Fetal Myocardium Research Articles

Microstripe pattern substrate consisting of alternating planar and nanoprotrusive regions improved hiPSC-derived cardiomyocytes' unidirectional alignment and functional properties.

The alignment of each cell in human myocardium is considered critical for the efficient movement of cardiac tissue. We investigated 96-well microstripe-patterned plates to align human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (CMs), which resemble fetal myocardium. The aligned CMs (ACMs) cultured on the microstripe-patterned plates exhibited pathology, motor function, gene expression, and drug response that more closely resembled those of adult cells than did unaligned CMs cultured on a flat plate (FCMs). We used these ACMs to evaluate drug side effects and efficacy, and to determine whether these were similar to adult-like responses. When CMs from patients with hypertrophic cardiomyopathy (HCMs) were seeded and cultured on the microstripe-patterned plates or layered on top of the ACMs, both sets of HCMs showed increased heart rate and synchronized contractions, indicating improved cardiac function. It is suggested that the ACMs could be used for drug screening as cells representative of adult-like CMs and be transplanted in the form of a cell sheet for regenerative treatment of heart failure.

Immunohistochemical Characterization of Heart Left Ventricle Morphogenesis in Rats Fetuses

Rats are the most common objects of preclinical studies, which determines the relevance of studying fetal cardiomorphogenesis in rats using modern methods of morphological studies. The aim is to study the dynamics of markers of proliferation (Ki67), apoptosis (caspase 3), vascularization (CD31), and stromal remodeling (MMP2 and MMP9) of the left ventricular myocardium of Wistar rat fetuses. Material and methods. A histological, immunohistochemical and morphometric study of the rat heart left ventricle wall was carried out on the 18th, 19th, 20th, 21st and 22nd days of the prenatal period of ontogenesis. Results. From the 18th to the 22nd day of the prenatal period of ontogenesis in rats, a twofold increase in the thickness of the left ventricle lateral wall is observed, due to both proliferation and differentiation and an increase in the size of cardiomyocytes. Ki67-positive cardiomyocytes are diffusely localized in the wall of the left ventricle, their number increases on day 19 of the prenatal period of development and remains at a high level until the end of the prenatal period in rats. From the 18th to the 22nd day of the prenatal period of ontogeny in rats, single caspase 3-positive cardiomyocytes are detected in the left ventricle. The growth of the left ventricular myocardium in the fetal period in rats is accompanied by an adequate rate of vascularization. The vascularization and proliferation of cardiomyocytes are accompanied by remodeling of the myocardial stroma, with the highest intensity of MMP2- and MMP9-immune staining observed at the beginning of the fetal period of ontogeny in rats. Conclusion. The short duration of prenatal ontogenesis in rats determines the high dynamics of cardiomorphogenetic processes. In the fetal period of rat ontogenesis in the left ventricle of the heart, the proliferation of cardiomyocytes prevails over the intensity of apoptosis. The intensity of proliferation of cardiomyocytes of the left ventricle of rats is high up to the 22nd day of the prenatal period of ontogenesis.

Sex-Specific Perturbation of Systemic Lipidomic Profile in Newborn Lambs Impacted by Prenatal Testosterone Excess.

Gestational hyperandrogenism adversely impacts offspring health. Using an ovine model, we found that prenatal testosterone (T) excess adversely affects growth and cardiometabolic outcomes in female offspring and produces sex-specific effects on fetal myocardium. Since lipids are essential to cardiometabolic function, we hypothesized that prenatal T excess leads to sex-specific disruptions in lipid metabolism at birth. Shotgun lipidomics was performed on the plasma samples collected 48 hours after birth from female (F) and male (M) lambs of control (C) and (T) sheep (CF = 4, TF = 7, CM = 5, TM = 10) and data were analyzed by univariate analysis, multivariate dimensionality reduction modeling followed by functional enrichment, and pathway analyses. Biosynthesis of phosphatidylserine was the major pathway responsible for sex differences in controls. Unsupervised and supervised models showed separation between C and T in both sexes with glycerophospholipids and glycerolipids classes being responsible for the sex differences between C and T. T excess increased cholesterol in females while decreasing phosphatidylcholine levels in male lambs. Specifically, T excess: 1) suppressed the phosphatidylethanolamine N-methyltransferase (PEMT) phosphatidylcholine synthesis pathway overall and in TM lambs as opposed to suppression of carnitine levels overall and TF lambs; and 2) activated biosynthesis of ether-linked (O-)phosphatidylethanolamine and O-phosphatidylcholine from O-diacylglycerol overall and in TF lambs. Higher cholesterol levels could underlie adverse cardiometabolic outcomes in TF lambs, whereas suppressed PEMT pathway in TM lambs could lead to endoplasmic reticulum stress and defective lipid transport. These novel findings point to sex-specific effects of prenatal T excess on lipid metabolism in newborn lambs, a precocial ovine model of translational relevance.

