Abstract
To investigate the mitigation effect and mechanism of oestrogen and PTH on disc degeneration in rats after ovariectomy, as well as on Wnt/β-catenin pathway activity, thirty 3-month-old rats were ovariectomized and divided into three groups. Ten additional rats were used as controls. Eight weeks later, the rats were administered oestrogen or PTH for 12 weeks, and then discs were collected for tests. Results showed that nucleus pulposus cells in the Sham group were mostly notochord cells, while in the OVX group, cells gradually developed into chondrocyte-like cells. Oestrogen or PTH could partly recover the notochord cell number. After ovariectomy, the endplate roughened and endplate porosity decreased. After oestrogen or PTH treatment, the smoothness and porosity of endplate recovered. Compared with the Sham group, Aggrecan, Col2a and Wnt/β-catenin pathway expression in OVX group decreased, and either oestrogen or PTH treatment improved their expression. The biomechanical properties of intervertebral disc significantly changed after ovariectomy, and oestrogen or PTH treatment partly recovered them. Disc degeneration occurred with low oestrogen, and the underlying mechanisms involve nutrition supply disorders, cell type changes and decreased Wnt/β-catenin pathway activity. Oestrogen and PTH can retard disc degeneration in OVX rats and enhance Wnt/β-catenin pathway activity in nucleus pulposus.
Highlights
Disc degeneration[10,11,12,13]
In the Sham group, nucleus pulposus (NP) cells were mostly notochord cells, and only a small number of chondrocyte-like cells emerged at the NP edge
In the OVX group, the number of notochord cells in the NP was significantly reduced, and many clustered chondrocyte-like cells appeared, surrounded by a mucoid degenerated matrix
Summary
Disc degeneration[10,11,12,13]. A finite element study showed that endplate stress would increase when the bone mass of the vertebral body decreased, and abnormal stress could lead to endplate calcification and obstruction of marrow contact channels, giving rise to disc degeneration[14]. The Wnt/β-catenin pathway plays an important role in development and growth of the intervertebral disc, especially for notochord cells[20,21]. Disc degeneration occurs very early in chondrodystrophoid dogs, with notochord cells in the NP gradually disappearing and being replaced by chondrocyte-like cells, and the process is accompanied by reduced Wnt/β-catenin pathway activity. Oestrogen and PTH can both act directly on the intervertebral disc, and their effects on the Wnt/β-catenin pathway in ovariectomized rats remain unclear[16,22,23]. We evaluated disc degeneration in ovariectomized rats, the ability of oestrogen or PTH to alleviate these effects and changes in the Wnt/β-catenin pathway during the process
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