Dysregulation of EGF Family of Growth Factors and COX-2 in the Uterus during the Preattachment and Attachment Reactions of the Blastocyst with the Luminal Epithelium Correlates with Implantation Failure in LIF- Deficient Mice

Abstract

Various mediators, including cytokines, growth factors, homeotic gene products, and prostaglandins (PGs), participate in the implantation process in an autocrine, paracrine, or juxtacrine manner. However, interactions among these factors that result in successful implantation are not clearly understood. Leukemia inhibitory factor (LIF), a pleiotropic cytokine, was shown to be expressed in uterine glands on day 4 morning before implantation and is critical to this process in mice. However, the mechanism by which LIF executes its effects in implantation remains unknown. Moreover, interactions of LIF with other implantation-specific molecules have not yet been defined. Using normal and delayed implantation models, we herein show that LIF is not only expressed in progesterone (P4)-primed uterine glands before implantation in response to nidatory estrogen, it is also induced in stromal cells surrounding the active blastocyst at the time of the attachment reaction. This suggests that LIF has biphasic effects: first in the preparation of the receptive uterus and subsequently in the attachment reaction. The mechanism by which LIF participates in these events was addressed using LIF-deficient mice. We observed that while uterine cell-specific proliferation, steroid hormone responsiveness, and expression patterns of several genes are normal, specific members of the EGF family of growth factors, such as amphiregulin (Ar), heparin-binding EGF-like growth factor (HB-EGF), and epiregulin, are not expressed in LIF(-/-) uteri before and during the anticipated time of implantation, although EGF receptor family members (erbBs) are expressed correctly. Furthermore, cyclooxygenase-2 (COX-2), an inducible rate-limiting enzyme for PG synthesis and essential for implantation, is aberrantly expressed in the uterus surrounding the blastocyst in LIF(-/-) mice. These results suggest that dysregulation of specific EGF-like growth factors and COX-2 in the uterus contributes, at least partially, to implantation failure in LIF(-/-) mice. Since estrogen is essential for uterine receptivity, LIF induction, and blastocyst activation, it is possible that the nidatory estrogen effects in the P4-primed uterus for implantation are mediated via LIF signaling. However, we observed that LIF can only partially resume implantation in P4-primed, delayed implanting mice in the absence of estrogen, suggesting LIF induction is one of many functions that are executed by estrogen for implantation.

Maternal heparin-binding-EGF deficiency limits pregnancy success in mice

“…9), supporting the view that reduced preimplantation P 4 secretion from the loss of HB-EGF doest not disrupt P 4 's role in uterine receptivity. Because estrogen is also critical for uterine receptivity, we examined the effect of reduced preimplantation E 2 secretion on uterine expression of leukemia inhibitory factor (LIF), an E 2 -target gene (34), and found that Lif was expressed in uterine glands in both WT and Hbegf Ϫ/Ϫ females on day 4 morning (SI Fig. 9).…”

Uterine and placental KISS1 regulate pregnancy: what we know and the challenges that lie ahead

“…Based on in situ analyses, Lif exhibits a biphasic expression pattern in the mouse uterus on D4 of pregnancy. In the morning it is expressed in the glandular epithelium and in the evening it is expressed in stromal cells at the site of embryo attachment (Song et al 2000, Song & Lim 2006. These observations suggest that on D4, LIF has two roles: first, in the preparation of the uterus, and second, in the attachment of the embryo to the endometrial lining.…”

“…This is based on the observations that the expression of uterine Lif is upregulated at ovulation and that Lif is not expressed in the uterus during experimentally induced delayed implantation but is rapidly induced following an injection of estrogen (Bhatt et al 1991, Song et al 2000. Using an RNase protection assay, Chen et al (2000) confirmed that estrogen rapidly upregulates uterine Lif expression and further demonstrated that LIF can replace nidatory estrogen at inducing both implantation and decidualization in ovariectomized mice.…”

Molecular cues to the anti-implantation effect of nano-puerarin in rats

“…LIF acts on the uterine epithelium in an autocrine/paracrine manner, and in vitro LIF stimulates proliferation of stromal fibroblasts (Salamonsen et al 1997). The uterine effect of LIF seems to be mediated via Hbegf since Lif-/-mice show deficient expression of Hbegf (Song et al 2000). Thus, the cell cycle regulatory signalling pathways involved in decidualization are under the commands of Hbegf, Hoxa10 and Lifr.…”