The immunology of the macaque placenta: A detailed analysis and critical comparison with the human placenta

Congenital Zika virus infection in laboratory animals: a comparative review highlights translational studies on the maternal-foetal interface

The 2015-16 Zika virus (ZIKV) epidemic has posed unprecedented concern for maternal-infant health, mainly due to the substantial risk of microcephaly and other neurological birth abnormalities associated with congenital ZIKV syndrome (CZS). As licenced vaccines and effective antivirals are still unavailable, attention has been focused on post-delivery in vitro or translational in vivo studies to understand the impact of maternal ZIKV infection on placentation and neurodevelopmental consequences for the foetus. Here, we review clinical and translational studies highlighting ZIKV-induced maternal-foetal interface dysfunction, adding to our previous observations of experimental ZIKV vertical transmission to pregnant rhesus monkeys and newly published post-epidemic findings about the theme. This comparative review focuses on the mechanisms by which the virus has a cytopathic effect on trophoblasts and macrophages during placentation in humans, nonhuman primates, and rodent transgenic models, crosses the placental barrier, replicates, and establishes a persistent uteroplacental infection. When considering the mechanism of ZIKV-induced birth defects in humans and other susceptible hosts, it becomes apparent how the various stages of the ZIKV cycle in the host (both the parent and offspring) unfold. This understanding presents specific opportunities for pharmacological intervention and the development of preventative vaccines.

In vitro culture of cynomolgus monkey embryos from blastocyst to early organogenesis

Human early embryonic development is the cornerstone of a healthy baby. Abnormal early embryonic development may lead to developmental and pregnancy-related disorders. Accordingly, understanding the developmental events and mechanisms of human early embryonic development is very important. However, attempts to reveal these events and mechanisms are greatly hindered by the extreme inaccessibility of in vivo early human embryos. Fortunately, the emergence of in vitro culture (IVC) systems for mammalian embryos provides an alternative strategy. In recent years, different two-dimensional and three-dimensional IVC systems have been developed for human embryos. Ethical limitations restrict the IVC of human embryos beyond 14 days, which makes non-human primate embryos an ideal model for studying primate developmental events. Different culture systems have supported the development of monkey embryos to days postfertilization 14 and 25, respectively. The successful recapitulation of in vivo developmental events by these IVC embryos has greatly enriched our understanding of human early embryonic development, which undoubtedly helps us to develop possible strategies to predict or treat various gestation-related diseases and birth defects. In this protocol, we establish different two-dimensional and three-dimensional IVC systems for primate embryos, provide step-by-step culture procedures and notes, and summarize the advantages and limitations of different culture systems. Replicating this protocol requires a moderate level of experience in mammalian embryo IVC, and the embryo culture requires strict adherence to the procedures we have described.

Evaluating the Impact of Heat Stress on Placental Function: A Systematic Review

Ambient heat stress poses a significant threat to public health, with rising temperatures exacerbating the risks associated with pregnancy. This systematic review examined the associations between heat stress exposure and placental function, synthesizing methodologies from the existing literature to inform future research approaches. Analyzing 24 articles, it explores various study designs, temperature exposure parameters, pregnancy windows, and placental outcome variables. Findings across human and animal studies reveal diverse effects on placental weight, efficiency, blood flow, anatomy, gene expression, and steroid levels under heat stress conditions. While animal studies primarily utilize randomized controlled trials, human research relies on observational methodologies due to ethical constraints. Both demonstrate alterations in placental morphology and function, underscoring the importance of understanding these changes for maternal and fetal health. The review underscores the urgent need for further research, particularly in human populations, to elucidate mechanisms and develop interventions mitigating heat stress's adverse effects on placental health. Ultimately, this synthesis contributes to understanding the complex interplay between environmental factors and pregnancy outcomes, informing strategies for maternal and fetal well-being amidst climate change challenges.

