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Peska E, Balki M, Pfeifer W, Maxwell C, Ye XY, Downey K, Carvalho JCA. Oxytocin at Elective Cesarean Delivery: A Dose-Finding Study in Pregnant People With Twin Pregnancy. Anesth Analg 2024; 138:814-820. [PMID: 36480452 DOI: 10.1213/ane.0000000000006309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND Multiple pregnancy is associated with higher risk of uterine atony, postpartum hemorrhage (PPH), blood transfusion, hysterectomy, and death. The optimal dose of oxytocin at cesarean delivery in people with twin pregnancy is unknown. We sought to determine the effective bolus dose of oxytocin required to initiate adequate uterine tone in 90% of people (ED90) with twin pregnancy undergoing elective cesarean delivery. Our hypothesis was that the dose of oxytocin would be higher than 0.5 international units (IU) but lower than 5 IU. METHODS A double-blind dose-finding study using the biased coin up-down method was undertaken in people with twin pregnancy ≥36 weeks gestational age undergoing elective cesarean delivery under neuraxial anesthesia. Those with additional risk factors for PPH, apart from twin pregnancy, were excluded. Oxytocin was administered as an intravenous bolus over 1 minute on delivery of the second fetus. The first patient received 0.5 IU, and subsequent oxytocin doses were administered according to a sequential allocation scheme. The actual doses administered were 0.5, 1, 2, 3, 4, and 5 IU of oxytocin. The primary outcome was the response defined as the satisfactory uterine tone at 2 minutes after completion of administration of the oxytocin bolus, as assessed by the operating obstetrician. Secondary outcomes included need for rescue uterotonic drugs, adverse effects, and estimated blood loss. The ED90 was estimated using the Dixon-Mood and the isotonic regression methods. RESULTS Thirty patients were included in study. The estimated ED90 of oxytocin was 4.38 IU (95% confidence interval [CI], 3.68-4.86 IU) and 3.41 IU (95% CI, 2.83-3.98 IU) by the isotonic regression and Dixon-Mood methods, respectively. Seven patients had inadequate tone at the 2-minute evaluation point and required rescue uterotonic drugs. The median (interquartile range [IQR]) estimated blood loss was 1031 mL (732-1462 mL) calculated by the change in 24-hour hematocrit. Incidence of hypotension after oxytocin administration was 27%, nausea 30%, and vomiting 17%. CONCLUSIONS Our results demonstrated that people with twin pregnancy require a much higher dose of oxytocin than those with singleton pregnancies. We recommended people with twin pregnancies should receive an initial 5 IU bolus over at least 1 minute when undergoing elective cesarean delivery under neuraxial anesthesia.
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Affiliation(s)
- Emil Peska
- From the Departments of Anesthesiology and Pain Medicine
| | - Mrinalini Balki
- From the Departments of Anesthesiology and Pain Medicine
- Obstetrics and Gynecology, Mount Sinai Hospital, University of Toronto, Toronto, ON, Canada
- Department of Physiology, University of Toronto, Toronto, ON, Canada
- Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, ON, Canada
| | - Wesla Pfeifer
- From the Departments of Anesthesiology and Pain Medicine
| | - Cynthia Maxwell
- Obstetrics and Gynecology, Mount Sinai Hospital, University of Toronto, Toronto, ON, Canada
| | - Xiang Y Ye
- Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, ON, Canada
- Maternal and Infant Care Research Centre, Mount Sinai Hospital, University of Toronto, Toronto, ON, Canada
| | - Kristi Downey
- From the Departments of Anesthesiology and Pain Medicine
| | - Jose C A Carvalho
- From the Departments of Anesthesiology and Pain Medicine
- Obstetrics and Gynecology, Mount Sinai Hospital, University of Toronto, Toronto, ON, Canada
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2
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Wray S, Prendergast C, Arrowsmith S. Calcium-Activated Chloride Channels in Myometrial and Vascular Smooth Muscle. Front Physiol 2021; 12:751008. [PMID: 34867456 PMCID: PMC8637852 DOI: 10.3389/fphys.2021.751008] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Accepted: 09/24/2021] [Indexed: 11/24/2022] Open
Abstract
In smooth muscle tissues, calcium-activated chloride channels (CaCC) provide the major anionic channel. Opening of these channels leads to chloride efflux and depolarization of the myocyte membrane. In this way, activation of the channels by a rise of intracellular [Ca2+], from a variety of sources, produces increased excitability and can initiate action potentials and contraction or increased tone. We now have a good mechanistic understanding of how the channels are activated and regulated, due to identification of TMEM16A (ANO1) as the molecular entity of the channel, but key questions remain. In reviewing these channels and comparing two distinct smooth muscles, myometrial and vascular, we expose the differences that occur in their activation mechanisms, properties, and control. We find that the myometrium only expresses “classical,” Ca2+-activated, and voltage sensitive channels, whereas both tonic and phasic blood vessels express classical, and non-classical, cGMP-regulated CaCC, which are voltage insensitive. This translates to more complex activation and regulation in vascular smooth muscles, irrespective of whether they are tonic or phasic. We therefore tentatively conclude that although these channels are expressed and functionally important in all smooth muscles, they are probably not part of the mechanisms governing phasic activity. Recent knockdown studies have produced unexpected functional results, e.g. no effects on labour and delivery, and tone increasing in some but decreasing in other vascular beds, strongly suggesting that there is still much to be explored concerning CaCC in smooth muscle.
