Biology subjects

McCarthy, R.

Publications and source records attributed to McCarthy, R..

6 recordsLinked to original sources

bioRxiv2025

Fetoplacental circadian rhythms develop and then synchronize to the mother in utero

Circadian rhythms in gene expression and hormones are ubiquitous across species and differentiated cell types, yet their developmental origins remain poorly understood. This study aimed to determine if daily rhythms can be detected in utero and if they synchronize to the mother. We developed methods to longitudinally monitor PERIOD2 (PER2), a core circadian clock protein, from embryonic day (E)8.5 to E17.5 by restricting PER2::LUCIFERASE (PER2::LUC) expression to the mouse fetoplacental unit (fetus and fetal-derived tissues). In utero fetoplacental bioluminescence imaging showed that PER2 levels rose exponentially during pregnancy, with variable daily peak times that stabilized to dusk by E15.5. Interestingly, pregnancies that did not exhibit daily in utero PER2 variation were more likely to fail. Because maternal glucocorticoids have been implicated in fetal development and synchronizing other circadian tissues, we tested its capability to shift fetoplacental PER2 rhythms in utero. Daily subcutaneous glucocorticoid injections over five days of late pregnancy phase-dependently shifted the fetoplacental PER2 rhythms in utero. Blocking glucocorticoid signaling in vitro reduced synchrony between maternal and fetal placenta by [~]40%. We conclude that in utero daily rhythms gradually develop and synchronize with the mother prior to birth, potentially through glucocorticoid signaling.

developmental biology↗

bioRxiv2025

Bacterial Vaginosis Toxins Impair Sperm Capacitation and Fertilization

Study questionWhat effect do toxins produced by bacterial vaginosis (BV) bacteria have on sperm function? Summary answerBacterial vaginosis toxins dysregulate sperm capacitation and intracellular calcium homeostasis and impair the ability of sperm to fertilize oocytes. What is known alreadyIn bacterial vaginosis, which is linked to infertility, overgrowth of Prevotella and Gardnerella in the vagina is accompanied by elevated concentrations of the toxins lipopolysaccharide (LPS) and vaginolysin (VLY). Study design, size, durationThis was a laboratory study in which human semen samples were collected from consenting healthy donors with normal semen parameters. Mouse sperm samples were obtained from the caudal epididymis. Participants/materials, setting, methodsMotile mouse and human sperm were isolated via swim-up and treated under non-capacitating or capacitating conditions. LPS from Escherichia coli was commercially available. VLY was produced by cloning the Gardnerella VLY protein in the ClearColi expression system. Mouse sperm were pre-incubated in in vitro fertilization medium with LPS or VLY and then co-cultured with ovulated cumulus-oocyte complexes. The effects of LPS and VLY on sperm motility and hyperactivation were assessed with computer-assisted sperm analysis. Effects on viability were assessed by Hoechst staining. Acrosomal exocytosis was assessed in sperm from transgenic Acr-eGFP mice and in human sperm stained with Pisum sativum agglutinin FITC. Intracellular calcium dynamics were assessed by staining sperm with the calcium-sensitive dye Fluo-4 AM and fluorescent imaging several sperm at the single-cell level. The effects of LPS on sperm from CatSper knock-out mice were assessed. Additionally, sperm were treated with a toll-like receptor 4 antagonist and further exposed to LPS. Main results and the role of chanceExposure of mouse sperm to LPS or VLY significantly decreased in vitro fertilization (P < 0.05). Under capacitating conditions, both toxins initially increased mouse and human sperm hyperactivation, then significantly decreased sperm motility (P < 0.05), hyperactivation (P < 0.05), and acrosomal exocytosis (P < 0.01). These changes were accompanied by a rapid and irreversible increase in intracellular calcium concentration. Effects of LPS, but not VLY, were prevented by polymyxin-B, which aggregates LPS. The LPS-induced intracellular calcium increase required external calcium but not the calcium channel CatSper and was inhibited by the Toll-like receptor 4 antagonist. Limitations, reasons for cautionFirst, the commercially available LPS we used was isolated from Escherichia coli, rather than from the BV-associated bacteria Prevotella bivia. Second, we did not quantify the absolute sperm intracellular calcium concentration before or after LPS or VLY treatment. Third, all of our experiments were in vitro. Wider implications of the findingsThese studies suggest that BV-associated toxins contribute to infertility by, in part, impairing sperm capacitation and reducing their fertilizing ability. Study funding/competing interest(s)This work was supported by the National Institutes of Health (grant #R01 HD069631). The authors declare that they have no conflict of interest.