A multi-tissue metabolome atlas of primate pregnancy

Pregnancy induces dramatic metabolic changes in females; yet, the intricacies of this metabolic reprogramming remain poorly understood, especially in primates. Using cynomolgus monkeys, we constructed a comprehensive multi-tissue metabolome atlas, analyzing 273 samples from 23 maternal tissues during pregnancy. We discovered a decline in metabolic coupling between tissues as pregnancy progressed. Core metabolic pathways that were rewired during primate pregnancy included steroidogenesis, fatty acid metabolism, and arachidonic acid metabolism. Our atlas revealed 91 pregnancy-adaptive metabolites changing consistently across 23 tissues, whose roles we verified in human cell models and patient samples. Corticosterone and palmitoyl-carnitine regulated placental maturation and maternal tissue progenitors, respectively, with implications for maternal preeclampsia, diabetes, cardiac hypertrophy, and muscle and liver regeneration. Moreover, we found that corticosterone deficiency induced preeclampsia-like inflammation, indicating the atlas's potential clinical value. Overall, our multi-tissue metabolome atlas serves as a framework for elucidating the role of metabolic regulation in female health during pregnancy.

Identifying a dynamic transcriptomic landscape of the cynomolgus macaque placenta during pregnancy at single-cell resolution

Supporting healthy pregnancy outcomes requires a comprehensive understanding of the cellular hierarchy and underlying molecular mechanisms in the primate placenta during gestation. Here, we present a single-cell transcriptome-wide view of the cynomolgus macaque placenta throughout gestation. Bioinformatics analyses and multiple validation experiments suggested that placental trophoblast cells exhibited stage-specific differences across gestation. Interactions between trophoblast cells and decidual cells also showed gestational stage-dependent differences. The trajectories of the villous core cells indicated that placental mesenchymal cells were derived from extraembryonic mesoderm (ExE.Meso) 1, whereas placental Hofbauer cells, erythrocytes, and endothelial cells were derived from ExE.Meso2. Comparative analyses of human and macaque placentas uncovered conserved features of placentation across species, and the discrepancies of extravillous trophoblast cells (EVTs) between human and macaque correlated to their differences in invasion patterns and maternal-fetal interactions. Our study provides a groundwork for elucidating the cellular basis of primate placentation.

Lessons from Acquired Natural Immunity and Clinical Trials to Inform Next-Generation Human Cytomegalovirus Vaccine Development

Human cytomegalovirus (HCMV) infection, the most common cause of congenital disease globally, affecting an estimated 1 million newborns annually, can result in lifelong sequelae in infants, such as sensorineural hearing loss and brain damage. HCMV infection also leads to a significant disease burden in immunocompromised individuals. Hence, an effective HCMV vaccine is urgently needed to prevent infection and HCMV-associated diseases. Unfortunately, despite more than five decades of vaccine development, no successful HCMV vaccine is available. This review summarizes what we have learned from acquired natural immunity, including innate and adaptive immunity; the successes and failures of HCMV vaccine human clinical trials; the progress in related animal models; and the analysis of protective immune responses during natural infection and vaccination settings. Finally, we propose novel vaccine strategies that will harness the knowledge of protective immunity and employ new technology and vaccine concepts to inform next-generation HCMV vaccine development.

Evolutionary Changes in Pathways and Networks of Genes Expressed in the Brains of Humans and Macaques

