['Brain injury caused by stroke is a frequent cause of perinatal morbidity and mortality with limited therapeutic options. Mesenchymal stem cells (MSC) have been shown to improve outcome after neonatal hypoxic-ischemic brain injury mainly by secretion of growth factors stimulating repair processes. We investigated whether MSC treatment improves recovery after neonatal stroke and whether MSC overexpressing brain-derived neurotrophic factor (MSC-BDNF) further enhances recovery.', 'We performed 1.5-hour transient middle cerebral artery occlusion in 10-day-old rats. Three days after reperfusion, pups with evidence of injury by diffusion-weighted MRI were treated intranasally with MSC, MSC-BDNF, or vehicle. To determine the effect of MSC treatment, brain damage, sensorimotor function, and cerebral cell proliferation were analyzed.', 'Intranasal delivery of MSC- and MSC-BDNF significantly reduced infarct size and gray matter loss in comparison with vehicle-treated rats without any significant difference between MSC- and MSC-BDNF-treatment. Treatment with MSC-BDNF significantly reduced white matter loss with no significant difference between MSC- and MSC-BDNF-treatment. Motor deficits were also improved by MSC treatment when compared with vehicle-treated rats. MSC-BDNF-treatment resulted in an additional significant improvement of motor deficits 14 days after middle cerebral artery occlusion, but there was no significant difference between MSC or MSC-BDNF 28 days after middle cerebral artery occlusion. Furthermore, treatment with either MSC or MSC-BDNF induced long-lasting cell proliferation in the ischemic hemisphere.'] Does mesenchymal stem cell transplantation attenuate brain injury after neonatal stroke?