Human Endometrial Organoid Complex Promotes Endometrial Regeneration and Functional Blood Vessel Formation in a Mouse Model

Mechanisms underlying the beneficial effects of HEO complex on endometrial injury repair and fertility: Evidence of human endometrial cell integration, expression of estrogen and progesterone receptors, and formation of functional blood vessels. To investigate the mechanisms underlying the beneficial effects of HEO complex on endometrial injury repair and fertility, we examined the localization of different endometrial complexes at various time points and assessed the expression of human endometrial-specific markers. Following the injection of HEO and EO complexes for 3 days, we observed that the complexes containing cells and hydrogel filled the uterine cavity of the mice (Figure 7a). Immunostaining revealed the presence of human-specific CK7, Vimentin, and CD31 in the HEO graft, indicating the existence of human endometrial epithelial cells, stromal cells, and vascular endothelial cells. In contrast, the EO graft lacked the expression of human-specific CD31. After 7 days, the human endometrial epithelial cells in both HEO and EO complexes integrated into the mouse endometrium, with CK7-positive epithelial cells appearing in the subendometrial tissue (Figure 7a). These cells also expressed human-specific estrogen receptors and progesterone receptors (Figure 7b). These findings demonstrate that cells in the HEO complex contribute to the regeneration of damaged mouse endometrium, in line with the improvements in endometrial repair and fertility in the HEO group. Furthermore, we subcutaneously injected the HEO complex into mice and retrieved the grafts after 14 days. Under stereomicroscopy, we observed well-developed blood vessels in the grafts (Figure 7c). By infusing human-specific fluorescent substances (UEA-1) and mouse-specific fluorescent substances, we confirmed the connection between the human and mouse blood vessel networks in the grafts (Figure 7d). Additionally, perfusion of fluorescein-conjugated dextran and UEA-1 revealed that the green-labeled human blood vessels exhibited a red fluorescent signal, indicating perfusion of mouse blood within the human blood vessel network in the grafts. In contrast, the EO complex led to graft shrinkage and the formation of inflammatory vesicles. The formation of functional blood vessels by the HEO complex in mice may also contribute to the enhanced endometrial repair and improved fertility following transplantation, as graft blood vessel formation is crucial for graft success and functionality