Study Of The Correlation Between Cartilage Magnetic Resonance T2/T2*-Mapping Imaging And The Expression Of MMP-1 In The OA Model Of Sheepknee Joint

OBJECTIVE:To study the performance of cartilage T2 and T2*-mapping in the sheep knee osteoarthritis（Keen Osteoarthritis,KOA）model,and analyze the positive expression of MMP-1 in different stages of degenerative cartilage,and explore the cartilage degeneration in each stage of the sheep knee OA model.The correlation between MRI quantitative manifestations and cartilage MMP-1 expression.Methods:Fifteen healthy Mongolian fine-wool sheep were selected as samples,8-10months old,weighing 20±3 kg,and randomly divided into five groups A,B,C,D,and E,with three in each group.Among them,group A is the blank control group without treatment;groups B,C,D,and E are experimental groups.The experimental group used the method of injecting papain solution into the left knee joint to make the degeneration model of Mongolian sheep’s knee articular cartilage.A total of three injections（1.4 ml each time）were performed on the first day,the fourth day,and the seventh day.The model was completed.Use SIEMENS Skyra 3.0T magnetic resonance scanner to perform MRI scan on the left knee joint of the animal model.Groups A,B,C,D,and E performed MRI scans on the left knee joint of the sheep at 1,3,5,and 7 weeks after the completion of the model.Cartilage undergoes MRI routine sequence inspection,T2-mapping,T2*-mapping sequence inspection.After the inspection,the original data is transmitted to the post-processing workstation,and the T2,T2*-mapping map and the TE anatomical map generated at the same time are used for image post-processing using Syngo Via VB10B software to obtain the corresponding T2,T2*pseudo-color map.Select the thickest part of the medial femoral condyle and the medial tibial plateau cartilage on the obtained pseudo-color image as the area of interest（ROI）,repeat the measurement for each ROI three times and take the average value,and record the T2 and T2*values of the ROI.After MRI data collection of each group of sheep,they were sacrificed and dissected to observe the knee articular cartilage,and then the articular cartilage was collected.After the specimens were decalcified,dehydrated,transparent,and embedded,they were made into slices with a thickness of 0.4 um and performed by the SP immunohistochemical method.Under an optical microscope,observe and analyze the expression of MMP-1in the control group and each experimental group.Image-Pro Plus 6.0 image processing system was used to determine the average of optical density（AOD）of MMP-1 positive expression rate in each group of slices.Statistics uses SPSS 20.0software to analyze the measured data.When the data satisfies normal homogeneity and variance homogeneity,use one-way analysis of variance,and use LSD test for pairwise comparison between groups;otherwise,use non-parametric test Kruskal-Wallis test and Mann-Whitney test,and use Pearson correlation analysis to analyze cartilage T2/Correlation analysis between T2*value and MMP-1 positive expression rate（AOD value）.P<0.05 is statistically significant.Results:（1）Compared with the control group,the T2 value of knee articular cartilage in each model was increased.With the prolongation of model building time,the T2value of the medial femoral condyle and the medial tibial plateau cartilage showed an upward trend.Among them,the T2 values of the medial femoral condyle cartilage were not statistically different between group A and group B,group D and group E（P>0.05）,and there were statistical differences between the other models（P<0.05）;tibia.There was no statistical difference in the T2 value between the D group and the E group of the medial plateau cartilage（P>0.05）,and the other models had statistical differences（P<0.05）.（2）Compared with the control group,the T2*values of knee articular cartilage in each model were increased.With the prolongation of the modeling time,the T2*values of the medial femoral condyle and the medial tibial plateau cartilage showed a gradual upward trend.There was no statistical difference in T2*values between group B and group A,group B and group C（P>0.05）,and there were statistical differences between the other models（P<0.05）.（3）The immunohistochemical microscope showed that the expression of MMP-1 in the cartilage of each experimental group was higher than that of the A group,and the AOD value showed an upward trend with the prolongation of the modeling time.The positive expression rates of MMP-1 in the medial femoral condyle and the medial tibial plateau cartilage were compared between each group,and there were statistical differences（P<0.05）.（4）According to Pearson correlation analysis,the positive expression of MMP-1 in the medial femoral condyle and medial tibial plateau cartilage in the sheep KOA model increased with the increase of the T2 value of cartilage MRI.There is a linear positive correlation between the two(r _{medial femoral condyle}=0.825,P<0.01;r _{medial tibial plateau}=0.751,P<0.01).（5）According to Pearson correlation analysis,the positive expression of MMP-1 in the medial femoral condyle and medial tibial plateau cartilage in the sheep KOA model increased with the increase of the T2*value of cartilage MRI.There is a linear positive correlation between the two(r _{medial femoral condyle}=0.882,P<0.01;r _{medial tibialplateau}=0.781,P<0.01).Conclusion:（1）Compared with the blank control group,the T2 and T2*values of cartilage magnetic resonance of each experimental group of sheep knee joint OA model increased,and showed an upward trend with the extension of the modeling time.（2）The positive expression rate of MMP-1 in the experimental group of sheep KOA model was higher than that in the control group,and showed a gradual increase with the prolongation of the modeling time.（3）The quantitative value of cartilage T2and T2*of the OA model has a linear positive correlation with the AOD value reflecting the positive expression rate of cartilage MMP-1.It shows that the quantitative value of magnetic resonance T2 and T2*can reflect the change of MMP-1 expression in cartilage and the degree of degeneration of articular cartilage.T2,T2*-mapping imaging technology can make quantitative diagnosis of early OA of articular cartilage,follow-up patients with early OA treatment and monitor the changes of their cartilage endobiochemical components.