Apoptosis is elevated in 2 week ColXN617K and C/X growth plate cartilage.

(A) Representative 2 week wildtype (Wt), Xbp1CartΔEx2, ColXN617K and C/X tibial growth plate sagittal cryosections analysed by TUNEL with DAPI counterstaining; HZ—hypertrophic zone. Boxes inset indicate magnified areas of the hypertrophic zones containing TUNEL-positive chondrocytes. (B) TUNEL analysis of at least 6 tibial growth plate sections from each of 3 Wt, Xbp1CartΔEx2, ColXN617K, and C/X mice, expressed as the number of TUNEL-positive chondrocytes in the hypertrophic zone as a percentage of the total number of chondrocytes per zone (as defined by DAPI-stained nuclei), and showing standard deviation around the mean. (C,D) Representative 2 week (C) ColXN617K and (D) C/X tibial growth plate cryosections, showing the distribution of TUNEL-positive cells along the antero-posterior axis of ColXN617K and C/X hypertrophic zones, as demarcated by 10 consecutive columns (1–10) of arbitrary width. Plots depict the number of TUNEL-positive chondrocytes in each column as a percentage of the total number of chondrocytes per column (as defined by DAPI-stained nuclei), from the same ColXN617K and C/X mice as analysed in (B), and showing standard deviation around the mean. Statistical analysis performed using Student’s t-test, ** p < 0.01, *** p < 0.001.