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Embryo implantation is early and complex stage of pregnancy begins when competent blastocyst makes a physiological attachment to receptive endometrium. Expression of numerous molecules are essential for initiation of pregnancy. leukemia inhibitory factor (LIF) is essential cytokines required for priming uterus to make it receptive for implantation. In mice, the ovarian estrogen regulated expression of LIF is absolutely required for implantation. Golden hamster showed ovarian estrogen independent process of embryo implantation. Hence, the regulation of LIF in uterus of golden hamster during early pregnancy is still ambiguous. In this study, we explored the possible regulation of LIF by uterine factor and their spatio-temporal localization and expression in the uterus of golden hamster during early pregnancy and pseudopregnancy. We further demonstrated their ability to activate prostaglandin synthesizing enzymes to achieve successful pregnancy. We used immunohistochemistry, quantitative and semiquantitative PCR to achieve the objectives. We observed the expression of LIF in all the day of early pregnancy and pseudopregnancy in the uterus of hamster. Their m-RNA was found to be upregulated around the day of implantation and decidualization. LIF showed high expression in D3 pseudopregnancy. LIF was found to be regulated by estrogen in ovariectomized uterus and significantly reduced expression of LIF was observed in letrozole treated uterine horn. Downregulated expression of prostaglandin synthesizing enzymes was observed in anti-LIF antibody treated uterus. Together, these findings highlights that uterine factor regulated LIF mediate their action via activating prostaglandin synthesizing enzymes to make uterus receptive for successful early pregnancy in hamster.

Highlight

• Expression of LIF in uterus during pregnancy in golden hamster is independent from the presence of blastocyst

• LIF is regulated by estrogen in ovariectomized hamster

• Expression of LIF mRNA is downregulated in letrozole treated uterine horn in day 5 of pregnancy indicating the possibility of their regulation by uterine estrogen in golden hamster

• Prostaglandin synthesizing enzyme and LIF might be associated with the activation of inflammatory signals which are essential for successful establishment of early pregnancy in golden hamster.