A bone replaceable artificial bone substitute: Osteoinduction by combiningwith bone inducing agent

Bone inducing agent (BIA) isolated from Saos-2 human osteosarcoma cells was added to an artificial bone substitute composed of 980 degreesC-heated car bonate apatite (CAp) and Type I atelocollagen (AtCol) extracted from bovine tail skins (88/12 in wt/wt %), and a CAp-AtCol-BIA substitute was prepared as an osteoinductive bone substitute. Rat calvaria osteoblasts treated by the isolated BIA demonstrated significantly increased alkaline phosphatase (ALP) activity after 3 days (p < 0.05). In vitro cell attachment and prolif eration and ALP activity were investigated for the bone substitute combined with BIA. Osteoblasts cultured onto the surface of the CAp-AtCol-BIA subst itute demonstrated remarkable morphological changes such as radial spreadin g, flattening, and projecting filopodia after 5 days. In comparison with th e substitute without BIA, osteoblasts grown in the BIA-combined CAp-AtCol s ubstitute expressed significantly increased proliferation and ALP activity, respectively (p < 0.05). Both the substitutes combined with and without BI A were implanted into artificial defects created in rabbit radii. After 4 w eeks, the CAp-AtCol-BIA substitute implanted lesion was completely replaced by regenerated host bone in radiological observation whereas the substitut e without BIA was partially resorbed. No histologic abnormalities appeared in the substitute either with or without BIA.