Abstract:

BACKGROUND: Scoliosis is a three-dimensional complex deformity occurring in the spine. It has been found that molecular mechanisms such as aggrecan, type II collagen, Sox9, and vascular endothelial growth factor protein are involved in the course of scoliosis, and may play a similar adverse role to the mechanical mechanism. However, there is no experimental study on the mechanism of scoliosis.
OBJECTIVE: To construct the scoliosis model of SD rats and explore the effect of asymmetric tension on bone structure development.
METHODS: Six SD rats were selected for operation and X-ray films were taken after feeding in high cage for 3 months. Three-dimensional reconstruction of the spine was performed to analyze the asymmetric tension distribution. Bone trabecular structure was examined by scanning. After the rats were killed, the epiphyseal cartilages of concave and convex vertebral bodies were extracted. The expression of aggrecan, type II collagen, Sox9, and vascular endothelial growth factor protein was detected. 
RESULTS AND CONCLUSION: (1) All the 6 SD rats were successfully modeled, with obvious kyphosis and left thoracic deformity. (2) The stress of the vertebral body was asymmetric, and the stress in the vertical direction of the convex side was remarkably higher than that in the concave side. (3) Western blot assay results demonstrated that the expression levels of aggrecan, type II collagen, Sox9, and vascular endothelial growth factor protein on the convex side were significantly higher than those on the concave side. The corresponding convex integral optical density value was also significantly higher (P < 0.05). (4) There was significant asymmetry in the bone trabecular microstructures on both sides of convex and concave. Compared with the concave side, the volume fraction and number of trabeculae on convex side were significantly higher (P < 0.05), while the trabecular separation and structural model index were significantly lower (P < 0.05). (5) Asymmetric tension may promote the occurrence and development of scoliosis by affecting the changes of related proteins and bone trabecular structure.

Key words: scoliosis, asymmetric tension, animal models, bone trabecular, aggrecan, type II collagen, Sox9, vascular endothelial growth factor