Estrogen receptor expression in lumbar intervertebral disc of the elderly: gender- and degeneration degree-related variations.

Objectives: Sexual dimorphism does occur in intervertebral disc (IVD) degeneration. The involvement of estrogen on IVD health has been well reported in recent years. The estrogen receptors (ER) are the main mediators of estrogen action. ER might play specific roles in the sexual variations of the IVD degeneration.

Methods: Thirty-six elderly patients with lumbar disc degeneration were selected and graded using Pfirrmann's system based on MRI images. Differences of ERα and ERβ immunoreactivity staining in nucleus pulposus of each sex and degeneration degree were recorded and compared.

Results: Both cytoplasmic and nuclear staining of ERα and ERβ immunoreactivity were observed in the nucleus pulposus cells. ERα and ERβ expression significantly decreased along with the aggravation of IVD degeneration both in males and females. Expression of ERα and ERβ protein in nucleus pulposus of males was significantly higher than that of females.

Conclusions: Gender-specific expression of ER might play a part in sexual dimorphism of IVD degeneration. Gender and degeneration condition differences should be taken into account when the effects of estrogen on IVD metabolism are studied further.