| Segmental bone defects of limbs due to trauma, inflammation and tumor are very common in clinical practice, which bring dysfunction and inferior life quality to patients. It is still a big problem to repair and reconstruct large segmental bone defects in orthopaedics, it's also one of the research focus in recent years. Until now, there have been a few methods to repair segmental bone defects including bone autograft, allograft and external fixation. Although these methods have their advantages and disadvantages respectively, they can not meet the needs of perfect reconstruction in the end. Tissue engineering that aims to "replicate tissue and organ" provides another innovative choice for repair and regeneration of segmental limb bone defects.Much progress has been achieved in bone tissue engineering field including seeded cells, scaffold materials, fabrication of tissue engineering bone and then using it to repair lacuna and critical bone defects so far. However, using tissue-engineering bone to repair bone defects is still in the stage of animal experiment. If we want to use this technology to repair large segmental bone defects in clinical practice with tissue engineering graft, we must answer the following essential questions at first: 1. Sources of seeded cells; 2. Fabrication of three-dimensional scaffold with optimal structure and function; 3.Revascularization of tissue engineering bone; 4.Feasibility of repairing large segmental bone defects with tissue engineering bone graft. Aimed at these problems, using the large segmental ulnar bone defects in rabbits as subjects, we studied the biological characteristics of seeded cells, scaffold materials,revascularization of tissue engineering bone and the effective of repairing large segmental bone defects with tissue engineering method.Firstly, the rabbit marrow stromal cells (MSCs) were harvested from bone marrow by puncture, and then induced into osteoblasts. Results showed: 1.It took 12~14 d for MSCs to be confluence with plating concentration of 3X 105cells/cm2, the double time of subculture MSCs and induced osteoblasts was 33.6h and 34.6h respectively. 2. The cells formed calcified nodule and expressed alkaline phosphatase, type I collagen and osteocalcin after osteoinduction. 3 Ultrastructure revealed naive condition in MSCs and mature state after osteoinduction with active secretion. 4 MSCs had the capacity to differentiate into osteoblasts and fat cells.Secondly, two scaffolds, CPPf/PLLA and CPPf/PLLA/Collagen, were fabricated with solvent-casting particulate-leaching method, following their characteristics were evaluated. Results suggested: 1.Networks was formed in the two scaffolds with high porosity; 2 The two scaffolds had good cell biocompatibility; 3.The capability of cell attachment in CPPf/PLLA/Collagen was superior to that of CPPf/PLLA; 4.The complex of osteoblasts-CPPf/PLLA/Collagen could form bone in ectopic site but the complex of osteoblasts-CPPf/PLLA could not.Finally, the vascularization, histology and biomechanical characteristics of tissue engineering bone autograft to repair large segmental ulnar bone defects in rabbits were studied. Results showed: 1. Juvenile bone like tissue occupied in defective region at 4w post-operation and it was almost normal bone tissue at 12w. 2.Rich vascular appeared in tissue engineering graft at 4w and no difference was found in vascular state between the tissue engineering graft and the normal cortical bone at 12w. 3.Mechanical strength was increased in tissue engineering graft as time goes by.Conclusions can be drawn as follows: 1. MSCs have great capability ofproliferation and can differentiate into osteoblasts with expression of alkaline phosphatase, type I collagen and osteocalcin, which is suitable for bone tissue engineering; 2. CPPf/PLLA/Collagen not only has the characteristics of excellent biocompatibility and biodegradable ability but also have good cell attachment ability. 3.The complex of osteoblasts-CPPf/PLLA/Collagen has the capacity to repair large segmenta...
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