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Age-related and Sex-related Changes in the Intervertebral Discs and Endplates of Rats at all Spinal Levels

The intervertebral disc (IVD) and endplates change throughout life, eventually resulting in tissue degeneration, which may have clinical significance. In this study, we analyzed age-related changes in the IVD and endplate of newborn (1 mo), middle-aged (12 mo), and older (24 mo) male and female Sprague-Dawley rats. We evaluated the presence of embryonic disc cells, chondrocyte proliferation, cell death, appearance of clefts/tears, granular degeneration, cell proliferation, and cartilage disorganization in the IVD and endplate under light microscopy, according to age and sex. Chondrocyte proliferation was greater in male rats than in female rats across all age groups in the cervical region and at 1 and 24 months in the thoracic region. A strong correlation between aging and cell death in female rats was observed. In females, cell death was significantly elevated in 12 and 24-month-old rats compared with 1-month-old rats. Examining the histologic changes with aging in the IVD and endplates at all levels of the spine is obviously difficult in humans. Animal research is essential for making the transition from scientific concepts to clinical applications. The aging spine shows the greatest changes in the cervical and thoracic regions in male rats, whereas it mostly affects the lumbar region in females.