Experimental Researches On The Collagen/Hydroxyapatite Integrated Composite Scaffold Used In Osteochondral Repair

Articulus cartilage defect caused by trauma,inflammation or degeneration is very common in clinical orthopaedics.Articular cartilage is a unique tissue with a limited healing capacity and cannot be adequately replaced with de novo synthesized normal articular cartilage after injury.Tissue engineered cartilage is constructed in vitro to restore the function of the joint after implanting into the articular cartilage defect.The interface between tissue engineered cartilage and the defect is a cartilage-to-cartilage one treating a cartilage defect,and with another cartilage-to-bone interface in treating an osteochondral defect. Therefore,to explore a suitable osteochondral substitute transplanting graft is of great importance.This paper centered on a promising osteochondral substitute transplant graft.we observed the biological properties of a novel collagen I/ hydroxyapatite composite scaffold in vitro and evaluated the possibility of its being used in tissue engineering in osteochondral repair.1. Research on the construction of a novel collagen I/ hydroxyapatite composite scaffoldObjective:To examine the construction of the collagen/hydroxyapatite composite scaffold and learn the physical characteristics.Methods:The novel scaffolds were constructed of collagen and hydroxyapatite using a freeze drying method. The ratio of collagen and hydroxyapatite was 1:3.Then the composite scaffold was put into the cross-linking solution for about 24 hours. The pore size, porosity and interpores of the scaffold were observed by scanning electron microscopy(SEM). The porosity was measured by liquid displacement method.Results:The study indicated that the novel collagen I/ hydroxyapatite osteochondral scaffold has good pore structure. The pore diameter of the collagen layer was about 90μm;the pore diameter of the HA layer was about 120μm. The porosity of the composite scaffold was above 75%. Conclusion:The integrated composite scaffold has good pore structure,and possibly will become a new biomaterial for osteochondral repair.2. Study on the biological properties of a novel collagen I/hydroxyapatite composite scaffold in vitroObjective:To evaluate the biocompatibility and histocompatibility of the collagen/hydroxyapatite composite scaffold.Methods:Rabbit bone mesenchy- mal stem cells(BMSCs) were isolated and amplified, then inoculated onto the scaffold. By SEM scanning, the condition of the cells adhering onto the scaffold was observed. The proliferation of the cells on the scaffolds was examined using MTT method, and the growth curve was drawn. The in vivo tissue response was investigated by implanting into the intra-muscular sites. At 4 and 8 weeks after implantation we harvested these specimens and examined histologically for morphologic features.Results:The examination revealed that BMSCs can adhere onto the scaffold well and the proliferation rate of the cells on the scaffolds was perfectly good.The cells extended and connected with each other through the synapse.Four weeks later the inflammatory cells can be seen in the interface of implant-tissue.And the inflammatory cells begin to reduce after 8 weeks. Conclusion: The proliferation rate of the bone mesenchymal stem cells on the scaffolds is very good. The osteochondral biomaterial scaffolds possess fine histocompatibility.3. Repairing of osteochondral defect of knee joint in rabbits with tissue engineered osteochondral composite biomaterialsObjective:To repair rabbits osteochondral defect of knee joint with the composite scaffolds and evaluate their biological activity.Methods: Twenty new Zealand white rabbits weighed from 2.3 to 3.0kg were used as experiment animals. Femoropatellar groove defects in rabbit,which were 5 mm in diameter and deep into medullary canal,were repaired surgically with tissue engineered osteochondral scaffolds or with nothing as the control group. Histological examination,including haematoxylin and eosin staining,toluidine blue staining were applied to measure the repair of defects at 12 , 24 weeks after operation.Results:The examination revealed that repairs of osteochondral defects in experimental groups were superior to those in control groups. Conclusions: The novel collagen/hydroxyapatite integrated composite scaffolds have good bioactivity in osteochondral defects repairing.In conclusion, the collagen/hydroxyapatite composite scaffold has proper porosity and biocompatibility as a novel scaffold for osteochondral tissue engineering.The scafflod has no effect to the growth and proliferation of bone marrow stromal cells,and it can repair osteochondral defects perfectly good .It will become a new biomaterial of tissue engineering for osteochondral repair.