Tissue inhibitor of metalloproteinase-1 contributes to ovulatory dysfunction in a rat model of endometriosis

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Endometriosis causes ovarian dysfunction, but the mechanisms are unknown. These experiments utilize a rat model of surgically-induced endometriosis (Endo) which mimics reduced fecundity in endometriosis. Matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) are involved in endometriosis, but both are crucial for ovulation. Endometriotic lesions produce TIMP1, upsetting the balance of MMPs and TIMPs which can affect the ovaries and other organs of the reproductive tract. If an ovarian follicle is unable to expel the oocyte during ovulation, a phenomenon known as luteinized unruptured follicle syndrome occurs (LUFs), and LUFS is found in endometriosis. TIMP1 is required for regulation MMPs as well as other biological functions independent of MMPs. Because Endo rats have more TIMP1 localizing in the thecal layer, we hypothesized that endometriotic TIMP1 contributes to ovarian dysfunction. To determine the direct effect of TIMP1 on ovulation, peritoneal TIMP1 was modulated in Endo and Sham rats. Sham rats given TIMP1 had LUFS, fewer follicles, and poor quality embryos like an Endo rat, but Endo rats given a TIMP1 function blocking antibody were more like Sham rats with no LUFS and fecundity problems. Next, rats were given treatments mutated TIMP1 without MMP inhibitory activity (Ala-TIMP1), normal TIMP1 (rTIMP1) or PBS. Ala-TIMP1 and rTIMP1 caused LUFs and had fewer follicles and corpora lutea. Ala-TIMP1 upregulation of genes associated with extracellular matrix (Fn1, Col3a1) and angiogenesis (Vegf). Treatments of rTIMP1 caused downregulation of apoptosis genes (Casp3). Ala-TIMP1 and rTIMP1 co-immunoprecipitated TIMP1 with GRP78 and GSTA3 which are both involved in protein protection. Ala-TIMP1 complexed more to CD63 than rTIMP1 showing a MMP-independent mechanism to apoptosis inhibition. Together these data show endometriotic TIMP1 role in preventing normal follicular wall breakdown inhibiting ovulation. These studies provide evidence that novel therapies modulating TIMP1 could treat reduced fecundity in endometriosis.