Jun Kido and Tomoaki Matsumoto
Objective: Neonatal hypoxic-ischemic encephalopathy causes death and severe neurological sequelae including cerebral palsy, epilepsy, and mental retardation. Because hypothermia therapy is the only effective treatment for neonatal hypoxic-ischemic encephalopathy and its efficacy is limited in severe cases, a more effective treatment is needed. Neural stem and progenitor cells are important for neuroprotection and neuronal replacement following hypoxic-ischemic encephalopathy. The aim of this study was to confirm the presence of neural stem cells and the acceleration of their mitotic activity in injured areas in a model of neonatal hypoxic-ischemic encephalopathy.
Method: Hypoxic-ischemic encephalopathy was induced in rat pups by left common carotid artery occlusion followed by hypoxia. Following ischemic injury, brains were sectioned, and columns of tissue were excised from infarct areas for cell culture using the neurosphere assay. Cell clusters were analyzed by immunocytochemistry and reverse transcription polymerase chain reaction. Clustered cells were also tested for their ability to differentiate into neurons, astrocytes, and oligodendrocytes.
Results: Neurosphere-like cell clusters from infarct areas of ischemia-injured animals were dramatically increased compared to samples from sham-operated control animals. Clusters included cells immunopositive for bromodeoxyuridine, nestin, neural/glial antigen 2, β-III tubulin, glial fibrillary acidic protein, oligodendrocyte marker O4, vimentin, and ionizing calcium-binding adaptor molecule 1. Cell clusters also expressed mRNA for NANOG, (sex determining region Y)-box 2, octamer-binding transcription factor 3/4, and Rex1, similar to embryonic stem cells, and could be differentiated into neurons, astrocytes or oligodendrocytes that expressed mRNAs for nestin, β-III tubulin, glial fibrillary acidic protein, and myelin basic protein.
Conclusion: We demonstrate the presence of many neural stem and progenitor cells with enhanced proliferative potential in infarct brain areas of a rat model of neonatal hypoxic-ischemic encephalopathy. Activation of neural stem and progenitor cells in the infarct brain area may contribute to neuroprotection and regeneration.