Fetal echocardiography and pulsed-wave Doppler ultrasound in a rabbit model of intrauterine growth restriction

Pathogenesis of viral infections during pregnancy

SUMMARYViral infections during pregnancy are associated with significant adverse perinatal and fetal outcomes. Pregnancy is a unique immunologic and physiologic state, which can influence control of virus replication, severity of disease, and vertical transmission. The placenta is the organ of the maternal-fetal interface and provides defense against microbial infection while supporting the semi-allogeneic fetus via tolerogenic immune responses. Some viruses, such as cytomegalovirus, Zika virus, and rubella virus, can breach these defenses, directly infecting the fetus and having long-lasting consequences. Even without direct placental infection, other viruses, including respiratory viruses like influenza viruses and severe acute respiratory syndrome coronavirus 2, still cause placental damage and inflammation. Concentrations of progesterone and estrogens rise during pregnancy and contribute to immunological adaptations, placentation, and placental development and play a pivotal role in creating a tolerogenic environment at the maternal-fetal interface. Animal models, including mice, nonhuman primates, rabbits, and guinea pigs, are instrumental for mechanistic insights into the pathogenesis of viral infections during pregnancy and identification of targetable treatments to improve health outcomes of pregnant individuals and offspring.

Brain development is altered in rabbit fetuses with congenital diaphragmatic hernia

INTRODUCTION

Children with congenital diaphragmatic hernia (CDH) are at risk for neurodevelopmental delay. Some changes are already present prenatally. Herein, we further examined how the brain develops in fetal rabbits with surgically created DH.

METHODS

Two fetuses underwent surgical DH creation on day 23 (term = d31). DH pups and littermate controls were harvested at term. Ten DH pups and 11 controls underwent transcardial perfusion for brain fixation and measurement of brain volume, brain folding, neuron and synaptic density, pre-oligodendrocyte count, proliferation, and vascularization. Twelve other DH and 11 controls had echocardiographic assessment of cardiac output and aortic and cerebral blood flow, magnetic resonance imaging (9.4 T) for cerebral volumetry, and molecular assessment of vascularization markers.

RESULTS

DH pups had lower lung-to-body weight ratio (1.3 ± 0.3 vs. 2.4 ± 0.3%; p < 0.0001) and lower heart-to-body weight ratio (0.007 ± 0.001 vs. 0.009 ± 0.001; p = 0.0006) but comparable body weight and brain-to-body weight ratio. DH pups had a lower left ventricular ejection fraction, aortic and cerebral blood flow (39 ± 8 vs. 54 ± 15 mm/beat; p = 0.03) as compared to controls but similar left cardiac ventricular morphology. Fetal DH-brains were similar in volume but the cerebellum was less folded (perimeter/surface area: 25.5 ± 1.5 vs. 26.8 ± 1.2; p = 0.049). Furthermore, DH brains had a thinner cortex (143 ± 9 vs. 156 ± 13 μm; p = 0.02). Neuron densities in the white matter were higher in DH fetuses (124 ± 18 vs. 104 ± 14; p = 0.01) with comparable proliferation rates. Pre-oligodendrocyte count was lower, coinciding with the lower endothelial cell count.

CONCLUSION

Rabbits with DH had altered brain development compared to controls prenatally, indicating that brain development is already altered prenatally in CDH.

Pregnancy affects the pharmacokinetics of sildenafil and its metabolite in the rabbit