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Affiliation(s)
- Susan Wray
- Department of Women and Children's Health, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Clodagh Prendergast
- Department of Women and Children's Health, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Sarah Arrowsmith
- Department of Life Sciences, Manchester Metropolitan University, Manchester, United Kingdom
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3
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Qu M, Lu P, Bellve K, Lifshitz LM, ZhuGe R. Mode Switch of Ca 2 + Oscillation-Mediated Uterine Peristalsis and Associated Embryo Implantation Impairments in Mouse Adenomyosis. Front Physiol 2021; 12:744745. [PMID: 34803733 PMCID: PMC8599363 DOI: 10.3389/fphys.2021.744745] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 10/12/2021] [Indexed: 11/13/2022] Open
Abstract
Adenomyosis is a debilitating gynecological disease of the uterus with no medicinal cure. The tissue injury and repair hypothesis for adenomyosis suggests that uterine hyperperistalsis or dysperistalsis plays a pivotal role in establishing adenomyotic lesions. However, specific impairments in uterine peristalsis and the underlying cellular signals for these changes in adenomyosis remain elusive. Here, we report a precision-cut uterine slice preparation that preserves in vivo uterine architecture and generates peristalsis similar to that seen in the whole uterus. We found that uterine peristalsis in neonatal mice at day 14 and adult mice at day 55 presents as bursts with multiple peaks induced by intracellular Ca2+ oscillations. Using a mouse model of adenomyosis induced by tamoxifen, a selective estrogen receptor modulator, we discovered that uterine peristalsis and Ca2+ oscillations from adenomyotic uteri on days 14 and 55 become spikes (single peaks) with smaller amplitudes. The peak frequency of Ca2+ oscillations or peristalsis does not show a difference between control and adenomyotic mice. However, both the estimated force generated by uterine peristalsis and the total Ca2+ raised by Ca2+ oscillations are smaller in uteri from adenomyotic mice. Uteri from adenomyotic mice on day 14, but not on day 55, exhibit hyperresponsiveness to oxytocin. Embryo implantations are decreased in adenomyotic adult mice. Our results reveal a mode switch from bursts to spikes (rather than an increased peak frequency) of uterine Ca2+ oscillations and peristalsis and concurrent hyperresponsiveness to oxytocin in the neonatal stage are two characteristics of adenomyosis. These characteristics may contribute to embryo implantation impairments and decreased fertility in adenomyosis.
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Affiliation(s)
- Mingzi Qu
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, MA, United States
| | - Ping Lu
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, MA, United States
| | - Karl Bellve
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA, United States
| | - Lawrence M Lifshitz
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA, United States
| | - Ronghua ZhuGe
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, MA, United States
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4
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Borysova L, Ng YYH, Wragg ES, Wallis LE, Fay E, Ascione R, Dora KA. High spatial and temporal resolution Ca 2+ imaging of myocardial strips from human, pig and rat. Nat Protoc 2021; 16:4650-4675. [PMID: 34400840 DOI: 10.1038/s41596-021-00590-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Accepted: 06/14/2021] [Indexed: 11/09/2022]
Abstract
Ca2+ handling within cardiac myocytes underpins coordinated contractile function within the beating heart. This protocol enables high spatial and temporal Ca2+ imaging of ex vivo multicellular myocardial strips. The endocardial surface is retained, and strips of 150-300-µm thickness are dissected, loaded with Ca2+ indicators and mounted within 1.5 h. A list of the equipment and reagents used and the key methodological aspects allowing the use of this technique on strips from any chamber of the mammalian heart are described. We have successfully used this protocol on human, pig and rat biopsy samples. On use of this protocol with intact endocardial endothelium, we demonstrated that the myocytes develop asynchronous spontaneous Ca2+ events, which can be ablated by electrically evoked Ca2+ transients, and subsequently redevelop spontaneously after cessation of stimulation. This protocol thus offers a rapid and reliable method for studying the Ca2+ signaling underpinning cardiomyocyte contraction, in both healthy and diseased tissue.
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Affiliation(s)
- Lyudmyla Borysova
- Vascular Pharmacology Group, Department of Pharmacology, University of Oxford, Oxford, UK
| | - Y Y Hanson Ng
- Vascular Pharmacology Group, Department of Pharmacology, University of Oxford, Oxford, UK
| | - Edward S Wragg
- Vascular Pharmacology Group, Department of Pharmacology, University of Oxford, Oxford, UK
| | - Lillian E Wallis
- Vascular Pharmacology Group, Department of Pharmacology, University of Oxford, Oxford, UK
| | - Emily Fay
- Vascular Pharmacology Group, Department of Pharmacology, University of Oxford, Oxford, UK
| | - Raimondo Ascione
- Bristol Heart Institute, Bristol Royal Infirmary, University of Bristol, Bristol, UK
| | - Kim A Dora
- Vascular Pharmacology Group, Department of Pharmacology, University of Oxford, Oxford, UK.
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5
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Malik M, Roh M, England SK. Uterine contractions in rodent models and humans. Acta Physiol (Oxf) 2021; 231:e13607. [PMID: 33337577 PMCID: PMC8047897 DOI: 10.1111/apha.13607] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 12/07/2020] [Accepted: 12/11/2020] [Indexed: 12/18/2022]
Abstract
Aberrant uterine contractions can lead to preterm birth and other labour complications and are a significant cause of maternal morbidity and mortality. To investigate the mechanisms underlying dysfunctional uterine contractions, researchers have used experimentally tractable small animal models. However, biological differences between humans and rodents change how researchers select their animal model and interpret their results. Here, we provide a general review of studies of uterine excitation and contractions in mice, rats, guinea pigs, and humans, in an effort to introduce new researchers to the field and help in the design and interpretation of experiments in rodent models.
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Affiliation(s)
- Manasi Malik
- Center for Reproductive Health Sciences Department of Obstetrics and Gynecology Washington University School of Medicine St. Louis MO USA
| | - Michelle Roh
- Center for Reproductive Health Sciences Department of Obstetrics and Gynecology Washington University School of Medicine St. Louis MO USA
| | - Sarah K. England
- Center for Reproductive Health Sciences Department of Obstetrics and Gynecology Washington University School of Medicine St. Louis MO USA
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6
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Wray S, Arrowsmith S. Uterine Excitability and Ion Channels and Their Changes with Gestation and Hormonal Environment. Annu Rev Physiol 2020; 83:331-357. [PMID: 33158376 DOI: 10.1146/annurev-physiol-032420-035509] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We address advances in the understanding of myometrial physiology, focusing on excitation and the effects of gestation on ion channels and their relevance to labor. This review moves through pioneering studies to exciting new findings. We begin with the myometrium and its myocytes and describe how excitation might initiate and spread in this myogenic smooth muscle. We then review each of the ion channels in the myometrium: L- and T-type Ca2+ channels, KATP (Kir6) channels, voltage-dependent K channels (Kv4, Kv7, and Kv11), twin-pore domain K channels (TASK, TREK), inward rectifier Kir7.1, Ca2+-activated K+ channels with large (KCNMA1, Slo1), small (KCNN1-3), and intermediate (KCNN4) conductance, Na-activated K channels (Slo2), voltage-gated (SCN) Na+ and Na+ leak channels, nonselective (NALCN) channels, the Na K-ATPase, and hyperpolarization-activated cation channels. We finish by assessing how three key hormones- oxytocin, estrogen, and progesterone-modulate and integrate excitability throughout gestation.
