Figure 1. Immunostaining of IdU showed replicating cells in the proliferative layer (arrowhead) and blood vessels (arrow) in the mandibular condyle of 42-day-old rats during natural growth (A). Quantitative analysis was carried out in a measurement frame in the posterior condyle. Three neighboring sections (B,C,D) were used to evaluate the cell cycle of the replicating mesenchymal cells. Negative control without primary antibody was used to quantify the total mesenchymal cells’ population (B). Cells labeled with BrdU were detected by Br-3 primary antibody (C). Cells labeled with both BrdU and IdU were detected by IU-4 primary antibody (D). Vertical bars denoted the proliferative layer. Scale bars: 400 µm for A; 50 µm for B, C, and D.