Cell specification and functional interactions in the pig blastocyst inferred from single-cell transcriptomics and uterine fluids proteomics.

The embryonic development of the pig comprises a long in utero pre- and peri-implantation development, which dramatically differs from mice and humans. During this peri-implantation period, a complex series of paracrine signals establishes an intimate dialogue between the embryo and the uterus. To better understand the biology of the pig blastocyst during this period, we generated a large dataset of single-cell RNAseq from early and hatched blastocysts, spheroid and ovoid conceptus and proteomic datasets from corresponding uterine fluids. Our results confirm the molecular specificity and functionality of the three main cell populations. We also discovered two previously unknown subpopulations of the trophectoderm, one characterised by the expression of LRP2, which could represent progenitor cells, and the other, expressing pro-apoptotic markers, which could correspond to the Rauber's layer. Our work provides new insights into the biology of these populations, their reciprocal functional interactions, and the molecular dialogue with the maternal uterine environment.

Neonatal inflammation impairs developmentally-associated microglia and promotes a highly reactive microglial subset.

Microglia and border-associated macrophages play critical roles in both immunity and neurodevelopment. The disruption of microglial development trajectories by neonatal inflammation is an important issue in research on neurodevelopmental disorders (NDDs), as models have suggested a strong association between inflammation and cognitive deficits. Here, we explored by single-cell RNA sequencing and flow cytometry the impact of neonatal inflammation in a mouse NDD model on brain myeloid cell subsets. A specific subset of microglia expressing the complement receptor C5ar1 has been identified, in which inflammatory pathways are most strongly activated. Based on transcriptional similarity, this subset appears to originate from the most mature and "homeostatic" microglia at this stage of development and demonstrated hypersensitivity to inflammation. Besides that, Spp1-microglia supporting oligodendrocyte differentiation, primitive and proliferative microglia were reduced by inflammation. These findings suggest major changes in microglial subsets developmental trajectories and reactivity contributing to NDDs induced by neonatal inflammation.

Targeting Microglial Disturbances to Protect the Brain From Neurodevelopmental Disorders Associated With Prematurity.

Microglial activation during critical phases of brain development can result in short- and long-term consequences for neurological and psychiatric health. Several studies in humans and rodents have shown that microglial activation, leading to a transition from the homeostatic state toward a proinflammatory phenotype, has adverse effects on the developing brain and neurodevelopmental disorders. Targeting proinflammatory microglia may be an effective strategy for protecting the brain and attenuating neurodevelopmental disorders induced by inflammation. In this review we focus on the role of inflammation and the activation of immature microglia (pre-microglia) soon after birth in prematurity-associated neurodevelopmental disorders, and the specific features of pre-microglia during development. We also highlight the relevance of immunomodulatory strategies for regulating activated microglia in a rodent model of perinatal brain injury. An original neuroprotective approach involving a nanoparticle-based therapy and targeting microglia, with the aim of improving myelination and protecting the developing brain, is also addressed.