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Affiliation(s)
- Susan Wray
- Department of Women's and Children's Health, University of Liverpool, Liverpool L69 3BX, United Kingdom;
| | - Sarah Arrowsmith
- Department of Women's and Children's Health, University of Liverpool, Liverpool L69 3BX, United Kingdom;
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7
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A myofibre model for the study of uterine excitation-contraction dynamics. Sci Rep 2020; 10:16221. [PMID: 33004882 PMCID: PMC7530703 DOI: 10.1038/s41598-020-72562-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 08/31/2020] [Indexed: 01/12/2023] Open
Abstract
As the uterus remodels in preparation for delivery, the excitability and contractility of the uterine smooth muscle layer, the myometrium, increase drastically. But when remodelling proceeds abnormally it can contribute to preterm birth, slow progress of labour, and failure to initiate labour. Remodelling increases intercellular coupling and cellular excitability, which are the main targets of pharmaceutical treatments for uterine contraction disorders. However, the way in which electrical propagation and force development depend on intercellular coupling and cellular excitability is not fully understood. Using a computational myofibre model we study the dependency of electrical propagation and force development on intercellular coupling and cellular excitability. This model reveals that intercellular coupling determines the conduction velocity. Moreover, our model shows that intercellular coupling alone does not regulate force development. Further, cellular excitability controls whether conduction across the cells is blocked. Lastly, our model describes how cellular excitability regulates force development. Our results bridge cellular factors, targeted by drugs to regulate uterine contractions, and tissue level electromechanical properties, which are responsible for delivery. They are a step forward towards understanding uterine excitation-contraction dynamics and developing safer and more efficient pharmaceutical treatments for uterine contraction disorders.
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8
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The Myometrium: From Excitation to Contractions and Labour. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1124:233-263. [PMID: 31183830 DOI: 10.1007/978-981-13-5895-1_10] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/06/2022]
Abstract
We start by describing the functions of the uterus, its structure, both gross and fine, innervation and blood supply. It is interesting to note the diversity of the female's reproductive tract between species and to remember it when working with different animal models. Myocytes are the overwhelming cell type of the uterus (>95%) and our focus. Their function is to contract, and they have an intrinsic pacemaker and rhythmicity, which is modified by hormones, stretch, paracrine factors and the extracellular environment. We discuss evidence or not for pacemaker cells in the uterus. We also describe the sarcoplasmic reticulum (SR) in some detail, as it is relevant to calcium signalling and excitability. Ion channels, including store-operated ones, their contributions to excitability and action potentials, are covered. The main pathway to excitation is from depolarisation opening voltage-gated Ca2+ channels. Much of what happens downstream of excitability is common to other smooth muscles, with force depending upon the balance of myosin light kinase and phosphatase. Mechanisms of maintaining Ca2+ balance within the myocytes are discussed. Metabolism, and how it is intertwined with activity, blood flow and pH, is covered. Growth of the myometrium and changes in contractile proteins with pregnancy and parturition are also detailed. We finish with a description of uterine activity and why it is important, covering progression to labour as well as preterm and dysfunctional labours. We conclude by highlighting progress made and where further efforts are required.
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9
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Borysova L, Dora KA, Garland CJ, Burdyga T. Smooth muscle gap-junctions allow propagation of intercellular Ca 2+ waves and vasoconstriction due to Ca 2+ based action potentials in rat mesenteric resistance arteries. Cell Calcium 2018; 75:21-29. [PMID: 30114532 PMCID: PMC6169741 DOI: 10.1016/j.ceca.2018.08.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Revised: 08/03/2018] [Accepted: 08/04/2018] [Indexed: 10/28/2022]
Abstract
The role of vascular gap junctions in the conduction of intercellular Ca2+ and vasoconstriction along small resistance arteries is not entirely understood. Some depolarizing agents trigger conducted vasoconstriction while others only evoke a local depolarization. Here we use a novel technique to investigate the temporal and spatial relationship between intercellular Ca2+ signals generated by smooth muscle action potentials (APs) and vasoconstriction in mesenteric resistance arteries (MA). Pulses of exogenous KCl to depolarize the downstream end (T1) of a 3 mm long artery increased intracellular Ca2+ associated with vasoconstriction. The spatial spread and amplitude of both depended on the duration of the pulse, with only a restricted non-conducting vasoconstriction to a 1 s pulse. While blocking smooth muscle cell (SMC) K+ channels with TEA and activating L-type voltage-gated Ca2+ channels (VGCCs) with BayK 8644 spread was dramatically facilitated, so the 1 s pulse evoked intercellular Ca2+ waves and vasoconstriction that spread along an entire artery segment 3000 μm long. Ca2+ waves spread as nifedipine-sensitive Ca2+ spikes due to SMC action potentials, and evoked vasoconstriction. Both intercellular Ca2+ and vasoconstriction spread at circa 3 mm s-1 and were independent of the endothelium. The spread but not the generation of Ca2+ spikes was reversibly blocked by the gap junction inhibitor 18β-GA. Thus, smooth muscle gap junctions enable depolarization to spread along resistance arteries, and once regenerative Ca2+-based APs occur, spread along the entire length of an artery followed by widespread vasoconstriction.
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Affiliation(s)
- Lyudmyla Borysova
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford, OX1 3QT, UK
| | - Kim A Dora
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford, OX1 3QT, UK
| | - Christopher J Garland
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford, OX1 3QT, UK
| | - Theodor Burdyga
- Department of Cellular and Molecular Physiology and Gastroenterology, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool, L69 3BX, UK.