Prospects for the study of some electrophysiological parameters in the diagnosis of fetal growth restriction

Background. Fetal growth restriction is a clinical syndrome that has adverse effects on both perinatal outcomes and human health in adulthood. Traditional approaches to the diagnosis of this syndrome are based on ultrasound biometry and dopplerometry of uteroplacental and fetal-umbilical blood flow. The equipment used for such research is very expensive, and the training of a qualified specialist takes a long time. Non-invasive electrocardiography makes it possible to evaluate fetal heart rate variability and morphological parameters of the pQRST complex. The purpose: to determine indices of heart rate variability and morphological parameters based on the data of fetal non-invasive electrocardiography, which can be used to diagnose fetal growth restriction. Materials and methods. Two hundred and twenty pregnant women aged 18 to 40 years on 24–41 weeks of gestation were enrolled in the study. All of them were divided into two groups: 108 women with fetal growth restriction were included in group I, and 112 patients with healthy fetuses in group II. The fetal electrocardiogram was recorded in abdominal lead for 30–60 minutes. Results. The performed work made it possible to detect statistically significant changes in some indices of heart rate variability on the background of fetal growth restriction: SI, TP, AC/DC, LF, LF/HF ratio, as well as morphological parameters: QTc duration, QRS complex width and T/QRS ratio. The obtained data demonstrated a violation of autonomic regulation following fetal growth restriction and reflected the tension of regulatory systems, namely, the degree of dominance of the activity of central regulatory mechanisms over autonomous ones. Impaired de- and repolarization processes were a consequence of fetal myocardium remodeling due to ischemia. Conclusions. The development of algorithms for the diagnosis of fetal growth restriction using non-invasive electrocardiography requires further research of the following parameters: SI, TP, AC/DC, LF, LF/HF ratio, QTc duration, QRS complex width, and T/QRS ratio.

Coronary conductance in the normal development of sheep during the perinatal period.

Birth is associated with substantial shifts in cardiovascular physiology. Little is known about coronary vascular adaptations during this period. We used fetal and neonatal lambs to measure coronary function at late gestation (92% of term) and shortly after birth (5-6 days postnatal age). In each animal we measured unanesthetized myocardial perfusion and oxygen delivery using a circumflex artery flow probe. We used inflatable occluders and adenosine to determine coronary conductance and flow reserve. In a subset of animals, we used myocardial contrast echocardiography (MCE, anesthetized) to assess its utility as a tool for studying changes in regional myocardial perfusion in normal development. Separate age-matched animals were instrumented with aortic and coronary sinus sampling catheters to determine myocardial oxygen extraction (unanesthetized). With an average of 17 days of developmental time separating our neonatal and fetal cohorts we found that heart-to-body weight ratio was significantly greater in neonates than fetuses. In resting animals, we found significant decreases in weight-normalized perfusion of, and oxygen delivery to, neonatal relative to fetal myocardium. Similar results were seen when measuring baseline MCE-derived perfusion. Pressure-flow relationship studies revealed lower baseline and maximal coronary conductance in neonates than fetuses, with similar coronary flow reserve between groups. There was greater oxygen extraction in neonates than fetuses. Combined analysis of oxygen extraction with coronary flow suggested greater oxygen consumption by the fetal than neonatal myocardium. We conclude that, during the immediate perinatal period, cardiac growth outpaces coronary microvascular growth resulting in lower capacity for microvascular perfusion in the early neonate.

