Titanium Delivery of Osteoblastic Cell Sheets: An In Vitro Study

We hypothesized that maximizing the number of cells on titanium implants would enhance its biological and bone-integration capabilities as a bone anchorage device. The purpose of this study was to determine the feasibility of fabricating osteoblastic cell sheets, combining them with titanium materials, and controlling their function. Rat femur-derived bone marrow cells cultured on poly(N-isopropylacrylamide) (PIPAAm) dishes were harvested in sheet form by exploiting temperature-responsive hydrophobic to hydrophilic conversion of the dish and subsequently transferring them to titanium disks. Cell sheets remained adherent and spread on micro-roughened titanium surfaces but not on machined surfaces. The post-transfer alkaline phosphatase (ALP) activity of the cell sheets responded to the presence or absence of dexamethasone and was increased by pre-treatment with the osteogenic amino-acid derivative N-acetyl cysteine (NAC) in a dose-dependent manner. Double-layering cell sheets on titanium enhanced ALP activity twofold compared to single sheets. Titanium implants enfolded with autologous osteoblastic cell sheets showed 2.5-times stronger bone-implant integration than controls in a rat femur model. We show that micro-roughened titanium materials can be combined with osteoblastic cell sheets to improve cellular supply at the implant interface. Furthermore, cell sheet function can be controlled and enhanced by biologic agents and technical modifications.