Functional recovery after the systemic administration of mesenchymal stem cells in a rat model of neonatal hypoxia-ischemia
OBJECTIVEChildren who have experienced neonatal hypoxic-ischemic encephalopathy often develop cerebral palsy. Although many treatments have been performed, few effective therapies are available. In this study, the authors tested in rats with hypoxia-ischemia (HI) injuries the hypothesis that the systemic infusion of mesenchymal stem cells (MSCs) would result in functional improvement by facilitating neural compensation in the contralesional cortex.METHODSPostnatal day (P) 7 (P7) rats that had undergone unilateral hemisphere hypoxia-ischemia (modified Rice-Vannucci model) were randomly assigned to MSC-infused or vehicle-infused groups. MSCs (1.0 × 106/200 μL) or vehicle were intravenously infused on P10. Brain volume was measured using in vivo MRI on P8 and P35. On P35, the rats were sacrificed after their behavior was evaluated using a beam walk test, and their brains were then prepared for histological analyses.RESULTSThe MSC-treated group had fewer slips on the beam walk test compared to those in the vehicle group (p = 0.041). MRI was used to measure the volumes of the whole brain, contralesional brain (hemisphere), and residual brain regions of interest, and the results indicated increased brain volume after the intravenous MSC infusions. The histological analyses revealed increased thicknesses of the contralesional cortex and corpus callosum in the MSC group compared with those in the vehicle group (p = 0.021, p = 0.019), which confirmed the volume increases. In the contralesional cortex, the MSC-treated group exhibited significant increases in the numbers of NeuN-positive cells (p = 0.004) and synaptic puncta (p = 0.000) compared with the numbers observed in the vehicle group.CONCLUSIONSThe intravenous infusion of MSCs resulted in improvements in functional outcome, increased brain volume, and enhanced synaptogenesis in HI rats.