NOTCH Activation at the Hematovascular Mesoderm Stage Facilitates Efficient Generation of T Cells with High Proliferation Potential from Human Pluripotent Stem Cells.

Human pluripotent stem cells (hPSCs) offer the potential to serve as a versatile and scalable source of T cells for immunotherapies, which could be coupled with genetic engineering technologies to meet specific clinical needs. To improve T cell production from hPSCs, it is essential to identify cell subsets that are highly enriched in T cell progenitors and those stages of development at which NOTCH activation induces the most potent T cells. In this study, we evaluated the efficacy of T cell production from cell populations isolated at different stages of hematopoietic differentiation, including mesoderm, hemogenic endothelium (HE), and multipotent hematopoietic progenitors. We demonstrate that KDRhiCD31- hematovascular mesodermal progenitors (HVMPs) with definitive hematopoietic potential produce the highest numbers of T cells when cultured on OP9-DLL4 as compared with downstream progenitors, including HE and multipotent hematopoietic progenitors. In addition, we found that T cells generated from HVMPs have the capacity to expand for 6-7 wk in vitro, in comparison with T cells generated from HE and hematopoietic progenitors, which could only be expanded for 4-5 wk. Demonstrating the critical need of NOTCH activation at the HVMP stage of hematopoietic development to establish robust T cell production from hPSCs may aid in establishing protocols for the efficient off-the-shelf production and expansion of T cells for treating hematologic malignancies.