| Background:Trauma, tumor, infection and so on led to a large number of bone defect. Repair and reconstruction of bone defects is a serious problem. Autogenous bone graft is the best bone graft material, and considered to be the gold standard for bone grafting with the osteogenesis, osteoinduction, osteoconduction and be absorbed. Despite the acceptable bone induction properties of autologous bone grafts, the high morbidity of these approaches and limited amount of material that can be obtained from the donors are leading to the development of bone tissue engineering products for the restoration of damaged or lost bone. At present, bone substitute research become the focus in the bone tissue engineering.Osteoinduction and osteoconduction are must considered in the bone tissue engineering at first. Osteoinduction refers to the graft is able to induce the mesenchymal cells differentiate into osteoblasts and bone formation; osteoconduction refers to the graft can provide scaffolds to guide blood vessels and bone formation.At present, most of bone substitute materials only have osteoconduction and the clinical use limited to small bone defects. Bovine bone is the most extensive research and application of xenogeneic bone material. The main anorganic component is hydroxyapatite.Recent progress in regenerative medicine raises the hope of repairing bone defects with the combination of biomaterials and growth factorsWith the development of genetic engineering, a good activity and low cost of rhBMP-2 has been developed. The source of BMP-2 has been solved. However, rhBMP-2 is easily dispersed from the implant site. It cannot effectively stimulate bone formation. A variety of carriers have been developed to restrict the free diffusion of BMP-2, and they often provide a slow releasing system.The mainly problems is how to choose the ideal bio-active material and its carrier in bone tissue engineering.Collagen is one of the today considered best carriers because of its versatility, high bio-compatiblility and low immunogenicity. However studies have shown the functions of collagen-based biomaterials alone are limited in bone repair. In this work, a collagen binding domain (CBD) of "TKKTLRT"was added to the N-terminal of recombinant human BMP-2.It restrict the free diffusion of rhBMP-2. The system could promote better bone formation.Our team in the previous work has been carried out the osteoplastic effect of anorganic bovine bone loadin with collagen-targeting rhBMP-2 on rabbit tibial metaphyseal bone defect model. The study found that anorganic bovine bone loadin with collagen-targeting rhBMP-2 promote the early bone formations and the materials rapid degradation. Anorganic bone bovin matrix provide scaffolds to guided bone formation continually,but degrades slowly. Combine the advantages of both may be possible for the development of new bone graft materials. Therefore, we choose different proportions of anorganic bovine bone loadin with collagen-targeting rhBMP-2 and anorganic bovine bone mixed to hope take full advantage of the early osteoinduction of anorganic bovine bone loadin with collagen-targeting rhBMP-2 and osteoconduction of osteoconduction in late stage of bone remodels.In order to know about the biological properties of bone substitutes and experimental reliability of the results, the establishment of a suitable animal model is the premise of studying bone substitutes. However, few researchers pay enough attention in experimental animal models. This slightly higher degree of bone healing was related to differences in the bone architecture of the implantation sites. To explore the advantage of animal model in a critical size defect in the distal part of the femur of the adult female rabbits, as well as feasibility and scientificity on study of bone substitutes, to provide a new idea on an ideal animal model of tissue engineering.Object:1.To explore the advantage of animal model in a critical size defect in the distal part of the femur of the adult female rabbits, as well as feasibility and scientificity on study of bone substitutes, to provide a new idea on an ideal animal model of tissue engineering..2 To study the effect of osteogenesis with anorganic bovine bone loadin with collagen-targeting rhBMP-23 To study the effect of osteogenesis of novel bone substitute materials with osteoinduction and osteoconduction.Methods1 Experimental animals and groupingPart 1:15 Healthy female New Zealand rabbits were prepared for critical size defect in the bilaterally distal part of the femur, and then randomized divided into two groups. In experimental group (n=12) implanted anorganic bovine