Dietary rumen-protected L-arginine or N-carbamylglutamate attenuated fetal hepatic inflammation in undernourished ewes suffering from intrauterine growth restriction

This study aimed to explore whether dietary rumen-protected L-arginine (RP-Arg) or N-carbamylglutamate (NCG) supplementation to feed-restricted pregnant ewes counteracts fetal hepatic inflammation and innate immune dysfunction associated with intrauterine growth retardation (IUGR) in ovine fetuses. On d 35 of pregnancy, twin-bearing Hu ewes (n = 32) were randomly assigned to 4 treatment groups (8 ewes and 16 fetuses per group) and fed diets containing 100% of the NRC requirements (CON), 50% of the NRC requirements (RES), RES + RP-Arg (20 g/d) (RESA), or RES + NCG (5 g/d) (RESN). At 08:00 on d 110 of gestation, fetal blood and liver tissue samples were collected. The levels of triglyceride, free fatty acid, cholesterol and β-hydroxybutyrate in the fetal blood of RESA and RESN groups were lower (P < 0.05) than those of the RES group, but were higher (P < 0.05) than those of the CON group. The interleukin (IL)-6 and IL-1 levels in fetal blood and liver tissue as well as the myeloid differentiation primary response 88 (MyD88), transforming growth factor β (TGFβ), and nuclear factor kappa B (NF-κB) mRNA levels in the fetal liver were decreased (P < 0.05) by the NCG or RP-Arg supplementation compared to the RES treatment. Similarly, the toll-like receptor (TLR)-4, MyD88, TGFβ, and p-c-Jun N-terminal kinase (JNK) protein levels in the fetal liver were reduced (P < 0.05) in the NCG and RP-Arg -supplemented groups compared to the RES group. These results showed that dietary supplementation of RP-Arg or NCG to underfed pregnant ewes could protect against IUGR fetal hepatic inflammation via improving lipid metabolism, down-regulating the TLR-4 and the inflammatory JNK and NF-κB signaling pathways, and decreasing cytokine production in ovine fetal blood and liver tissue.

Changes in S100B and troponin levels in a fetal sheep model of worsening acidosis

BACKGROUND

S100B and cardiac troponin T (c-TnT) are relevant biomarkers at birth of hypoxic-ischemic encephalopathy (HIE) and myocardial ischemia secondary to metabolic acidosis during labor, respectively. The purpose was to assess in-utero changes in S100B and c-TnT levels in an experimental model of labor-like acidosis.

METHODS

Repeated umbilical cord occlusions (UCOs) in ten experiments were performed in mild (phase A, 1 UCO/5 mn), moderate (phase B, 1 UCO/3 mn), and severe (phase C, 1 UCO/2 mn) period. The experiments were stopped if arterial pH reached 6.90.

RESULTS

UCOs resulted in fetal acidosis with pH dropping to 6.99 ±0.13. When compared to the baseline period fetal S100B increased between phases A and B (7% ± 4 vs 17% ± 13, p = 0.030) and between phases A and C (7% ± 4 vs 24% ± 8, p < 0.001). Fetal c-TnT serum levels increased during occlusions: 102 ng/L (58-119) in phase A, vs 119 ng/L (103-198) in phase B vs 169 ng / L (128-268) in phase C (p < 0.05, for all). When compared to the baseline control period, fetal ΔcTnT was significantly modified throughout UCO series: 5.0% (-3; 45) in phase A, 51% (4; 263) in phase B, and 77% (56.5; 269) in phase C (p < 0.05 for all).

CONCLUSIONS

S100B and c-TnT increased when fetal acidosis occurred, which reflects the potential neurological damage and fetal cardiovascular adaptation.

Effect of different cardioprotective methods on extracorporeal circulation in fetal sheep: a randomized controlled trial

Background

Congenital heart disease is a leading cause of death in newborns and infants. The feasibility of fetal cardiac surgery is linked to extracorporeal circulation (ECC); therefore, cardioplegic solutions need to be effective and long-lasting.

