Effects of static traction on the nucleus pulposus and annulus fibrosus of the rat intervertebral disc

Mo Jun; Luo Zongping

doi:10.12307/2023.995

Abstract：BACKGROUND:Traction is clinically used for the early treatment of intervertebral disc degeneration,but its effect on the normal intervertebral disc remains unknown.Whether it directly causes intervertebral disc degeneration or has a positive effect is the key point of this study. OBJECTIVE:To design a static traction model and observe the effect of static traction on the nucleus pulposus and annulus fibrosus of the intervertebral disc METHODS:Twenty Sprague-Dawley rats,3 months of age,were included in the study.The intervertebral disc spaces between 7/8,8/9 and 9/10 were stretched by 1 mm,and the intervertebral disc spaces between 6/7 and 10/11 were used as control.Five rats were randomly selected at 2,4,6,and 8 weeks of traction to perform MRI T2-weighted scans of the caudal vertebra,tissue section staining,and RT-PCR gene assays for anabolic metabolism to observe the effects of static traction on the nucleus pulposus and annulus fibrosus of the intervertebral disc. RESULTS AND CONCLUSION:After short-term static traction of the rat caudal vertebra,the T2-weighted image signal in the nucleus pulposus region was enhanced.During the traction period,nucleus pulposus cells grew well,the intercellular matrix was abundant,and the annulus fibrosus arranged regularly.The RT-PCR results showed that after traction,the mRNA expression of proteoglycan increased,the expression of matrix metalloproteinase-3 decreased,the expression of type Ⅰ and Ⅱ collagen decreased,and the expression of matrix metalloproteinase-13 increased and tissue inhibitor of matrix metalloproteinase 1 increased.These gene results also indicated that traction made proteoglycan more inclined to an anabolic state,and type Ⅰ and Ⅱ collagen more inclined to a catabolic state.To conclude,static traction promotes proteoglycan anabolism making the nucleus pulposus moist.