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10
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Testrow CP, Holden AV, Shmygol A, Zhang H. A computational model of excitation and contraction in uterine myocytes from the pregnant rat. Sci Rep 2018; 8:9159. [PMID: 29904075 PMCID: PMC6002389 DOI: 10.1038/s41598-018-27069-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Accepted: 05/24/2018] [Indexed: 12/17/2022] Open
Abstract
Aberrant uterine myometrial activities in humans are major health issues. However, the cellular and tissue mechanism(s) that maintain the uterine myometrium at rest during gestation, and that initiate and maintain long-lasting uterine contractions during delivery are incompletely understood. In this study we construct a computational model for describing the electrical activity (simple and complex action potentials), intracellular calcium dynamics and mechanical contractions of isolated uterine myocytes from the pregnant rat. The model reproduces variant types of action potentials - from spikes with a smooth plateau, to spikes with an oscillatory plateau, to bursts of spikes - that are seen during late gestation under different physiological conditions. The effects of the hormones oestradiol (via reductions in calcium and potassium selective channel conductance), oxytocin (via an increase in intracellular calcium release) and the tocolytic nifedipine (via a block of L-type calcium channels currents) on action potentials and contractions are also reproduced, which quantitatively match to experimental data. All of these results validated the cell model development. In conclusion, the developed model provides a computational platform for further investigations of the ionic mechanism underlying the genesis and control of electrical and mechanical activities in the rat uterine myocytes.
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Affiliation(s)
- Craig P Testrow
- The University of Manchester, School of Physics and Astronomy, Manchester, M13 9PL, UK
| | - Arun V Holden
- The University of Leeds, School of Biomedical Sciences, Leeds, LS2 9JT, UK
| | - Anatoly Shmygol
- United Arab Emirates University, College of Medicine and Health Sciences, Department of Physiology, Al-Ain, P.O. Box 17666, Emirates, UAE
| | - Henggui Zhang
- The University of Manchester, School of Physics and Astronomy, Manchester, M13 9PL, UK.
- School of Computer Science and Technology, Harbin Institute of Technology (HIT), Harbin, 150001, China.
- Space Institute of Southern China, Shenzhen, 518117, China.
- Key laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease/Institute of Cardiovascular Research, Southwest Medical University, Luzhou, 646000, China.
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11
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Carlson NS, Hernandez TL, Hurt KJ. Parturition dysfunction in obesity: time to target the pathobiology. Reprod Biol Endocrinol 2015; 13:135. [PMID: 26684329 PMCID: PMC4683915 DOI: 10.1186/s12958-015-0129-6] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 11/24/2015] [Indexed: 12/23/2022] Open
Abstract
Over a third of women of childbearing age in the United States are obese, and during pregnancy they are at increased risk for delayed labor onset and slow labor progress that often results in unplanned cesarean delivery. The biology behind this dysfunctional parturition is not well understood. Studies of obesity-induced changes in parturition physiology may facilitate approaches to optimize labor in obese women. In this review, we summarize known and proposed biologic effects of obesity on labor preparation, contraction/synchronization, and endurance, drawing on both clinical observation and experimental data. We present evidence from human and animal studies of interactions between obesity and parturition signaling in all elements of the birth process, including: delayed cervical ripening, prostaglandin insensitivity, amniotic membrane strengthening, decreased myometrial oxytocin receptor expression, decreased myocyte action potential initiation and contractility, decreased myocyte gap junction formation, and impaired myocyte neutralization of reactive oxygen species. We found convincing clinical data on the effect of obesity on labor initiation and successful delivery, but few studies on the underlying pathobiology. We suggest research opportunities and therapeutic interventions based on plausible biologic mechanisms.
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Affiliation(s)
- Nicole S Carlson
- Emory University, Nell Hodgson Woodruff School of Nursing, 1520 Clifton Road NE, Atlanta, GA, 30322, USA.
| | - Teri L Hernandez
- Department of Medicine, Division of Endocrinology, Metabolism, & Diabetes, College of Nursing, University of Colorado School of Medicine, 12801 E. 17th Ave, MS 8106, Aurora, CO, 80045, USA.
| | - K Joseph Hurt
- Department of Obstetrics & Gynecology, Divisions of Maternal-Fetal Medicine & Reproductive Sciences, University of Colorado School of Medicine, 12700 East 19th Ave, MS 8613, Aurora, CO, 80045, USA.
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12
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Kazaryan KV, Hunanyan NG, Savayan AA, Piliposyan TA, Mkrtchyan AV, Manukyan AM. Characterization of spontaneous electric activity of the myometrial rhythmogenic areas in rats. J EVOL BIOCHEM PHYS+ 2015. [DOI: 10.1134/s002209301505004x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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13
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Rabotti C, Mischi M. Propagation of electrical activity in uterine muscle during pregnancy: a review. Acta Physiol (Oxf) 2015; 213:406-16. [PMID: 25393600 DOI: 10.1111/apha.12424] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Revised: 08/13/2014] [Accepted: 11/07/2014] [Indexed: 11/29/2022]
Abstract
The uterine muscle (the myometrium) plays its most evident role during pregnancy, when quiescence is required for adequate nourishment and development of the foetus, and during labour, when forceful contractions are needed to expel the foetus and the other products of conception. The myometrium is composed of smooth muscle cells. Contraction is initiated by the spontaneous generation of electrical activity at the cell level in the form of action potentials. The mechanisms underlying uterine quiescence during pregnancy and electrical activation during labour remain largely unknown; as a consequence, the clinical management of preterm contractions during pregnancy and inefficient uterine contractility during labour remains suboptimal. In an effort to improve clinical management of uterine contractions, research has focused on understanding the propagation properties of the electrical activity of the uterus. Different perspectives have been undertaken, from animal and in vitro experiments up to clinical studies and dedicated methods for non-invasive parameter estimation. A comparison of the results is not straightforward due to the wide range of different approaches reported in the literature. However, previous studies unanimously reveal a unique complexity as compared to other organs in the pattern of uterine electrical activity propagation, which necessarily needs to be taken into consideration for future studies to be conclusive. The aim of this review is to structure current variegated knowledge on the properties of the uterus in terms of pacemaker position, pattern, direction and speed of the electrical activity during pregnancy and labour.