Methods

Eighteen pregnant sheep were divided into an ECC-only group, St. Thomas’ Hospital cardioplegic solution (STH1) group (STH group), and HTK preservation solution (Custodiol®) group (HTK group). Markers of myocardial injury including troponin I (cTnI), troponin T (cTnT) and creatine kinase myocardial band (CKMB) were measured at specific time points (T1: pre-ECC, T2: 30 min of ECC, T3: 60 min of ECC, T4: 60 min post-ECC, T5: 120 min post-ECC). Myocardial tissue was removed from the fetal sheep at T5, and apoptosis was detected by TUNEL staining.

Results

Changes in the serum cTnI, cTnT and CKMB concentrations were not significantly different among the three groups before and during the ECC(T1,T2,T3). At 60 min after ECC shutdown(T4), cTnI and cTnT concentrations were significantly higher in the STH group than before the start of ECC. The concentration of cTnI was higher in the STH group than in the HTK and ECC-only groups. The concentration of cTnT was higher in the STH group than in the ECC-only group. At 120 min after ECC shutdown(T5), cTnI and cTnT concentrations were significantly higher in the ECC and HTK groups than before the start of ECC, and CKMB concentration was significantly higher in STH and HTK groups. The concentrations of cTnT, cTnI and CKMB was higher in the STH group than in the HTK and ECC-only groups. The number of TUNEL-positive cells in the HTK and STH groups was higher than in the ECC-only group. The number of TUNEL-positive cells in the STH group was higher than in the HTK group. There was no statistically significant difference among the groups in the heart rate and mean arterial pressure after ECC.

Conclusion

The HTK preservation solution was significantly better than STH1 in reducing the release of cardiomyocyte injury markers and the number of apoptotic cells in fetal sheep ECC. Fetal sheep receiving ECC-only had an advantage in all indicators, which suggests ECC-only fetal heart surgery is feasible.

Opioid effect on the autonomic nervous system in a fetal sheep model

PURPOSE

Opioid use during labour can interfere with cardiotocography patterns. Heart rate variability indirectly reflects a fluctuation in the autonomic nervous system and can be monitored through time and spectral analyses. This experimental study aimed to evaluate the impact of nalbuphine administration on the gasometric, cardiovascular, and autonomic nervous system responses in fetal sheep.

METHODS

This was an experimental study on chronically instrumented sheep fetuses (surgery at 128 ± 2 days of gestational age, term = 145 days). The model was based on a maternal intravenous bolus injection of nalbuphine, a semisynthetic opioid used as an analgesic during delivery. Fetal gasometric parameters (pH, pO₂, pCO₂, and lactates), hemodynamic parameters (fetal heart rate and mean arterial pressure), and autonomic nervous system tone (short-term and long-term variation, low-frequency domain, high-frequency domain, and fetal stress index) were recorded. Data obtained at 30-60 min after nalbuphine injection were compared to those recorded at baseline.

RESULTS

Eleven experiments were performed. Fetal heart rate, mean arterial pressure, and activities at low and high frequencies were stable after injection. Short-term variation decreased at T30 min (P = 0.02), and long-term variation decreased at T60 min (P = 0.02). Fetal stress index gradually increased and reached significance at T60 min (P = 0.02). Fetal gasometric parameters and lactate levels remained stable.

CONCLUSION

Maternal nalbuphine use during labour may lead to fetal heart changes that are caused by the effect of opioid on the autonomic nervous system; these fluctuations do not reflect acidosis.

