Abstract
Contact guidance is the tendency of cells to be guided by the shape of the substratum to which they are attached. Although contact guidance has been exhibited by many kinds of cells, contact guidance of osteoclasts on grooved substrata has not been examined. The present study investigated how osteoclasts are guided by grooved substrata. Four types of titanium-coated grooved substrata were used. Osteoclast precursor cells were placed on the substrata and stimulated with agents promoting differentiation of osteoclasts according to the supplier's protocol. Observation with a stereoscopic microscope confirmed the cells were positively stained with Tartrate- Resistant Acid Phosphatase (TRAP) on the titanium substrata, indicating they were osteoclastic cells. SEM observation revealed the osteoclastic cells were polygonal or round in shape, arranged in a disorganized pattern on the smooth substratum. The orientation index (OI) for contact guidance was calculated as the perpendicular length divided by horizontal length. The cells on the micro substratum (0.2-0.4 μm-deep groove) showed a significantly lower OI than those on the narrow substratum (1.5 μm-deep grooves with a 3 mm pitch comprising a 1 μm-wide groove and a 2 μm-wide ridge) or the wide substratum (1.5 μm-deep grooves with a 6 mm pitch comprising a 2 μm-wide groove and a 4 μm-wide ridge) at 5 days. These findings indicate that a significantly lower proportion of osteoclasts were aligned on the micro substratum than on the narrow or wide substrata.
In conclusion, the present study demonstrated that the grooved surface of the substratum can control the orientation of osteoclasts. Peri-implant bone remodeling requires coordinated activity by osteoclasts and osteoblasts. These findings may lead to changes in the surface design of implants to promote improved bone remodeling around the implant.
