The Expression Of Matrix Metalloproteinase-3 And Tissue Inhibitor Of -1 Between The Rabbit Lumbar Spine Bone Defects And The Growth Plate

1 IntroductionEndochondral ossification is process of bone growth along the template of cartilage, which occurs in bone development, fracture healing and bone growth plate in the bone formation process, and involves transformation from typeⅡcollagen and aggrecan rich avascular cartilage to collagen type I and mineral rich vascular bone tissue. In the process of endochondral ossification, precursor cartilage cells, namely mesenchymal cells differentiate into cartilage cells, which then mature into hypertrophic chondrocytes. Hypertrophic chondrocytes start to calcify, cartilage matrix degradates and the vessels ingrowth. Apoptosis of hypertrophic chondrocytes occurs, followed by bone deposition in the calcified cartilage trabeculae. Although more and more researches involve the mechanism of endochondral ossification, the exact relationship between each part remains unclear.Bone graft healing is a complex process involving the degradation of surface osteoid and mineralized matrix by matrix metalloproteinases (MMPs). The activity of MMPs is regulated by tissue inhibitors of matrix metalloprotemases (TIMPs). TIMPs inactivate MMPs by forming non-covalent bimolecular complexes and prevent pro-MMP activation. TIMPs and MMPs have been implicated to play important roles in bone formation and remodeling.2 ObjectiveTo observe the expression of MMP-3 and TIMP-1 in the repair process of bone defect; Also to observe the changes over time of expression of MMP-3 and TIMP-1 in the rabbit spinal epiphyseal.3 MethodsThere were 16 New Zealand white rabbits, we excised anterior discs and built defect areas between L5/6, L6/7 and L7/S1 through anterior lumbar approach operation in each animal. Of these, no material was implanted in defect area between L5/6; injectable n-HA/Col was implanted in defect area between L6/7; and solid type n-HA/Col was implanted in defect area between L7/S1. We killed 4 animals at 4w,8w,12w,16w postoperatively respectively, and harvested lumbosacral vertebrae specimens. We made organization slices of L5/6,L6/7,L7/S1 segment in every specimen. Immunohistochemistry procedures with MMP-3 and TIMP-1 antibodies were performed to compare expression differences of the 3 groups and expression changes with time in growth plate.4 ResultsIn the experimental group and the positive control group, repair of bone defects occurs mainly through endochondral ossification. In the repair process, the cartilage cells express matrix metalloproteinase-3 (MMP-3) and tissue inhibitor of metalloproteinase-1(TIMP-1). Over time, MMP-3 expression first increased and then decreased, while the expression of TIMP-1 showed gradual upward trend. The expression of MMP-3 in bone defects filled with injectable n-HA/Col in the experimental group is higher than that in bone defects filled with solid n-HA/Col in positive control group. The expression of TIMP-1 in bone defects filled with injectable n-HA/Col in the experimental group is earlier than that in bone defects filled with solid n-HA/Col in positive control group.5 ConclusionBone defect repair mediated by injectable n-HA/Col is more efficient than that mediated by solid n-HA/Col. ECM remodeling balance in bone defect repair mediated by injectable n-HA/Col is earlier than that in bone defect repair mediated by solid n-HA/Col.