Analysis of dynamic and widespread lncRNA and miRNA expression in fetal sheep skeletal muscle

The sheep is an economically important animal, and there is currently a major focus on improving its meat quality through breeding. There are variations in the growth regulation mechanisms of different sheep breeds, making fundamental research on skeletal muscle growth essential in understanding the regulation of (thus far) unknown genes. Skeletal muscle development is a complex biological process regulated by numerous genes and non-coding RNAs, including microRNAs (miRNAs) and long non-coding RNAs (lncRNAs). In this study, we used deep sequencing data from sheep longissimus dorsi (LD) muscles sampled at day 60, 90, and 120 of gestation, as well as at day 0 and 360 following birth, to identify and examine the lncRNA and miRNA temporal expression profiles that regulate sheep skeletal myogenesis. We stained LD muscles using histological sections to analyse the area and circumference of muscle fibers from the embryonic to postnatal development stages. Our results showed that embryonic skeletal muscle growth can be characterized by time. We obtained a total of 694 different lncRNAs and compared the differential expression between the E60 vs. E90, E90 vs. E120, E120 vs. D0, and D0 vs. D360 lncRNA and gene samples. Of the total 701 known sheep miRNAs we detected, the following showed a wide range of expression during the embryonic stage: miR-2387, miR-105, miR-767, miR-432, and miR-433. We propose that the detected lncRNA expression was time-specific during the gestational and postnatal stages. GO and KEGG analyses of the genes targeted by different miRNAs and lncRNAs revealed that these significantly enriched processes and pathways were consistent with skeletal muscle development over time across all sampled stages. We found four visual lncRNA–gene regulatory networks that can be used to explore the function of lncRNAs in sheep and may be valuable in helping improve muscle growth. This study also describes the function of several lncRNAs that interact with miRNAs to regulate myogenic differentiation.

Fetal sheep cerebral electrical activity: A new technique to record EEG

BACKGROUND

Sheep models are commonly used to study fetal cortical activity, including response to hypoxia. The standard technique consists of recording electrocorticogram (ECOG) in utero using electrodes placed on the dura mater.

NEW METHOD

We propose a new method for recording the electroencephalogram (EEG) of fetal sheep, using electrodes placed above the skull bone and fixed to the cranial periosteum.

RESULTS

Twelve animals were instrumented with this new technique. The EEG signal recorded in utero was of sufficient quality for visual and quantitative analysis of the fetal cortical activity.

COMPARISON WITH EXISTING METHOD

This new method is less invasive than the standard method commonly used to record cerebral activity in fetal sheep, because it avoids drilling the skull by hand. The EEG signal recorded in utero had visual and quantitative characteristics comparable to ECOG.

CONCLUSIONS

We present a new method of EEG recording that appears to be an acceptable alternative to the standard ECOG recording method. Fetal sheep EEG can be used to better understand the physiological mechanisms involved in the cerebral response to hypoxia.

Autonomic response to fetal acidosis using an experimental sheep model

BACKGROUND

The autonomic nervous system has a major role in fetal adaptation to hypoxia. Its activity might be assessed using heart rate variability and heart rate deceleration analyses.

OBJECTIVE

To evaluate the ability of different heart rate variability and morphological deceleration analyses to predict fetal acidosis during labor in an experimental fetal sheep model.

STUDY DESIGN

Repeated 1-minute total umbilical cord occlusions were performed at mild (1minute every 5 min), moderate (1 min every 3 min), and severe (1 min every 2 min) umbilical cord occlusion periodicities until arterial pH reached 7.10. Hemodynamic,blood gas analysis, morphological analysis of decelerations (magnitude, slope, and area ofdecelerations), and heart rate variability parameters were recorded throughout the experiment.Heart rate variability analysis included temporal analysis (root mean square of successivedifferences between adjacent RR intervals, standard deviation of normal to normal RR intervals, short term variability), spectral analysis (low frequencies, high frequencies,normalized high frequencies), and a new index developed by our team, the Fetal Stress Index.We defined and compared three pH groups: >7.20, 7.10-7.20, and <7.10.

RESULTS

Eleven experiments were performed. Repetitive umbilical cord occlusions resulted in progressive fetal acidosis. Fetal Stress Index was correlated with pH and lactate (p < 0.05) and increased with acidosis. There were no significant correlations between pH, lactate, and other indices (spectral analysis, temporal analysis, or morphological analysis of decelerations).

CONCLUSION

This protocol allowed us to identify the progressive onset of fetal acidosis in an experimental model close to labor. Fetal Stress Index is a heart rate variability method that varies with acidosis and indicates an increase in parasympathetic nervous system activity in response to fetal acidosis.

