Histological Observation And The Expression Of Matrix Metalloproteinase After Anterior Cruciate Ligament Reconstruction: Comparison Of Allograft Versus Autograft

Objective: To explore the histological result and the expression of matrix metalloproteinase after autograft anterior cruciate ligament reconstruction compared with the allograft.Methods: The study was performed on twenty-one healthy New Zealand White rabbits.All the rabbits underwent a complete anterior cruciate ligament surgical transaction on both knees and then reconstruction would be performed with autogenous or allogeneic semitendinosus tendon,respectively.Animals were euthanized at 4 weeks,8 weeks and 12 weeks postoperatively.In each group,two out of the seven rabbits were carried out the histological analysis under optical microscope with hematoxylin-eosin staining.In particular,healing between the tendon was assessed morphologically by determining the presence of fibrovascular tissue and collagen fibers.Reconstruction ligament tissue of the rest rabbits was harverted.And real-time PCR was performed using primers for MMP-1,MMP-2,MMP-13.Results:1 Histological observation: At 4 weeks postoperatively for the autograft tendon samples,central necrosis can be seen.Poorly organized collagen fibers and some inflammatory cells were filled in the interface between bone and tendon.No connection was visual with low cellular density.At 4 weeks postoperatively,we can observe the similar necrosis process in the allograft.Collagen fibers arranged disorderly and the low density of cells was observed;At 8 weeks after anterior cruciate ligament reconstruction,arrangement of fibers became orderly.Between the fibers and the bone wall,transition domain contained abundant cell,of which the shapes were spherical or ovoid.tidal line can be seen.Differed to the autograft,there was necrosis in the allograft even at the 8weeks after anterior cruciate ligament reconstruction.Although the density of cell at 8weeks was higher than at 4 weeks,it was easy to observe that cellular density in the autograft was lower compared with the allograft.Connection between the bone and the fibers can not be seen;At 12 weeks postoperatively for the autograft tendon samples,Perpendicular collagen fibers similar to Sharpey fibers were observed between the bone and the graft.Augmentor of the cellular density and the fiber arrangement were demonstrated.However,the fibers similar to Sharpey fibers can not be seen in the allograft at the 12 weeks after anterior cruciate ligament reconstruction.The fibers were perpendicular to interface between the fibers and bone wall.The ligament tissue show lower cellular density than in the autograft.2 The expression of MMPs: At 4 weeks postoperatively for the autograft tendon samples,relative gene expression data of MMP-1,MMP-2,MMP-13 was 0.60(0.36,14.22),0.52(0.28,6.5),0.43(0.35,7.60);In the allograft,the expression data of three genes was 0.30(0.09,16.84),0.52(0.14,8.43),0.09(0.04,11.42),there was no statistical difference between the autograft and the allograft.(MMP-1: Z=-0.67,P>0.05;MMP-2: Z=-1.35,P>0.05;MMP-13: Z=-6.74,P>0.05);At 8 weeks postoperatively for the autograft tendon samples,relative gene expression data of MMP-1,MMP-2,MMP-13 was 1.62(0.30,3.36),1.54(0.39,3.58),0.82(0.66,1.99);In the allograft,the expression data of three genes was 5.38(2.77,22.87),3.37(2.57,4.28),4.73(3.79,8.59).There was no statistical difference between the autograft and the allograft.(MMP-1:Z=-1.46,P>0.05;MMP-2:Z=-1.09,P>0.05;MMP-13: Z=-1.83,P>0.05);At 12 weeks postoperatively for the autograft tendon samples,relative gene expression data of MMP-1,MMP-2,MMP-13 was 0.90(0.43,3.23),0.83(0.53,2.61),0.24(0.04,51.7);In the allograft,the expression data of three genes was 2.12(1.80,21.86),1.37(0.45,5.08),0.13(0.05,93.6).There was no statistical difference between the autograft and the allograft.(MMP-1:Z=-0.94,P>0.05;MMP-2: Z=-6.74,P>0.05,MMP-13:Z=-1.21,P>0.05)Conclusions: Our study suggest that both autograft and allograft have undergone necrosis,cell migration,and the formation of new insertion,after the reconstruction surgery.Although the histological result of autograft seem to be better than the allograft,there was no statistical difference.Also,relative gene expression data of MMP-1,MMP-2,MMP-13 had no statistical difference between the autograft and the allograft.