FIG. 5.

Shows cells that are still in the cell cycle in the patellar tendon at E17.5 (A), P1 (B), P7 (C), and P14 (D), using an antibody against Ki67 (red stain). Nuclei are stained blue with DAPI, tenocytes are green, using the ScxGFP reporter mouse line. Cycling cells in the connective tissue of the epitenon are GFP-negative (arrowheads), whereas tenocytes in the cell cycle are GFP-positive (arrows). Scale bar=100 μm. (E) shows counts of cycling cells in the patellar tendon at each stage (mean±SEM) gained by counting Ki67-positive cells from 10 random sections from 3 knee joints at each stage. The asterisk represents statistical significance (p=0.3387 at E17.5, p=0.338 at P1, p=0.001 at P7, and p=0.0001 at P14). ScxGFP, scleraxis-green fluorescent protein.