Maruyama_2017_Placenta_53_8

INTRODUCTION: Prolyl oligopeptidase (prolyl endopeptidase, Prep), a multifunctional protease hydrolyzing -Pro-X- peptide bonds, is highly expressed in the mouse placenta, but the function during development is not known. We explored the possibility of Prep's involvement in placental differentiation. METHODS: We cultured trophoblast stem cells (TSCs) derived from the E6.5 mouse embryo and investigated the detailed expression pattern of Prep during their differentiation. Prep-specific inhibitors were added to the TSC culture, and the effect on the differentiation was assessed by microscopic observation and the expression of marker gene for each placental cell. RESULTS: During TSC differentiation for 6 days, Prep was constantly detected at mRNA, protein, and activity levels, and the protein was found mainly in the cytoplasm. The addition of 30 muM and 10 muM SUAM-14746, a Prep-specific inhibitor, effectively inhibited the differentiation into spongiotrophoblasts (SpTs) and trophoblast giant cells (TGCs), while the TSC viability was not affected. 5 muM SUAM-14746 impaired the differentiation into SpTs, and 1 muM SUAM-14746 exhibited no effects. Another Prep-specific inhibitor, KYP-2047, did not affect the differentiation. We confirmed efficient inhibition of Prep enzymatic activity in TSCs by both inhibitors. CONCLUSION: The dose-dependent effect of SUAM-14746 on TSCs suggests that Prep plays an important role in the differentiation into SpTs and TGCs in the mouse placenta.