Effects of elevated bile acid levels on fetal myocardium in intrahepatic cholestasis of pregnancy, a retrospective study from a neonatal perspective

AimIntrahepatic cholestasis of pregnancy (ICP) is a liver disease which may lead to a sudden fetal death.Previous studies have suggested that the fetal accident may be related to their cardiac dysfunction.However,the relationship between fetal cardiac dysfunction and their maternal bile acid levels is not clear.This objective was to clarify the relationship from a neonatal perspective and to furtherly make clear the aftereffect by analyzing the cardiac parameters of the older neonates. MethodsIn this case-control study,patients and their neonates,managed between 10 September 2018 and 30 June 2021 at a Chinese university hospital center,were divided into severe ICP group,mild ICP group and control gestational group.The maternal bile acid levels and the cardiac paramerers of one-day-old neonates and five-day-old neonates were analyzed,respectively. ResultsThe specific-myocardial enzyme(CK-MB) and left ventricular fraction shortening(FS) of neonates showed significant difference between ICP group and control group, and were meaningfully correlated with maternal bile acid levels.However,There was no significant difference in cardiac injury parameters of older neonates between the ICP group and control group. ConclusionsThe elevated maternal bile acid levels can lead to fetal myocardial injury and the injury can be recovered after removel from high concentrations of bile acid.

Circulating microRNA: Myocardium-derived prenatal biomarker of ventricular septal defects.

Background: Recently, circulating microRNAs (miRNAs) from maternal blood and amniotic fluid have been used as biomarkers for ventricular septal defect (VSD) diagnosis. However, whether circulating miRNAs are associated with fetal myocardium remains unknown. Methods: Dimethadione (DMO) induced a VSD rat model. The miRNA expression profiles of the myocardium, amniotic fluid and maternal serum were analyzed. Differentially expressed microRNAs (DE-microRNAs) were verified by qRT–PCR. The target gene of miR-1-3p was confirmed by dual luciferase reporter assays. Expression of amniotic fluid-derived DE-microRNAs was verified in clinical samples. Results: MiRNAs were differentially expressed in VSD fetal rats and might be involved in cardiomyocyte differentiation and apoptosis. MiR-1-3p, miR-1b and miR-293-5p were downregulated in the myocardium and upregulated in amniotic fluid/maternal serum. The expression of amniotic fluid-derived DE-microRNAs (miR-1-3p, miR-206 and miR-184) was verified in clinical samples. Dual luciferase reporter assays confirmed that miR-1-3p directly targeted SLC8A1/NCX1. Conclusion: MiR-1-3p, miR-1b and miR-293-5p are downregulated in VSD myocardium and upregulated in circulation and may be released into circulation by cardiomyocytes. MiR-1-3p targets SLC8A1/NCX1 and participates in myocardial apoptosis. MiR-1-3p upregulation in circulation is a direct and powerful indicator of fetal VSD and is expected to serve as a prenatal VSD diagnostic marker.

Biventricular biaxial mechanical testing and constitutive modelling of fetal porcine myocardium passive stiffness

The evaluation of fetal heart mechanical function is becoming increasingly important for determining the prognosis and making subsequent decisions on the treatment and management of congenital heart diseases. Finite Element (FE) modelling can potentially provide detailed information on fetal hearts, and help perform virtual interventions to assist in predicting outcomes and supporting clinical decisions. Previous FE studies have enabled an improved understanding of healthy and diseased fetal heart biomechanics. However, to date, the mechanical properties of the fetal myocardium have not been well characterized which limits the reliability of such modelling. Here, we characterize the passive mechanical properties of late fetal and neonatal porcine hearts via biaxial mechanical testing as a surrogate for human fetal heart mechanical properties. We used samples from both the right and left ventricles over the late gestational period from 85 days of gestation to birth. Constitutive modelling was subsequently performed with a transversely isotropic Fung-type model and a Humphrey-type model, using fiber orientations identified with histology. We found no significant difference in mechanical stiffness across all age groups and between the right and left ventricular samples. This was likely due to the similarity in LV and RV pressures in the fetal heart, and similar gestational maturity across these late gestational ages. We thus recommend using the constitutive model for the average stress-stress behaviour of the tissues in future modelling work. Furthermore, we characterized the variability of the stiffness to inform such work.