1. There is growing interest in the use of sildenafil during pregnancy for various maternal and fetal conditions. This study aims to investigate the effect of pregnancy on the maternal pharmacokinetics (PK) of sildenafil and its main metabolite desmethylsildenafil in rabbits. Using NONMEM, population PK modeling was performed based on plasma samples from 31 rabbits of whom 15 were pregnant and 16 were not. All received a single subcutaneous sildenafil dose of 10 mg/kg. One sample was obtained per rabbit at either 30, 60, 120, 360, 720 or 1320 min after sildenafil administration. 2. A two- and one-compartment PK-model best described the data for sildenafil and desmethylsildenafil, respectively. Compared to non-pregnant rabbits, the central and peripheral volume of distribution and inter-compartmental clearance of sildenafil were lower in pregnant rabbits [32.1 versus 12.2 L, 110 versus 44.4 L and 25.5 versus 12.1 L/h; all p < 0.05]. The formation clearance from sildenafil to desmethylsildenafil was also reduced during pregnancy [13.3 versus 7.8 L/h; p < 0.05]. 3. In contrast, the elimination clearance of desmethylsildenafil, was higher in pregnancy [73.5 versus 116. 9; p < 0.05]. In rabbits, pregnancy impacts PK parameters of sildenafil and its metabolite, leading to an increased peak concentration and 24 h exposure for sildenafil and a decreased 24 h exposure for desmethylsildenafil.

Dexamethasone-Induced Intrauterine Growth Restriction Is Associated With Altered Expressions of Metastasis Tumor Antigens and Cell Cycle Control Proteins in Rat Placentas

Molecular mechanisms affecting placental formation in intrauterine growth-restricted (IUGR) pregnancies are not clearly understood. Since metastasis tumor antigens (MTAs) MTA1 and MTA2 promote cell proliferation and MTA3 suppresses it, we hypothesized that IUGR alters cell survival/cell death programs driven by placental MTAs. To induce IUGR, pregnant Sprague Dawley rats were given daily intraperitoneal injections of either saline or dexamethasone (0.4 mg/kg) starting from 14 days of gestation (dg) to either 19 dg or 21 dg. Gene and protein expressions of MTA1-3 in the placental basal and labyrinth zones were investigated by real-time polymerase chain reaction, Western blotting, and immunohistochemistry. We also explored the expressions of proliferating cell nuclear antigen (PCNA), caspase-3, p53, p21, and β-catenin. Dexamethasone-induced IUGR resulted in decreased expression of MTA1 in the nuclei of cells in the basal zone. The expression of p21 was increased and that of PCNA was reduced in both placental zones of IUGR rats. Cytoplasmic expression of MTA1 and p53 increased in the labyrinth zone of IUGR placentas in association with an increase in cell death as indicated by an increased caspase-3 expression. The labyrinth zone of IUGR placentas showed a significant reduction in MTA2-MTA3 gene expression and an increase in p53 protein levels. Total MTA3 level increased and β-catenin level decreased in the labyrinth zone of IUGR placentas associated with a reduction in cell proliferation. Taken together, these results strongly suggest that dexamethasone-induced IUGR is associated with changes in MTA expression, decreased cell proliferation, and increased cell death in placentas.

The use of human amniotic fluid stem cells as an adjunct to promote pulmonary development in a rabbit model for congenital diaphragmatic hernia

OBJECTIVE

This study aimed to evaluate the potential benefit of intra-tracheal injection of human amniotic fluid stem cells (hAFSC) on pulmonary development combined with TO in a rabbit model for CDH.

METHODS

In time-mated pregnant does a left diaphragmatic defect was created at d23 (term = 31). At d28, previously operated fetuses were assigned to either TO and injection with 70 μL of phosphate buffered saline (PBS) or 1.0 × 10(6) c-Kit positive hAFSC expressing LacZ or were left untouched (CDH). Harvesting was done at d31 to obtain their lung-to-body weight ratio (LBWR), airway and vascular lung morphometry, X-gal staining and immunohistochemistry for Ki67 and surfactant protein-B (SP-B).

RESULTS

CDH-induced pulmonary hypoplasia is countered by TO + PBS, this reverses LBWR, mean terminal bronchiole density (MTBD) and medial thickness to normal. The additional injection of hAFSC decreases MTBD and results in a non-significant decrease in muscularization of intra-acinary vessels. There were no inflammatory changes and LacZ positive hAFSC were dispersed throughout the lung parenchyma 4 days after injection.

CONCLUSION

HAFSC exert an additional effect on TO leading to a decrease in MTBD, a measure of alveolar number surrounding the terminal bronchioles, without signs of toxicity. © 2015 John Wiley & Sons, Ltd.