We evaluated the usefulness of atelo-collagen sponge (ACS)(TERUPLUG®, TERMO CORPORATION, Tokyo) as a carrier for Escherichia coli-derived recombinant human bone morphogenetic protein-2 (ErhBMP-2) as compared with that of atelo-peptide collagen (CL)(Cellmatrix LA, Nitta Gelatin Inc., Osaka, Japan), which we previously demonstrated to be useful for bone induction. Five micrograms of ErhBMP- 2 with either 3 mg of ACS (ACS group) or 3 mg of CL (CL group) was implanted into the calf muscle of 13 10-week-old Wistar rats. The implanted material was sampled on days 7, 14, and 21 after implantation (5 specimens each per time, group). Radiographic evaluation, histological analysis, and biochemical examinations were performed. On radiographic evaluation, no opaque shadows were observed 7 days after implantation in either group. Oval shadows were observed 14 days after implantation. Twentyone days after implantation, the area of the shadows had increased. On histological analysis, much new cartilage was observed 7 days after implantation in both groups, but immature endochondral ossification was observed in only the ACS group. Endochondral ossification was found on the outermost edge of the implant after 14 days in both groups. After 21 days, mature bone had formed. On biochemical examinations on days 7 to 14 after implantation, alkaline phosphatase (ALP) activity and the calcium (Ca) content had increased markedly in both groups. On days 14 to 21 after implantation, ALP activity and Ca content increased gradually. These findings were similar in both groups.
Our results suggest that, similar to CL, ACS is useful as a carrier for ErhBMP-2 designed to promote new bone formation.
