Abstract: BACKGROUND: Excessive keratinization of astrocytes after spinal cord injury forms a mechanical barrier to repair the spinal cord and also plays an active role in spinal cord repair and regeneration. The regulation of keratinization to a suitable extent, to make it fully exert positive effects and decrease negative effects, is really a challenge to the research of spinal cord injury.
OBJECTIVE: To observe the alteration of sensory neurons and astrocytes in the rat spinal dorsal horn, as well as the expression of interleukin-1β and glial fibrillary acidic protein in the abovementioned cells after a selective dorsal rhizotomy.
METHODS: Thirty-three adult healthy Wistar rats were randomly divided into control group (n=3) and experimental group (n=30). On the operation side of the experimental group, the dorsal roots of the left lumbar 3 and 4 spinal nerves were exposed, separated, and cut off, while on the control side of the experimental group, the dorsal roots of the right lumbar 3 and 4 spinal nerves were only exposed and separated. The control group did not undergo any treatment. The rats were sacrificed under anesthesia at 1, 2, and 4 weeks after operation, and the segmental tissues of lumbar segments 3 and 4 were taken to make paraffin sections. The morphological changes of neurons and astrocytes in the rat spinal dorsal horn were observed by hematoxylin-eosin staining. The expression of interleukin-1β and glial fibrillary acidic protein in the spinal cord dorsal horn was observed by immunohistochemical staining.
RESULTS AND CONCLUSION: (1) Hematoxylin-eosin staining: 1 and 2 weeks after selective dorsal rhizotomy, there were changes in the nuclei and cytoplasm of sensory neurons on the surgical side of the experimental group and at 4 weeks after operation, apoptosis in neurons appeared. Astrocytes were activated and the number of the cells increased accompanied by enlarged cell body and increased processes and reached a peak at 2 weeks after operation. The number of sensory nerve fibers on the surgical side of the experimental group was less than that on the control side of the experimental group and in the control group at 2 and 4 weeks after operation (P < 0.05), while the number of astrocytes was higher than that on the control side of the experimental group and in the control group at 1, 2, and 4 weeks after operation (P < 0.05). (2) Immunohistochemical staining: The positive expressions of interleukin-1β and glial fibrillary acidic protein on the surgical side of the experimental group were enhanced and peaked at 2 weeks after selective dorsal rhizotomy. The average absorbance values of glial fibrillary acidic protein and interleukin-1β positive cells on the surgical side of the experimental group were higher than those on the control side of the experimental group and in the control group (P < 0.05). (3) To conclude, selective dorsal rhizotomy can lead to a decrease in the number of sensory neurons in the dorsal horn of the spinal cord, reactive proliferation of astrocytes, and increased expression of interleukin-1β and glial fibrillary acidic protein.

Key words: selective dorsal rhizotomy, glial fibrillary acidic protein, interleukin-1β, astrocyte, sensory neurons in the spinal dorsal horn