Abstract
Introduction
Our previous study using microarray analysis showed that Rad (Ras associated with diabetes) was highly expressed in nonunion. The purpose of this study is to investigate the gene expression and immunolocalization of Rad, and other Ras-related G proteins: Rem1 and Rem2 in fracture/nonunion site using rat experimental models.
Hypothesis
We hypothesized that Rad had a significant role in nonunion formation.
Materials & Methods
For standard healing model, K-wire was inserted into the femur and a closed fracture was created. Nonunion model was produced by periosteal cauterization at the fracture site. At post-fracture days 3, 7, 10, 14, 21, and 28, RNA was extracted from callus or fibrous tissue for real-time PCR. At day 14, specimens were harvested for immunohistochemistry.
Results
Significant difference of Rad gene expression was not observed between standard healing fracture and nonunion at the earlier time points. In contrast, significantly higher expression in nonunion was observed at the later time points. There were no significant differences between standard healing fracture and nonunion in gene expression of Rem1 and Rem2. In immunohistochemical analysis, Rad and Rem1 were detected in the fracture site, and Rem2 was not detected. On the other hand, Rad was only detected in fibrous tissue in nonunion.
Discussion & Conclusion
Our results suggest a significant role of Rad in fracture healing and nonunion formation. Rad may become a target agent for treatment of nonunion.
