Precision-cut slice culture method for rat placenta

Precision-Cut Slice Culture Method for Rat Placenta

Organotypic slice cultures provide several advantages over primary and cell line culture models. Unlike monolayer cultures, organotypic slice cultures retain the tissue's 3-D architecture, multi-lineage cell populations, and many complex functional characteristics. Organotypic slice cultures can be exposed to biological, pharmacological, or environmental agents and analyzed to predict in vivo responses. Herein, we describe a method for preparing organotypic slice cultures generated from rat placenta.

Ovine placental explants: A new ex vivo model to study host‒pathogen interactions in reproductive pathogens

Reproductive failure is one of the main performance constraints in ruminant livestock. Transmissible agents such as Toxoplasma gondii and Neospora caninum are commonly involved in the occurrence of abortion in ruminants, but little is known about the mechanisms involved. While in vivo models are optimal for the study of abortion pathogenesis, they have a high economic cost and come with ethical concerns. Unfortunately, alternative in vitro models fail to replicate the complex in vivo placental structure. To overcome the limitations of currently available models, we developed an ex vivo model based on the cultivation of fresh and cryopreserved sheep placental explants, enabling the biobanking of tissues. Reproducible and simple markers of tissue integrity (histology, RNA concentrations), viability (resazurin reduction), and functionality (synthesis of steroid hormones) were also investigated, allowing a clear quality assessment of the model. This work shows that, similar to fresh explants, tissues cryopreserved in ethylene glycol using slow freezing rates maintain not only their structure and function but also their receptivity to T. gondii and N. caninum infection. In addition, the findings demonstrate that explant lifespan is mainly limited by the culture method, with protocols requiring improvements to extend it beyond 2 days. These findings suggest that cryopreserved tissues can be exploited to study the initial host‒pathogen interactions taking place in the placenta, thus deepening the knowledge of the specific mechanisms that trigger reproductive failure in sheep. Importantly, this work paves the way for the development of similar models in related species and contributes to the reduction of experimental animal use in the future.

A highly potent human neutralizing antibody prevents vertical transmission of Rift Valley fever virus in a rat model

Rift Valley fever virus (RVFV) is an emerging mosquito-transmitted virus that circulates in livestock and humans in Africa and the Middle East. Outbreaks lead to high rates of miscarriages in domesticated livestock. Women are also at risk of vertical virus transmission and late-term miscarriages. MAb RVFV-268 is a highly potent recombinant neutralizing human monoclonal antibody that targets RVFV. Here we show that mAb RVFV-268 reduces viral replication in rat placenta explant cultures and prevents vertical transmission in a rat model of congenital RVF. Passive transfer of mAb RVFV-268 from mother to fetus occurs as early as 6 h after administration and persists through 24 h. Administering mAb RVFV-268 2 h prior to RVFV challenge or 24 h post-challenge protects the dams and offspring from RVFV infection. These findings support mAb RVFV-268 as a pre- and post-infection treatment to subvert RVFV infection and vertical transmission, thus protecting the mother and offspring.

Precision-cut rat placental slices as a model to study sex-dependent inflammatory response to LPS and Poly I:C

Introduction

Maternal inflammation in pregnancy represents a major hallmark of several pregnancy complications and a significant risk factor for neurodevelopmental and neuropsychiatric disorders in the offspring. As the interface between the mother and the fetus, the placenta plays a crucial role in fetal development and programming. Moreover, studies have suggested that the placenta responds to an inflammatory environment in a sex-biased fashion. However, placenta-mediated immunoregulatory mechanisms are still poorly understood.

Methods

Therefore, we have developed a model of ex vivo precision-cut placental slices from the rat term placenta to study acute inflammatory response. Rat placental slices with a precise thickness of 200 µm were generated separately from male and female placentas. Inflammation was stimulated by exposing the slices to various concentrations of LPS or Poly I:C for 4 and 18 hours.

Results

Treatment of placental slices with LPS significantly induced the expression and release of proinflammatory cytokines TNF-α, IL-6, and IL-1β. In contrast, Poly I:C treatment resulted in a less-pronounced inflammatory response. Interestingly, the female placenta showed higher sensitivity to LPS than male placenta. Anti-inflammatory agents, curcumin, 1α,25- dihydroxyvitamin D3, and progesterone attenuated the LPS-induced proinflammatory cytokine response at both mRNA and protein levels.

