To investigate the effect of osteoporosis and intervertebral disc degeneration on the endplate cartilage injury in rats.

OBJECTIVES

To investigate the effect of osteoporosis and intervertebral disc degeneration on the endplate cartilage injury in rats.

METHODS

A total of 48 female Sprague Dawley rats (3 months) were randomly divided into Groups A, B, C and D with 12 rats in each group. Osteoporosis and intervertebral disc degeneration composite model, simple degeneration model and simple osteoporosis model were prepared in Groups A, B and C respectively. After modeling, four rats of each group at 12th, 18th and 24th week were sacrificed. Intervertebral height of cervical vertebra C6/C7 was measured. Micro-CT was used to image the endplate of cephalic and caudal cartilage at C6/C7 intervertebral disc. Abraded area rate of C6 caudal and C7 cephalic cartilage endplate was calculated, and then C6/C7 intervertebral disc was routinely embedded and sectioned, stained with safranin O to observe histological changes microscopically.

RESULTS

At 12, 18 and 24 weeks, intervertebral disc height of C6/C7 were (0.58±0.09) mm, (0.53±0.04) mm and (0.04±0.06) mm in Group A rats, (0.55±0.05) mm, (0.52±0.07) mm and (0.07±0.05) mm in Group B rats. At 24th week, intervertebral disc height of Group A rats was significantly lower than that of Group B rats (P<0.05); intervertebral disc height of Groups A and B rats at each time point were significantly lower than that of Groups C and D (P<0.05). There was no significantly statistical difference of intervertebral disc height between Groups C and D (P>0.05). At 12 and 18 weeks, the abraded rate of C6 caudal and C7 cephalic cartilage endplate in Group A rats were significantly higher than that in Groups B, C and D rats (P<0.05); the abraded rate in Group B was significantly higher than that in Groups C and D (P>0.05). Microscopic observation of CT showed that ventral defects in C6 caudal or C7 cephalic cartilage endplate in Groups A and B appeared after 12 weeks of modeling; obvious cracks were found in front of the C6 and C7 vertebral body, and cartilage defect shown the trend of "repairing" at 18 and 24 weeks after modeling.

CONCLUSIONS

Intervertebral disc degeneration and osteoporosis can cause damage to the cartilage endplate. Co-existence of these two factors can induce more serious damage to the endplate, which has possitive correlation with intervertebral disc degeneration. Osteoporosis plays a certain role in intervertebral disc degeneration process, and accelerates the degeneration of intervertebral disc in a specific time window.