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 function, including embryo implantation and placentation. Expression of mRNA for TIMP-1 and TIMP-2 was examined by Northern analysis of endometrial RNA derived from steroid-treated ovariectomized ewes and from intact 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 progesterone. In cyclic and pregnant animals, abundance remained low until Day 10 and then increased, with high abundance continuing to Day 20 in the pregnant animals, Two transcripts for TIMP-2 were detected in ovine tissues-the 3.5-kb transcript and, in greater abundance, the 1.0-kb transcript. In ovariectomized awes, endometrial abundance of both transcripts was low, and it decreased following estrogen treatment but was 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 very low levels by Day 20. In contrast with this pattern of regulated expression of TIMP, mRNA for proMMP-1 and for proMMP-3 was not detectable in any of the same tissues by Northern analysis, TIMP-1 protein was immunolocalized to both epithelium and stroma of intact endometrium, and the intensity of immunostaining was correlated with mRNA levels. TIMP-1 was secreted by both epithelial and stromal cells in primary culture, 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 of TIMP in the endometrium remains to be established.