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Affiliation(s)
- C. Rabotti
- Electrical Engineering Department; Eindhoven University of Technology; Eindhoven the Netherlands
| | - M. Mischi
- Electrical Engineering Department; Eindhoven University of Technology; Eindhoven the Netherlands
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14
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Wray S, Burdyga T, Noble D, Noble K, Borysova L, Arrowsmith S. Progress in understanding electro-mechanical signalling in the myometrium. Acta Physiol (Oxf) 2015; 213:417-31. [PMID: 25439280 DOI: 10.1111/apha.12431] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Revised: 11/11/2014] [Accepted: 11/17/2014] [Indexed: 11/30/2022]
Abstract
In this review, we give a state-of-the-art account of uterine contractility, focussing on excitation-contraction (electro-mechanical) coupling (ECC). This will show how electrophysiological data and intracellular calcium measurements can be related to more modern techniques such as confocal microscopy and molecular biology, to advance our understanding of mechanical output and its modulation in the smooth muscle of the uterus, the myometrium. This new knowledge and understanding, for example concerning the role of the sarcoplasmic reticulum (SR), or stretch-activated K channels, when linked to biochemical and molecular pathways, provides a clearer and better informed basis for the development of new drugs and targets. These are urgently needed to combat dysfunctions in excitation-contraction coupling that are clinically challenging, such as preterm labour, slow to progress labours and post-partum haemorrhage. It remains the case that scientific progress still needs to be made in areas such as pacemaking and understanding interactions between the uterine environment and ion channel activity.
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Affiliation(s)
- S. Wray
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Liverpool Women's Hospital; Liverpool UK
| | - T. Burdyga
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Liverpool Women's Hospital; Liverpool UK
| | - D. Noble
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Liverpool Women's Hospital; Liverpool UK
| | - K. Noble
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Liverpool Women's Hospital; Liverpool UK
| | - L. Borysova
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Liverpool Women's Hospital; Liverpool UK
| | - S. Arrowsmith
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Liverpool Women's Hospital; Liverpool UK
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Loftus FC, Shmygol A, Richardson MJE. Fine spatiotemporal activity in contracting myometrium revealed by motion-corrected calcium imaging. J Physiol 2014; 592:4447-63. [PMID: 25085893 PMCID: PMC4280886 DOI: 10.1113/jphysiol.2014.275412] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Successful childbirth depends on the occurrence of precisely coordinated uterine contractions during labour. Calcium indicator fluorescence imaging is one of the main techniques for investigating the mechanisms governing this physiological process and its pathologies. The effective spatiotemporal resolution of calcium signals is, however, limited by the motion of contracting tissue: structures of interest in the order of microns can move over a hundred times their width during a contraction. The simultaneous changes in local intensity and tissue configuration make motion tracking a non-trivial problem in image analysis and confound many of the standard techniques. This paper presents a method that tracks local motion throughout the tissue and allows for the almost complete removal of motion artefacts. This provides a stabilized calcium signal down to a pixel resolution, which, for the data examined, is in the order of a few microns. As a byproduct of image stabilization, a complete kinematic description of the contraction–relaxation cycle is also obtained. This contains novel information about the mechanical response of the tissue, such as the identification of a characteristic length scale, in the order of 40–50 μm, below which tissue motion is homogeneous. Applied to our data, we illustrate that the method allows for analyses of calcium dynamics in contracting myometrium in unprecedented spatiotemporal detail. Additionally, we use the kinematics of tissue motion to compare calcium signals at the subcellular level and local contractile motion. The computer code used is provided in a freely modifiable form and has potential applicability to in vivo calcium imaging of neural tissue, as well as other smooth muscle tissue.
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Affiliation(s)
- Fiona C Loftus
- Warwick Systems Biology Centre, University of Warwick, Coventry, UK Division of Translational and Systems Medicine, Warwick Medical School, University of Warwick, Coventry, UK Warwick Systems Biology Doctoral Training Centre, University of Warwick, Coventry, UK
| | - Anatoly Shmygol
- Division of Translational and Systems Medicine, Warwick Medical School, University of Warwick, Coventry, UK
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Store-operated Ca²⁺ entry and depolarization explain the anomalous behaviour of myometrial SR: effects of SERCA inhibition on electrical activity, Ca²⁺ and force. Cell Calcium 2014; 56:188-94. [PMID: 25084623 PMCID: PMC4169181 DOI: 10.1016/j.ceca.2014.07.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Revised: 07/03/2014] [Accepted: 07/09/2014] [Indexed: 11/23/2022]
Abstract
SERCA pump inhibition by CPA caused membrane depolarization, activation of action potentials, Ca2+ spikes and force. Depletion of Ca2+ store by agonists leads to membrane depolarization and activation of electrical and mechanical activity. Ca2+ release/Ca2+ entry coupling is playing a key role in control of spontaneous electrical and mechanical activity in rat pregnant myometrium.
In the myometrium SR Ca2+ depletion promotes an increase in force but unlike several other smooth muscles, there is no Ca2+ sparks-STOCs coupling mechanism to explain this. Given the importance of the control of contractility for successful parturition, we have examined, in pregnant rat myometrium, the effects of SR Ca2+-ATPase (SERCA) inhibition on the temporal relationship between action potentials, Ca2+ transients and force. Simultaneous recording of electrical activity, calcium and force showed that SERCA inhibition, by cyclopiazonic acid (CPA 20 μM), caused time-dependent changes in excitability, most noticeably depolarization and elevations of baseline [Ca2+]i and force. At the onset of these changes there was a prolongation of the bursts of action potentials and a corresponding series of Ca2+ spikes, which increased the amplitude and duration of contractions. As the rise of baseline Ca2+ and depolarization continued a point was reached when electrical and Ca2+ spikes and phasic contractions ceased, and a maintained, tonic force and Ca2+ was produced. Lanthanum, a non-selective blocker of store-operated Ca2+ entry, but not the L-type Ca2+ channel blocker nifedipine (1–10 μM), could abolish the maintained force and calcium. Application of the agonist, carbachol, produced similar effects to CPA, i.e. depolarization, elevation of force and calcium. A brief, high concentration of carbachol, to cause SR Ca2+ depletion without eliciting receptor-operated channel opening, also produced these results. The data obtained suggest that in pregnant rats SR Ca2+ release is coupled to marked Ca2+ entry, via store operated Ca2+ channels, leading to depolarization and enhanced electrical and mechanical activity.
