| 【Objective】In this study,three types of adipose-derived mesenchymal stem cells(AD-MSCs),autologous,allogeneic and xenogeneic,were injected into the knee cavity of rhesus macaques successfully modeled in the previous experiments to observe the imaging performance of different stages of knee treatment in rhesus macaques and to investigate the value of T2*mapping technique in To investigate the value of T2*mapping technique in the assessment of osteoarthritis(OA)progression,regenerative cartilage quality and efficacy.【Materials and Methods】In this study,a total of 18 knee joints from 9 rhesus macaques with successfully modeled OA were included.Autologous,allogeneic,and xenogeneic AD-MSCs were injected into 4 joints of each group in the experimental group,and equal amounts of saline were injected into 6 knee joints of the control group.Routine magnetic resonance imaging(MRI)sequences and T2*mapping scans were performed at 1 month,2 months,3 months,6 months,and 14 months after injection,and all joints were evaluated using the Whole-Organ Magnetic Resonance Imaging Score(WORMS).The knee was divided into nine sub-regions and paracondylar regions according to the WORMS anatomical criteria:region of patellar(P),region of medial femoral anterior(MFa),region of medial femoral central(MFc),region of medial femoral posterior(MFp),region of lateral femoral anterior(LFa),region of lateral femoral central(LFc),region of lateral femoral posterior(MFp),central(LFc),region of medial femoral posterior(LFp),region of medial tibial(MT),and region of lateral tibial(LT).T2*values were measured in nine subregions of the macaque knee,the paramedian region,and the regenerated cartilage region for comparison.To verify the reliability of the imaging results,one joint from each of the experimental and control groups was randomly selected for histologic analysis at 6months after injection.T2*values were measured independently by two radiologists,and the agreement between the two radiologists’measurements was assessed using Kendall’s W coefficient test.The differences in T2*values between and within groups were statistically analyzed using one-way repeated measures analysis of variance,and P<0.05was considered a statistically significant difference.【Results】The data for the total WORMS score and T2*values measured by the two radiologists were highly consistent(Kendall w coefficients of 0.935 and 0.948,respectively,P<0.05).The results of T2*values showed that T2*values in all subregions of the control group,except for the MT subregion,increased significantly over time after saline injection.In the experimental group of macaque knee joints,the T2*values of four subregions,MFa and LFa in the non-weight-bearing region and LFc and LT in the weight-bearing non-molded region,showed a decreasing trend after the injection of AD-MSCs,and the differences were statistically significant after the 2nd month of injection and before the injection(P<0.005).The T2*values of the MFc and LFp subregions in the weight-bearing region decreased significantly during 3 months after injection,and then showed an increasing trend at 6 and 14 months after injection,and the differences were statistically significant at 14 months after injection compared with 2 and 3 months after injection(P<0.05).In the MFP subregion of the weight-bearing zone,the T2*values of each experimental group showed a decreasing trend at 3 months and then increased,and the differences were not statistically significant.In the MT subregion of the weight-bearing zone,there was no significant difference in T2*values between the experimental groups before and after injection.In the P zone,T2*values showed an increasing trend in all experimental groups,and the differences were not statistically significant.There was no statistically significant difference in T2*values between the control,autosomal,homozygous and heterozygous groups before injection in each subzone,and the T2*values of all experimental groups were smaller than those of the control group after injection,and the differences were statistically significant except for the MT and P subzones(P<0.05);there was no statistically significant difference between the autosomal,homozygous and heterozygous groups in each time period.In the three experimental groups,regenerative cartilage formation was seen in the cartilage defects 6months after injection of AD-MSCs,and the T2*values of regenerative cartilage were not significantly different from normal cartilage and were slightly lower than those of paracondylotic cartilage,only the T2*values of the autologous group were lower than those of paracondylotic cartilage,and the difference was statistically significant(P=0.018).The total WORMS score was significantly lower in the allograft group at 1month after injection(P=0.002),and the differences were not statistically significant in the remaining groups.Histological assessment of the experimental group saw regenerative cartilage formation in the defect area with good quality regenerative cartilage and active superficial cartilage chondrocyte proliferation in the non-defect area,while the control group had fibrous tissue repair in the cartilage defect and superficial cartilage fibrous tissue proliferation in the non-defect area,consistent with the results of T2*mapping assessment.【Conclusion】1.T2*values can quantitatively and sensitively reflect changes in the microstructure and biochemical composition of articular cartilage,and T2*mapping can be used as an effective tool for the diagnosis,progression and efficacy monitoring of OA,and can provide some basis for the development of rehabilitation plans after intra-articular injection of MSCs.2.T2* values can be used as an effective index to evaluate the quality of regenerated cartilage. |
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