Neuroblasts in the subventricular zone proliferate markedly after
stroke, and migrate to the site of injury along with blood vessels. However, a large fraction of
stroke-generated neuroblasts die shortly after being born, because of local
inflammation.
E-selectin is specifically expressed on endothelial cells, but only when the endothelium activates. Since endothelial activation occurs after
stroke,
E-selectin can serve as an immunologic tolerization
antigen that can focus
immunomodulation to regions of the vascular tree. Intranasal instillation of recombinant
E-selectin will induce mucosal tolerance to that
antigen with the generation of
E-selectin-specific regulatory T cells (Tregs). Tregs may protect newly-generated neuroblasts from ischemic damage through 'bystander suppression' in which immunomodulatory
cytokines such as TGF-β and
IL-10 are released locally. In this series of experiments, we have shown that after
E-selectin tolerization in permanent
middle cerebral artery occlusion (pMCAO) rats Tregs transmigrate to the peri-
infarct region of ischemic brain, TNF expression in the local neurovascular niche is reduced, and the survival of newly generated neuroblasts or neurons in the peri-
infarct region is increased. Under these conditions, an improvement in sensorimotor function after pMCAO also occurs.
E-selectin-specific Tregs can modulate the efficacy of adult neurogenesis after
ischemia and promote repair after
brain injury.