Human trophoblast stem cells can be used to model placental susceptibility toToxoplasma gondiiand highlight the critical importance of the trophoblast cell surface in pathogen resistance

Abstract

ABSTRACTThe placenta is a critical barrier against viral, bacterial, and eukaryotic pathogens. For most teratogenic pathogens, the precise molecular mechanisms of placental resistance are still being unraveled. Given the importance to understand these mechanisms and challenges in replicating trophoblast-pathogeninteractions usingin vitromodels, we tested an existing stem-cell derived model of trophoblast development for its relevance to infection withToxoplasma gondii. We grew human trophoblast stem cells (TSCT) under conditions leading to either syncytiotrophoblast (TSSYN) or cytotrophoblast (TSCYT) and infected them withT. gondii. We evaluatedT. gondiiproliferation and invasion, cell ultrastructure, as well as for transcriptome changes after infection. TSSYNscells showed similar ultrastructure compared to primary cells and villous explants when analyzed by TEM and SEM, a resistance toT. gondiiadhesion could be visualized on the SEM level. Furthermore, TSSYNswere highly refractory to parasite adhesion and replication, while TSCYTwere not. RNA-seq data on mock-treated and infected cells identified differences between cell types as well as how they responded toT. gondiiinfection. We also evaluated if TSSC-derived SYNs and CYTs had distinct resistance profiles to another vertically transmitted facultative intracellular pathogen,Listeria monocytogenes. We demonstrate that TSSYNsare highly resistant toL. monocytogenes, while TSCYTsare not. LikeT. gondii, TSSYNresistance toL. monocytogeneswas at the level of bacterial adhesion. Altogether, our data indicate that stem-cell derived trophoblasts recapitulate resistance profiles of primary cells toT. gondiiand highlight the critical importance of the placental surface in cell-autonomous resistance to teratogens.