Figure 5.
Effect of MMP-9 deficiency on number and distribution of TRAP+ cells in developing metatarsals. Litters of E17, E18, and E19 embryos were obtained from MMP-9+/− and MMP-9−/− parents. The embryos were genotyped as MMP-9+/− or MMP-9−/−. Metatarsal triads were analyzed with respect to number of nuclei of TRAP+ cells localized outside or inside the calcified cartilage. Means ± SD were calculated for each age group and genotype. Total numbers of embryos were as follows: at E17, 12 MMP-9+/− and 11 MMP-9−/− (pool of 3 litters); at E18, 31 MMP-9+/− and 20 MMP-9−/− (pool of 7 litters); and at E19, 9 MMP-9+/− and 8 MMP-9−/− (pool of 3 litters). Mean counts outside the calcified cartilage are shown by a block to the left of the zero axis, and mean counts inside the calcified cartilage by a block to the right. Each horizontal bar resulting from the alignment of these two blocks represents the mean number of total nuclei in one section of a metatarsal triad. At E18 and E19, MMP-9−/− and MMP-9+/− metatarsals differed significantly with respect to both total number of nuclei of TRAP+ cells and their proportion in the calcified cartilage (P < 0.05). In contrast, at E17 no significant differences were found.