Morphometric analysis of chondrocyte apoptosis and degeneration of vertebral cartilage endplate in rats / 复旦学报（医学版）

ABSTRACT

Objective To investigate the impact of aging and weight bearing on cartilage endplate morphology and chondrocyte apoptosis in rats. Methods The bipedal rat model (n=45) was developed by forelimb amputation and special breeding methods. The normal rats of the same age served as the control group (n=40). When the rats became 3, 6, 9, and 12 months old, 8 rats randomly selected from each group were sacrificed and paraffin-embedded mid-sagittal sections of the L4-5 spine were obtained. Sections were stained with hematoxylin and eosin and the TUNEL procedure was performed. The numbers of apoptotic cells and viable cells in the cartilage endplates of the intervertebral discs were counted, the thickness of the cartilage endplate was measured and the degree of impairment of the cartilage endplate was evaluated. Results Apoptosis first appeared in the cartilage endplate, then increased with aging and resulted in a remarkable decrease in cell density. The apoptotic rate of chondrocytes within the cartilage endplate of the bipedal rat model group was significantly higher than the control group at the 6-month time point. A statistically significant difference was observed in the bipedal rat model group between the 6-month time point and 9-month time point (P<0.05). Correlation analyses indicated that there was a highly negative correlation between the number of the viable cells of the cartilage endplate and the degree of the cartilage endplate degeneration (r=-0.97, P<0.05). Compared with the naturally aged group, the bipedal rat model group experienced more severe degeneration in the structure of the cartilage endplate, more obvious thickening of the cartilage endplate's calcified layer, and more defects in the structure of the cartilage. Conclusions Besides aging, weight bearing is probably a key factor of the increase of chondrocyte apoptosis and the degeneration of vertebral cartilage endplate.