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Bru-Mercier G, Gullam JE, Thornton S, Blanks AM, Shmygol A. Characterization of the tissue-level Ca2+ signals in spontaneously contracting human myometrium. J Cell Mol Med 2014; 16:2990-3000. [PMID: 22947266 PMCID: PMC4393727 DOI: 10.1111/j.1582-4934.2012.01626.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Accepted: 08/28/2012] [Indexed: 11/30/2022] Open
Abstract
In the labouring uterus, millions of myocytes forming the complex geometrical structure of myometrium contract in synchrony to increase intrauterine pressure, dilate the cervix and eventually expel the foetus through the birth canal. The mechanisms underlying the precise coordination of contractions in human myometrium are not completely understood. In the present study, we have characterized the spatio-temporal properties of tissue-level [Ca(2+)](i) transients in thin slices of intact human myometrium. We found that the waveform of [Ca(2+)](i) transients and isotonic contractions recorded from thin slices was similar to the waveform of isometric contractions recorded from the larger strips in traditional organ bath experiments, suggesting that the spatio-temporal information obtained from thin slices is representative of the whole tissue. By comparing the time course of [Ca(2+)](i) transients in individual cells to that recorded from the bundles of myocytes we found that the majority of myocytes produce rapidly propagating long-lasting [Ca(2+)](i) transients accompanied by contractions. We also found a small number of cells showing desynchronized [Ca(2+)](i) oscillations that did not trigger contractions. The [Ca(2+)](i) oscillations in these cells were insensitive to nifedipine, but readily inhibited by the T-type Ca(2+) channel inhibitor NNC55-0396. In conclusion, our data suggest that the spread of [Ca(2+)](i) signals in human myometrium is achieved via propagation of long-lasting action potentials. The propagation was fast when action potentials propagated along bundles of myocytes and slower when propagating between the bundles of uterine myocytes.
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Arrowsmith S, Kendrick A, Hanley JA, Noble K, Wray S. Myometrial physiology - time to translate? Exp Physiol 2014; 99:495-502. [DOI: 10.1113/expphysiol.2013.076216] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Sarah Arrowsmith
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Crown Street Liverpool UK
| | - Annabelle Kendrick
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Crown Street Liverpool UK
| | - Jacqui-Ann Hanley
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Crown Street Liverpool UK
| | - Karen Noble
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Crown Street Liverpool UK
| | - Susan Wray
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Crown Street Liverpool UK
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Corriveau S, Berthiaume M, Girard I, Nolin MA, Rousseau E, Pasquier JC. Effect of cytochrome P-450 epoxygenase and hydroxylase metabolites on rat myometrium contractility in non-pregnancy, late pregnancy and late pregnancy under inflammatory conditions. J Obstet Gynaecol Res 2013; 40:661-9. [PMID: 24321039 DOI: 10.1111/jog.12247] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Accepted: 07/22/2013] [Indexed: 12/18/2022]
Abstract
AIM The aim of the present experimental study was to assess the tocolytic effect of eicosanoids on myometrium from non-pregnant and pregnant rats with or without an induced inflammatory condition. METHODS Three hundred myometrial rings were obtained by median laparotomy from 50 Sprague-Dawley rats divided into three groups: (i) non-pregnant (n = 15); (ii) pregnant in absence (n = 20); or (iii) pregnant in presence (n = 15) of lipopolysaccharide treatment, timed at 22 days of pregnancy. Spontaneous contractile activities were compared by isometric tension measurements. The effects of epoxy- and hydroxyeicosanoids derived from arachidonic acid as well as specific enzyme inhibitors were assessed. Changes were expressed as percentage of basal activity by calculating the area under the curve as a function of drug concentration and compared to the effect of the vehicle. RESULTS A decrease in contractile activity ranging 10-25% was observed upon addition of epoxy- and hydroxyeicosanoids. Increasing epoxyeicosanoid bioavailability by inhibiting their degradation induced a tocolytic effect in the non-pregnant group (20%) and in inflammation-induced condition (40%). There was a significant difference in reactivity between groups and pregnancy condition. Semiquantification of metabolic enzymes that produce (cytochrome P-450 epoxygenase) and degrade (soluble epoxide hydrolase) epoxyeicosanoids by western blot analysis revealed that these enzymes were mainly detected in the non-pregnant group. CONCLUSION Eicosanoids can modify myometrial reactivity and their presence and effects are amplified in non-pregnant and in inflammation-induced condition. Our data suggest that in contrast to prostaglandins, epoxyeicosatrienoic acids are likely involved in the quiescence phase of parturition because they reduce the rhythmic contractile activity of uterine tissues in pregnant rats.
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Affiliation(s)
- Stéphanie Corriveau
- Obstetrics and Gynecology, CRC E-Lebel - CHUS, Sherbrooke, Quebec, Canada; Physiology and Biophysics, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec, Canada
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20
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Turton P, Arrowsmith S, Prescott J, Ballard C, Bricker L, Neilson J, Wray S. A comparison of the contractile properties of myometrium from singleton and twin pregnancies. PLoS One 2013; 8:e63800. [PMID: 23671701 PMCID: PMC3646038 DOI: 10.1371/journal.pone.0063800] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Accepted: 04/05/2013] [Indexed: 12/02/2022] Open
Abstract
Objective Over half of twin pregnancies in US and UK deliver prematurely but the reasons for this are unclear. The contractility of myometrium from twin pregnancies has not been directly investigated. The objective of this research was to determine if there are differences in the contractile activity and response to oxytocin, between myometrium from singleton and twin pregnancies, across a range of gestational ages. Furthermore, we wished to determine if contractile activity correlates with increasing level of stretch, using neonatal birth weights as a marker of uterine stretch. Methods This was an in vitro, laboratory based study of myometrial contractility in women pregnant with one or two babies, using biopsies obtained from non-labouring women undergoing Caesarean section. Spontaneous, oxytocin-stimulated and depolarization induced contractile activity was compared. Results Direct measurements of myometrial contractility under controlled conditions show that the frequency of contractions and responses to oxytocin are significantly increased in twins compared to singletons. The duration of contraction however was significantly reduced. We find that contractile activity correlates with increasing levels of stretch, using neonatal birth weights as a surrogate for uterine stretch, with response to oxytocin being significantly positively correlated with birth weight. Conclusions We have found significant differences in contractile properties between myometrium from singleton and twin pregnancies and that increasing uterine stretch can alter the contractile properties of myometrium. We discuss the implication of these findings to preterm delivery and future studies.
