Culturing Large Living Bone-repairing Tissue In Vivo By A Novel Porous Calcium Phosphate Bioceramics Scaffold

In clinic, it is difficult to repair the massive bone defect. Autografts and allografts are applied to solve this problem, but autografts are limited due to donor bone supply, the second surgery and the resorption during healing while allografts have to face the risks such as the potential immune rejection and pathogen transfer. The disadvantages of autografts or allografts prompt the development of reconstructing tissues or organs by means of artificial substitutes.Tissue engineering applies methods of materials engineering and life sciences to develop, design and reconstruct a substitute with similar morphology and function for implantation in the injured tissues to accomplish tissue repair. The process of tissue engineering is simply described:"a three-dimensional (3D) scaffold attached specific cells is cultured in vitro or in vivo for a certain period, subsequently delivered to the desired site for the purpose of tissue repair". In many experiments of reconstructing tissue engineered bone in vitro, specially in cultivating large tissue engineered bone, the currently used bone substitutes still face many unsolved problems including incomplete formation of new bone tissue, failure of neovascularization, and slow growth of the capillary network. Some researches reported the livability and quality of large tissue engineered bone would be improved with the betterment of the uniformity of biological substance and scaffold. Therefore, apart from the tailored porosity and pore structure, the scaffolds must possess the capability of improving the uniformity of biological substance such as seeded cells or growth factors inside scaffolds.In this study, a novel scaffold with large size and controlled porous structure was designed for the aim of massive tissue engineered bone in vivo. It was composed of HA spherulites and porous HA tube coated with poly (L-lactic acid) (PLA). Taking advantage of this design, HA spherulites can easily compound with biological substance before being filled into the HA tubes. This kind of pre-compounding manner can improve the uniformity of biological substance within the scaffold to promote the formation of new tissue and neovasculariztion in large volume of engineered bone. The novel scaffolds, in subsequent experiment, were cultured in vivo in the non-repairing sites such as muscle, femur bone side, peritoneum and canine abdominal omentum to construct the real living tissue by use of the nature environment in body which can provide the abundant substances needed for the growth of tissue including cells, nourishements, enzymes and biomolecular signals. The resluts displayed, after 6 months, the rich ingrowth of capillary blood vessel and bone tissue was found in scaffolds planted in the retroperitoneal group, femoral periosteum group and muscle group. Neovascularization and new bone were less than the other three groups significantly in intra-abdominal omental group. At the same time, the results also showed that peritoneal can be used as the better target site for bone tissue engineering in vivo.