Growth behavior, matrix production, and gene expression of human osteoblasts in defined cylindrical titanium channels

The purpose of the current study was to investigate the effect of different diameters of cylindrical titanium channels on human osteoblasts. Titanium samples having continuous drill channels with diameters of 300, 400, 500, 600, and 1000 μm were put into osteoblast cell cultures that were isolated from 12 adult human trauma patients. Cell migration into the drill channels was investigated by transmitted‐light microscopy. The DNA content in the drill channels was measured photometrically, collagen type I production was analyzed by enzyme‐linked immunosorbent assay (ELISA) and osteocalcin gene expression by reverse transcriptase–polymerase chain reaction (RT‐PCR). Formation of mineralized tissue was assessed by microradiographs of histological sections. Within 20 days, cells grew an average of 838 μm (±128 μm) into the drill channels with a diameter of 600 μm and were significantly faster (p < 0.05) than in all other channels. Cells produced significantly more osteocalcin messenger RNA (mRNA) in 600‐μm channels (p < 0.05) than they did in 1000‐μm channels and demonstrated the highest osteogenic differentiation. The channel diameter did not influence collagen type I production. The highest cell density was found in 300‐μm channels (p < 0.05). The DNA content of the channels linearly decreased with increasing channel diameters. After 40 days of culture, the proportion of mineralized tissue at the mouth section amounted to 6% in 300‐μm channels and to 9–11% in 400–600‐μm channels. In 1000‐μm channels, only traces of mineralization were detected. Our data suggest that the diameter of cylindrical titanium channels has a significant effect on migration, gene expression, and mineralization of human osteoblasts. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 325–334, 2004