Fig. 3: Systematic regulation events during labyrinth development.

a Temporal dynamics of labyrinth cell proportion (allantois, yolk sac, and Reichert’s membrane/Chorionic plate (CP) were excluded). b Ucell score variation across different stages in sets of genes that are involved in vascular-related biological processes. c Spatial expression profiles of key hormones from several signaling pathways. d Visualization of the spatial expression of Mdk, Apela, and Pdgfb. e Significant spatially restricted ligand–receptor interacting pairs were identified in the labyrinth at different stages. f Ligand–receptor gene pairs involving key growth factors that mediate cell–cell communications in the labyrinth as identified in scRNA-seq datasets. The outside ring shows cell types, and the inside ring shows the details of each interacting ligand–receptor pair. Both are color-coded. The width of the line and arrowheads inside are scaled to indicate the relative expression levels of the ligand and receptor, respectively. g IHC staining showing the location of MDK expression in the chorionic plate and SynT of the labyrinth (indicated by an arrow). h Schematic diagram showing the process of iMDK treatment. i Placental efficiency as expressed by the ratio of fetal weight to placental weight (n = 24 for control, n = 41 for iMDK). j Measurements of the labyrinth area and JZ area and the ratio of the labyrinth area to the JZ area (n = 8 control, n = 14 iMDK). k Representative image of a cross-section through the labyrinth and JZ in a mid-section of a mouse placenta. The blue solid line outlines the labyrinth and JZ that was measured in (k). l Real-time quantitative polymerase chain reaction (RT-qPCR) analysis of the expression of markers of SynT-I (Mct1) and endothelial cells (Cd31). RT-qPCR data were normalized to the reference gene Hprt. m–o The CCK-8 assay was used to evaluate the proliferation of endothelial cells treated with iMDK (m), recombinant murine MDK (n), and cell-conditioned medium collected from shRNA-MDK-treated trophoblast cells and shRNA-Neg-treated trophoblast cells (o). The data were presented as the means ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, ns not significant.