Biology subjects

Salameh, S.

Publications and source records attributed to Salameh, S..

7 recordsLinked to original sources

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

Deep skin fibroblast-mediated macrophage recruitment supports acute wound healing

Epithelial and immune cells have long been appreciated for their contribution to the early immune response after injury; however, much less is known about the role of mesenchymal cells. Using single nuclei RNA-sequencing, we defined changes in gene expression associated with inflammation at 1-day post-wounding (dpw) in mouse skin. Compared to keratinocytes and myeloid cells, we detected enriched expression of pro-inflammatory genes in fibroblasts associated with deeper layers of the skin. In particular, SCA1+ fibroblasts were enriched for numerous chemokines, including CCL2, CCL7, and IL33 compared to SCA1-fibroblasts. Genetic deletion of Ccl2 in fibroblasts resulted in fewer wound bed macrophages and monocytes during injury-induced inflammation with reduced revascularization and re-epithelialization during the proliferation phase of healing. These findings highlight the important contribution of deep skin fibroblast-derived factors to injury-induced inflammation and the impact of immune cell dysregulation on subsequent tissue repair.

cell biology↗

bioRxiv2024

Connecting Transcriptomics with Computational Modeling to Reveal Developmental Adaptations in the Human Pediatric Myocardium

BackgroundNearly 1% or 1.3 million babies are born with congenital heart disease (CHD) globally each year - many of whom will require palliative or corrective heart surgery within the first few years of life. A detailed understanding of cardiac maturation can help to expand our knowledge on cardiac diseases that develop during gestation, identify age-appropriate cardiovascular drug therapies, and inform clinical care decisions related to surgical repair, myocardial preservation, or postoperative management. Yet, to date, our knowledge of the temporal changes that cardiomyocytes undergo during postnatal development is largely limited to animal models. MethodsRight atrial tissue samples were collected from n=117 neonatal, infant, and pediatric patients undergoing correct surgery due to (acyanotic) CHD. Patients were stratified into five age groups: neonate (0-30 days), infant (31-364 days), toddler to preschool (1-5 years), school age (6-11 years), and adolescent to young adults (12-32 years). We measured age-dependent adaptations in cardiac gene expression, and used computational modeling to simulate action potential and calcium transients. ResultsEnrichment of differentially expressed genes (DEG) was explored, revealing age-dependent changes in several key biological processes (cell cycle, cell division, mitosis), cardiac ion channels, and calcium handling genes. Gene-associated changes in ionic currents exhibited both linear trends and sudden shifts across developmental stages, with changes in calcium handling (INCX) and repolarization (IK1) most strongly associated with an age-dependent decrease in the action potential plateau potential and increase in triangulation, respectively. We also note a shift in repolarization reserve, with lower IKr expression in younger patients, a finding likely tied to the increased amplitude of IKs triggered by elevated sympathetic activation in pediatric patients. ConclusionThis study provides valuable insights into age-dependent changes in human cardiac gene expression and electrophysiology among patients with CHD, shedding light on molecular mechanisms underlying cardiac development and function across different developmental stages.

cell biology↗

bioRxiv2024

Electroanatomical Adaptations in the Guinea Pig Heart from Neonatal to Adulthood

BackgroundElectroanatomical adaptations during the neonatal to adult phase have not been comprehensively studied in preclinical animal models. To explore the impact of age as a biological variable on cardiac electrophysiology, we employed neonatal and adult guinea pigs, which are a recognized animal model for developmental research. MethodsHealthy guinea pigs were categorized into three age groups (neonates, n=10; younger adults, n=13; and older adults, n=26). Electrocardiogram (ECG) recordings were collected in vivo from anesthetized animals (2-3% isoflurane). A Langendorff-perfusion system was employed for optical assessment of epicardial action potentials and calcium transients, using intact excised heart preparations. Optical data sets were analyzed and metric maps were constructed using Kairosight 3.0. ResultsThe allometric relationship between heart weight and body weight diminishes with age, as it is strongest at the neonatal stage (R2 = 0.84) and completely abolished in older adults (R2 = 1E-06). Neonatal hearts exhibit circular activation waveforms, while adults show prototypical elliptical shapes. Neonatal conduction velocity (40.6{+/-}4.0 cm/s) is slower than adults (younger adults: 61.6{+/-}9.3 cm/s; older adults: 53.6{+/-}9.2 cm/s). Neonatal hearts have a longer action potential duration (APD) and exhibit regional heterogeneity (left apex; APD30: 68.6{+/-}5.6 ms, left basal; APD30: 62.8{+/-}3.6), which was absent in adult epicardium. With dynamic pacing, neonatal hearts exhibit a flatter APD restitution slope (APD70: 0.29{+/-}0.04) compared to older adults (0.49{+/-}0.04). Similar restitution characteristics are observed with extrasystolic pacing, with a flatter slope in neonatal hearts (APD70: 0.54{+/-}0.1) compared to adults (Younger adults: 0.85{+/-}0.4; Older adults: 0.95{+/-}0.7). Finally, neonatal hearts display unidirectional excitation-contraction coupling, while adults exhibit bidirectionality. ConclusionThe transition from neonatal to adulthood in guinea pig hearts is characterized by transient changes in electroanatomic properties. Age-specific patterns can influence cardiac physiology, pathology, and therapies for cardiovascular diseases. Understanding postnatal heart development is crucial to evaluating therapeutic eligibility, safety, and efficacy. What is KnownAge-specific cardiac electroanatomical characteristics have been documented in humans and some preclinical animal models. These age-specific patterns can influence cardiac physiology, pathology, and therapies for cardiovascular diseases. What the Study AddsCardiac electroanatomical characteristics are age-specific in guinea pigs, a well-known preclinical model for developmental studies. Age-dependent adaptations in cardiac electrophysiology are readily observed in the electrocardiogram recordings and via optical mapping of epicardial action potentials and calcium transients. Our findings reveal unique activation and repolarization characteristics between neonatal and adult animals. Graphical AbstractAge-dependent adaptations in the guinea pig heart include adjustments in allometric scaling and cardiac electrophysiology. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=113 SRC="FIGDIR/small/577234v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@5fcdaforg.highwire.dtl.DTLVardef@1b8acc3org.highwire.dtl.DTLVardef@1567089org.highwire.dtl.DTLVardef@1f63c4a_HPS_FORMAT_FIGEXP M_FIG 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↗

bioRxiv2023

The scheduling of adolescence with Netrin-1 and UNC5C

Dopamine axons are the only axons known to grow during adolescence. Here, using rodent models, we examined how two proteins, Netrin-1 and its receptor, UNC5C, guide dopamine axons towards the prefrontal cortex and shape behaviour. We demonstrate in mice (Mus musculus) that dopamine axons reach the cortex through a transient gradient of Netrin-1 expressing cells - disrupting this gradient reroutes axons away from their target. Using a seasonal model (Siberian hamsters; Phodopus sungorus) we find that mesocortical dopamine development can be regulated by a natural environmental cue (daylength) in a sexually dimorphic manner - delayed in males, but advanced in females. The timings of dopamine axon growth and UNC5C expression are always phase-locked. Adolescence is an ill-defined, transitional period; we pinpoint neurodevelopmental markers underlying this period.

neuroscience↗