The response to estrogen deprivation on cartilage collagen degradation markers; CTX-II is unique compared to other markers of collagen turnover

ABSTRACT: INTRODUCTION: The urinary level of type II collagen degradation marker CTX-II is increased in postmenopausal women and in ovariectomized rats, suggesting that estrogen deprivation induces cartilage breakdown. Here we investigate whether this response to estrogen holds true for other type II collagen turnover markers known to be affected in osteoarthritis, and whether it relates to its presence in specific areas of cartilage tissue. METHODS: The type II collagen degradation markers CTX-II and Helix-II were measured in body fluids of pre- and postmenopausal women and of ovariectomized rats receiving estrogen or not. Levels of PIIANP, a marker of type II collagen synthesis, were also measured in rats. Rat knee cartilage was analyzed for immunoreactivity of CTX-II and PIIANP and for type II collagen expression. RESULTS: As expected, urinary levels of CTX-II are significantly increased in postmenopausal women and in estrogen deprived rats, only transiently in the latter. However, in neither case were these elevations paralleled by a significant increase of Helix-II levels. Nor did PIIANP levels change at any time. CTX-II immunoreactivity and collagen expression were detected in different cartilage areas. The upper zone is the area where CTX-II immunoreactivity and collagen expression reflected best the differences in urinary levels of CTX-II measured in response to estrogen. However, correlations between urinary levels of CTX-II and tissue immunostainings in individual rats were not statistically significant. CONCLUSIONS: We found only a small effect of estrogen deprivation on cartilage. It was detected by CTX-II, but not by other type II collagen turnover markers typically affected in osteoarthritis.