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Background and Purpose-Intra-arterial neural stem cell (NSC) transplantation shows promise as a minimally invasive therapeutic option for stroke. We assessed the effect of timing of transplantation on cell engraftment, survival, and differentiation. Methods-Mouse NSCs transduced with a green fluorescent protein and renilla luciferase reporter gene were transplanted into animals 6 and 24 hours and 3, 7, and 14 days after hypoxia-ischemia (HI). Bioluminescent imaging was used to assess cell survival at 6 hours and 4 and 7 days after transplantation. Immunohistochemistry was used to assess NSC survival and phenotypic differentiation 1 month after transplantation. NSC receptor expression and brain gene expression were evaluated using real-time reverse transcription-quantitative polymerase chain reaction to elucidate mechanisms of cell migration. Boyden chamber assays were used to assess cell migratory potential in vitro. Results-NSC transplantation 3 days after HI resulted in significantly higher cell engraftment and survival at 7 and 30 days compared with all other groups (PϽ0.05). Early transplantation at 6 and 24 hours after HI resulted in significantly higher expression of glial fibrillary acidic protein (Pϭ0.0140), whereas late transplantation at 7 and 14 days after HI resulted in higher expression of ␤-tubulin (PϽ0.0001). Corroborating the high cell engraftment 3 days after HI was robust expression of vascular cell adhesion molecule-1, CCL2, and CXCL12 in brain homogenates 3 days after HI. Conclusion-Intra-arterial transplantation 3 days after HI results in the highest cell engraftment. Early transplantation ofNSCs leads to greater differentiation into astrocytes, whereas transplantation at later time points leads to greater differentiation into neurons. (Stroke. 2012;43:1624-1631.)Key Words: animal models Ⅲ cell transplantation Ⅲ cerebral infarct Ⅲ experimental Ⅲ stem cells I ntravascular transplantation of neural stem cells (NSCs) represents a promising therapeutic opportunity for stroke. [1][2][3][4][5][6] Several studies have demonstrated cell engraftment and functional recovery in rodent models of hypoxia-ischemia, 1,4,7 and these treatments are being evaluated for safety and efficacy in humans. 8,9 After cerebral ischemia, circulating peripheral immune cells are recruited by a chemoattractive gradient. 10 -14 Using a similar mechanism, NSCs are able to use endogenous adhesion and chemoattractant molecules to extravasate from the vascular compartment and migrate to the ischemic lesion. 1,10 -12,15-18 We have previously studied the mechanism of NSC homing to the ischemic penumbra, implicating the adhesion molecule vascular cell adhesion molecule-1 (VCAM-1) 1 and the chemokines CCL2 and CXCL12 in this process. 7 We also demonstrated increased NSC engraftment using intra-arterial delivery compared with intravenous delivery, 19 and the absence of microstrokes after NSC injection. 5 However, the optimal timing of intra-arterial NSC transplantation remains largely uncharacterized. If intravascular NSC therap...

Purpose The purpose of this study is to evaluate the 18 kDa translocator protein (TSPO) radioligand [18F]N-fluoroacetyl-N-(2,5-dimethoxybenzyl)-2-phenoxyaniline ([18F]PBR06) as a positron emission tomography (PET) imaging biomarker of stroke-induced neuroinflammation in a rodent model. Procedures Stroke was induced by transient middle cerebral artery occlusion in Balb/c mice. Dynamic PET/CT imaging with displacement and preblocking using PK111195 was performed 3 days later. PET data were correlated with immunohistochemistry (IHC) for the activated microglial markers TSPO and CD68 and with autoradiography. Results [18F]PBR06 accumulation peaked within the first 5 min postinjection, then decreased gradually, remaining significantly higher in infarct compared to noninfarct regions. Displacement or preblocking with PK11195 eliminated the difference in [18F]PBR06 uptake between infarct and noninfarct regions. Autoradiography and IHC correlated well spatially with uptake on PET. Conclusions [18F]PBR06 PET specifically images TSPO in microglial neuroinflammation in a mouse model of stroke and shows promise for imaging and monitoring microglial activation/neuroinflammation in other disease models.