Estrogen Deficiency Exacerbates Intervertebral Disc degeneration Induced by Spinal Instability in Rats.

STUDY DESIGN: An experimental animal study of osteoporosis and intervertebral disc degeneration.

OBJECTIVES: The aim of this study was to clarify the effects of estrogen deficiency and supplement on cervical intervertebral disc degeneration (IDD) induced by bilateral facetectomy in rats.

SUMMARY OF BACKGROUND DATA: The relationship between intervertebral disc degeneration (IDD) and osteoporosis (OP) are still controversy with the wide prevalence in aged people.

METHODS: Seventy-two Sprague-Dawley female rats were randomly divided into OVX (bilateral ovariectomy) group, FR (bilateral facetectomy of C4-6) group, FR-OVX group, ERT (17β-estradiol supplement to the FR-OVX rats) group and Sham group. Specimens of C4-6 segment were harvested at 12 and 24 weeks. The microstructures and morphology of C5 vertebrae, vertebral endplate lesions and calcification, and IDD of C5/6 disc were evaluated by micro-CT and histology. The protein and gene levels of aggrecan, Col2α1, matrix metalloprotease (MMP)-3 and MMP-13 in the C5/6 and C4/5 discs were measured.

RESULTS: Micro-structures of C5 vertebral body was weakened significantly after ovariectomy, while restored effectively with 17β-estradiol supplementation. The facetectomy led to significant IDD, while the IDD was aggravated when combined with OVX. The IDD was alleviated effectively in rats of the ERT group, and similar to the FR group in intervertebral disc height, vertebral endplate lesions and calcification, and disc degeneration scores. In addition, the estrogen supplement maintained the extracellular matrix by decreasing MMP-3 and MMP-13, and increasing aggrecan and Col2α1 expression.

CONCLUSIONS: The present study demonstrated that estrogen deficiency exacerbated intervertebral disc degeneration induced by spinal instability, while estrogen supplementation alleviated the progression of disc degeneration.

LEVEL OF EVIDENCE: N/A.