The establishment and evaluation of animal model for modic changes / 中华骨科杂志

ABSTRACT

Objective To investigate the possibility of establishing a Modic changes (MCs) animal model,and explore the pathogenesis of MCs through imaging,histology and molecular biology experiments.Methods Fifty four New Zealand rabbits (weight 2.5-3.0 kg,half male and half female) were randomly divided into 3 groupssham group (n=l8),muscle embedment group (n=18) and NP embedment group (n=18).In NP embedment group,the L4-5 and L5-6 discs were exposed by the lumbar anterolateral surgical approach.A 16 G needle was used to puncture the L5-6 vertebral body close to the epiphyseal plate.The depth of the drilling was approximately 3 mm.A 5 ml syringe was then put into the L4-5 intervertebral disc and extracted the NP,which was injected into the drilled hole of the vertebral body.The muscle embedment group and sham group shared the same operating procedures and drilling methods with the NP embedment group.Some pieces of muscle acquired from paraspinal muscles were put into the drilled hole in muscle embedment group,while nothing was put into the drilled hole in sham group.After that,the bleeding stopping,tissue washing and suture were done in all groups.12 weeks,16 weeks and 20 weeks after the surgery,MRI scan was applied to each group.All the specimens were tested by HE staining,real-time fluorescence quantitative PCR and Western blot to observe the expression of inflammatory cytokines.Results After modeling for 12 weeks,16 weeks and 20 weeks,MRI showed low signal changes on T1WI and mixed high signal in the context of low signal changes on T2WI in the NP embedment group.However,the muscle embedment and sham group showed no significant signal changes.Gross observation and HE staining confirmed that there was abnormal tissue proliferation in the imbed site of the NP embedment group.RT-PCR and Western blot showed high expression of IL-4,IL-17 and IFN-γin the NP embedment group,which were positively correlated with the length of the postoperative period.There was no significant difference between the muscle embedment group and sham group.Conclusion The puncturing of vertebral body close to endplate and putting nucleus into it can create an animal model of MCs.Autoimmune factors may play an important role in MCs.