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Affiliation(s)
- Peter Turton
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Sarah Arrowsmith
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Jonathan Prescott
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Celia Ballard
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Leanne Bricker
- Liverpool Women's NHS Foundation Trust, Liverpool, United Kingdom
| | - James Neilson
- Department of Women's and Children's Health, Institute of Translational Medicine, University of Liverpool, United Kingdom
| | - Susan Wray
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
- * E-mail:
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21
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Arrowsmith S, Quenby S, Weeks A, Burdyga T, Wray S. Poor spontaneous and oxytocin-stimulated contractility in human myometrium from postdates pregnancies. PLoS One 2012; 7:e36787. [PMID: 22590608 PMCID: PMC3349652 DOI: 10.1371/journal.pone.0036787] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Accepted: 04/11/2012] [Indexed: 11/18/2022] Open
Abstract
Prolongation of pregnancy i.e. going more than 10 days over the estimated due date, complicates up to 10% of all pregnancies and is associated with increased risk to both mother and fetus. Despite the obvious need for contractions of the uterus to end pregnancy, there have been no studies directly examining the role of uterine smooth muscle, myometrium, in the aetiology of prolonged pregnancy. This study tested the hypothesis that the intrinsic contractile characteristics of myometrium taken from women with prolonged pregnancy (>41 weeks and 3 days) was reduced compared to those delivering at term (39–41 weeks). We recruited women undergoing Caesarean Section (CS) delivery either pre-labour (n = 27) or in labour (n = 66) at term or postdates. The contractile ability of the postdates myometrium, whether spontaneous or elicited by oxytocin or high-K solution, was significantly reduced compared to term myometrium. These differences remained when adjusted for parity and other maternal characteristics. The findings remained significant when expressed per cross sectional area. Histological examination revealed no differences between the two groups. The contractile differences were however related to intracellular Ca transients suggesting an effect of [Ca] on reduced force production in the postdates group. In summary, myometrium from prolonged pregnancies contracts poorly in vitro even when stimulated with oxytocin and in active labour. Responses to high K+ and measurements of Ca suggest that alterations in excitation contraction coupling, rather than any histological changes of the myometrium, may underlie the differences between term and postdates myometrium. We show that postdates pregnancy is associated with poor myometrial activity and suggest that this may contribute to increased myometrial quiescence and hence, prolonged gestation.
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Affiliation(s)
- Sarah Arrowsmith
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
- * E-mail:
| | - Siobhan Quenby
- Clinical Sciences Research Institute, University of Warwick, Warwick, United Kingdom
| | - Andrew Weeks
- Department of Women and Children's Health, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Theodor Burdyga
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Susan Wray
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
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Cretoiu SM, Simionescu AA, Caravia L, Curici A, Cretoiu D, Popescu LM. Complex effects of imatinib on spontaneous and oxytocin-induced contractions in human non-pregnant myometrium. ACTA ACUST UNITED AC 2011; 98:329-38. [PMID: 21893472 DOI: 10.1556/aphysiol.98.2011.3.10] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Human myometrium includes two important cell populations involved in its contractility: smooth muscle fibers and interstitial cells. The pacemaking mechanism is not yet identified, but it is possible that myometrial smooth muscle cells contract in response to a signal generated by c-kit positive interstitial cells. The aim of this study was to investigate the effects of imatinib as a c-kit receptor antagonist on the spontaneous or oxytocin (OT) induced contractions of human non-pregnant myometrium in vitro. Myometrial strips were obtained from non-pregnant women (reproductive age) undergoing hysterectomy for benign indications. The strips were suspended in organ baths for recording of isometric tension. Imatinib effects were assessed on spontaneous contraction and after preexposure to OT.Direct exposure of myometrial strips to imatinib inhibits both amplitude and frequency of contractions (80-320 μM) in a dose dependent manner. Amplitude reverted back to 90% of the baseline amplitude by consequent addition of imatinib (until 480 μM). Total inhibition of myometrial contraction was obtained after addition of OT 60 nM. If myometrium was pre-exposed to OT (320 nM), imatinib 80-160 μm increased amplitude, while decreasing frequency. These data provide evidence that telocytes may be involved as modulators of the spontaneous contractions of the non-pregnant human uterus, via a tyrosine-kinase independent signaling pathway.
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Affiliation(s)
- S M Cretoiu
- Department of Cellular and Molecular Medicine, 'Carol Davila' University of Medicine and Pharmacy, Bucharest, Romania
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23
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Aslanidi O, Atia J, Benson A, van den Berg H, Blanks A, Choi C, Gilbert S, Goryanin I, Hayes-Gill B, Holden A, Li P, Norman J, Shmygol A, Simpson N, Taggart M, Tong W, Zhang H. Towards a computational reconstruction of the electrodynamics of premature and full term human labour. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2011; 107:183-92. [DOI: 10.1016/j.pbiomolbio.2011.07.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Accepted: 07/05/2011] [Indexed: 01/02/2023]
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A Modified Hai–Murphy Model of Uterine Smooth Muscle Contraction. Bull Math Biol 2011; 74:143-58. [DOI: 10.1007/s11538-011-9681-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2011] [Accepted: 07/14/2011] [Indexed: 10/17/2022]
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25
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Borysova L, Shabir S, Walsh MP, Burdyga T. The importance of Rho-associated kinase-induced Ca2+ sensitization as a component of electromechanical and pharmacomechanical coupling in rat ureteric smooth muscle. Cell Calcium 2011; 50:393-405. [PMID: 21839512 DOI: 10.1016/j.ceca.2011.07.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2011] [Revised: 07/05/2011] [Accepted: 07/07/2011] [Indexed: 01/30/2023]
Abstract
Ureteric peristalsis, which occurs via alternating contraction and relaxation of ureteric smooth muscle, ensures the unidirectional flow of urine from the kidney to the bladder. Understanding of the molecular mechanisms underlying ureteric excitation-contraction coupling, however, is limited. To address these knowledge deficits, and in particular to test the hypothesis that Ca2+ sensitization via activation of the RhoA/Rho-associated kinase (ROK) pathway plays an important role in ureteric smooth muscle contraction, we carried out a thorough characterization of the electrical activity, Ca2+ signaling, MYPT1 (myosin targeting subunit of myosin light chain phosphatase, MLCP) and myosin regulatory light chain (LC20) phosphorylation, and force responses to membrane depolarization induced by KCl (electromechanical coupling) and carbachol (CCh) (pharmacomechanical coupling). The effects of ROK inhibition on these parameters were investigated. We conclude that the tonic, but not the phasic component of KCl- or CCh-induced ureteric smooth muscle contraction is highly dependent on ROK-catalyzed phosphorylation of MYPT1 at T855, leading to inhibition of MLCP and increased LC20 phosphorylation.
