Expression Of Maspin In The Early Pregnant Mouse Endometrium And Its Role During Embryonic Implantation

BackgroundEmbryo implantation, the first step in a successful pregnancy, is acrucial process in mammal reproduction. The invasion of trophoblastic cellsinto the endometrium and formation of the placenta are the key steps inembryonic implantation. The ‘dialogue’ among trophoblasts, endometrialepithelial cells, and stromal cells leads to precise regulation of thedifferentiation and proliferation of trophoblast and endometrialdecidualization[1]. In addition, the invasion process involves the interactionand regulation of adhesion molecules, proteolytic enzymes, growth factors,cytokines, and vasoactive factors[2-4]. Successful blastocyst implantationdepends on invasive blastocyst, acceptive endometrium and theirsynchronization[2,5]. Comparative research has revealed striking similaritiesin the behavioral patterns of invasive trophoblastic cells and cancer cells[6].Maspin(Serpinb5-Mouse Genome Informatics) is a member of the serineprotease inhibitor family with participating in cell migration, adhesion,invasion, and apoptosis[7-8]. These processes are also critical for embryoimplantation, but the role of Maspin in embryo implantation remains poorlyunderstood. Trophoblast cell invasion is very similar to tumor infiltration,but tumor invasion is unrestrained expansion and embryo implantation isphysiological restraint invasion. Dokras[9]found that Maspin expressed inhuman placental trophoblast cell. Taken together, these results suggest that Maspin, a tumor suppressor, may play an important role in embryoimplantation.ObjectiveThe aim of the present study was to investigate the spatiotemporalexpression of Maspin in early pregnant mouse endometrium and its role inembryo implantation.MethodsReal-time quantitative PCR analysis, Immunohistochemistry, andWestern blotting were used to detect mRNA and protein expression ofMaspin in the endometria of nonpregnant and early pregnant (days0to7)mice. There are eight groups contained20mice in each experiment.In vivo: On day4of pregnancy, mice in the treated group (n=20) wereinjected in the left uterine horn with antimaspin polyclonal antibody and inthe right horn with purified rabbit IgG; control mice (n=20) were injectedonly with purified rabbit IgG in the right uterine horn. Implanted embryoswere counted on pregnant day8.Results1. FQ-PCR results showed that the mRNA expression of Maspin wasgradually increased from day0, peaked on day5(p<0.05).2. Immunohistochemistry analyses showed that the strongest signals forMaspin were found in the luminal and glandular epithelium on day5ofpregnancy.3. Western blot results showed the expression of Maspin protein inendometria of non-pregnant mice was lower than that of pregnant mice, andgradually increased from pregnant day1, peaked on pregnancy day5(p<0.05)and then decreased on day6and day7.4. Injection of antimaspin polyclonal antibody into the uterine horn inthe early morning of pregnant day4could significantly inhibit embryonic implantation, with significantly lower numbers of implanted embryos inmice that received antimaspin antibody (p<0.05).ConclusionThe expression of Maspin followed a spatiotemporal pattern in themouse endometrium during early pregnancy. The high levels of Maspin inthe mouse endometrium suggest that Maspin may be a novel moleculeinvolved in the early processes of pregnancy, especially in embryoimplantation. However, further studies are needed to understand the precisemechanism underlying the role of Maspin in embryo implantation.