Spatiotemporal messenger ribonucleic acid expression of ovarian tissue inhibitors of metalloproteinases throughout the rat estrous cycle

The tissue inhibitors of metalloproteinases (TIMPs) within the ovary closel y regulate the matrix metalloproteinases, enzymes capable of degrading comp onents of the extracellular matrix. The purpose of this study was to examin e the spatial and temporal messenger RNA (mRNA) expression of the TIMPs in the ovaries of normally cycling rats. Ovaries were collected at 1100 h on e ach day of the 4-day estrous cycle, and TIMP mRNA expression was examined b y Northern blot, RT-PCR, or in situ hybridization. TIMP-1 mRNA levers were significantly higher on estrus than on any other day. Although the 1.0-kb T IMP-2 transcript did not change across the cycle, the 3.5-kb transcript dec reased significantly between metestrus and diestrus. Expression of TIMP-3 m RNA decreased significantly between proestrus and estrus. TIMP-1, TIMP-2, a nd TIMP-3 mRNAs were primarily localized to the theca, stroma, and corpora lutea (CL) on all days of the cycle, but with distinct cyclic changes. Thec al expression of TIMP-1 and TIMP-2 mRNAs was especially high immediately be fore and after ovulation. TIMP-1 and TIMP-3 mRNAs, which were low to undete ctable in the granulosa cells of preovulatory follicles, were greatly incre ased in the luteinizing cells of newly forming CL on estrus. Although. the presence of TIMP-1 mRNA in the granulosa cells of preovulatory follicles by in situ hybridization was near background levels, it was specifically iden tified in granulosa cells of follicles on all days of the cycle using laser capture microdissection and RT-PCR. Both TIMP-2 and TIMP-3 transcripts wer e up-regulated in luteinized follicles on proestrus and were present throug hout the cycle in regressing CL. In summary, the unique and dynamic express ion patterns of the TIMPs suggest that they have important, yet distinct, f unctions in the ovary. The high levels of TIMP-1 mRNA in the CL on estrus i ndicate a likely role for this inhibitor in luteal formation. The presence of TIMP 2 mRNA in regressing CL suggests an involvement in luteal demise, w hereas TIMP-3 may play a role in the health of the follicle as well as in C L regression.