Figure 2.

High-temperature requirement A4 (HTRA4) expression in primary human placental cells and tissues. A: Tumor protein p63 (TP63) and HTRA4 show an inverse gene expression pattern by RNA-sequencing (RNA-seq) analysis in primary cytotrophoblasts [CTBs; identified by high epidermal growth factor receptor (EGFR) and integrin alpha-6 (ITGA6) expression] compared with extravillous trophoblasts [EVTs; identified by high human leukocyte antigen G (HLAG) and matrix metalloproteinase 9 (MMP9) expression], isolated from first-trimester placenta. B: Similarly, re-analysis of RNA-seq data from Okae et al¹⁷ shows TP63 to be highly expressed in CTB, whereas HTRA4 is more highly expressed in differentiated trophoblast [EVT and syncytiotrophoblast (STB)] of the first-trimester placenta. Unpaired t-test and one-way analysis of variance was applied for cell expression comparison tests, and P values are shown. C:In situ hybridization of primary human placental tissues across gestation at indicated weeks (w) of gestation, using HTRA4-specific probes. HTRA4 expression is enriched in both STB of floating villi (V) and cell column EVT (CC) in first trimester, but remained only in EVT (basal plate) at later gestational ages (20 weeks and beyond). All panels show tissue at a total magnification of ×100, except for the top right panel, which is a magnified version of the red boxed area in the top left panel (magnified ×400); within the top right panel, arrows show HTRA4 expression in villous STB and arrowheads highlight absence of HTRA4 in villous CTB. ∗P < 0.05, ∗∗∗P < 0.001, and ∗∗∗∗P < 0.0001.