Objective. To determine whether endometrial stem/progenitor cells play a role in the pathogenesis of endometriosis using newly identified markers for human endometrial mesenchymal stem cells (eMSC) and epithelial progenitor cells (eEPC).
Design. Cycling women undergoing laparoscopy (n=19) on day two-three of their menstrual period were recruited and uterine menstrual blood (UMB), peritoneal fluid (PF) and peripheral blood (PB) were collected. Endometriosis was diagnosed and scored at surgery according to AFS guidelines.
Materials and Methods. UMB was collected using soft tubing inserted into the uterine cavity. PF was collected via the laparoscope before other procedures. Single cell suspensions were obtained, leukocytes removed by CD45 magnetic beads, cell cloning undertaken, and flow cytometry used to quantify the concentration of eMSC (W5C5+ cells) and eEPCs (marker+ cells).
Results. In menstrual blood, no difference in concentration of clonogenic cells (1,581,800 CFU/mL, n=11 vs 576,700 CFU/mL, n=5; P=0.4388) and marker+ eEPCs (256,200/mL, n=7 vs 345,000/mL, n=3; p=0.7929) between endometriosis and control samples was observed. The concentration of W5C5+ eMSCs was increased in endometriosis compared to controls (2,006,700/mL, n=11 vs 280,500/mL, n=8, p=0.0499). No CFU, W5C5+ eMSCs or marker+ eEPCs were found in peripheral blood from either group. The volume of peritoneal fluid, concentration of CFU and marker+ eEPCs (32,400/mL, n=7 in endometriosis vs 3,600/mL in controls, n=3; P= 0.1167) was similar for women with and without endometriosis. However, the concentration of viable cells (P=0.012) and W5C5+ eMSCs (55,600/mL, n=10 vs 780/mL, n=8; P<0.0001) was significantly elevated in the endometriosis group.
Conclusions. Our data suggest there may be preferential retrograde shedding of endometrial stem/progenitor cells into the pelvic cavity during menstruation in women with endometriosis compared to controls. These stem/progenitor cells may have greater ability to survive in the peritoneal fluid of women with endometriosis, enabling them to initiate endometriosis lesions.