Neuroinflammation is critical in the neural cell death seen in
stroke. It has been shown that CNS and peripheral responses drive this neuroinflammatory response in the brain. The
Toll-like receptors (TLRs) are important regulators of
inflammation in response to both exogenous and endogenous stressors. Taking advantage of a downstream adapter molecule that controls the majority of TLR signalling, this study investigated the role of the TLR adaptor
protein myeloid differentiation factor 88 (MyD88) in the control of CNS and peripheral
inflammation. Reversible
middle-cerebral artery occlusion was used as the model of
stroke in vivo; in vitro primary cultured neurons and glia were subject to four hours of
oxygen and
glucose deprivation (OGD). Both in vitro and in vivo Myd88(-/-) animals or cells were compared with wild type (WT). We found that after
stroke Myd88(-/-) animals have a larger
infarct volume compared to WT animals. Interestingly, in vitro there was no difference between the survival of Myd88(-/-) and WT cells following OGD, suggesting that peripheral responses were influencing
stroke outcome. We therefore generated bone marrow chimeras and found that Myd88(-/-) animals have a smaller
stroke infarct than their radiation naive counterparts if their hematopoietic cells are WT. Furthermore, WT animals have a larger
stroke than their radiation naive counterparts if the hematopoietic cells are Myd88(-/-) . We have demonstrated that MyD88-dependent signalling in the hematopoietic cell lineage reduces
infarct size following
stroke and that infiltrating cells to the site of
neuroinflammation are neuroprotective following
stroke.