Objective To investigate the expression of cytokeratin,actin and hCG,E2 and P of human hacthed blastocysts in the model.Methods Human hatched blastocysts were co-cultured with human endometrial decidualization stromal cell monolayer.The process of orientation,attachment,outgrowth and invasion in morphology were observed.Immunofluorescence staining for cytokeratin and actin,immunofluorescence measurement of hCG and radioimmunoassay measurement of E2 and P were performed.Results Blastocysts attached to stromal cell layer after 5h in co-culture.After 24h in co-culture,the trophoblast protruded from two opposite poles of the blastocyst and underwent outgrowth into the stromal cell monolayer,blastocyst became bigger and invaded finally into the stromal cells.After 48h in co-culture,cytokeratin staining was only visible in trophoblast but not stromal cells,actin staining was visible in both of trophoblast and stromal cells with distinct conformation and structure.Stromal cells had prominent linear actin filaments,aligned along the long axis of the cells.Cytokeratin staining in trophoblast cells was localized in short filaments arranged in a mesh.hCG,E2 and P levels in the supernate of stromal cell-blastocyst co-culture were higher than the supernate from blastocyst cultured only (P<0.01).Conclusion An implantation model for the reflection of the process of human blastocysts attachment,outgrowth and invasion into stromal cells has been established in vitro.Cytokeratin,actin and hCG,E2 and P take place corresponding changes in the human implantation blastocyst cells. Objective To investigate the expression of cytokeratin, actin and hCG, E2 and P of human hacthed blastocysts in the model. Methods Human hatched blastocysts were co-cultured with human endometrial decidualization stromal cell monolayer. The process of orientation, attachment, outgrowth and invasion in morphology were observed. Immunofluorescence staining for cytokeratin and actin, immunofluorescence measurement of hCG and radioimmunoassay measurement of E2 and P were performed. Results Blastocysts attached to stromal cell layer after 5h in co-culture. After 24h in co-culture, the trophoblast protruded from two opposite poles of the blastocyst and underwent outgrowth into the stromal cell monolayer, blastocyst became bigger and invaded finally into the stromal cells. After 48h in co-culture, cytokeratin staining was only visible in trophoblast but not stromal cells, actin staining was visible in both of trophoblast and stromal cells with distinct conformation and structure. Stromal cells had prominent linear actin filaments, aligned along the long axis of the cells. Cytokeratin staining in trophoblast cells was localized in short filaments arranged in a mesh. HCG, E2 and P levels in the supernate of stromal cell-blastocyst co-culture were higher than the supernate from blastocyst cultured only (P <0.01). Conclusions An implantation model for the reflection of the process of human blastocysts attachment, outgrowth and invasion into stromal cells has been established in vitro. Cytokeratin, actin and hCG, E2 and P take place corresponding changes in the human implantation blastocyst cells.