BACKGROUND: Studies have shown that cell death can activate proliferation of endogenous neural stem cells and promote newly generated cells to migrate to a lesion site. OBJECTIVE: To observe regeneration and differentiation of neural cells following spinal cord injury in adult rats and to quantitatively analyze the newly differentiated cells. DESIGN, TIME AND SETTING: A cell biology experiment was performed at the Institute of Orthopedics and Medical Experimental Center, Lanzhou University, between August 2005 and October 2007. MATERIALS: Fifty adult, Wistar rats of both sexes; 5-bromodeoxyuridine (BrdU, Sigma, USA); antibodies against neuron-specific enolase, glial fibrillary acidic protein, and myelin basic protein (Chemicon, USA). METHODS: Twenty-five rats were assigned to the spinal cord injury group and received a spinal cord contusion injury. Materials were obtained at day 1, 3, 7, 15, and 29 after injury, with 5 rats for each time point. Twenty-five rats were sham-treated by removing the lamina of the vertebral arch without performing a contusion. MAIN OUTCOME MEASURES: The phenotype of BrdU-labeled cells, i.e., expression and distribution of surface markers for neurons (neuron-specific enolase), astrocytes (glial fibrillary acidic protein), and oligodendrocytes (myelin basic protein), were identified with immunofluorescence double-labeling. Confocal microscopy was used to detect double-labeled cells by immunofluorescence. Quantitative analysis of newly generated cells was performed with stereological counting methods. RESULTS: There was significant cell production and differentiation after adult rat spinal cord injury. The quantity of newly-generated BrdU-labeled cells in the spinal cord lesion was 75-fold greater than in the corresponding area of control animals. Endogenous neural precursor cells differentiated into astrocytes and oligodendrocytes, however spontaneous neuronal differentiation was not detected. Between 7 and 29 d after spinal cord injury, newly generated cells expressed increasingly more mature oligodendrocyte and astrocyte markers. CONCLUSION: Spinal cord injury is a direct inducer of regeneration and differentiation of neural cells. Endogenous neural precursor cells can differentiate into astrocytes and oligodendrocytes following adult rat spinal cord injury.
