Tissue Engineered Bone Using Calcium Alginate Gels

Bone grafting is commonly performed using autogenous bone, allogeneic bone and synthetic bone graft substitute. Autogenous bone grafting, thought to be an ideal form, cannot be used to reconstruct extensive bone defect because of limitation of bone that can be harvested. This method also has the drawback of causing damage to normal bone and soft tissue. Allogeneic bone can be obtained in sufficient quantities, but does not always show satisfactory results due to immunological rejection. In recent years, the development of tissue engineered bone show us a potential way to solve this problem. In research of tissue engineered bone, some kinds of ideal scaffold that can provide three-dimension space for cells growing and tissue formation, have to be investigated.Alginate acid is a polysacchatide isolated from seaweed. In the presence of divalent cations such as calcium polymerizes, it can form an open-lattice hydrogels by means of ionic cross-links. The resulting hydrogel maintains shape well and is not toxic. Calcium alginate has been used successfully to encapsulate and maintain cells in tissue culture and is degraded by enzymatics to its two monomeric subunits: guluronic acid and mannuronic acid. All these characteristics are advantageous for a polymer support matrix in chondrocyte transplatation. In this study, bone defect repair and bone formation were conducted employing the method of tissue engineering and using calcium alginate gels as scaffold.-4-1. A preliminary study of injectable tissue-engineered boneObjective: the study investigates the utilization of alginate carrier for delivering osteoblasts and creating new bone tissue in nude mice model via injection. Methods: Bone marrow cells harvested from iliac bone of New Zealand rabbits differentiate into bone stromal osteoblasts. The osteoblasts were mixed with 2.0%alginate sodium solution to generate osteoblasts/alginate composites with final cellular density of 5 X 106/ml. Calcium chloride was used as cross-linking agent to gel aqueous alginate solution. The osteoblasts/alginate composites were injected into the dorsal subcutaneous tissue of nude mice. Results: Four and eight weeks after injection, the hard knobbles were easily palpated under the dorsal skin of animals. X-ray photograph showed that the knobbles has calcified image with more density than sounding soft tissue. In histological analysis, new bone formation was observed in the osteoblasts/alginate composites. The osteogenesis was in association with regenerated hematopoietic bone marrow. Conclusion: These results revealed that new bone tissue could be created through the injection of alginate sodium mixed with marrow stromal osteoblasts.2. Repair of skull defects of rabbit with cultured marrow stem cells combined with alginateObjective: The study investigates the utilization of alginate carrier for delivering rabbit marrow stem cells(MSCs) and creating new bone tissue in the repair of bone defects. Methods: Rabbit MSCs cells were cultured and expanded in vitro and stromal osteoblasts were harvested. The stromal osteoblasts were mixed with 2.0%alginate sodium solution to generate stromal-5-osteoblasts/alginate composites with final cellular density of 5 X 106/ml. Calcium chloride was used as cross-linking agent to gel aqueous alginate solution. The stromal osteoblasts/alginate composites were implanted into rabbit skull defects in the diameter of 15mm. Eight weeks after operation, the animals were sacrificed and new bone regeneration in the defects was investigated by gross specimen inspection, X-ray examination and histological observation. Results: 8 weeks after operation, most area of the stromal osteoblasts/alginate composites transplanted defects were filled with newly formed bone. Conclusion: These results revealed that stromal osteoblasts/alginate composites may be feasible in the repair of bone defects.