Figure 8: IHC of COL X shows the presence of weak signal in week 3 and week 4 micromass cartilage (a), whereas apoptosis assays show no apoptosis in micromass cartilage (b). Mouse decalcified P1 limb showed hypertrophic chondrocytes zone (arrows) as positive control for COL X (a). Mouse involuting MG (mammary gland) at postpartum day 4 showed apoptotic cells in mammary epithelium (arrow) that served as positive control, whereas no apoptotic cell was found at week 4 in micromass cartilage compared with positive control. mm, micromass.