Angiogenesis of tissue engineered bone in the repair of rhesus tibia defects / 中国组织工程研究

ABSTRACT

BACKGROUND: Many experiments indicate that the angiogenesis of tissue engineered bone graft plays a key role in the osteogenesis.OBJECTIVE: An experimental pattern was set up designed to prepare a kind of vascularized engineered-bone graft for repairing rhesus tibia defects and analyze the relation of angiogenesis and osteogenesis in vivo by rontgenographic and morphological approaches.DESIGN: Random controlled animal experiment.SETTING: Department of Orthopaedics and Traumatology, Nanfang Hospital, Southern Medical University.MATERIALS The composite graft was constructed by seeding the induced bone marrow stem cells (BMSCs) on to a beta-tricalcium phosphate(3-TCP) scaffold in vitro, a circular cylinder (20 mm × 8 mm diameter) with a slit (width 2 mm and length 3 mm ) open to both ends and slot. Porosity 60% and pore diameter 100-150 μm. Twenty-nine healthy rhesuses aged 4-5 years and weighted 3.5-5 kg were adopted without gender limitation.METHODS: The experiment was conducted in the Department of Orthopaedics and Traumatology, Nanfan Hospital, Southern Medical University from October 2003 to July 2005. ①Bone-periosteum defect of 20 mm was made in the middle part of right tibia of the 27 rhesuses, and randomly divided into 3 groups equally. ②The defect gaps in fascia-blood vessel group (A) were plugged with in vitro engineered composites constructed by bone marrow stem cells and 3-TCP scaffold, which were totally hugged by a sheet of pedicled deep fascia and additionally a corresponding portion of saphenous artery and veins. The gaps in fascia group (B) and control group(C), however, were inserted with fascia-coated tissue engineered bone and tissue engineered bone only, respectively. Furthermore, two rhesuses without filling materials on the defect were picked up as blanks fixed by steel pins. ③The angiogenesis and osteogenesis for each treatment was assessed by radioactive imaging, roentgenographic analyses, blocking density and vaso-area image analysis at time intervals of 4, 8 and 12 weeks postoperative.MAIN OUTCOME MEASURE: The score of radioactive imaging,roentgenographic, morphological and vaso-area image analyses RESULTS: Totally 29 rhesuses were involved in the result analysis.① General observation of samples In group A, all the surfaces of the implanted material and the central part were wholly wrapped up or replaced by bonelike tissues which were hard and could not be broken. And 2/3 materials had been absorbed; In group B and C, partial materials of the medial surface and the front were not coated or replaced by bonelike tissues, which could be broken with force, and 1/3 material had been absorbed.②Histological observation of scaffolds With time passing, the scaffold materials were absorbed to different degrees in group A, B and C, among which, group A was most significant; Under the microscope, the implanted materials at 12 weeks were completely coated with the bonelike tissues, while the blood vessels structures in the materials were mostly alveoli alike and multi-braches. In group B, most of the materials at 12 weeks were wrapped up by the new bone, and few blood vessels could be seen in the center of the materials. In group C, the implanted materials at 12 weeks were slightly absorbed. The new bone and the vascular structures were both increased a little, but still very few.③Analyses of vaso-area The vaso-areas of both central and peripheral parts in group A were significantly bigger than those of group B and C (P ＜ 0.05). Furthermore, it tended to increase with the time.④X-rays observation At 12 weeks, group A's images presented obviously decreased density which was lower than that of the normal bone in individual areas and the continual bony callus manifested. Whereas group B and C's images showed slightly decreased density and the continual bony callus appeared on the sections. ⑤The roentgenographic scores of bone defects The results indicates that the scores of group A was better than those of group B and C at 4, 8 and 12 weeks, respectively (P ＜ 0.05).CONCLUSION: ①This study shows that a feasible and effective angiogenesis approach of tissue engineered bone can accelerate osteogenesis in vivo. ②The absorption level is positively related to local angiogenesis.