A histological evaluation on self-setting α-tricalcium phosphate applied in the rat bone cavity

This study aimed to elucidate the biological effects of a self-setting tricalcium phosphate bone substitute (BIOPEX®) applied in rat femoral cortical bone cavities. Narrow penetrations through the cavity and bone marrow were prepared to obtain cellular sources. In the experimental group at day 1, a thin cell layer intruded into a narrow space between the grafted BIOPEX® and the bottom of the cavity. From days 5 to 10, a range of tartrate-resistant acid phosphatase (TRAPase)-reactive osteoclasts accumulated on the surface of the BIOPEX® facing the bottom of the cavity, whilst many alkaline phosphatase (ALPase)-positive osteoblasts were localized on the bone surface opposing the BIOPEX®. However, at day 20, osteoblasts were localized neighboring the osteoclasts on the BIOPEX®, and deposited bone matrices onto this material, implying a coupling between osteoclasts and osteoblasts. At days 30 and 40 post-operation, small remnants of BIOPEX® particles were present in the new bone with a profile of compact bone. Thus, BIOPEX® is resorbed by osteoclasts, and succeeded by osteoblastic bone apposition with a coupling of osteoclasts and osteoblasts at the later stage. In conclusion, the use of BIOPEX® provides adequate bone regeneration with the profile of compact bone.