| Objective:To investigate the impact of Diabetes Mellitus on the tissue,structure and biomechanical properties of tendon-bone healing by establishing the models of Diabetes Mellitus rats and rotator cuff tear rats.In order to thoroughly understand the relationship between Diabetes Mellitus and tendon-bone healing and explore the mechanism by which Diabetes Mellitus affects the tendon-bone healing.Methods:Seventy male Sprague-Dawley rats were randomly divided into Diabetes Mellitus rotator cuff tear group(DM-RCT group,n=40)and rotator cuff tear group(RCT group,n=30).Diabetes Mellitus was induced preoperatively via intraperitoneal injection of streptozotocin(STZ)citrate solution in the DM-RCT Group.Rats in the RCT group were intraperitoneally injected with 0.1ml/L Citric acid buffer in the same way.We measured the blood glucose by tail vein sampling before injection and 72 hours after injection.If the random blood glucose was ≥16.7mmol/L 72 h after injection,the DM model is successfully established.Four weeks after the establishment of the DM model,both groups of rats underwent unilateral detachment of the supraspinatus tendon followed by immediate anatomic repair with transosseous fixation.At 4 weeks and 8 weeks after surgery we measured the blood glucose,sacrificed the rats and obtained the specimens to perform Gross observation,Micro-CT,histological observation,Raman spectroscopy,Microindentation test and biomechanical test and obtained the pancreas to perform histopathological examination.Results:1.The success rate of diabetes model establishment was 80%(32/40).The blood glucose level of successfully established DM model rat was significantly higher than that of RCT group(24.17±5.91vs4.98±0.64)(P<0.001),and the blood glucose level after model establishment was stable.Dietary intake,water intake,and urine output in the DM-RCT group were significantly increased and the body weight was lower compared with the RCT group.2.The pathological results of pancreas: Compared with the RCT group,the islets in the DMRCT group were destructed seriously,the volume was significantly reduced,and the structure was loose;the quantity and volume of β cells of islet had decreased obviously,the structure was loose and disordered,the cytoplasm becomes shallow,and the nucleus was pyknosis or afterimage,showing the state before the atrophy disappears.3.Gross observation results: At 4 weeks after operation,the tendon tissue of the RCT group was white,shiny,tough and elastic,and the enthesis was tightly connected;in the DM-RCT group there were yellow,dark,and poor quality tendon,the surface of the tendon is rough,a small amount of scar tissue at the enthesis,and the connection of the enthesis is looser than the RCT group.At 8 weeks after operation,the tendon-bone connection was tighter in the RCT group,and a large amount of scar tissue was formed.The tendon-bone connection area was significantly larger than that in the DM-RCT group.In the DM-RCT group,the scar tissue increased,and the tendon-bone connection was stable,but worse than that in the RCT group.4.Histologic analysis results: At 4 weeks after operation,in the RCT group we can see bone growing into the tendon-bone interface,and there were a small amount of chondrocytes and some type III collagen fibers(Sharpey’s fibers),the cells were arranged regularly and capillary proliferation;in the DM-RCT group disordered cells,collagen fibers,scattered chondrocytes and a small amount of type III collagen fibers was observed.At 8 weeks after operation,in the RCT group we could observe the bone grew into the tendon-bone interface obviously,and a large number of Sharpey’s fibers structures appeared.The collagen fibers were neatly and fascicular,and both were oriented in the direction of the tendon pulling,and the cells were arranged more regularly.In the DM-RCT group,the cells were arranged disorderly.The Sharpey’s fibers and chondrocytes cells increased then before,but were less than that in the RCT group.5.Micro-CT : The bone mineral density(BMD),tissue mineral density(TMD),and bone volume fraction(BV/TV)in the RCT group at 4 and 8 weeks after surgery were higher than those in the DM-RCT group at the same time(P <0.05).6.Raman spectroscopy: The calcified matrix ratio of the calcified fibrocartilage in the bonetendon junction of the RCT group was higher than that in the DM-RCT group at 4 and 8weeks after surgery(P<0.05).7.Micro-indentation results: The trabecular elastic modulus and hardness of the calcified fibrocartilage in the bone-tendon junction of the RCT group were higher than those of the DM-RCT group at 4 and 8 weeks after operation(P <0.05).8.Biomechanical test results: The ultimate load and stiffness of the bone-tendon junction complex in the DM-RCT group were significantly lower than those in the RCT group at 4and 8 weeks after surgery(P <0.05).Conclusions:Diabetes mellitus delayed the healing of the tendon-bone and reduced the quality of healing of rats’ rotator cuff. |
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