Cell-mediated BMP-2 liberation promotes bone formation in a mechanically unstable implant environment.
The flexible alloplastic materials that are used in bone-reconstruction surgery lack the mechanical stability that is necessary for sustained bone formation, even if this process is promoted by the application of an osteogenic agent, such as BMP-2. We hypothesize that if BMP-2 is delivered gradually, in a cell-mediated manner, to the surgical site, then the scaffolding material's lack of mechanical stability becomes a matter of indifference. Flexible discs of Ethisorb were functionalized with BMP-2, which was either adsorbed directly onto the material (rapid release kinetics) or incorporated into a calcium-phosphate coating (slow release kinetics). Unstabilized and titanium-plate-stabilized samples were implanted subcutaneously in rats and retrieved up to 14 days later for a histomorphometric analysis of bone and cartilage volumes. On day 14, the bone volume associated with titanium-plate-stabilized discs bearing an adsorbed depot of BMP-2 was 10-fold higher than that associated with their mechanically unstabilized counterparts. The bone volume associated with discs bearing a coating-incorporated depot of BMP-2 was similar in the mechanically unstabilized and titanium-plate-stabilized groups, and comparable to that associated with the titanium-plate-stabilized discs bearing an adsorbed depot of BMP-2. Hence, if an osteogenic agent is delivered in a cell-mediated manner (via coating degradation), ossification can be promoted even within a mechanically unstable environment.
Hägi
Tobias T
TT
Center of Regenerative Medicine for Skeletal Tissues, Department of Clinical Research, University of Bern, Bern, Switzerland.
Wu
Gang
G
Liu
Yuelian
Y
Hunziker
Ernst B
EB
D000818:Animals; D001696:Biomechanical Phenomena / Q000502:physiology; D055396:Bone Morphogenetic Protein 2 / Q000378:metabolism*; D008297:Male; D008853:Microscopy; D010012:Osteogenesis / Q000502:physiology*; D019736:Prostheses and Implants; D051381:Rats; D017208:Rats, Wistar
D055396:Bone Morphogenetic Protein 2