Biventricular Biaxial Mechanical Testing and Constitutive Modelling of Fetal Porcine Myocardium Passive Stiffness

Biventricular Biaxial Mechanical Testing and Constitutive Modelling of Fetal Porcine Myocardium Passive Stiffness

Significance of Atrial and Brain Natriuretic Peptide Measurements in Fetuses With Heart Failure.

Fetal heart failure is mainly caused by congenital heart defect and arrhythmia. It is difficult to appropriately diagnose the severity of fetal heart failure simply by ultrasonography because the development of a fetal heart in fetoplacental circulation and how well the fetal myocardium can adapt to postnatal cardiopulmonary circulation are challenging to assess. In adult cardiology, natriuretic peptides (NPs) are the most useful biomarker of heart failure; however, studies investigating NP levels in the fetuses and amniotic fluid are quite limited. Furthermore, little is known about their production and metabolism. This review summarized the most relevant findings on NP levels in the umbilical cord blood and amniotic fluid. The findings can then extend their use as a diagnostic biomarker of heart failure in fetuses with congenital heart defect and/or arrhythmia.

ВЛИЯНИЕ ПРОМЫШЛЕННОЙ ВИБРАЦИИ НА МИНЕРАЛЬНЫЙ ОБМЕН, ОРГАНЫ ПОЛОСТИ РТА И МИОКАРД ПЛОДА

In the study, the morphometric analysis of bone trabeculae of the developing jaws, tooth buds, tongue muscles, masseter muscle, and myocardium of 20-day fetuses of Wistar rats, exposed to vibration from the 9th to the 18th day of prenatal ontogenesis, was performed. The concentration of Ca, Cd, Cu, Fe, Mg, P, Pb, Se, Zn was determined in the liver of pregnant females exposed to vibration. The morphometric study revealed an acceleration of the osteogenesis of jaws and dentinogenesis of tooth buds. In the myocardium and masseter muscle signs of interstitial edema and a decrease in the area of the vessels of the microvasculature are determined. In the liver, there is a decrease in the amount of Ca, Mg and Fe, which is accompanied by an increase in the content of Cd and Pb. The revealed shifts in mineral metabolism indicate gross impairment of chemicals' homeostasis in the mother-fetus system, which underlies the imperfect morphogenesis of the fetal dentition and will be the basis for the formation of pathology of orofacial organs and cardiovascular pathology in offspring.

Myocardial hypertrophy in fetuses of women with gestational diabetes

Fetuses of diabetic mothers are known to have structural and functional cardiac changes. There are minuscule data on fetal cardiac changes from the Indian subcontinent. Hence, this study aimed to detect myocardial hypertrophy using 2D and M-mode fetal echocardiography (ECHO) in South Indian women with gestational diabetes mellitus (GDM) in their late phase of pregnancy. We have compared ECHO findings among nondiabetic controls and well-controlled and poorly controlled GDM through a cross-sectional observational study. Myocardial and interventricular septum (IVS) thicknesses were measured at the end of systole and diastole. The study included a total of 247 pregnant women; among them, 152 were diabetics [(well-controlled (n = 74) and poorly controlled (n = 78)], and 95 were nondiabetic controls. Myocardial hypertrophy is evident only beyond 29 weeks of gestation. During 29–34 weeks, myocardial hypertrophy is less severe among those with glycemic control. The fetuses beyond 35 weeks have a consistent and significant progressive thickening of fetal myocardium in all dimensions (p-value < 0.05). The overall thickness of ventricular walls and IVS increases with the diabetic status from nondiabetic controls to poorly controlled GDM women. There is a clear need to explore the perinatal implications of structural changes, considering the huge burden of diabetes in the Indian population.

Assessement of myocardial contractile function in fetuses with obstructive aortic lesions

The potential possibilities to assess the contractile function of the myocardium in fetuses with obstructive aortic lesions using speckle tracking are presented.

