Abstract: BACKGROUND: Currently, there are various rat models of lumbar disc herniation used in experiments, each with its own advantages and disadvantages. The most common modeling methods include autologous nucleus pulposus transplantation and annulus fibrosus puncture models.
OBJECTIVE: To establish two autologous nucleus pulposus transplantation models (with spinous process and mastoid process excision and with transverse process and mastoid process excision) as well as an annulus fibrosus puncture model, and to compare and evaluate the characteristics of the three models.
METHODS: Forty male adult Sprague-Dawley rats were randomly divided into four groups (n=10 per group): sham surgery group, spinous process group, transverse process group, and annulus fibrosus puncture group. In the sham surgery group, surgical preparation was performed, the skin was incised, and the spinous process was exposed, and then sutured. In the spinous process group, L5 spinous process and transverse process were excised, and two pieces of tail nucleus pulposus were placed in the intervertebral foramen. In the transverse process group, L5 transverse process and transverse process were excised, and two pieces of tail nucleus pulposus were placed in the intervertebral foramen. In the annulus fibrosus puncture group, the transverse process was excised and annulus fibrosus puncture and intervertebral disc injection of interleukin 1β were then performed. Thermal paw withdrawal latencies were tested before and after modeling. Lumbar spine MRI was performed 2 weeks after modeling. Pathological changes in the intervertebral discs were observed using hematoxylin-eosin staining and safranin-O-fast green staining. Immunofluorescence was used to observe CD68+ positive expression.
RESULTS AND CONCLUSION: (1) Thermal withdrawal threshold testing results showed that compared with the sham surgery group, pain sensitivity and tolerance time of rats decreased significantly after modeling (P < 0.05). (2) Lumbar spine MRI images showed that the spinous process and transverse process groups had obvious protrusion of nucleus pulposus tissue, which more closely resembled MRI images of patients with common lumbar disc herniation. (3) Hematoxylin-eosin staining revealed that compared with the sham surgery group, nucleus pulposus tissues in the model groups showed varying degrees of degeneration, inflammatory cell infiltration, and degradation of spinal cord cells, with the appearance of cystic changes, among which the annulus fibrosus puncture group had the most severe pathological changes. (4) Safranin-O-fast green staining showed that compared with the sham surgery group, the boundaries of nucleus pulposus tissues in the three model groups were blurred, with extensive inflammatory reactions and varying degrees of degeneration in the annulus fibrosus. (5) CD68+ immunofluorescence staining results showed that compared with the sham surgery group, the expression of CD68+ in the model groups was higher and more widespread, with the annulus fibrosus puncture model showing the highest expression. All the three methods could be used to effectively establish rat models of lumbar disc herniation, with the annulus fibrosus puncture model established after excision of the transverse process being superior to the autologous nucleus pulposus transplantation model (spinous process+mastoid process), and the first two models being superior to the autologous nucleus pulposus transplantation model (transverse process+mastoid process).

中国组织工程研究杂志出版内容重点：组织构建；骨细胞；软骨细胞；细胞培养；成纤维细胞；血管内皮细胞；骨质疏松；组织工程

Key words: autologous nucleus pulposus transplantation, annulus fibrosus puncture, lumbar disc herniation, MRI, CD68+, animal model