Establishment Of Discitis Animal Model And Study On Autoimmune Reaction

Objective:Establishing discitis animal model by destroying the fibrous ring and the cartilage lamina through the surgery, discussing the mechanism of autoimmune reaction in the discitis by observing its image performance and the changing process of autoimmune condition.Methods:50 healthy adult New Zealand white rabbits no matter the sexual were enrolled and divided into three groups:The surgery group (30):The rabbit discitis animal model was set up by using the anterior external surgery to destroy the fibrous ring and the cartilage lamina;Sham group (10) and control group (10).Control group were executed to get the intervertebral disc specimens after took the X-ray and the MRI instantly.The surgery group and Sham group were executed on 1 week,2 weeks,4 weeks,8 weeks,12 weeks after surgery,to get the intervertebral disc in the surgical area after took the X-ray and the MRI.The specimen were used to:(1) Conventional HE stain, morphology comparison and lymphocyte expression;(2) Masson stain,observing the inflammatory fibrosis.(3) Observing the expression of the CD4/CD8 positive lymphocyte and the IgG/IgM by using immunocytochemistry and immumofluorescence. Analysising the expression and the change process of the indexs by comparing the three groups to discuss the role autoimmune reaction plays in the discitis.(4) Bacteriological cultivation.Results:1.Imaging findings:On 2 weeks after surgery, abnormalities on X-ray imaging can not be see in the surgery group.On 4 weeks after surgery,the intervertebral space showed narrow.On 12 weeks,destruction and sclerosis of centrums ossein were observed.On 4 week,abnormal signal on intervertebral disc and different extent of destruction,fragmentation,shrinking was showed in MRI, and on T2WI there was low signal change instead of high signal of normal nucleus pulposus,destruction on cancellous bone of cartilage lamina and Under the cartilage lamina was different,which led to the the boundary between centrum and intervertebral disc became unclear.The neighboring centrum was also affected,on T2WI assumed the combination spot shape of T2 high signal.2.HE stain:Under the light microscope,interior/external layer fibrous ring showed confused and lost the normal structure in surgery group,we also observed the discontinuity and hyperplasia of collagenous fibers, Fibroblast in external layer fibrous ring increased;Hyperplasia of cartilage cell occurred in the nucleus pulposus next to the interior layer fibrous ring and the nucleus pulposus became thicker.But there were no the same change in Sham group and control group.3.Masson stain:Under the light microscope,the color of the external layer fibrous ring was green in surgery group,the surrounding muscular tissue showed red, inflammation reaction led to muscle fibrosis and the area between the external layer fibrous ring and the muscle showed gray.4.Immunohistochemistry stain:on 1 weeks,2 weeks,4 week after the surgery,the CD4/CD8 positive lymphocyte can be seen in the area next to the surgical.The CD4 positive lymphocyte mainly expressed on 1 week,2 weeks,the CD8 positive lymphocyte mainly expressed on 2 weeks,4weeks.But only little expression of lymphocyte assumed on 1 week,2 weeks in sham group,no expression of lymphocyte can be seen in control group.5.Immumofluorescence:in surgery group,we can observe little expression of IgG,IgM on 1 week after the surgery and massive expressions on 2 weeks,4 weeks,8 weeks.Little expression of IgG showed in the sham group and the control group.6.The result of bacteriological cultivation was negative.Conclusions:1.Discitis animal model can be established by using the anterior external surgery to destroy the fibrous ring and the cartilage lamina.Its imaging consistent with the representation reported in the clinic literature.2.Contact between the autoantigen of the nucleus pulposus and the blood circulation will provocate autoimmune reaction after destroying the fibrous ring and the cartilage lamina, the autoimmune reaction can be display in both cellular immunity and humoral immunity;3.Autoimmune reaction plays a vital role in pathogenesy,pathological change and symptom generating of discitis.