[Change of autophagy in endplate chondrocytes of rats during aging process].

OBJECTIVE: To explore the expression and significance of autophagy in endplate cartilage of rats during aging process. METHODS: The end-plate chondrocytes were isolated from 3, 6 and 12-month SD rats respectively. And the natural culture and rapamycin groups were assigned. Alizarin red staining was used to observe the morphological changes of cells. And RT-PCR was employed to detect the expressions of type II collagen, proteoglycan, SOX-9 and matrix metalloproteinase (MMP-13). The expressions of Beclin-I and LC3 were detected by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot. The rate of autophagy was observed by monodansylcadaverine (MDC) staining and methyl thiazolyl tetrazolium (MTT) for cell survival rate. RESULTS: Alizarin red staining showed that cells might reflect the process of intervertebral disc degeneration. The expressions of polysaccharide, Sox-9, type II collagen, Beclin-1 and LC3 in endplate chondrocytes significantly decreased with advancing age (P < 0.05). The incidence of autophagy significantly decreased (P < 0.05). The cell viability of each group significantly decreased (P < 0.05). Compared with control group, the cell viability of rapamycin group significantly increased (P < 0.05). CONCLUSION: During aging process, the expressions of autophagy related-gene LC3 and Beclin-1 significantly decrease with the reduced activity of end-plate chondrocyte. And autophagy activity may be correlated with the development and degeneration of intervertebral disc.