#222 : Exosomes Derived of Menstrual Blood Stem Cells Suppress IUA Endometrial Fibrosis Through P65-UBR4-YAP Pathway

Abstract

Background and Aims: IUA is the second leading cause of secondary infertility in women, and it is urgent to find a new therapeutic method to achieve functional regeneration of endometrial. We previously found that menstrual blood stem cells (MenSCs) transplantation could improve endometrial fibrosis and restore fertility in IUA rats through exosomes (MenSCs-exos). We identified UBR4 as an E3 ubiquitin ligase that was abundantly enriched in MenSCs-exos by mass spectrometry sequencing, however, the role of UBR4 in MenSCs-exos treatment of IUA and the potential molecular mechanism remains unclear. Method: IUA rats and endometrial stromal cells (EndoSCs) of IUA patients were treated with knock-down UBR4 exosomes (EXOUBR4−) and normal exosomes (EXO). HE staining and Masson staining were used to evaluate endometrial morphology and fibrosis area. The expression levels of fibrotic indicators COL I and CTGF were detected. The molecular mechanisms by which UBR4 in MenSCs-exos alleviate EndoSCs fibrosis were then explored using immunofluorescence, western blot, and co-immunoprecipitation. The molecular mechanism of transcription factor P65 regulating the expression of UBR4 were explored using ChIP and dual luciferase. Results: MenSCs-exos could significantly restore the endometrial morphology of IUA rats, increase endometrial thickness and number of glands, and reduce the endometrial fibrosis area, however reducing the content of UBR4 in MenSCs-exos would alleviate its therapeutic effect on IUA rats. UBR4 in MenSCs-exos reduced the expression levels of COL I and CTGF through significantly decreasing the expression level of YAP by specifically ubiquitin-degrading YAP. In addition, P65 could bind to the UBR4 promoter region to transcriptionally promote the expression level of UBR4 in MenSCs. Conclusion: This study clarified that UBR4, as the key molecule in repairing IUA fibrotic endometrium by MenSCs-exos, could inhibit endometrial fibrosis by ubiquitin-degrading YAP, while transcription factor P65 could promote the expression level of UBR4 in MenSCs by directly binding to the UBR4 promoter region.