Abstract:

Objective    To observe structure changes of neurons, neuroglia and myelin at different times in the rat model of complete transected spinal injury. Methods    A total of 60 Wistar rats were randomly divided into the sham operation group (sham group) and the spinal cord injury group (SCI group), the SCI group was randomly subdivided into 1, 3, 7, 14 and 21 days subgroups according to operation time, 10 in each group. SCI groups rats were established at the T9 spinal cord segment, and  rats of the sham group had laminectomy performed. After being sacrificed at various time points, the morphological changes at different times were observed under a light microscope and a transmission electron microscope(TEM). Results    For the 1d group, the crevice of broken ends were widened. For the 3d group,  the broken ends had light oedema. For the 7d group, those structures had become a zone of necrosis. For the 14d group, the scar of broken ends had become porous.  For the 21d group, broken ends showed  atrophy and thinning. Under the light microscope, for the 1d group, the nissl body of some of neurons in the grey matter had dissolved and disappeared, and simultaneously the white matter structure became disordered. For the 3d group, some of the neurons in the grey matter showed dropsy. The boundary of  the grey matter and the white matter had disappeared.  Some reactive glial appeared. For the 7d group, those structure had completely been demolished, and some vacuoles and reactive glial appeared. For the 14d group,  the oedema of the neurons had been gradually mitigated. For the 21d group,  the neurons and glia morphous had become approximately normal. Compared with the sham group under TEM, for the 1d group,  some of the neurons became edematous, their chromosomes  were deformed  and even vacuolation occurred, and the lamellar of myelin sheath became deranged. For the 3d group,  the neurons, glia, and myelin damage were gradually increased, and the volume of glial cells were augmented,  and increased in number. For the 7d group, the neurons showed karyopyknosis, the nuclear membranes were disrupted, the nuclear pores were dilated, and the chromatin were concentrated into a massive structure. Organelles in cytoplasm had  disintegrated， the myelin was deformed with distortion, and lamellar separation,  and cumulated glial cells could be observed. For the 14d group,  impairment of neurons, glial cells and myelin had been gradually mitigated. For the 21d group, the neurons had a distinct nuclear membrane and nucleoli,  and the rough endoplasmic reticulum and ribosomes in cytoplasm were all clearer. Conclusion    The ultrastructural change of neurons, glial cells and myelin after spinal cord injury had diversity with change over time, this might provide  a reliable theoretical basis for the clinical diagnosis  and treatment of spinal cord injury. 

Key words: Spinal cord injury; Neuron; Neuroglia; Myelin sheath; Structure; Rats，Wistar