Endothelial Progenitor Cells Promote Astrogliosis following Spinal Cord Injury through Jagged1-Dependent Notch Signaling

Interactions between endothelial and neural stem cells are believed to play a critical role in the kinetics of neural stem cells in the central nervous system. Here we demonstrate that endothelial progenitor cells promote the repair of injured spinal cord through the induction of Notch-dependent astrogliosis and vascular regulation. The transplantation of Jagged1(+/+) endothelial progenitor cells, but not Jagged1(-/-) endothelial progenitor cells, increased the number of reactive astrocytes during the acute phase, and improved functional recovery following spinal cord injury. Expression of the Notch effector Hes5 was upregulated in the injured spinal cord after Jagged1(+/+) endothelial progenitor cell transplantation. Furthermore, we found that the Notch ligand Delta-like-1 was highly expressed in Jagged1(-/-) endothelial progenitor cells. Transplantation of Delta-like-1, as well as Jagged1-overexpressing 3T3 cells, revealed that only Jagged1-overexpressing 3T3 stromal cells enhanced astrogliosis following spinal cord injury. In addition, Jagged1(+/+) endothelial progenitor cells exhibited not only dramatic proangiogenic effects, but also morphologically abnormal vessel stabilization, compared with Jagged1(-/-) endothelial progenitor cells in injured spinal cord. Thus, transplanted endothelial progenitor cells promote astrogliosis, vascular regulation, and spinal cord regeneration through activation of Jagged1-Notch signaling.