Anodic oxidation and hydrothermal treatment of commercially pure titanium surfaces increases expression of bone morphogenetic protein-2 in the adherent macrophage cell line J774A.1

The surface property of commercially pure titanium (cpTi) was improved by forming a thin hydroxyapatite (HA) layer by anodic oxidation and hydrothermal treatment (HA/cpTi). We hypothesize that the adhesion of macrophages to HA/cpTi surfaces is important to the process of osseointegration. This study investigates the effect of adhesion of macrophages to HA/cpTi surfaces on the expression of bone morphogenetic protein‐2 (BMP‐2). The murine macrophage cell line J774A.1 was cultured on HA/cpTi and polished cpTi (S/cpTi). Macrophage cell adhesion was examined by SEM, 0–72 h following plating onto HA/cpTi and S/cpTi. BMP‐2 gene expression was examined by RT‐PCR analysis. The level of BMP‐2 secreted into the supernatant was measured using an ELISA assay. The extent of macrophage adhesion increased with time on both the HA/cpTi and S/cpTi surfaces, with a&#147; higher degree of spreading observed on HA/cpTi than onS/cpTi surfaces after 24 or 72 h. The ratio of BMP‐2 mRNA was higher on HA/cpTi than on S/cpTi after 24 h (0.348 vs. 0, p < 0.05) and 72 h (0.584 vs. 0.189, p < 0.05). After 24 h, secretion of BMP‐2 was detected in cultures grown on HA/cpTi, but not on S/cpTi. After 72 h, secretion of BMP‐2 was detected in cultures grown on S/cpTi, but the levels were higher in cultures grown on HA/cpTi. These findings show that macrophages have the capacity to adhere to HA/cpTi endosseous implants and provide a source of osteoinductive cytokines that may play a key role in the process of osseointegration. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2007