Study On Early Pathological Changes Of Sacroiliac Joint In Animal Model Of Ankylosing Spondylitis Based On IVIM-DWI And DCE-MRI Imaging Technique

ObjectiveA wistar rat model of early stage sacroiliac arthritis（SIS）of ankylosing spondylitis（AS）induced by bovine proteoglycan was established.The IVIM-DWI and DCE-MRI parameters were measured,comparing with pathological findings and evaluating the value of early imaging diagnosis of AS.Materials and methodsTwenty male wistar rats were induced by bovine proteoglycan combined with complete/incomplete Freund adjuvant for several times as experimental group,and 20healthy homogenous rats were used as control group.The D_slow,D_fast,f value of IVIM-DWI sequence parameters and Fenh%、Senh%value of DCE-MRI sequence in synovial region of SIJ were measured at 7 weeks,12 weeks,17 weeks and 22 weeks after the last induction,and the pathology of sacroiliac joint was taken,to study the pathogenesis and pathological characteristics of sacroiliac region in Wistar rats.Independent sample t test and single factor analysis of variance were used for statistical analysis.ResultsThere was no significant difference in D_slow,D_fast,f,Fenh%,Senh%between the experimental and the control group at the 7,12 week after the last induction.SIJ cartilage,bone marrow and synovium were not abnormal in experimental and control group.At the 17th week after induction,The Fenh%,Senh%values of the experimental group were higher than that in control group.There was significant difference in Fenh%,Senh%between the two groups（t=2.056,P=0.040,t=-2.290,P=0.028）.The D_slow,D_fast,f values of wistar rats in the experimental group were higher than that in control group,only f between the experimental and the control group was statistically significant（t=2.974,P=0.009）.No abnormal signals were found in conventional MRI sequences.The SIJ of experimental group showed infiltration of inflammatory cells in synovitis,while that of SIJ in control group was not abnormal.At the 22nd week after induction,The Fenh%,Senh%values of the experimental group were higher than that in control group.The Fenh%,Senh%values of the two groups were statistically significant（t=9.162,P=0.000,t=0.293,P=0.000）.The D_slow,D_fast,f values of wistar rats in the experimental group were higher than that in control group.The D_slow、D_fast、f value between the experimental and the control group was statistically signi-ficant（t=3.781,P=0.001,t=2.476,P=0.021,t=8.760,P=0.000）.No abnormal signals were found in conventional MRI sequences.The histopathological manifestations of SIJ were pannus formation in synovial membrane,while no abnormal synovial membrane was found in SIJ in control group.The values of Fenh%in experimental group was no significant difference between12-week and17-week（P=0.198）,the values of Fenh%in experimental group between12-week and 22-week,17-week and 22-week were statistically significant（p=0.000,P=0.017）.The values of Senh%in experimental group between 12-week and 17-week was no significant difference（P=0.529）.The values of Senh%between 12-week and 17-week,12-week and 22-week was significant difference（P=0.000）.The values of D_slow、D_fast in experimental group between 12-week and 22-week,17-week and 22-week were of stati-stical significance(D_slowP=0.000,P=0.019;D_fastP=0.005,P=0.040),12-week and 17-week D_slow、D_fast values was not statistically significant（P=0.070,P=0.390）.The value of f in the 12-week,17-week and 22-week groups was statistically significant（P=0.000）.Bovine proteoglycan combined with complete/incomplete Freund adjuvant can induce SIJ synovitis in wistar male rats at the 17th week,and the induction rate was 100%.ConclusionThe AS rat model induced by bovine proteoglycan showed the pathological features of sacroiliac joint synovitis at 17 weeks after induction.MR IVIM-DWI and DCE-MRI sequences can sensitively reflect the changes of local microenvironment in the early stage of inflammation,thus providing reliable imaging evidence for clinical diagnosis of AS.