Figure 5.

Transient activation of Wnt/β-catenin signaling increases the depth of superficial layer of articular cartilage.

Transgenic mice (CA-β-catER) that harbor a constitutive-active form of β-catenin fused to a modified estrogen receptor ligand-binding domain (CA-β-catER) to promoter/enhancer sequences from the Collagen 11a2 gene were generated. Two-week-old CA-β-catER transgenic mice (B) and their wild-type littermates (A) received seven daily peritoneal injections of tamoxifen (200 μg/20 μl/mouse) and were sacrificed at 5 weeks. Longitudinal sections of proximal tibial articular cartilage were stained with hematoxyline and eosin. The superficial layer was thickened in the mutant (B, double arrowed line) compared to that of the wild type mouse (A, arrow).