Therapeutic Hypothermia in Neonatal Hypoxic-Ischemic Encephalopathy

PURPOSE OF REVIEW

Therapeutic hypothermia reduces death or disability in term and near-term infants with moderate-severe hypoxic-ischemic encephalopathy. Nevertheless, many infants still survive with disability, despite hypothermia, supporting further research in to ways to further improve neurologic outcomes.

RECENT FINDINGS

Recent clinical and experimental studies have refined our understanding of the key parameters for hypothermic neuroprotection, including timing of initiation, depth, and duration of hypothermia, and subsequent rewarming rate. However, important knowledge gaps remain. There is encouraging clinical evidence from a small phase II trial that combined treatment of hypothermia with recombinant erythropoietin further reduces risk of disability but definitive studies are still needed. In conclusion, recent studies suggest that current protocols for therapeutic hypothermia are near-optimal, and that the key to better neurodevelopmental outcomes is earlier diagnosis and initiation of hypothermia after birth. Further research is essential to find and evaluate ways to further improve outcomes after hypoxic-ischemic encephalopathy, including add-on therapies for therapeutic hypothermia and preventing pyrexia during labor and delivery.

Human Umbilical Cord Blood Therapy Protects Cerebral White Matter from Systemic LPS Exposure in Preterm Fetal Sheep

BACKGROUND

Infants born preterm following exposure to in utero inflammation/chorioamnionitis are at high risk of brain injury and life-long neurological deficits. In this study, we assessed the efficacy of early intervention umbilical cord blood (UCB) cell therapy in a large animal model of preterm brain inflammation and injury. We hypothesised that UCB treatment would be neuroprotective for the preterm brain following subclinical fetal inflammation.

METHODS

Chronically instrumented fetal sheep at 0.65 gestation were administered lipopolysaccharide (LPS, 150 ng, 055:B5) intravenously over 3 consecutive days, followed by 100 million human UCB mononuclear cells 6 h after the final LPS dose. Controls were administered saline instead of LPS and cells. Ten days after the first LPS dose, the fetal brain and cerebrospinal fluid were collected for analysis of subcortical and periventricular white matter injury and inflammation.

RESULTS

LPS administration increased microglial aggregate size, neutrophil recruitment, astrogliosis and cell death compared with controls. LPS also reduced total oligodendrocyte count and decreased mature myelinating oligodendrocytes. UCB cell therapy attenuated cell death and inflammation, and recovered total and mature oligodendrocytes, compared with LPS.

CONCLUSIONS

UCB cell treatment following inflammation reduces preterm white matter brain injury, likely mediated via anti-inflammatory actions.

The change of fetal heart rate short-term variability during the course of histological chorioamnionitis in fetal sheep

OBJECTIVE

Histological chorioamnionitis (CAM) is related to neonatal mortality and morbidity. However, identifying intrauterine inflammation before delivery is challenging. The aim of this study was to investigate the changes in fetal heart rate (FHR) short-term variability (STV) during the course of histological CAM.

STUDY DESIGN

Changes in STV were measured in 7 chronically instrumented fetal sheep at 111-120 days of gestation. Lipopolysaccharide (LPS) was infused into the amniotic cavity for 2 days following the 4th postoperative day to develop histological CAM. STV was determined based on the R to R interval of the fetal electrocardiogram. We continued to observe the changes in STV until the time of intrauterine fetal death (IUFD). The umbilical cord and fetal membranes were evaluated histologically after IUFD. The experiment was divided into two phases: 1) the acute phase, defined as the 24-hour period between the first and second injections of LPS and 2) the perimortem phase, defined as the period between the second injection of LPS and IUFD. Changes in STV in both the acute and perimortem phases were evaluated using Friedman's test. A probability of <0.05 was accepted as statistically significant.

