Notch Signaling-Mediated Neural Lineage Selection Facilitates Intrastriatal Transplantation Therapy for Ischemic Stroke by Promoting Endogenous Regeneration in the Hippocampus

Abstract

Acquisition of highly efficient neural differentiation based on understanding of initial lineage commitment of human embryonic stem (hES) cells remains a challenge. This study describes a simple three-stage protocol to induce hES cells into neural lineage cells using a 2-week coculture with murine bone marrow stromal cell (BMSC) PA6 followed by a 2-week propagation culture in PA6-conditioned medium and an additional 2-week selection culture in chemically defined neurobasal medium. This protocol generated a relatively high yield of neural lineage cells without mesodermal and endodermal lineage cell contamination. Notably, we demonstrated that PA6 coculture can significantly enhance the expression level of Notch signaling components and promote neural lineage entry of hES cell derivatives. Manipulation of Notch signaling can boost or suppress neural differentiation of hES cell derivatives, suggesting that Notch signaling may underlie the PA6-mediated neural induction. In vivo studies demonstrated that derived neural cells could improve the cognitive function of ischemic stroke rats. Intrastriatal human neural cell grafts were noted to migrate to damaged cerebral regions, enhance basic fibroblast growth factor production in the hippocampus, and restore the pyramidal neuron density and morphology in the hippocampal CA1 region, although only a small number of human donor cells were present in the hippocampus, suggesting that donor cells can boost hippocampal reconstruction by promoting the endogenous regeneration process. These findings demonstrate a pivotal role for Notch in hES cell fate determination and that manipulation of Notch signaling is therefore likely to be a key factor in taking command of hES cell lineage choice. This study suggested the potential of utilizing PA6 coculture to imitate the embryonic niche for hES cell neural induction via Notch signaling and a high application potential of BMSC-involved protocol, which can yield a whole lineage of human neural cells to promote endogenous regeneration in the hippocampus upon transplantation for potential therapy of ischemic stroke.