Figure 3.

Altered response of VEGF^188/188 chondrocytes to hypoxia. Hind limbs from WT and VEGF^188/188 embryos were cultured in normoxia (21% O₂) or hypoxia (0.5% O₂) for 48 hours. (a) Sections were stained with TUNEL (green) and DAPI (blue). Measurements were performed in fixed areas in the resting and proliferating chondrocyte zones, as indicated. Scale bar: 150 μm. (b) Magnified view of TUNEL-stained resting chondrocyte zone of limbs cultured in hypoxia (turned 90° clockwise). (c) Quantification of total cell number and percentage of apoptotic cells (of total cell number) showing lack of growth inhibition in hypoxia and increased hypoxia-induced apoptosis in the resting chondrocyte zone of VEGF^188/188 limbs as compared with WT; n = 4–5; significant differences are ^§P < 0.05 versus normoxia of the same genotype (effect of condition); *P < 0.05 versus WT in the same condition (effect of genotype). These effects could be partially or completely rescued, respectively, by supplementation of rmVEGF₁₆₄ to the mutant limbs (n = 4–5; *P < 0.05 versus WT and ^°P < 0.05 versus VEGF^188/188 in the same condition (effect of supplementation).