physiology↗

bioRxiv2024

SLO2.1/NALCN Functional Complex Activity in Mouse Myometrial Smooth Muscle Cells During Pregnancy.

At the end of pregnancy, the uterus transitions from a quiescent to a highly contractile state. This is partly due to depolarization of the resting membrane potential in uterine (myometrial) smooth muscle cells (MSMCs). In human MSMCs, the membrane potential is regulated by a functional complex between the sodium (Na+)-activated potassium (K+) channel SLO2.1 and the Na+ Leak Channel Non-Selective (NALCN). Na+ entering through NALCN activates SLO2.1, leading to K+ efflux, membrane hyperpolarization (cells become more negative inside), and reduced contractility. Decreased SLO2.1/NALCN activity results in reduced K+ efflux, leading to membrane depolarization, Ca2+ influx via voltage-dependent calcium channels, and increased MSMC contractility. However, all of these data are from MSMCs isolated from women at term, so the role of the SLO2.1/NALCN complex early in pregnancy was speculative. To address this question here, we examined the role of the SLO2.1/NALCN complex in regulating mouse MSMC membrane potential across pregnancy. We report that Slo2.1 and Nalcn are more highly expressed in MSMCs from non-pregnant and early pregnant mice than in those from late-pregnant mice. Functional studies revealed that SLO2.1 channels mediate a significant portion of the K+ current in mouse MSMCs, particularly in cells from non-pregnant and early pregnant mice. Activation of SLO2.1 by Na+ influx through NALCN led to membrane hyperpolarization in MSMCs from early pregnancy but not in MSMCs from later pregnancy. Moreover, the NALCN/SLO2.1 complex regulates intracellular Ca2+ responses more in MSMCs from non-pregnant and early pregnancy mice than in MSMCs from late pregnancy. Together, these findings reveal that the SLO2.1/NALCN functional complex is conserved between mouse and humans and functions throughout pregnancy. This work could open avenues for targeted pharmacological interventions for pregnancy-related complications.

physiology↗

bioRxiv2023

Fetal daily rhythms develop during pregnancy and entrain to the maternal circadian system

Circadian rhythms in gene expression and hormones are ubiquitous across species and differentiated cell types. This study aimed to determine when daily rhythms begin in the fetus and synchronize to the mother. We developed methods to monitor the expression of fetal PERIOD2 (PER2), a core circadian clock protein, in mice longitudinally from embryonic day (E)8.5 to E17.5 through in utero bioluminescence imaging. We found that embryonic PER2 expression increased rapidly throughout pregnancy and exhibited day-night rhythms from the start of our recordings at E8.5. The daily peak time of PER2 varied between pregnancies until it reliably peaked at night and synchronized to the mother starting around E15.5. Loss of fetal circadian rhythms associated with pregnancies that ultimately failed. Because maternal glucocorticoids have been implicated in fetal development and synchronizing circadian tissues, we tested their sufficiency to shift fetal daily rhythms in utero. Daily glucocorticoids injections over five days of late pregnancy advanced fetal PER2 rhythms in utero and blocking glucocorticoid signaling in vitro reduced PER2 synchrony between the maternal and fetal placenta by [~]40%. We conclude that fetal daily rhythms arise early in pregnancy and then synchronize with the maternal rhythm prior to birth depending, in part, on glucocorticoid signaling.