RESULTS

The fetuses died, on average, at 23.7 ± 4.9 h after the second injection of LPS. Both the umbilical cord and fetal membranes showed histological evidence of severe inflammation. During the perimortem phase, there were statistically significant differences in STV at each time point. STV increased significantly at 6, 4, and 3 h before intrauterine fetal death compared to the baseline.

CONCLUSION

Our study suggests that STV increased as the fetal condition deteriorated during the course of histological CAM.

When should foetal pH measurements be performed after a prolonged deceleration? An experimental study in a fetal sheep model

OBJECTIVE

The aim of fetal heart rate monitoring during labour is to identify and prevent foetal distress, but its evaluation is not perfect. Fetal scalp blood sampling for pH measurement is one of the second-line methods of monitoring when fetal heart rate is classified as suspicious. This study aims to determine when pH testing should be performed after a prolonged deceleration.

STUDY DESIGN

This was an experimental study in a fetal sheep model. A partial umbilical cord occlusion was performed for seven minutes followed by a recuperation period of 30 min. Hemodynamic parameters (heart rate, mean blood pressure and intra-amniotic pressure) and blood gases were recorded before occlusion (T0), during occlusion (T4), just after the end of occlusion (T7), and then 10, 20 and 30 min after occlusion (T17, T27 and T37 respectively).

RESULTS

Ten experiments were carried out. During partial cord occlusion, the fetal pH decreased significantly to acidosis. After a prolonged deceleration with fetal acidosis, the pH recovered to a normal value, defined by a pH greater than or equal to 7.25, after 20 min of recuperation.

CONCLUSION

After a prolonged deceleration, fetal pH normalizes between 20 and 30 min thereafter. Thus, if a foetal blood sample is indicated, this delay must be respected in order to avoid inducing an unnecessary intervention decision.

Mechanisms of hypothermic neuroprotection

Prolonged, moderate cerebral hypothermia initiated within a few hours after severe hypoxia-ischemia and continued until resolution of the acute phase of delayed cell death can reduce acute brain injury and improve long-term behavioral recovery in term infants and in adults after cardiac arrest. The specific mechanisms of hypothermic neuroprotection remain unclear, in part because hypothermia suppresses a broad range of potential injurious factors. This article examines proposed mechanisms in relation to the known window of opportunity for effective protection with hypothermia. Knowledge of the mechanisms of hypothermia will help guide the rational development of future combination treatments to augment neuroprotection with hypothermia and identify those most likely to benefit.

Connexin hemichannel blockade is neuroprotective after, but not during, global cerebral ischemia in near-term fetal sheep

There is increasing evidence that connexin hemichannels, the half gap junctions that sit unopposed in the cell membrane, can open during ischemia and that blockade of connexin43 hemichannels after cerebral ischemia can improve neural outcomes. However, it is unclear whether connexin blockade during ischemia is protective. In the present study global cerebral ischemia was induced by 30 min of bilateral carotid artery occlusion in near-term (128 ± 1 day gestation age) fetal sheep. A specific mimetic peptide that blocks connexin43 hemichannels was infused into the lateral ventricle for either 1h before and during ischemia (intra-ischemia group, n=6) or for 25 h starting 90 min after the end of ischemia (post-ischemia group, n=7). The vehicle was infused in the ischemia-vehicle group (n=6) and sham-controls received sham occlusion plus vehicle (n=10). The post-ischemia group showed enhanced recovery of EEG power from day five until the end of the experiment (-5 ± 1.6 dB) compared to ischemia-vehicle (-13 ± 1.9 dB, p<0.05) and intra-ischemia infusion (-14.4 ± 3.6 dB, p<0.05). Post-ischemic infusion was associated with higher neuronal counts compared to ischemia-vehicle and intra-ischemia in the cortex (p<0.05) but not the CA1 and CA3 regions of the hippocampus. Oligodendrocyte cell counts in the intragyral and periventricular white matter were significantly higher in the post-ischemia group compared to ischemia-vehicle and intra-ischemia infusion (p<0.05). These large animal data support the hypothesis that connexin hemichannel opening after, but not during, ischemia contributes to the spread of white and gray matter injury of the developing brain.