bone matrix, the rabbits were sacrificed at weeks 2,4,6,12 respectively. The control group (n=3) with no treatment were sacrificed at 12 weeks.Part 2:72 Healthy female New Zealand rabbits were randomized divided into A,B,C,D,E,F 6 groups, each group contain 12 animals and different bone substitutes were implanted. Group A:anorganic bovine bone; Group B:anorganic bovine bone:/collagen composite;Group C:free rhBMP-2 on anorganic bovine bone:/collagen composite; Group D anorganic bovine bone loadin with collagen-targeting rhBMP-2:; Group E:anorganic bovine bone loadin with collagen-targeting rhBMP-2 and anorganic bovine bone with the proportion of 1:1; Group F:anorganic bovine bone loadin with collagen-targeting rhBMP-2 and anorganic bovine bone with the proportion of 1:3.2. To set up experimental animal modelThe bone defect,6-mm diameter and 10-mm deep, was created on the bilaterally distal part of the femur.3.Main outcome measures:Evaluation and analysis the osteogenic properties and its resorption or degradation of bone graft substitute by gengral Observation, X-ray observation, anatomical measurement of the distal femur condyles of rabbits and tissue slice observation.Result:1. The animals recovered well after the surgery. All animals tolerated the bilateral model without complication, the diet and activity were normal on the day after surgery. The animal model is reliable, there is no animal die and no sign of fracture after operation.2.The degradation and the healing of bone defect of bone substitute materials were evaluation by general observation. In control group at 12 weeks, a few new bone formation was observed at the edge of the defect at Histological sections, while in the middle of the defect,we found more fibroblasts and inflammatory cells, but no bone connection was found.3. Statistical analysis was performed on the software SPSS13.0.2 weeks later, the proportion of new bone area was best in group D(30.21±2.35)% and was statistically significant compard to A(15.22±2.44)%,B(21.18±1.9) %,C(22.93±2.56)%,E(21.44±2.81)% and F(20.19±2.3)%,but no statistically significant was found among B and C(P=0.218), E and F(P=0.377),C and E(P=0.292).Else each other was found statistically significant(p<0.05).4 weeks later, the proportion of new bone area was best in group D(35.98±1.68) % and was statistically significant compard to A(19.12±2.02)%,B(26.92±1.78) %,C(25.16±2.18)%,E(30.08±1.93)% and F(26.63±3.82)%,but no statistically significant was found among B,C and F(P>0.05).Else each other was found statistically significant(p<0.05).6 weeks later, the proportion of new bone area was best in group E(38.18±2.09) % and was statistically significant compard to A(21.42±1.95)%,B(26.56±1.14) %,C(21.98±1.89)%,D(32.42±1.95)% and F(31.14±3.55)%,but no statistically significant was found among A and C(P=0.665), D and F(P=0.327).Else each other was found statistically significant(p<0.05).12 weeks later,the absorption of the new bone of the B,C and D group were seen. The proportion of new bone area was best in group E(53.46±7.48)% and was statistically significant compard to A(27.63±1.95)% and F(35.22±2.67) %,between A and E(p<0.05).Conclusion:1. The animal model has a obviously anatomical properties. It has been shown that metaphyseal line and lateral border of facies patellaris may regard as critical reference mark in intra-operation. There is amount of cancellous bone in the distal part of femur metaphyseal of rabbits. The CSD is mainly located in the area of cancellous bone.The experimental data are more science and more reproduce because of the bone substitute's implantation site in a homogeneous tissue. This study shows that a ideal critical bone defect in the distal part of the femur metaphyseal of adult female rabbits should be preferred for testing bone graft substitutes before preclinical implantation in large animals.2. Anorganic bovine bone loadin with collagen-targeting rhBMP-2 showed strong osteogenic capacity and good bone induction properties in the early stage;3. Anorganic bovine bone loadin with collagen-targeting rhBMP-2 is better than free rhBMP-2 on anorganic bovine bone:/collagen composite in osteogenic capacity.4. Collagen can promote bone formation and bone substitute materials absorption at an early stage;5. Anorganic bovine bone loadin with collagen-targeting rhBMP-2 and anorganic bovine bone matrix mixture showed good osteoinduction, and osteoconduction.6. The Osteogenesis effect of Anorganic bovine bone loadin with collagen-targeting rhBMP-2/anorganic bovine bone mixture relates to the proportion of DBM loadin with collagen-targeting rhBMP-2.
|
PDF Full Text Request