Large-scale production of human blastoids amenable to modeling blastocyst development and maternal-fetal cross talk.

Recent advances in human blastoids have opened new avenues for modeling early human development and implantation. One limitation of our first protocol for human blastoid generation was relatively low efficiency. We now report an optimized protocol for the efficient generation of large quantities of high-fidelity human blastoids from naive pluripotent stem cells. This enabled proteomics analysis that identified phosphosite-specific signatures potentially involved in the derivation and/or maintenance of the signaling states in human blastoids. Additionally, we uncovered endometrial stromal effects in promoting trophoblast cell survival, proliferation, and syncytialization during co-culture with blastoids and blastocysts. Side-by-side single-cell RNA sequencing revealed similarities and differences in transcriptome profiles between pre-implantation blastoids and blastocysts, as well as post-implantation cultures, and uncovered a population resembling early migratory trophoblasts during co-culture with endometrial stromal cells. Our optimized protocol will facilitate broader use of human blastoids as an accessible, perturbable, scalable, and tractable model for human blastocysts.

Bovine blastocyst-like structures derived from stem cell cultures.

Understanding the mechanisms of blastocyst formation and implantation is critical for improving farm animal reproduction but is hampered by a limited supply of embryos. Here, we developed an efficient method to generate bovine blastocyst-like structures (termed blastoids) via assembling bovine trophoblast stem cells and expanded potential stem cells. Bovine blastoids resemble blastocysts in morphology, cell composition, single-cell transcriptomes, in vitro growth, and the ability to elicit maternal recognition of pregnancy following transfer to recipient cows. Bovine blastoids represent an accessible in vitro model for studying embryogenesis and improving reproductive efficiency in livestock species.

Ex utero monkey embryogenesis from blastocyst to early organogenesis.

The third and fourth weeks of gestation in primates are marked by several developmental milestones, including gastrulation and the formation of organ primordia. However, our understanding of this period is limited due to restricted access to in vivo embryos. To address this gap, we developed an embedded 3D culture system that allows for the extended ex utero culture of cynomolgus monkey embryos for up to 25 days post-fertilization. Morphological, histological, and single-cell RNA-sequencing analyses demonstrate that ex utero cultured monkey embryos largely recapitulated key events of in vivo development. With this platform, we were able to delineate lineage trajectories and genetic programs involved in neural induction, lateral plate mesoderm differentiation, yolk sac hematopoiesis, primitive gut, and primordial germ-cell-like cell development in monkeys. Our embedded 3D culture system provides a robust and reproducible platform for growing monkey embryos from blastocysts to early organogenesis and studying primate embryogenesis ex utero.

A spatially resolved atlas of the human lung characterizes a gland-associated immune niche.

Single-cell transcriptomics has allowed unprecedented resolution of cell types/states in the human lung, but their spatial context is less well defined. To (re)define tissue architecture of lung and airways, we profiled five proximal-to-distal locations of healthy human lungs in depth using multi-omic single cell/nuclei and spatial transcriptomics (queryable at lungcellatlas.org ). Using computational data integration and analysis, we extend beyond the suspension cell paradigm and discover macro and micro-anatomical tissue compartments including previously unannotated cell types in the epithelial, vascular, stromal and nerve bundle micro-environments. We identify and implicate peribronchial fibroblasts in lung disease. Importantly, we discover and validate a survival niche for IgA plasma cells in the airway submucosal glands (SMG). We show that gland epithelial cells recruit B cells and IgA plasma cells, and promote longevity and antibody secretion locally through expression of CCL28, APRIL and IL-6. This new 'gland-associated immune niche' has implications for respiratory health.