RUNX-2, DLX-5, OPG, RANKL, RANK and CD31 expression in growth plate (n = 23). Longitudinal sections of the three investigated histological zones defined as calcification zone (CZ), hypertrophic zone (HZ) and proliferating zone (PZ) were stained with hematoxilin and eosin (HE) (A) and Immunhistochemical staining with specific mABs for RUNX-2 (B), DLX-5 (C), OPG (D), RANKL (E), RANK (F) were shown in one representative sample including one representative isotype control (H). Large arrowheads indicate the area of the insert (scale bar equals 50 μm), small arrowheads indicate specific cells. Hypertrophic chondrocytes expressed RUNX-2 (B) and DLX-5 (C). Multinucleated RANK+ chondroclasts with brush borders were found in the CZ (F), and vessels in newly formed bone but not in POCs expressed CD31 the marker for mature endothelial cells (G).