Articular cartilage compressive stiffness following oophorectomy or treatment with 17beta-estradiol in young postpubertal rabbits.

BACKGROUND: Changes in estrogen concentrations during adolescence (contraceptives, secondary amenorrhea) may influence cartilage mechanics and therefore its capacity to respond adequately to physical demands. The purpose of this study was to investigate the influence of oophorectomy or continuous administration of estradiol on cartilage compressive properties in an immature animal model.
METHODS: Young postpubertal female New Zealand white rabbits were either oophorectomized (n=9) or underwent a sham-operation (n=8). The sham-operated animals received in addition a daily dosage of 4 mg 17beta-estradiol orally starting 3 weeks after surgery until death. After 5 months the animals were killed, and cartilage compressive properties (ramp and creep moduli) were determined at 4 defined knee joint regions by in situ indentation tests. Five age-matched rabbits were used as controls.
RESULTS: Femoral cartilage stiffness (ramp and 15-s creep moduli) and thickness in oophorectomized animals were significantly higher than those in controls or estradiol-treated animals (p<0.05 and less), but there was no difference between the latter groups. Tibial cartilage showed less obvious treatment-dependent differences. The cartilage in the medial compartment was thicker than in the lateral one, and femoral cartilage was thinner than tibial cartilage (p<0.00005), irrespective of the treatment.
CONCLUSIONS: Oophorectomy during adolescence led to increased femoral cartilage thickness and stiffness. The relevance of these findings for the development of cartilage disease has to be elucidated in the future.