Rat Bone Marrow Stromal Cell-Conditioned Medium Promotes Early Osseointegration of Titanium Implants

Purpose: To enhance the stability of titanium (Ti) implants using conditioned medium (CM) derived from rat bone marrow stromal cell (BMSC). Materials and Methods: BMSCs were isolated from rat femurs and grown in culture, and the culture medium was used as CM. The CM was immobilized on the surface of Ti implants with calcifying solution. The topology of the Ti implants after immobilization of CM was observed by scanning electron microscopy (SEM). The Ti-immobilized CM was analyzed by liquid chromatography with tandem mass spectrometry. The adhesiveness and the osteogenic differentiation of BMSCs grown on CM-coated discs were analyzed by reverse-transcription polymerase chain reaction. Ti implants with specimen-immobilized CM labeled with quantum dots (QDs) were placed into rat femurs. The localization of the CM was detected by in vivo imaging at 1, 7, 14, and 28 days after implantation. The removal torque test and histologic bone implant contact (BIC) were also analyzed. Results: Rat BMSC-CM was successfully immobilized on Ti implants. The immobilized CM contained about 2000 proteins, including collagen type I, bone sialoprotein, fibronectin, and vascular endothelial growth factor that are important in new bone formation. CM promoted cell adhesion and osteocalcin gene expression of rat BMSCs. The labeled CM remained associated with the Ti implant at 1, 7, 14, and 28 days postimplantation. The removal torque value and BIC of Ti implants with immobilized CM were higher than those of control implants on days 1, 7, and 14 after implantation. Conclusion: Immobilized CM components on the surface of Ti implants promoted integration into bone during an early stage.