Experimental Study On Monitoring Cartilage Regeneration And Sodium Alginate Degradation Using Multimodal MRI In Vivo

Objective:This experiment explored whether multimodal MRI can dynamically monitor and evaluate the efficacy of bone marrow mesenchymal stem cells in repairing cartilage in vivo.Meanwhile,explore whether multimodal MRI can noninvasive monitor the degradation of sodium alginate scaffold materials.It was further confirmed by gross and histopathological analysis of rabbit regenerated cartilage.Methods:1.Obtain BMSCs from the bone marrow of one-month old New Zealand white rabbits;2.Determine the proliferation and differentiation ability of BMSCs;3.Twenty-four 4-month-old New Zealand white rabbits were randomly divided into three groups,with 8 rabbits in each group.A cartilage defect model was made at the right knee joint of the rabbit.The specific experimental groups were as follows: blank group(Group A),without any treatment of the joint defect;In pure sodium alginate group(Group B),pure sodium alginate scaffold material was implanted into the joint defect;In the BMSCs+sodium alginate group(Group C),BMSCs+sodium alginate scaffold composites were implanted in the joint defects.All groups were sutured with surgical sutures to seal the articular cavity and raised in cages;4.At 1,2,4 and 12 weeks after surgery,the rabbits in the experimental group and the blank group were scanned with sagittal T1 WI,T2WI,T2 mapping and 3D IDEAL,and the T2 value was measured.The diameter and depth of the cartilage defect areas in each group at different time points were measured.Finally,specimens were taken for gross observation and histological analysis;5.Collect data and conduct statistical analysis.Results:1.MRI,gross,and pathological observations of rabbit knee cartilage showed that there was no significant repair of the defect area in Group A and Group B at the first and second weeks after surgery.At week 4,a small amount of repair tissue filling was visible.At week 12,the defect area was replaced by a large number of irregular new cartilage,partially integrated into the surrounding normal cartilage,and there were still defects on the surface.In group C,no obvious repair was found at week 1,and a small amount of repair tissue filling was visible at week 2.At week 4,a large amount of repair tissue can be seen integrating into the surrounding normal cartilage.At week 12,the defect was successfully restored and integrated,with a smooth surface.2.The diameter of the rabbit knee cartilage defect repair model was measured using MRI software.The diameter of Group A and Group B at the same time point(1,2,4,and12 weeks)was compared,P >0.05,with no statistically significant difference.The diameter of Group B and Group C at the same time point was compared,P <0.05,with a statistically significant difference.At the same time point,there was no significant difference in depth between Group A and Group B(P>0.05).In the same period,compared with the depth of group C and group B,at the first and second weeks,P>0.05,the difference was not statistically significant,while at the fourth and twelfth weeks,P<0.05,the difference was statistically significant.The T2 value of rabbit knee cartilage defect repair was measured by MRI post processing software.After comparing the T2 value of Group A and Group B at the same time point,P>0.05,the difference was not statistically significant.During the same period,the T2 value of Group B and Group C was compared,P>0.05,the difference was not statistically significant at the first week;At the 2nd,4th,and 12 th weeks,P<0.05,the difference was statistically significant.The T2 value in vivo reflects that with the continuous repair of cartilage,the T2 value gradually decreases and gradually tends to normal cartilage,but is still higher than normal cartilage.3.In group B,obvious sodium alginate gel could be seen in MRI and gross specimen observation within 1 week.The signal of sodium alginate gel decreased slightly at 2 and4 weeks compared with that at 1 week.At 12 weeks,no obvious sodium alginate gel was found.In group C,significant BMSCs+sodium alginate complexes were observed at the first week.At the second week,a small amount of BMSCs+sodium alginate complex was found;At week 4,no significant BMSCs+sodium alginate complex was observed.The T2 value of sodium alginate in vivo reflects that the sodium alginate in Group B was not completely degraded at the fourth week,while the sodium alginate in Group C was basically completely degraded at the fourth week,indicating that the sodium alginate implanted in BMSCs decreased faster than pure sodium alginate.Conclusion:1.Multimodal magnetic resonance imaging can noninvasive and dynamically monitor cartilage regeneration,repair,and sodium alginate degradation in vivo;2.The T2 value of regenerated cartilage gradually decreases with the passage of time after surgery,and tends to be close to normal cartilage.It has been confirmed by pathology that the T2 value is related to the arrangement direction of extracellular matrix components and collagen reticular structure during the repair process;3.At the fourth week after surgery,the sodium alginate implanted with BMSCs was basically completely degraded,and the presence of BMSCs can promote the degradation of sodium alginate.4.BMSCs can promote cartilage regeneration and repair,and sodium alginate as a scaffold material will not affect cartilage regeneration.