Effect Of Injectable RhBMP-2 Nano Controlled-release Capsule On Repair Of Anterior Cruciate Ligament After Tendon-bone Interface Injury In Rabbits

Objective:1.To establish animal models of repairing bone-tendon interface after the reconstruction of anterior cruciate ligament?ACL?in rabbits;2.To evaluate the repair effect for bone-tendon interface with injectable rhBMP-2 nano controlled-release capsules and the influence on the repairing of bone-tendon interface with injectable rhBMP-2 nano controlled-release capsules in histology and biomechanics.3.To provide experimental evidences for clinical treatments of anterior cruciate ligament injury.Methods:1.46 rabbits?average weight of 3.31±0.45kg?were involved.Rabbits were injected with a single intravenation of general narcosis in the ear and underwent anterior cruciate ligament resection,after which anterior cruciate ligament was reconstructed with opposite Achilles tendon,which were animal models of repairing bone-tendon interface after the reconstruction of anterior cruciate ligament?ACL?in rabbits.2.The influence on the repairing of bone-tendon interface with injectable rhBMP-2 nano controlled-release capsules:histomorphological and immunohistochemical observation.18healthy adult rabbits were devided into 2 groups with 9 rabbits in each group.bilateral knees.One group were injected with rhBMP-2 nano controlled-release capsules bone-tendon interface,which was compared with the other group that did not receive injection.After operation 6 rabbits were sacrificed and devided into 2 groups randomly with 3 rabbits in each group,and specimens were obtained.Histopathological observation was performed after specimens were stained sections.3.The influence on the repairing of bone-tendon interface with injectable rhBMP-2 nano controlled-release capsules:the biomechanical studies.24 rabbits were devided into 2 groups randomly with 12 rabbits in each group,.One group were injected with BMP-2 into bone-tendon interface,which was compared with the other group that did not receive injection.Two groups?4rabbits each group?were sacrificed at the 2nd,4th or 8th weeks postoperatively in batches.Knee joints were dissected,and specimens were kept in a deep hypothermic refrigerator.During the pre-experiment,the specimens were thawed at ordinary temperature and fixed immediately.Then we carried the biomechanical study?the tensile test?,recorded the experiment data and analyzed.Results:The influence on the repairing of bone-tendon interface with injectable rhBMP-2 nano controlled-release capsules:histomorphological and immunohistochemical observation.Two groups were compared in the 2^nd week postoperatively.In group BMP-2,antitrope HE stain showed a positive reaction and was stained deeper and homogeneous.In the control group,the width of bone-tendon interface.Bone-tendon interface cell growth was less frequent,and mainly consisted of granulation tissue with heterogeneous distribution.Under light microscope in the 4^th week postoperatively,proliferation of fibroblasts was observed;the inflammation cell obviously reduced;bone-tendon interface tissue was found.In group BMP-2,the gap width of bone-tendon interface was reduced,and bulk fibroblast was found.In two groups,antitrope staining area showed a positive reaction and was stained light.In group BMP-2,it showed more homogeneous stain.In group BMP-2,antitrope expression showed a positive reaction and was stained deeper while light-stained in the control group.In the 8^th week postoperatively,connective tissues were found in the control group.In group BMP-2,the number of fibroblast bone-tendon interface were increased compared with the control group,similar to the structure of tendon attachment.The influence on the repairing of bone-tendon interface with injectable rhBMP-2 nano controlled-release capsules:the biomechanical observation.In group BMP-2,the ultimate tensile stress of bone-tendon interface of knee joints was higher than that in the control group at the 2nd,4th or 8th weeks postoperatively.On the basis of the control group,the maximal tensile stress postoperatively in group BMP-2 were 116.19%?122.05%?148.67%.Between the two groups,there was significantly difference?P<0.005?in the maximal tensile stress postoperatively of bone-tendon interface.On the basis of the control group,the stiffness of bone-tendon interface postoperatively in group BMP-2 were111.73%?115.65%?150.59%.In group BMP-2,the stiffness of bone-tendon interface of knee joints was higher than that in the control group at the 2nd,4th or 8th weeks postoperatively.The difference?P<0.005?of the two groups was statistically significant.Conclusion:1.The model of local application of rhBMP-2 nano controlled-release capsules on the knee joints of the rabbits can be used as the model for experimental research of repairing bone-tendon interface with BMP-2.2.BMP-2 can promote the formation of tendon attachment after the reconstruction of anterior cruciate ligament bone-tendon interface.With BMP-2 the maximal tensile stress and the stiffness of tendon in bone tract were greatly improved after the reconstruction.The experiments showed that BMP-2 had obvious promoting effect on bone-tendon interface after the reconstruction of anterior cruciate ligament...