Osteogenic Growth Peptide Modulates Fracture Callus Structural and Mechanical Properties

The osteogenic growth peptide (OGP) is a key factor in the mechanism of the systemic osteogenic response to local bone marrow injury. Recent histologic studies have shown that OGP enhances fracture healing in experimental animals. To assess the effect of systemically administered OGP on the biomechanical and quantitative structural properties of the fracture callus, the present study used an integrated approach to evaluate the early stages (up to 4 weeks) of healing of unstable mid-femoral fractures in rats, which included biomechanical, micro-computed tomographic (microCT) and histomorphometric measurements. During the first 3 weeks after fracture, all the quantitative microCT parameters increased in the OGP- and vehicle-treated animals alike. After 4 weeks, the volume of total callus, bony callus, and newly formed bone was approximately 20% higher in animals administered with OGP, consequent to a decrease in the controls. The 4-week total connectivity was 46% higher in the OGP-treated animals. At this time, bridging between the fracture ends by newly formed bone was observed predominantly in the OGP-treated fractures. After 3 and 4 weeks, the OGP-treated animals showed higher biomechanical toughness of the fracture callus as compared to the PBS controls. Significant correlations between structural and biomechanical parameters were restricted to the OGP-treated rats. These data imply that the osteogenic effect of OGP results in enhanced bridging across the fracture gap and consequently improved function of the fracture callus. Therefore, OGP and/or its derivatives are suggested as a potential therapy for the acceleration of bone regeneration in instances of fracture repair and perhaps other bone injuries.