The repair of osteochondral defects is a continuous challenging area of orthopedic surgery. Although some (pre)clinical tries have achieved success in repairing osteochondral defects, there is no clinically accepted and complete repair method for osteochondral defects. Thus, there is a demand for a new medical repair procedure to outperforms currently used orthopedic surgery.
Tissue engineering using scaffolds holds the potential for regeneration of osteochondral defects. Scaffolds in tissue engineering strategies play a critical role, because the scaffolds represent a wide range of in vivo possibilities that can be tailored for regeneration of osteochondral defects. Thus, the design and development of various scaffolds is an essential means for achieving scaffolds with desired and well-developed properties. The aim of this thesis is the development of hybrid scaffolds for regeneration of osteochondral defects.
In the chapter 2, biphasic calcium phosphate (BCP) scaffolds composed of hydroxyapatite (HAP) and β-tricalcium phosphate (β-TCP) was prepared by polyurethane foaming (gas foaming) fabrication. The prepared BCP scaffolds have the interconnected pores with a pore size ranging from 300 ㎛ to 800 ㎛ and a porosity ranging from 75% to 85%. In addition, the compressive strength of the scaffolds can be controlled by the foam density and sintering temperature. In in vitro and in vivo tests, it was confirmed that the BCP scaffolds manufactured by gas foaming can be effectively used as a bone scaffold, which is biocompatible and has the ability to induce bone differentiation and repair.
In the chapter 3, hybrid scaffolds composed of hyaluronic acid (HA) and collagen was prepared and evaluated for cartilage regeneration. The hybrid scaffolds were prepared by adding different concentrations of collagen to HA. The prepared HA/collagen hybrid scaffolds exhibited a three-dimensional structure with interconnected pores. The HA/collagen hybrid scaffolds showed an increase in tensile strength with increasing collagen concentration. The degradation period of the HA/collagen hybrid scaffolds in vitro increased with increasing collagen concentration. The cell growth in the HA/collagen hybrid scaffolds increased with increasing collagen concentration for 2 weeks of cell culture. After the hybrid scaffolds with different collagen concentrations were implanted into cartilage defects of rabbit ears for 3 months, the GAG concentration of the hybrid scaffolds was higher than the HA scaffold itself. Therefore, it was concluded that the collagen-containing porous scaffolds can be effectively used for cartilage repair.
In the chapter 4, the biphasic scaffold was fabricated by placing the freeze-dried chondral phase over the HAP and β-TCP scaffold prewetted with HA/atelocollagen solution. As the animal test results, the ICRS score was similar in cell–biphasic scaffold as group Ⅰ(9.0 score), only the biphasic scaffold as group II (9.1 score), and autologous transplantation as group IIIa (9.1 score), followed by autologous chondrocyte as group IIIb (7.4 score) and the defects empty as group IV (6.2 score). Except for three defects noted in group IV, all defects were filled with cartilaginous or fibrous tissue. The indentation study showed that the maximum loads and time constant of group I, II, and IIIa defects were comparable to that of native cartilage, whereas the equilibrium loads of these groups were slightly greater than that of native cartilage. In conclusion, this chapter showed the regeneration of a rabbit osteochondral defect by using a biphasic osteochondral composite using a chondral phase consisting of HA and atelocollagen and an osseous phase consisting of HAP and β-TCP.
In this thesis, we successfully prepared a series of hybrid scaffolds. The in vivo bone and cartilage engineering by using hybrid scaffolds has been shown a high potential in the defect regeneration of the animal models. Thus, the hybrid scaffolds may have big impact in tissue engineering.