Objective To investigate the expression of ceramide kinase (Cerk) and related regulation in mouse uterus during early pregnancy. Methods Several mouse models, including early pregnancy, pseudopregnancy, delayed or activated implantation, artificial decidualization, and steroid hormonal treatment were performed (n=10). Immunohistochemistry and in situ hybridization were used to detect the expression of Cerk protein and mRNA in uterus. Results Expression of Cerk mRNA and protein was strongly detected in the luminal and glandular epithelium on day 1 of pregnancy. However, Cerk mRNA and protein signals were strongly detected in the subluminal stroma surrounding the implanting blastocyst on day 5 and decidua from day 6 to day 8 whereas not in the luminal epithelium. The expression of Cerk in luminal and glandular epithelium of pseudopregnancy was similar to that of early pregnancy from day 1 to day 4 whereas on day 5 of pseudoprgenancy still with remarkable signals in the luminal epithelium. Under delayed implantation, no obvious Cerk expression was detected in the uterus. After delayed implantation was terminated by estrogen treatment and embryo implantation was initiated, both Cerk mRNA and protein were detected in the subluminal stroma surrounding the implanted blastocyst. A strong Cerk signal was detected in decidualized cells under artificial decidualization, whereas only a basal level of Cerk signal was observed in the control uterus which did not inject sesame oil. Progesterone induced a slight expression of Cerk in the luminal and glandular epithelium. Both estradiol and a combination of progesterone with estradiol strongly increased the level of Cerk signal in the luminal and glandular epithelium. Conclusion Cerk expression is under the regulation of progesterone and estrogen. The strong expression of Cerk in implantation site and decidua suggests that Cerk might play an important role during implantation and decidualization. Objective To investigate the expression of ceramide kinase (Cerk) and related regulation in mouse uterus during early pregnancy. Methods Several mouse models, including early pregnancy, pseudopregnancy, delayed or activated implantation, artificial decidualization, and steroid hormonal treatment were performed (n = 10 ). Immunohistochemistry and in situ hybridization were used to detect the expression of Cerk protein and mRNA in uterus. Results Expression of Cerk mRNA and protein was strongly detected in the luminal and glandular epithelium on day 1 of pregnancy. However, Cerk mRNA and protein signals were strongly detected in the subluminal stroma surrounding the implanting blastocyst on day 5 and decidua from day 6 to day 8 not not in the luminal epithelium. The expression of Cerk in luminal and glandular epithelium of pseudopregnancy was similar to that of early pregnancy from day 1 to day 4 whereas on day 5 of pseudoprgenancy still with remarkable signals in the luminal epithelium After delayed implantation was terminated by estrogen treatment and embryo implantation was initiated, both Cerk mRNA and protein were detected in the subluminal stroma surrounding the implanted blastocyst. A strong Cerk signal was detected in decidualized cells under artificial decidualization, and only only a basal level of Cerk signal was observed in the control uterus which did not inject sesame oil. Progesterone induced a slight expression of Cerk in the luminal and glandular epithelium. Both estradiol and a combination of progesterone with estradiol strongly increased the level of Cerk signal in the luminal and glandular epithelium. Conclusion Cerk expression is under the regulation of progesterone and estrogen. The strong expression of Cerk in implantation site and decidua suggests that Cerk might play an important role during implantation and decidualization .