Discussion

We conclude that rat placental slices represent a novel alternative model to study the role of sexual dimorphism in the acute inflammatory response and immune activation in pregnancy.

Maternal siRNA silencing of placental SAA2 mitigates preterm birth following intrauterine inflammation

The placental inflammatory processes induced maternally result in preterm birth (PTB). Serum amyloid A (SAA) is a well-known biomarker of inflammation. The objective of this study was to investigate whether murine placental SAA isoforms (SAA1–4) participate in the mechanism of spontaneous PTB and whether maternal regulation of SAA production may serve as a therapeutic approach. During the gestation, all isoforms of SAA were detectable except SAA2. The mouse model of intrauterine inflammation was established using LPS infusion to the uterus. Following intrauterine inflammation, placental SAA2 increased significantly. Inhibition of Saa2, using siSaa2, markedly decreased PTB. The increased placental expression of pro-inflammatory cytokines Il1β, Il6, and Tnfα were downregulated by siSaa2 treatment. Maternal inhibition of Saa2 did not change the expression of Saa1–4 in the fetal brain. Explant inflammatory culture of placentas with siSaa2 showed similar results to our in vivo experiments. This study demonstrates the highly expressed placental SAA2 as a novel therapeutic target, and maternal administration of siRNA as a promising approach to alleviate PTB.

Generation of precision-cut slice cultures of human placenta

We present a protocol to generate an advanced ex vivo model of human placenta. We use a vibrating tissue slicer to obtain precision-cut slices representative of the entire thickness of human placenta. This approach delivers standardized cultures with a preserved microstructure and cellular composition comparable to the native tissue. We applied this system to study SARS-CoV-2 infection at the maternal-fetal interface. Moreover, this system can be used to investigate the basic functions of the human placenta in health and disease.

For complete details on the use and execution of this protocol, please refer to Fahmi et al. (2021).

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Protocol to generate an advanced model of the human maternal-fetal interface

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Standardized cultures representative of the full thickness of human placenta

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Cultures preserve the microstructure and cellular composition of the native tissue

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Can be applied to study basic functions of the human placenta in health and disease

SARS-CoV-2 can infect and propagate in human placenta explants

The ongoing SARS-CoV-2 pandemic continues to lead to high morbidity and mortality. During pregnancy, severe maternal and neonatal outcomes and placental pathological changes have been described. We evaluate SARS-CoV-2 infection at the maternal-fetal interface using precision-cut slices (PCSs) of human placenta. Remarkably, exposure of placenta PCSs to SARS-CoV-2 leads to a full replication cycle with infectious virus release. Moreover, the susceptibility of placental tissue to SARS-CoV-2 replication relates to the expression levels of ACE2. Viral proteins and/or viral RNA are detected in syncytiotrophoblasts, cytotrophoblasts, villous stroma, and possibly Hofbauer cells. While SARS-CoV-2 infection of placenta PCSs does not cause a detectable cytotoxicity or a pro-inflammatory cytokine response, an upregulation of one order of magnitude of interferon type III transcripts is measured. In conclusion, our data demonstrate the capacity of SARS-CoV-2 to infect and propagate in human placenta and constitute a basis for further investigation of SARS-CoV-2 biology at the maternal-fetal interface.

The placental immune response is dysregulated developmentally vitamin D deficient rats: Relevance to autism

Emerging evidence suggests that maternal or developmental vitamin D (DVD) deficiency is a risk factor for Autism Spectrum Disorders. A well-established association has also been found between gestational infection and increased incidence of autism. Placenta mediates the maternal immune response in respect to the foetus. The placenta is also a major source of vitamin D and locally produced vitamin D is an essential regulator of immune function during pregnancy. Here we investigate the effects of DVD-deficiency on baseline placental immune status and in response to the well-known viral and bacterial immune activating agents polyriboinosinic-polyribocytidylic acid (poly(I:C) and lipopolysaccharide (LPS). We show DVD-deficiency does not affect baseline inflammatory cytokines in placenta. However, when challenged with poly(I:C) but not LPS, DVD-deficient placentas from male foetuses had higher production of IL-6 and 1L-1β compared to control placentas. This suggests the developing DVD-deficient male foetus may be particularly vulnerable to maternal viral exposures. This in turn may have adverse implications for the developing male brain. In conclusion, a dysregulated placental immune response may provide a plausible mechanism for both the epidemiological links between DVD-deficiency and increased male incidence of developmental conditions such as autism.

