Fig 5. Decreased chondrocyte proliferation but no change in apoptosis in ColIITg^cog mice.

(A) 3 week old +/+ and c/c mice were administered with 0.01 ml/g of the nucleotide analogue BrdU 2 hours prior to sacrifice. Representative images of immunostaining for BrdU performed on tibial growth plate sections from +/+ and c/c mice are shown. BrdU positive cells are stained in black. Methyl green staining was used as a nuclear counter-stain. Three sections per slide and three slides spaced at least 75 μm apart were stained, counted and analysed. The table shows the percentage of BrdU-labelled nuclei calculated against the total number of cells in the proliferative zone. c/c mice had significantly lower proliferation rates (by 12%) when compared with +/+ (one-way ANOVA, mean ± SEM (n), * p < 0.05). (B) End-stage apoptosis (DNA fragmentation) was measured in the tibia of 3 week old +/+ and c/c mice using the DeadEnd fluorometric TUNEL system. Representative images of the tibial growth plates showing DAPI and FITC (TUNEL-positive) stained sections are shown. The relative levels of apoptosis were calculated by comparing the number of apoptotic chondrocytes (FITC-labelled nuclei) with the total number of chondrocytes (DAPI-labelled nuclei & FITC-labelled nuclei) at the vascular invasion front (VIF). Scale bar = 100 μm.