P-790 Engineering Vascularized Human Endometrial Organoids for In Vivo Tissue Regeneration and Repair Applications
Authors: Dai Y , Zhao F , Zhang S , Chen Q , Zeng B , Wang X , Gu W , Zhang Y , Lin X , Liu N , Zhou F , Yang J , Xin S , Feng Y 
Published: July 2024

Abstract

Study question
Is it possible to construct a vascularized endometrial organoid in vitro using endometrial epithelial organoids, endometrial stromal cells, and HUVECs? And its application value?

Summary answer
We have successfully engineered a vascularized endometrial organoid and demonstrated its remarkable ability to repair damaged endometrium. ScRNA-sequencing revealed intricate regulatory relationships among the cells.

What is known already
In vivo, endometrial epithelial organoids (EEOs) have been proven effective in repairing damaged endometrium. In vitro, when co-cultured with endometrial stromal cells (ESCs) in matrigel, EEOs self-assemble into endometrial assembloids that accurately replicate the native tissue’s characteristics. Endothelial cells play a critical regulatory role in various physiological processes across different tissues, such as lipid metabolism in hepatocytes, neurogenesis within the brain, and the menstrual cycle regulation in uterine endometrium. By leveraging organ-on-a-chip technology using HUVECs (commonly utilized endothelial cells), it is possible to construct functional and complex organoids with vascularization, including liver buds, brain organoids, and pancreatic islets.

Study design, size, duration
Different ratios of Fibrin and Matrigel were explored to optimize the hydrogel conditions. The composite medium was optimized with ExM and ECM. Cellular interactions were identified through cell-specific staining. Addition of reproductive hormones was performed to determine if the complexes exhibited hormone-responsive behavior. Transplantation of the organoid complexes into mice with endometrial injury was conducted to assess their repair capacity. Single-cell RNA sequencing was employed to identify cell clusters and analyze intercellular interactions.

Participants/materials, setting, methods
EEOs, ESCs, and HUVECs self-assemble into HEO complexes. EEOs and ESCs self-assemble into EO complexes as controls. Immunofluorescence and immunohistochemical analysis are conducted to detect cell-specific markers. PBS, Matrigel, EO and HEO complexes are transplanted into mice with endometrial injury. JC-1 staining and transmission electron microscopy are used to verify mitochondrial functionality. Electrical resistance measured by EVOM2, HUVEC tubule formation and sprouting assays are performed to investigate the formation of vascular networks within the complexes.

Main results and the role of chance
Under dynamic flow conditions of ExM and ECM at a ratio of 5:5, HEO complexes and EO complexes were self-assembled in a fibrin-matrigel hydrogel. The HEO complexes exhibited a capillary network-like structure, intricate cellular interactions, and a transcriptome profile similar to that of the in vivo endometrium. Moreover, HEO complexes responded to sex hormones, facilitating endometrial regeneration and improving the reproductive capacity of mice with endometrial injury. The subcutaneous transplantation of HEO complexes in mice revealed the perfusion of mouse blood within the human blood vessel network in the grafts, highlighting the participation of HUVECs in the vascular formation of the transplanted grafts. ScRNA sequencing analysis of HEO complexes demonstrated a notable rise in the proportion of proliferative subclusters of endometrial epithelial cells and stromal cells compared to EO complexes, especially under estrogen culture conditions. Additionally, HUVECs enhanced the mitochondrial functionality of endometrial cells and remodeled the extracellular matrix. Cell communication analysis revealed that endometrial epithelial and stromal cells enhance the formation of vascular networks in HUVECs within the HEO complexes through WNT7A and WNT5A signaling pathways.

Limitations, reasons for caution
Due to the time constraints of the study, we did not observe the birth rate of offspring mice following endometrial repair. ScRNA sequencing also uncovered that HUVECs promote ribosomal functionality in endometrial cells within HEO complexes, but further validation of this finding is necessary.

Wider implications of the findings
The implantation of HEO complexes derived from woman EEOs, ESCs, and HUVECs into the endometrium holds potential for “endometrial re-engineering” in the therapeutic management of Asherman’s syndrome or thin endometrium.

Trial registration number
not applicable