Abstract: The aim of this study was to explore the temporal and spatial relationship among pinopodes, implantation sites and implantation window and to suggest a method to obtain a sufficient number of pinopodes for further study. The endometrium was divided into two groups: the natural pregnancy group and the pseudopregnancy group. The distribution and density of pinopodes in different phases were observed by scanning electron microscopy in order to determine the phase and location that pinopodes enriched on the surface of endometrium. In the natural pregnancy group, a small number of tiny and round pinopodes started to protrude on the endometrial surface from day 3.5 of pregnancy. On day 4.5, a large number of pinopodes protruded from the endometrial surface, concentrating in where the implantation sites were located. On day 5.5, pinopodes started to regress. Pinopodes reached their peak at the implantation sites on the phase of implant window. In comparison, in the pseudopregnancy group, pinopodes reached their largest scale and density on day 3 of pseudopregnancy and earlier than they were in the natural pregnancy group. Pinopodes concentrated in the crypts of anti mesometrial side. In the natural pregnancy group, the peak of pinopodes appeared temporal and spatial coincident with implantation sites and implantation window. In the pseudopregnancy group which was earlier than they were in the natural pregnancy group. Whether in the natural pregnancy group or in the pseudopregnancy group, researchers can obtain endometrium containing pinopodes without interference of other tissues containing none or scarce pinopodes. This makes it possible to better understand the biochemical characteristic of pinopodes by studying biological molecules in pinopodes. This also helps to further explain the mechanism of recognition in other words, the relationship between the maternal endometrium and embryo in the process of apposition and attachment during the early implantation.
Ning Wang, Linlin Geng, Shucheng Zhang and Jiedong Wang, 2013. Temporal and Spatial Relationship among Pinopodes, Implantation Sites and Implantation Window. Journal of Animal and Veterinary Advances, 12: 1147-1150.