Figure 4

p38 MAPK activity is required for CNP-induced hypertrophy. E15.5 tibiae were isolated and incubated with or without CNP (1 μM) and DMSO or SB202190 (10 μM). Hematoxylin and Eosin staining of tibia sections after six days of culture show that p38 inhibition reversed CNP-induced expansion of the hypertrophic zone (A). Tibiae were stained with Alizarin Red and Alcian Blue, and representative images demonstrate increased bone growth by CNP and the reversal of these effects upon p38 inhibition (B). The area of the mineralized zone (red) was measured as absolute area (C, bottom) and as a percentage of total area (C, top), demonstrating that CNP-treated bones displayed significantly smaller mineralized area in relation to the whole bone area. This was reversed upon p38 inhibition. Representative images are shown, while all data represent means ± SD of four independent trials, each with six bones (p < 0.05).