Periodic formation of epithelial somites from human pluripotent stem cells

Abstract

During embryonic development, epithelial cell blocks called somites are periodically formed according to the segmentation clock, becoming the foundation for the segmental pattern of the vertebral column. The process of somitogenesis has recently been recapitulated with murine and human pluripotent stem cells. However, an in vitro model for human somitogenesis coupled with the segmentation clock and epithelialization is still missing. Here, we report the generation of human somitoids, organoids that periodically form pairs of epithelial somite-like structures. Somitoids display clear oscillations of the segmentation clock that coincide with the segmentation of the presomitic mesoderm. The resulting somites show anterior-posterior and apical-basal polarities. Matrigel is essential for epithelialization but dispensable for the differentiation into somite cells. The size of somites is rather constant, irrespective of the initial cell number. The amount of WNT signaling instructs the proportion of mesodermal lineages in somitoids. Somitoids provide a novel platform to study human somitogenesis.

Primate gastrulation and early organogenesis at single-cell resolution

“…Next, we used the monkey reference to evaluate several human stem cell embryo models. By performing integrated analyses, we found that the main cell types from several gastruloids 42,43 , heart-forming organoids (HFOs) 44,45 , neuruloids (for example, the MiSTR patterned neural tube that mimics the A-P axis 46 and the two-dimensional micropatterned, light-induced or chip-based neural tube that mimics the D-V axis [47][48][49] ) and somitoids 50 generally overlapped with the CS8-11 monkey embryos reference (Extended Data Figs. 8g,h, 9 and 10 and Supplementary Tables 12 and 13), although notable differences were observed.…”

“…To do integration analysis for monkey and human single-cell data, the human CS7 embryo 2 and various embryoid datasets including gastruloids 42,43 , HFOs 45 , neuruloids [46][47][48][49] and somitoids 50 were prepared (Extended Data Figs. 8a-d,g, 9a,b and 10a,d,g).…”

“… a , b , UMAPs showing the comparison of monkey Para.Meso-related cells and human somitoid cells 50 . c – g , Heatmaps showing the expression of key genes of the Hippo, Notch, TGF-β, WNT, and FGF signalling pathways enriched in monkey Para.Meso-related cells and human somitoid cells.…”

Morphogenesis and development of human telencephalic organoids in the absence and presence of exogenous ECM

“…The impact of endogenous and exogenous ECM sources on epithelial morphogenesis has been addressed in other in vitro systems. An example are experimental paradigms that show the formation of somites, for which either a low concentration of Matrigel in the culture medium ( Sanaki-Matsumiya et al ., 2022; van den Brink et al ., 2020; Veenvliet et al ., 2020) or differentiation of ECM-producing cells within the tissue are required ( Amadei et al ., 2022; Bao et al ., 2022; Lau et al ., 2022). Similarly, breast luminal epithelial cells can be polarized in vitro by exogenous addition of laminin-1, or co-culture with ECM-producing myoepithelial cells ( Gudjonsson et al ., 2002).…”

Single-cell technologies: a new lens into epigenetic regulation in development

“…Given their accessibility and scalability, in vitro models of embryogenesis offer the potential for high-throughput readouts of broad chemical screens, offering an exciting toolkit to accelerate our understanding of epigenetic regulator function in the establishment of cell identities. Finally, the recent implementation of human in vitro models of embryogenesis faithfully recapitulating critical stages of pre- [80,81] and postimplantation [82][83][84] development may help overcome ethical limitations associated with human embryo research and offer a unique path to understand how conserved epigenetic principles are across mammals as well as to more directly address aspects of these findings as they relate to reproductive and fetal health.…”