Fig. 1.

BMP6 facilitates human trophoblast invasion and vascular mimicry and increases the expression of ID1, which is associated with PE. A, BMP6 is expressed at the maternal-fetal interface. Immunohistochemistry localization of BMP6 in first-trimester villi, first-trimester decidua, and third-trimester placenta. Scale bar, 100 μm. B-C, BMP6 facilitates human trophoblast invasion and vascular mimicry. B, HTR8/SVneo cells were treated with or without BMP6, followed by analysis of cell invasion. Scale bar, 100 μm. C, HTR8/SVneo cells were treated with or without BMP6, followed by analysis of endothelial-like tube formation. Scale bar, 100 μm. D-I, Bulk RNA-Seq analysis reveals that BMP6 treatment significantly upregulates ID1, ID2, and ID3 in HTR8/SVneo cells. D-F, Heatmap (D), volcano plots (E), and waterfall plots (F) obtained from RNA-Seq analysis of HTR8/SVneo cells with or without BMP6 treatment for 6 h. G-I, Heatmap (G), volcano plots (H), and waterfall plots (I) obtained from RNA-Seq analysis of HTR8/SVneo cells treated with or without BMP6 for 24 h. J, Purity of the primary human EVTs. Primary human EVTs were stained by CK7 (left panel) and HLA-G (right panel). Scale bar, 50 μm. K-P, single-cell analysis of the placenta shows ID1 is predominantly expressed in invasive EVTs. K and M, Analysis of previously published single-cell transcriptomes of human placentas collected during early pregnancy (6–12 gestational weeks, n = 5). L, N-P, Analysis of previously published single-cell transcriptomes of placentas collected during late pregnancy: three control placentas at 38 gestational weeks and three preeclamptic placentas at 34‒35 gestational weeks. K and L, UMAP visualization of all captured cell types in the placenta during early pregnancy (K) and late pregnancy (L), respectively. M and N, UMAP plot displaying the ID1 expression levels in all cell types in the early placenta (M) and the late placenta (N), respectively. O, UMAP visualization of all captured cell types in control women and PE patients. P, Violin plot displaying the expression level of ID1 in the EVT cell type. The quantitative results are expressed as the means ± SEMs of at least three independent experiments. One-way ANOVA was used for analyses in B and C, and Student’s t-test was used for comparisons between two groups in P. Groups without common letters are significantly different from each other (P < 0.05)BMP6, bone morphogenetic protein 6; GE, glandular epithelium; SC, stromal cell; CK7, cytokeratin-7; HLA-G, human leukocyte antigen G; UMAP, uniform manifold approximation and projection; EVT, extravillous cytotrophoblast; SCT, syncytiotrophoblast; VCT, villous cytotrophoblast; ID1, inhibitor of DNA-binding 1; PE, preeclampsia