TISSUE INHIBITORS OF METALLOPROTEINASES IN ENDOMETRIUM OF OVARIECTOMIZED STEROID-TREATED EWES AND DURING THE ESTROUS-CYCLE AND EARLY-PREGNANCY

Tissue inhibitors of metalloproteinases (TIMPs) have an important role in remodeling of tissues and are likely to be implicated in uterine f unction, including embryo implantation and placentation. Expression of mRNA for TIMP-1 and TIMP-2 was examined by Northern analysis of endom etrial RNA derived from steroid-treated ovariectomized ewes and from i ntact ewes during the estrous cycle and early pregnancy, Expression of mRNA for TIMP-1 (transcript size 0.9 kb), high in ovariectomized ewes , was substantially reduced by estrogen and to a lesser extent by prog esterone. In cyclic and pregnant animals, abundance remained low until Day 10 and then increased, with high abundance continuing to Day 20 i n the pregnant animals, Two transcripts for TIMP-2 were detected in ov ine tissues-the 3.5-kb transcript and, in greater abundance, the 1.0-k b transcript. In ovariectomized awes, endometrial abundance of both tr anscripts was low, and it decreased following estrogen treatment but w as stimulated by progesterone alone or progesterone in the presence of estrogen. Abundance of TIMP-2 mRNA increased from Day 4 to Day 14 of the cycle. During early pregnancy, expression of the 1.0-kb transcript increased from Day 4 to Days 12-14 and was maintained at a high level to Day 20, whereas the 3.5-kb transcript decreased after Day 14 to ve ry low levels by Day 20. In contrast with this pattern of regulated ex pression of TIMP, mRNA for proMMP-1 and for proMMP-3 was not detectabl e in any of the same tissues by Northern analysis, TIMP-1 protein was immunolocalized to both epithelium and stroma of intact endometrium, a nd the intensity of immunostaining was correlated with mRNA levels. TI MP-1 was secreted by both epithelial and stromal cells in primary cult ure, and its identity was confirmed by Western analysis, while reverse zymography demonstrated TIMP-1 and TIMP-2 along with a putative ovine TIMP-3 in the culture medium from both cell types, The precise role o f TIMP in the endometrium remains to be established.