Unravelling the Role of Trophoblastic-Derived Extracellular Vesicles in Regulatory T Cell Differentiation

Regulatory T cells (T(reg)) are mandatory elements in the maintenance of human pregnancy, but their de novo differentiation has not been completely exposed. HSPE1 chaperone expressing trophoblast cells may have a role in it. Trophoblast-derived extracellular vesicles (EVs), either at the feto–maternal interface or in circulation, target CD4(+) T cells. We hypothesized that HSPE1-associated trophoblastic cell line (BeWo)-derived EVs are active mediators of T(reg) cell differentiation. We proved at first that recombinant HSPE1 promote human T(reg) cell differentiation in vitro. Developing a CRISPR-Cas9 based HSPE1 knockout BeWo cell line we could also demonstrate, that EV-associated HSPE1 induces T(reg) development. Next-generation sequencing of miRNA cargo of BeWo-EVs characterized the regulatory processes of T(reg) polarization. By the use of single-cell transcriptomics analysis, seven T(reg) cell subtypes were distinguished and we demonstrated for the first time that the expression level of HSPE1 was T(reg) subtype dependent, and CAPG expression is characteristic to memory phenotype of T cells. Our data indicate that HSPE1 and CAPG may be used as markers for identification of T(reg) subtypes. Our results suggest, that trophoblastic-derived iEVs-associated HSPE1 and miRNA cargo have an important role in T(reg) cell expansion in vitro and HSPE1 is a useful marker of T(reg) subtype characterization.