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Affiliation(s)
- Lyudmyla Borysova
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool L69 3BX, UK
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Skarra DV, Cornwell T, Solodushko V, Brown A, Taylor MS. CyPPA, a positive modulator of small-conductance Ca(2+)-activated K(+) channels, inhibits phasic uterine contractions and delays preterm birth in mice. Am J Physiol Cell Physiol 2011; 301:C1027-35. [PMID: 21795518 DOI: 10.1152/ajpcell.00082.2011] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Organized uterine contractions, including those necessary for parturition, are dependent on calcium entry through voltage-gated calcium channels in myometrial smooth muscle cells. Recent evidence suggests that small-conductance Ca(2+)-activated potassium channels (K(Ca)2), specifically isoforms K(Ca)2.2 and 2.3, may control these contractions through negative feedback regulation of Ca(2+) entry. We tested whether selective pharmacologic activation of K(Ca)2.2/2.3 channels might depress uterine contractions, providing a new strategy for preterm labor intervention. Western blot analysis and immunofluorescence microscopy revealed expression of both K(Ca)2.2 and K(Ca)2.3 in the myometrium of nonpregnant (NP) and pregnant (gestation day 10 and 16; D10 and D16, respectively) mice. Spontaneous phasic contractions of isolated NP, D10, and D16 uterine strips were all suppressed by the K(Ca)2.2/2.3-selective activator CyPPA in a concentration-dependent manner. This effect was antagonized by the selective K(Ca)2 inhibitor apamin. Whereas CyPPA sensitivity was reduced in D10 and D16 versus NP strips (pIC(50) 5.33 ± 0.09, 4.64 ± 0.03, 4.72 ± 0.10, respectively), all contractions were abolished between 30 and 60 μM. Blunted contractions were associated with CyPPA depression of spontaneous Ca(2+) events in myometrial smooth muscle bundles. Augmentation of uterine contractions with oxytocin or prostaglandin F(2α) did not reduce CyPPA sensitivity or efficacy. Finally, in an RU486-induced preterm labor model, CyPPA significantly delayed time to delivery by 3.4 h and caused a 2.5-fold increase in pup retention. These data indicate that pharmacologic stimulation of myometrial K(Ca)2.2/2.3 channels effectively suppresses Ca(2+)-mediated uterine contractions and delays preterm birth in mice, supporting the potential utility of this approach in tocolytic therapies.
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Affiliation(s)
- Dana V Skarra
- Department of Physiology, University of South Alabama College of Medicine, Mobile, AL 36688, USA
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27
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Tong WC, Choi CY, Karche S, Holden AV, Zhang H, Taggart MJ. A computational model of the ionic currents, Ca2+ dynamics and action potentials underlying contraction of isolated uterine smooth muscle. PLoS One 2011; 6:e18685. [PMID: 21559514 PMCID: PMC3084699 DOI: 10.1371/journal.pone.0018685] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2010] [Accepted: 03/15/2011] [Indexed: 11/18/2022] Open
Abstract
Uterine contractions during labor are discretely regulated by rhythmic action potentials (AP) of varying duration and form that serve to determine calcium-dependent force production. We have employed a computational biology approach to develop a fuller understanding of the complexity of excitation-contraction (E-C) coupling of uterine smooth muscle cells (USMC). Our overall aim is to establish a mathematical platform of sufficient biophysical detail to quantitatively describe known uterine E-C coupling parameters and thereby inform future empirical investigations of physiological and pathophysiological mechanisms governing normal and dysfunctional labors. From published and unpublished data we construct mathematical models for fourteen ionic currents of USMCs: currents (L- and T-type), current, an hyperpolarization-activated current, three voltage-gated currents, two -activated current, -activated current, non-specific cation current, - exchanger, - pump and background current. The magnitudes and kinetics of each current system in a spindle shaped single cell with a specified surface area∶volume ratio is described by differential equations, in terms of maximal conductances, electrochemical gradient, voltage-dependent activation/inactivation gating variables and temporal changes in intracellular computed from known fluxes. These quantifications are validated by the reconstruction of the individual experimental ionic currents obtained under voltage-clamp. Phasic contraction is modeled in relation to the time constant of changing . This integrated model is validated by its reconstruction of the different USMC AP configurations (spikes, plateau and bursts of spikes), the change from bursting to plateau type AP produced by estradiol and of simultaneous experimental recordings of spontaneous AP, and phasic force. In summary, our advanced mathematical model provides a powerful tool to investigate the physiological ionic mechanisms underlying the genesis of uterine electrical E-C coupling of labor and parturition. This will furnish the evolution of descriptive and predictive quantitative models of myometrial electrogenesis at the whole cell and tissue levels.
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Affiliation(s)
- Wing-Chiu Tong
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
- Maternal and Fetal Health Research Centre, St. Mary's Hospital, University of Manchester, Manchester, United Kingdom
| | - Cecilia Y. Choi
- School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom
| | - Sanjay Karche
- School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom
| | - Arun V. Holden
- Institute of Membrane and System Biology, University of Leeds, Leeds, United Kingdom
| | - Henggui Zhang
- School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom
- * E-mail: (HZ); (MT)
| | - Michael J. Taggart
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
- Maternal and Fetal Health Research Centre, St. Mary's Hospital, University of Manchester, Manchester, United Kingdom
- * E-mail: (HZ); (MT)
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