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Background and Purpose-Grafts of MHP36 cells have previously been shown to reduce dysfunction after global ischemia in rats. To test their efficacy after focal ischemia, MHP36 cells were grafted 2 to 3 weeks after transient intraluminal middle cerebral artery occlusion (tMCAO) in rats. Methods-MHP36 cells were implanted into the hemisphere contralateral to the lesion, with 8 deposits of 3 L of cell suspension (25 000 cells per microliter). Sham grafted rats received equivalent volumes of vehicle. Three groups, sham-operated controls (nϭ11), MCAOϩsham grafts (nϭ10), and MCAOϩMHP36 grafts (nϭ11), were compared in 3 behavioral tests. Results-In the bilateral asymmetry test, MCAOϩMHP36 grafted rats exhibited neglect before grafting but subsequently showed no significant dysfunction, whereas MCAOϩsham grafted rats showed stable sensorimotor deficits over 18 weeks relative to controls. MCAOϩsham grafted rats demonstrated spontaneous motor asymmetry and increased rotational bias after injection of dopamine agonists. MCAOϩMHP36 and control groups exhibited no bias in either spontaneous or drug-induced rotation. In contrast to motor recovery, MCAOϩMHP36 grafted rats showed no improvement relative to MCAOϩsham grafted rats in spatial learning and memory in the water maze. MCAO produced large striatal and cortical cavitations in both occluded groups. Lesion volume was significantly reduced (PϽ0.05) in the MCAOϩMHP36 grafted group. The majority of MHP36 cells were identified within the intact grafted hemisphere. However, MHP36 cells were also seen in the cortex, striatum, and corpus callosum of the lesioned hemisphere. Conclusions-MHP36 cells may improve functional outcome after MCAO by assisting spontaneous reorganization in both the damaged and intact hemispheres.

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