Could the E/A ratio be included in the cardiological evaluation of the offspring of diabetic mothers? A case-control study in South Sardinia

Introduction Diabetes mellitus (DM) is a chronic disease widespread in the world. Sardinia represents, together with Finland, the region with the highest incidence of type 1 DM (DM1), as well as a high prevalence of gestational DM (GDM). Despite the improvement in obstetric surveillance, perinatal and long-term adverse outcomes are still frequent in the offspring of diabetic mothers. During gestations complicated by DM, fetal heart is one of the most affected organ potentially undergoing structural heart defects or several degrees of fetal myocardium hypertrophy and impaired cardiac function. Aim The aim of our study was to evaluate, through echocardiographic examination, cardiac features and performance in a South Sardinian population of newborns of diabetic mothers comparing them to a group of control subjects. Conclusions In our sample, the E/A ratio resulted a significant marker of early diastolic dysfunction in asymptomatic neonates born by diabetic mothers, even if such result should be confirmed on larger samples.

Impact of maternal diabetes and obesity on fetal cardiac functions

BackgroundIn several developing industrial countries, the incidence of obesity among populations is spreading quickly and dramatically; also, the frequency of maternal obesity is in continuous elevation, which represents a considerable public health problem. Maternal hyperglycemia is a common gestational risk factor for the fetus. Several studies proposed that maternal DM and obesity lead to intrauterine impacts which induce changes in the fetal myocardium, and the pre-pregnancy obesity and diabetes are accompanied with development of cardiovascular alterations in the offspring and subsequent pathological changes in their early life. The aim of this study is to assess the cardiac function in fetuses of obese pregnant women (FOW) and fetuses of diabetic women (FDW) in comparison with fetuses of normal pregnant women (FNW) using tissue Doppler imaging.ResultsThere was impairment in systolic and diastolic cardiac function in both fetuses of obese and diabetic women with decreased global longitudinal strain tissue Doppler velocities at 30 weeks of gestation compared to fetuses of normal women.ConclusionImaging of the fetus of pregnant women by Echo Doppler at about 30 weeks of gestations showed a reduced cardiac function of fetuses of obese and diabetic women matched with fetuses of normal BMI women. Our finding proposed that early subclinical alterations in the fetal cardiac output can arise from maternal obesity alone. This explains the predilection of children of obese mothers at advanced ages to cardiovascular disorder.

P1378 Impact of maternal diabetes on fetal left atrial function

Abstract Background/Introduction: Diabetes impacts 12- 14% of pregnancies. Evaluating the impact of maternal diabetes on the fetal heart is challenging due to variable image quality and limited time for structural changes to manifest. Left atrial reservoir strain (ER) is a sensitive marker of early left atrial dysfunction which may elucidate fetal atrial dysfunction resulting from maternal diabetes. Purpose We sought to evaluate if fetal ER can detect impairment of left atrial function in the fetal heart as a result of maternal diabetes. Methods We performed a prospective observational study evaluating patients who were referred to the high risk pregnancy service as a result of maternal diabetes (pre-existing or gestational) and healthy controls. Patients were excluded if adequate imaging of the fetal myocardium was not possible. Baseline characteristics of the mother and cardio-metabolic risk factors were recorded. The fetal echocardiogram focused on the 4 chamber view. We used the 4 chamber view with closure of the mitral valve as the zero reference point (R-R) gating. The strain curves from 6 atrial segments were averaged. Normality of the data was assessed using the Shapiro-Wilk test. The Mann-Whitney U test was used to compare ER between fetuses, whose mothers had diabetes versus those fetuses whose mothers were healthy controls. Results A total of 120 fetal scans were performed. 5 were excluded due to poor image quality, which prevented strain analysis. 115 fetal scans were analysed (87 with maternal diabetes and 27 healthy controls). The diabetic subjects and controls did not defer significantly in age Mean ± SD (31± 5 vs 30± 5, p= 0.81). The mothers with diabetes had a higher body mass index than controls (Median [IQR]) (30.5 kg/m2 [25.1, 35.3] vs 24.6 kg/m2 [22.1, 28.6] p &amp;lt; 0.001). The presence of maternal diabetes resulted in lower fetal ER (28.5% [22.1, 36.2] vs 33.4% [26.6, 41.6] P = 0.01). Figure 1 illustrates the Box-Whisker plot comparing Fetal ER between fetuses exposed to maternal diabetes and fetuses where mothers were healthy controls. Conclusion The presence of maternal diabetes results in impaired fetal left atrial function as measured by fetal left atrial strain (ER). Abstract P1378 Figure 1

Adaptation within embryonic and neonatal heart environment reveals alternative fates for adult c-kit+ cardiac interstitial cells.

