Transplantation of cultured explants of human endometrium into nude mice

The objective of this study was to analyse the histological and immunohistochemical characteristics of cultured explants of human endometrium transplanted into nude mice. Biopsies of eutopic endometrium were taken from six patients during laparoscopic surgery and classified according to the phase of the cycle. All the explants were cultured with oestrogen and progesterone for 24 h before transplantation into 15 mice. Four mice were grafted with explants of menstrual endometrium, four with explants of late proliferative endometrium, and seven with explants of late secretory-premenstrual endometrium. Typical endometrial glands and stroma were observed in 87% of cases 3 weeks after the transplantation. All the grafts revealed histological characteristics of the proliferative phase, even when the endometrial biopsy was taken during the late secretory phase. Immunohistochemical studies revealed that the proliferation index was high, whatever the menstrual phase of the endometrial biopsy. An extensive vascular network developed at the interface between the graft and the surrounding tissue. Vascular endothelial growth factor (VEGF) positive stained cells were observed in all grafts, the VEGF score being significantly higher in epithelial cells than in stromal cells. In conclusion, human endometrial explants, cultured for 24 h, could be successfully transplanted into nude mice. Immunohistochemical studies proved that human cultured endometrial tissue could not only survive in nude mice but could also become very active and develop characteristics different from the tissue of origin. An active vascular network is a necessary condition for the survival of the graft and may be explained by the high VEGF content.