Establishment And Evaluation Of Intervertebral Disc Degeneration Animal Model

?Objective?Intervertebral disc degeneration(IDD)is a complex multi-factor process,which is mainly manifested by increased breakdown of extracellular matrix and abnormal matrix synthesis,resulting in decreased hydration,loss of intervertebral disc height,and decreased absorptive capacity.Diskogenic pain secondary to intervertebral disc degeneration is an important cause of low back pain.The specific causes and mechanisms of low back pain have not yet been fully elucidated.It is particularly important to establish a reasonable animal model.In this study,an animal model of intervertebral disc degeneration was established by posterior decompression of the lumbar spine and erection of the hind limbs.The established animal models were evaluated by imaging,histopathology and immunohistochemistry to detect degenerative associated proteins.Exploring to construct a new type of animal model that is closer to the degeneration of intervertebral discs under human straight stereoposites.?Methods?Forty-eight female Wistar rats were randomly divided into 4 groups: Group A,12 non-upright sham-operated groups;Group B,12 sham-operated upright groups;Group C,12 non-upright decompression groups;Group D,decompression upright group of 12.Sham group A and B: incision of skin and fascia,separation of paraspinal muscles and exposure of lamina,and closure of wounds layer-by-layer,group B started erection at 1 week postoperatively;lumbar posterior decompression C and D groups: The skin muscles and fascia were incised layer by layer,the spinous ligament,interspinous ligament,and the zygapophyseal joints on both sides of the lumbar spine 1–3 were excised,and muscle,subcutaneous,and skin wounds were sutured layer by layer,and group D began to stand upright 1 week after surgery.Daily erection time of rats in groups B and D was 8 hours,4 hours in the morning and in the afternoon.Group A and C animals were kept normally.The following assessments were performed at 4 weeks,8 weeks,and 12 weeks after the start of erection.Decompression segmental disc specimens were used to detect pathological changes in the intervertebral discs of four groups of animals by HE,Masson,and immunohistochemistry;Animals were examined by magnetic resonance imaging(MRI)and the height and signal values of lumbar intervertebral discs in each group were observed under T2-weighted images.?Results?1.Histological results: HE and Masson staining in group A(sham-operated non-upright group)and group B(sham-operated erect group)showed a clear boundary between the nucleus pulposus area and the annulus fibrosus,and the outer annulus fibrosus arranged closely.There were a large number of normal nucleus pulposus cells in the nucleus pulposus.There was no significant difference in the histological characteristics between groups A and B.In group C(decompression and non-upright groups)HE and Masson staining showed partial arrangement of the annulus fibrosus.Disorderly and loss of normal regular structure;HE and Masson staining of group D(decompression and erection group)showed that the annulus fibrosus was fractured and destroyed,and the fibrosus of nucleus pulposus near the nucleus pulposus was obviously hyperplasia,and the nucleus pulposus tissue was compressed and decreased correspondingly.The area is reduced.2.Degeneration-associated protein expression levels: Compared with group A,the expression of matrix metalloproteinase-2(MMP-2)and matrix metalloproteinase-9(MMP-9)protein was significantly increased in groups C and D,and the expression of hypoxia-inducible factor(HIF-1?)protein was significantly reduced(P<0.05).There was no significant difference between group B and group A(P>0.05).In group 4,the expression level of D group protein was the highest;TUNEL staining results showed that: Compared with group A,the number of apoptotic cells increased significantly in group C and D,with apoptotic bodies(P<0.05).There was no significant difference between group B and group A(P>0.05).In the four groups,the number of apoptotic cells increased significantly in group D,and a large number of apoptotic bodies appeared.3.Imaging results(magnetic resonance imaging): At 4 weeks,the most obvious imaging changes were in groups C and D.The MRI T2 signal of L1/2,L2/3 intervertebral disc showed low-intensity signal changes,which was significantly lower than that of group A.A small number of posterior protrusions of the disc occurred,and some of the intervertebral discs narrowed.The signal value of the disc in the D group was significantly lower than that in the C group.The changes in the B group were not significant.At 8 weeks and 12 weeks,the group C and D was inferior to the group A disc MRI.T2 signal showed obvious degeneration,intervertebral disc became gray,T2 signal value decreased significantly,the difference was statistically significant(P<0.05),the signal value of the four groups of discs were progressively decreased with time,and the T2 signal value of group D was decreased most.Obviously,the degree of intervertebral disc degeneration was the heaviest and the difference was statistically significant(P<0.05).?Conclusions?In this study,an animal model of lumbar intervertebral disc degeneration in rats was established by posterior decompression of the lumbar spine and erection of the hindlimb.Imaging changes,histological changes and immunohistochemical changes after lumbar intervertebral disc degeneration in rats were observed.Reduced decompression and direct legislation can make lumbar intervertebral disc progressive degeneration,especially in the surgical segment lumbar nucleus pulposus signal intensity was significantly reduced,the expression of degeneration-related protein was significantly higher.The model is stable,effective,simple and feasible.The establishment of this model provides a reliable animal model for further revealing the mechanism and intervention of intervertebral disc degeneration,as well as further study of discogenic low back pain and pre-clinical treatment.