first two weeks following defrost. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=106 SRC="FIGDIR/small/560475v1_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@3740e7org.highwire.dtl.DTLVardef@1861a86org.highwire.dtl.DTLVardef@1376dd7org.highwire.dtl.DTLVardef@c5364_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract Image created with Biorender.com C_FIG

physiology↗

bioRxiv2023

Comparative cardiotoxicity assessment of bisphenol chemicals and estradiol using human induced pluripotent stem cell-derived cardiomyocytes

BackgroundBisphenol A (BPA) is commonly used to manufacture consumer and medical-grade plastics. Due to health concerns, BPA substitutes are being incorporated - including bisphenol S (BPS) and bisphenol F (BPF) - without a comprehensive understanding of their toxicological profile. ObjectivePrevious studies suggest that bisphenol chemicals perturb cardiac electrophysiology in a manner that is similar to 17{beta}-estradiol (E2). We aimed to compare the effects of E2 with BPA, BPF, and BPS using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM). MethodsCardiac parameters were evaluated using microelectrode array (MEA) technology and live-cell fluorescent imaging at baseline and in response to chemical exposure (0.001-100 M). ResultsCardiac metrics remained relatively stable after exposure to nanomolar concentrations (1-1,000 nM) of E2, BPA, BPF, or BPS. At higher micromolar concentrations, chemical exposures resulted in a decrease in the depolarizing spike amplitude, shorter field potential and action potential duration, shorter calcium transient duration, and decrease in hiPSC-CM contractility (E2 > BPA > BPF >> BPS). Cardiomyocyte physiology was largely undisturbed by BPS exposure. BPA-induced effects were exaggerated when co-administered with an L-type calcium channel antagonist (verapamil) or E2 - and reduced when co-administered with an L-type calcium channel agonist (Bay K8644) or an estrogen receptor alpha antagonist (MPP). E2-induced effects generally mirrored those of BPA, but were not exaggerated by co-administration with an L-type calcium channel antagonist. DiscussionCollectively across multiple cardiac endpoints, E2 was the most potent and BPS was the least potent disruptor of hiPSC-CM function. Although the observed cardiac effects of E2 and BPA were similar, a few distinct differences suggest that these chemicals may act (in part) through different mechanisms. hiPSC-CM are a useful model for screening cardiotoxic chemicals, nevertheless, the described in vitro findings should be validated using a more complex ex vivo and/or in vivo model.

pharmacology and toxicology↗

bioRxiv2020

Chronic Perinatal Hypoxia Delays Cardiac Maturation in a Mouse Model for Cyanotic Congenital Heart Disease

BackgroundCompared to acyanotic congenital heart disease (CHD), cyanotic CHD has an increased risk of lifelong mortality and morbidity. These adverse outcomes may be attributed to delayed cardiomyocyte maturation, since the transition from a hypoxic fetal milieu to oxygen rich postnatal environment is disrupted. We established a rodent model to replicate hypoxic myocardial conditions spanning perinatal development, and tested the hypothesis that chronic hypoxia impairs cardiac development. MethodsMouse dams were housed in hypoxia beginning at embryonic day 16. Pups stayed in hypoxia until postnatal day (P)8 when cardiac development is nearly complete. Global gene expression was quantified at P8 and at P30, after recovering in normoxia. Phenotypic testing included electrocardiogram, echocardiogram, and ex-vivo electrophysiology study. ResultsHypoxic animals were 48% smaller than controls. Gene expression was grossly altered by hypoxia at P8 (1427 genes affected), but normalized after recovery (P30). Electrocardiograms revealed bradycardia and slowed conduction velocity in hypoxic animals at P8, which resolved after recovery (P30). Notable differences that persisted after recovery (P30) included a 65% prolongation in ventricular effective refractory period, sinus node dysfunction, and a 24% reduction in contractile function in animals exposed to hypoxia. ConclusionsWe investigated the impact of chronic hypoxia on the developing heart. Perinatal hypoxia was associated with changes in gene expression and cardiac function. Persistent changes to the electrophysiologic substrate and contractile function warrant further investigation, and may contribute to adverse outcomes observed in the cyanotic CHD population.

physiology↗