Establishment of an in vitro model of the human placental barrier by placenta slice culture and ussing chamber

Our purpose was to establish an in vitro model of the human placental barrier based on placenta slice culture and Ussing chamber. The villous morphology, beta-human chorionic gonadotropin (β-hCG), mRNA and efflux function of P-glycoprotein (P-gp), and the permeability of the fluorescent marker were confirmed. The results showed that syncytiotrophoblast cells with abundant endoplasmic reticulum and mitochondria were covered with a dense microvillus in the placenta slice. The β-hCG secretion levels in the Ussing chamber were 274.13 ± 13.52 mIU/mL at 5 h, significantly higher than that in the incubator 95.2 ± 13.14 mIU/mL, and β-hCG continued to secrete for 48 h. P-gp mRNA was expressed in the placenta slice. The Rho123 apparent permeability coefficient (Papp) value from maternal side to the fetal side was 26.34 ± 1.87 nm/s, but it was significantly increased, to 289.55 ± 6.02 nm/s after adding verapamil. The Rho123 efflux value was >2. The fluorescein Papp value was (3.42 ± 0.24) × 10(-3) nm/s. In contrast, the fluorescein isothiocyanate-dextran (FD70) Papp value was (3.93 ± 0.08) × 10(-5) nm/s. This indicates that the placenta slice in the Ussing chamber had the activity of a placenta, and can act as a valuable in vitro model of placental barrier.

Ex vivo perfusion of mid-to-late-gestation mouse placenta for maternal-fetal interaction studies during pregnancy

Ex vivo perfusion systems offer a reliable, reproducible method for studying acute physiological responses of an organ to various environmental manipulations. Unlike in vitro culture systems, the cellular organization, compartmentalization and three-dimensional structure of ex vivo-perfused organs are maintained. These particular parameters are crucial for the normal physiological function of the placenta, which supports fetal growth through transplacental exchange, nutritional synthesis and metabolism, growth factor promotion and regulation of both maternally and fetally derived molecules. The perfusion system described here, which can be completed in 4-5 h, allows for integrated, physiological studies of de novo synthesis and metabolism and transport of materials across the live mouse placenta, not only throughout a normal gestation period but also following a variety of individual or combined genetic and environmental perturbations compromising placental function.

Pharmacotherapy in pregnancy; effect of ABC and SLC transporters on drug transport across the placenta and fetal drug exposure

Pharmacotherapy during pregnancy is often inevitable for medical treatment of the mother, the fetus or both. The knowledge of drug transport across placenta is, therefore, an important topic to bear in mind when deciding treatment in pregnant women. Several drug transporters of the ABC and SLC families have been discovered in the placenta, such as P-glycoprotein, breast cancer resistance protein, or organic anion/cation transporters. It is thus evident that the passage of drugs across the placenta can no longer be predicted simply on the basis of their physical-chemical properties. Functional expression of placental drug transporters in the trophoblast and the possibility of drug-drug interactions must be considered to optimize pharmacotherapy during pregnancy. In this review we summarize current knowledge on the expression and function of ABC and SLC transporters in the trophoblast. Furthermore, we put this data into context with medical conditions that require maternal and/or fetal treatment during pregnancy, such as gestational diabetes, HIV infection, fetal arrhythmias and epilepsy. Proper understanding of the role of placental transporters should be of great interest not only to clinicians but also to pharmaceutical industry for future drug design and development to control the degree of fetal exposure.

Rat placentation: an experimental model for investigating the hemochorial maternal-fetal interface

The rat possesses hemochorial placentation with deep intrauterine trophoblast cell invasion and trophoblast-directed uterine spiral artery remodeling; features shared with human placentation. Recognition of these similarities spurred the establishment of in vitro and in vivo research methods using the rat as an animal model to address mechanistic questions regarding development of the hemochorial placenta. The purpose of this review is to provide the requisite background to help move the rat to the forefront in placentation research.