Cardiac interstitial cells (CICs) perform essential roles in myocardial biology through preservation of homeostasis as well as response to injury or stress. Studies of murine CIC biology reveal remarkable plasticity in terms of transcriptional reprogramming and ploidy state with important implications for function. Despite over a decade of characterization and in vivo utilization of adult c‐Kit+ CIC (cCIC), adaptability and functional responses upon delivery to adult mammalian hearts remain poorly understood. Limitations of characterizing cCIC biology following in vitro expansion and adoptive transfer into the adult heart were circumvented by delivery of the donated cells into early cardiogenic environments of embryonic, fetal, and early postnatal developing hearts. These three developmental stages were permissive for retention and persistence, enabling phenotypic evaluation of in vitro expanded cCICs after delivery as well as tissue response following introduction to the host environment. Embryonic blastocyst environment prompted cCIC integration into trophectoderm as well as persistence in amniochorionic membrane. Delivery to fetal myocardium yielded cCIC perivascular localization with fibroblast‐like phenotype, similar to cCICs introduced to postnatal P3 heart with persistent cell cycle activity for up to 4 weeks. Fibroblast‐like phenotype of exogenously transferred cCICs in fetal and postnatal cardiogenic environments is consistent with inability to contribute directly toward cardiogenesis and lack of functional integration with host myocardium. In contrast, cCICs incorporation into extra‐embryonic membranes is consistent with fate of polyploid cells in blastocysts. These findings provide insight into cCIC biology, their inherent predisposition toward fibroblast fates in cardiogenic environments, and remarkable participation in extra‐embryonic tissue formation.

Light and electron microscopic studies on lung and myocardium of the mice fetuses maternally treated with monosodium glutamate and role of vitamin E against toxicity

The lung and myocardium of fetal mice were used in the present investigation as a model to evaluate the possible effect of monosodium glutamate as one of the flavor food additives. Vitamin E was also used as one of the antioxidant agents against wide range of cellular damage. In this study, light microscopic examination revealed that monosodium glutamate caused narrowing of the lung airways, thickening of the alveolar walls and collapsing of the alveoli. The cardiac muscles showed severe atrophy and abundance of blood capillaries. The ultrastructure studies revealed remarkable damage of type I and type II pneumocytes as well as the endothelial cells. Severely degenerated alveolar areas and accumulated collagen bundles were detected in the alveolar wall. The ultrastructure of the fetal myocardium revealed severe atrophy and destruction of cardiac muscle fibers. Some of these fibers tend to accumulate around blood capillaries which lined by attenuated endothelium. Numerous fibroblasts, fibrillary network, collagen and macrophages were obvious in the myocardium of these fetuses. Light and ultrastructural results showed that the treatment of pregnant mice with vitamin E leads to apparent repair of the lung tissues that may suggest a remarkable efficacy of this vitamin against pulmonary damage. On the other hand, the protective effect of vitamin E on the fetal myocardium was weak.

Fetal electrocardiography ST-segment analysis for intrapartum monitoring: a critical appraisal of conflicting evidence and a way forward