As the key organ that separates humans from nonhuman primates, the brain has continuously evolved to adapt to environmental and climatic changes. Although humans share most genetic, molecular, and cellular features with other primates such as macaques, there are significant differences in the structure and function of the brain between humans and these species. Thus, exploring the differences between the brains of human and nonhuman primates in the context of evolution will provide insights into the development, functionality, and diseases of the human central nervous system (CNS). Since the genes involved in many aspects of the human brain are under common pressures of natural selection, their evolutionary features can be analyzed collectively at the pathway level. In this study, the molecular mechanisms underlying human brain capabilities were explored by comparing the evolution features of pathways enriched in genes expressed in the human brain and the macaque brain. We identified 31 pathways with differential evolutionary properties, including those related to neurological diseases, signal transduction, immunological response, and metabolic processes. By analyzing genes differentially expressed in brain regions or development stages between humans and macaques,  9 and 4 pathways with differential evolutionary properties were detected, respectively. We further performed crosstalk analysis on the pathways to obtain an intuitive correlation between the pathways, which is helpful in understanding the mechanisms of interaction between pathways. Our results provide on a comprehensive view of the evolutionary pathways of the human CNS and can serve as a reference for the study of human brain development.

Research on nanoparticles in human perfused placenta: State of the art and perspectives

Increasing human exposure to nanoparticles (NPs) from various sources raises concerns for public health, especially for vulnerable risk groups like pregnant women and their developing fetuses. However, nanomedicine and the prospect of creating safe and effective NP-based formulations of drugs hold great promise to revolutionize treatment during pregnancy. With maternal and fetal health at stake, risks and opportunities of NPs in pregnancy need to be carefully investigated. Importantly, a comprehensive understanding of NP transport and effects at the placenta is urgently needed considering the central position of the placenta at the maternal-fetal interface and its many essential functions to enable successful pregnancy. The perfusion of human placental tissue provides a great opportunity to achieve predictive human relevant insights, circumventing uncertainties due to considerable differences in placental structure and function across species. Here, we have reviewed the current literature on the ex vivo human placenta perfusion of NPs. From 16 available studies, it was evident that placental uptake and transfer of NPs are highly dependent on their characteristics like size and surface modifications, which is in line with previous observations from in vitro and animal transport studies. These studies further revealed that special considerations apply for the perfusion of NPs and we identified relevant controls that should be implemented in future perfusion studies. While current studies mostly focused on placental transfer of NPs to conclude on potential fetal exposure, the ex vivo placental perfusion model has considerable potential to reveal novel insights on NP effects on placental tissue functionality and signaling that could indirectly affect maternal-fetal health.

PPAR signaling pathway in the first trimester placenta from in vitro fertilization and embryo transfer

Placenta is a temporary critical organ related to fetal development and pregnancy outcomes. And epidemiologic data demonstrate an increased risk of placental abnormality after in vitro fertilization and embryo transfer (IVF-ET). This study aims to explore the molecular mechanism for PPAR signaling pathway in placenta subjected to IVF-ET in the first trimester. Four first trimester placenta samples from double chorionic twins to single reduction in IVF-ET only because of oviducts factors. The other four control placenta samples from double chorionic twin were derived from those unplanned spontaneously conceived pregnancy after the legal termination. Affymetrix HG-U133 Plus 2.0 Array was performed to evaluate the global gene expressions. We confirmed microarray results from 10 significant differential genes using RT-qPCR. And 10 deregulated gene products were stained in the first trimester placenta by immunohistochemistry. These differentially expressed genes in IVF-ET placentas were submitted to functional annotation of clustering tools of bioinformatics resources and gene ontology enrichment analysis. Schematic representation of placental PPAR signaling pathway was labelled by Kyoto Encyclopedia of Genes and Genomes (KEGG). Analysis results of early placental PPAR signaling pathway gene expression from 8 women demonstrated 34 genes with a significant change in expression between IVF-ET and control group, 25 up-regulated; 9 down-regulated. KEGG pathway analysis indicated that IVF-ET manipulation extensively over-activated PPAR signaling pathway. Immune tolerance, trophoblast invasion, syncytia formation, lipid and glucose metabolism, inflammatory response and other complex biological functions were disturbed. RT-qPCR results and proteins staining intensity were consisted with microarray. Placental gene expressions and functions in PPAR signaling pathway were affected by IVF-ET treatment in the first trimester, which may offer a potential mechanism for the pathogenesis of various adverse outcomes during the perinatal period.