Immunoregulatory Neuroprotection of Cerebral Ischaemia by Haematopoietic Stem and Precursor Cells

Abstract

Cerebral ischaemia leads to early immune system activation followed by delayed immunosuppression. Post-ischaemic inflammation contributes to neurodegeneration. Although experimental approaches using adult stem or precursor cells have repeatedly demonstrated neuroprotective effects in cerebral ischaemia, the underlying mechanism of cell-mediated neuroprotection is still debated. It was suggested that stem or precursor cells invade ischaemic brain regions and act locally. However, recent data demonstrate that systemically transplanted stem or precursor cells have strong immunoregulatory effects leading to reduced post-ischaemic brain tissue inflammation. This article argues that the systemic balance of the immune system might explain the reduced neurodegeneration observed after stem cell treatment in cerebral ischaemia. Consequently, systemic immunoregulatory neuroprotection using stem and precursor cells should be considered an important therapeutic option to prevent post-ischaemic neurodegeneration in cerebral ischaemia.