A. Representative images showing the ultrastructure of vertebral cartilage, chondrocytes and pericellular matrix (top panel, middle panel and bottom panel, respectively) at 1, 2 and 3-years (left, middle and right panels, respectively). Chondrocytes display morphologies suggestive of programmed cell death at all stages. Note prominent lacunae in 2 and 3 year samples and increase in electron density of surrounding ECM. B. Graph showing mean lacunal area at each age. Note significant increase in 2 and 3-year samples, relative to 1 year samples tested by One-way ANOVA; 1 vs 2 year P=3.26E-07, 1 vs 3 year P=0.00945, 2 vs 3 year P=0.0512. C. Graph showing percentage area occupied by cell at each age. Note significant decrease in 2 and 3 year samples, relative to 1 year samples tested by One-way ANOVA; 1 vs 2 year P=1.13E-15, 1 vs 3 year P=1.61E-10, 2 vs 3 year P=0.357. l, lacunae; v.; intracellular vacuoles; black
asterisks, vesicular debris; black
arrows denote myelin figures; white
arrows show condensed nuclear material; black
arrowhead shows discontinuity of cell membrane. Scalebar in microns.