Figure 2. Expression of specific osteoblast-associated genes were upregulated in wild-type hypertrophic zone compared to proliferative zone and were suppressed by transgenic expression of SOX9.

1^st and 3^rd panels: LCM and qPCR was used to quantitatively assess gene expression in specific genes known to be expressed in the hypertrophic zone (Mef2c, Mef2d, Col10a1, Alpl) or predominantly in trabecular bone (Mmp9, Mmp13, Vegfa, Sp7, Runx2, Col1a1, Ibsp, Bglap). For many of the genes expected to be high in the trabecular bone, their expression was already beginning to increase in the hypertrophic zone. RZ, resting zone; PZ, proliferative zone; HZ, hypertrophic zone; TB, trabecular bone. 2^nd and 4^th panels: expression of these genes in the proliferative zone and hypertrophic zone was assessed in Col2a1-cre Sox9-GFP transgenic mice (Tg, open circle) versus Col2a1-cre only littermates (WT, closed circle). For some of these genes (Mmp9, Mmp13, Col1a1, Ibsp), the physiological upregulation of gene expression in the hypertrophic zone was suppressed by the presence of the Sox9 transgene. (Number of animals, N=6)