In the past century, some areas of obstetric including intrapartum care have been slow to benefit from the dramatic advances in technology and medical care. Although fetal heart rate monitoring (cardiotocography) became available a half century ago, its interpretation often differs between institutions and countries, its diagnostic accuracy needs improvement, and a technology to help reduce the unnecessary obstetric interventions that have accompanied the cardiotocography is urgently needed. During the second half of the 20th century, key findings in animal experiments captured the close relationship between myocardial glycogenolysis, myocardial workload, and ST changes, thus demonstrating that ST waveform analysis of the fetal electrocardiogram can provide information on oxygenation of the fetal myocardium and establishing the physiological basis for the use of electrocardiogram in intrapartum fetal surveillance. Six randomized controlled trials, 10 meta-analyses, and more than 20 observational studies have evaluated the technology developed based on this principle. Nonetheless, despite this intensive assessment, differences in study protocols, inclusion criteria, enrollment rates, clinical guidelines, use of fetal blood sampling, and definitions of key outcome parameters, as well as inconsistencies in randomized controlled trial data handling and statistical methodology, have made this voluminous evidence difficult to interpret. Enormous resources spent on randomized controlled trials have failed to guarantee the generalizability of their results to other settings or their ability to reflect everyday clinical practice. The latest meta-analysis used revised data from primary randomized controlled trials and data from the largest randomized controlled trials from the United States to demonstrate a significant reduction of metabolic acidosis rates by 36% (odds ratio, 0.64; 95% confidence interval, 0.46-0.88) and operative vaginal delivery rates by 8% (relative risk, 0.92; 95% confidence interval, 0.86-0.99), compared with cardiotocography alone.

Thyroid hormone receptor function in maturing ovine cardiomyocytes.

Plasma thyroid hormone (tri-iodo-l-thyronine; T3 ) concentrations rise near the end of gestation and is known to inhibit proliferation and stimulate maturation of cardiomyocytes before birth. Thyroid hormone receptors are required for the action of thyroid hormone in fetal cardiomyocytes. Loss of thyroid hormone receptor (TR)α1 abolishes T3 signalling via extracellular signal-related kinase and Akt in fetal cardiomyocytes. The expression of TRα1 and TRβ1 in ovine fetal myocardium increases with age, although TRα1 levels always remain higher than those of TRβ1. Near term fetal cardiac myocytes are more sensitive than younger myocytes to thyroid receptor blockade by antagonist, NH3, and to the effects of TRα1/α2 short interfering RNA. Although T3 is known to abrogate ovine cardiomyocyte proliferation stimulated by insulin-like growth factor 1, this effect is mediated via the genomic action of thyroid hormone receptors, with little evidence for non-genomic mechanisms. We have previously shown that the late-term rise in tri-iodo-l-thyronine (T3 ) in fetal sheep leads to the inhibition of proliferation and promotion of maturation in cardiomyocytes. The present study was designed to determine whether these T3 -induced changes are mediated via thyroid hormone receptors (TRs) or by non-genomic mechanisms. Fetal cardiomyocytes were isolated from 102±3 and 135±1days of gestational age (dGA) sheep (n=7 per age; term ∼145dGA). Cells were treated with T3 (1.5nm), insulin-like growth factor (IGF)-1 (1μgmL-1 ) or a combination in the presence of TR antagonist NH3 (100nm) or following short interfering RNA (siRNA) knockdown of TRα1/α2. Proliferation was quantified by 5-bromo-2'-deoxyuridine (BrdU) uptake (10μm). Western blots measured protein levels of extracellular signal-related kinase (ERK), Akt, TRα1/β1 and p21. Age specific levels of TRα1/β1 were measured in normal hearts from fetuses [95dGA (n=8), 135dGA (n=7)], neonates (n=8) and adult ewes (n=7). TRα1 protein levels were consistently >50% more than TRβ1 at each gestational age (P<0.05). T3 reduced IGF-1 stimulated proliferation by ∼50% in 100dGA and by ∼75% in 135dGA cardiomyocytes (P<0.05). NH3 blocked the T3 +IGF-1 reduction of BrdU uptake without altering the phosphorylation of ERK or Akt at both ages. NH3 did not suppress T3 -induced p21 expression in 100dGA cardiomyocytes in 135dGA cardiomyocytes, NH3 alone reduced BrdU uptake (-28%, P<0.05), as well as T3 -induced p21 (-75%, P<0.05). In both ages, siRNA knockdown of TRα1/α2 blocked the T3 +IGF-1 reduction of BrdU uptake and dramatically reduced ERK and Akt signalling in 135dGA cardiomyocytes. In conclusion, TRs are required for normal proliferation and T3 signalling in fetal ovine cardiomyocytes, with the sensitivity to TR blockade being age-dependent.