Figure 4. ERK activation is essential for Cx43-induced HO.

(A) MC-3T3 cells were induced in osteogenic medium and exposed to U0126 for 2 weeks. Calcium deposits were detected by Alizarin Red S at week 2, and ALP staining was performed at week 1. (B) Calcium deposits and ALP activity was quantified. (C) Tenotomy mice were treated by intraperitoneal or local injection of U0126 every 3 days. Local injection of DMSO was served as the control. HO was visualized by a weekly radiograph (One-way ANOVA, n = 5, *p < 0.05 vs the control; no significant difference was observed between the intraperitoneal and local injection groups). (D) The HO volumes were quantified. (E) At week 8, three-dimensional reconstruction (Left), cross-section (Right upper) and sagittal section (Right below) of microCT scans of the tenotomy mice. The red, green and blue lines represent the cross, sagittal and coronal plane in other sections, respectively. (F) The HO volumes were quantified. (G) The bone mineral density (BMD) of HO was qualified. (t- test, n = 3, *p < 0.05).