Defects in the DNA Damage Response of Patient-derived Endometriosis Stromal Cells

With each menstrual cycle, endometrial cells rapidly proliferate and decidualize in preparation for pregnancy. Such rapid proliferation generates replication stress and results in DNA damage with irreparable cells undergoing senescence. Here, we examine the DNA damage response (DDR) of patient-derived stromal cell lines from menstrual effluent (MenSC) of healthy donors and donors with endometriosis. We found that proliferating MenSCs from endometriosis patients (Endo) have a defective DDR that is also present when these cells reach confluence. In G1, these cells contain more 53BP1-nuclear bodies (NBs) and are less senescent than healthy samples. We also treated with hydroxyurea (Hu) to generate replication stress and found that Endo MenSCs responded to this treatment by activating the DDR and generating more 53BP1-NBs. We examined the MRN complex, upstream of the ATM-dependent DDR. Hu treatment of our cell lines resulted in downregulation of all genes encoding the MRN complex, and RAD50 and NBS1 proteins. In a scRNA-seq dataset of endometriosis stromal tissue, we also identified downregulation of RAD50 and NBS1. To evaluate the growth potential of MenSCs, we decidualized cells after Hu treatment and then replated them in growing medium. Untreated endometriosis MenSCs formed more colonies than healthy MenSCs; neither sample type formed colonies after Hu treatment. Together, our studies suggest that endometriosis MenSCs have a defective DDR that may be exploited therapeutically.