developmental biology↗

bioRxiv2021

A NOVEL PREGNANT RAT MODEL FOR LABOR INDUCTION AND AUGMENTATION WITH OXYTOCIN

BackgroundDespite the widespread use of oxytocin for induction of labor, mechanistic insights into maternal and neonatal wellbeing are lacking because of the absence of an animal model that recapitulates modern obstetric practice. ObjectiveThe objectives of this research were to create and validate a hi-fidelity animal model that mirrors labor induction with oxytocin in parturients and to assess its translational utility. Study DesignThe study was performed in timed-pregnant Sprague Dawley dams. The model consisted of a subcutaneously implanted microprocessor-controlled infusion pump on gestational day 18 that was pre-programmed to deliver an escalating dose of intravenous oxytocin on gestational day 21 to induce birth. Once predictable delivery of healthy pups was achieved, we validated the model with molecular biological experiments on the uterine myometrium and telemetry-supported assessment of changes in intrauterine pressure. Finally, we applied this model to test the hypothesis that labor induction with oxytocin was associated with oxidative stress in the newborn brain with a comprehensive array of biomarker assays and oxidative stress gene expression studies. ResultsDuring the iterative model development phase, we confirmed the optimal gestational age for pump implantation, the concentration of oxytocin, and the rate of oxytocin administration. Exposure to anesthesia and surgery during pump implantation was not associated with significant changes in the cortical transcriptome. Activation of pump with oxytocin on gestational day 21 resulted in predictable delivery of pups within 8-12 hours. Increased frequency of change of oxytocin infusion rate was associated with dystocic labor. Labor induction and augmentation with oxytocin was associated with increased expression of the oxytocin receptor gene in the uterine myometrium, decreased expression of the oxytocin receptor protein on the myometrial cell membrane, and cyclical increases in intrauterine pressure. Examination of the frontal cortex of vaginally delivered newborn pups born after oxytocin-induced labor did not reveal an increase in oxidative stress compared to saline-treated control pups. Specifically, there were no significant changes in oxidative stress biomarkers involving both the oxidative stress (reactive oxygen/nitrogen species, 4-hydroxynonenal, protein carbonyl) and the antioxidant response (total glutathione, total antioxidant capacity). In addition, there were no significant differences in the expression of 16 genes emblematic of the oxidative stress response pathway. ConclusionsCollectively, we provide a viable and realistic animal model for labor induction and augmentation with oxytocin. We demonstrate its utility in addressing clinically relevant questions in obstetric practice that could not be mechanistically ascertained otherwise. Based on our findings, labor induction with oxytocin is not likely to cause oxidative stress in the fetal brain. Adoption of our model by other researchers would enable new lines of investigation related to the impact of perinatal oxytocin exposure on the mother-infant dyad.

pharmacology and toxicology↗

bioRxiv2020

Blood clot fracture properties are dependent on red blood cell and fibrin content

Thrombus fragmentation during endovascular stroke treatment, such as mechanical thrombectomy, leads to downstream emboli, resulting in poor clinical outcomes. Clinical studies suggest that fragmentation risk is dependent on clot composition. This current study presents the first experimental characterization of the fracture properties of blood clots, in addition to the development of a predictive model for blood clot fragmentation. A bespoke experimental test-rig and compact tension specimen fabrication has been developed to measure fracture toughness of thrombus material. Fracture tests are performed on three physiologically relevant clot compositions: a high fibrin 5% H clot, a medium fibrin 20% H clot, a low-fibrin 40% H clot. Fracture toughness is observed to significantly increase with increasing fibrin content, i.e. red blood cell-rich clots are more prone to tear during loading compared to the fibrin-rich clots. Results also reveal that the mechanical behaviour of clot analogues is significantly different in compression and tension. Finite element cohesive zone modelling of clot fracture experiments show that fibrin fibres become highly aligned in the direction perpendicular to crack propagation, providing a significant toughening mechanism. The results presented in this study provide the first characterization of the fracture behaviour of blood clots and are of key importance for development of next-generation thrombectomy devices and clinical strategies.

bioengineering↗