Exogenous microglia enter the brain and migrate into ischaemic hippocampallesions

We compared migration of systemically injected microglia into normal brain vs. ischaemic brain using a model of ischaemic hippocampal lesion. Microgli a were labeled by a fluorescent dye using our standard phagocytosis procedu re of microscopic particles and then injected intra-arterially into Mongoli an gerbils subjected to ischaemia reperfusion neuronal injury. Delayed deat h of pyramidal neurons was confirmed by conventional histological analysis and dUTP nick end labeling (TUNEL) method. Clusters of dye-tagged cells mig rating into the hippocampal ischaemic lesions were confirmed histochemicall y to be microglia. Since peripherally injected microglia exhibit specific a ffinity for ischaemic brain lesions and does not exacerbate ischaemic neuro nal injury in the present model, we suggest that microglia may have a poten tial to be used as a piggy-back ride to deliver therapeutic genes and/or dr ugs for CNS repair following transitory global ischaemic insult. (C) 1999 E lsevier Science Ireland Ltd. All rights reserved.