SYNOPSIS
There are many reports on the induction of new bone with synthetic bone substitutes. However, the histological reaction to scaffold, are still not completely understood. In this study we clarified the the effects on capillary differentiation and the mechanisms of bioabsorption in coral and artificial hydroxyapatite ceramic bone (ceramic bone), both of which have porous structures. The micromorphology of both coral and ceramic bone was observed by SEM, and their compressive strength was measured. In vitro, normal human dermal fibroblasts and human umbilical vein endothelial cells were co-cultured with added particles of coral and ceramic bone in experimental groups. Meanwhile, no particles were added in a control group. After co-culturing for 14 days, cell proliferation was observed with DAPI nuclear stain and capillary formation was observed with anti-human CD31 antibodies in the experimental and control groups. Next, in vivo, coral and ceramic bone particles were implanted in the dorsal subcutaneous tissue of rats, and the bioabsorption process of the respective particles was observed histologically. The coral had a porous structure with numerous tubes of 50-300μm in diameter with interconnection pathways of 50-100μm, and the ceramic bone had a porous structure with spherical pores of 100-200μm with interconnection pathways of 15-50μm. The compressive strength of coral was higher than that of ceramic bone. In vitro, cell proliferation and formation of capillaries were seen adjacent to the added coral and ceramic bone particles. In vivo, all the implanted coral and ceramic bone particles remained after 2 weeks, and many were seen to be enclosed by granulation tissue. After 4 and 6 weeks, replacement of particles by granulation tissue and phagocytosis of particles by foreign body giant cells were observed. At 8 and 12 weeks, many cases of particle disappearance were seen in the coral group, and coral particles were replaced with fibrous connective tissue. In the ceramic bone group, there were few cases of particle disappearance. These findings suggest that the porous structures of both coral and ceramic bone induce cell proliferation and capillary formation. Coral particles have greater compressive strength and bioabsorbability than ceramicone.

Key words: coral, ceramic bone, tissue affinity, capillary differentiation, bioabsorption