Menstrual endometrial cells from women with endometriosis demonstrate increased adherence to peritoneal cells and increased expression of CD44 splice variants

Abstract

Using an in vitro model for the early endometriotic lesion, we previously demonstrated that adherence of endometrial epithelial (EECs) and stromal (ESCs) cells to peritoneal mesothelial cells (PMCs) is regulated in part by ESC/EEC surface CD44 interactions with hyaluronan produced by PMCs. CD44, a transmembrane glycoprotein that is the major ligand for hyaluronan, has numerous splice variants and some are associated with an increased ability to bind hyaluronan. Here, we assessed whether ESCs/EECs from women with endometriosis demonstrate increased adherence to PMCs and examined the potential role of CD44 splice variants in this process. In vitro study. Endometrium was collected at the time of menses from women with (N = 21) and without (N = 8) endometriosis (controls) as confirmed surgically. EEC/ESC adherence to the PMC line LP9 was compared using an established in vitro assay. CD44 splice variants were assessed in ESCs/EECs using exon specific hybridization with dot blot analysis. ESCs from women with endometriosis demonstrated increased adherence to PMCs when compared to ESCs from controls (43% vs. 32%, P<0.002). EECs from women with endometriosis also demonstrated an increased adherence to PMCs that approached statistical significance when compared to EECs from controls (22% vs. 15%, P=0.07). The predominant CD44 splice variants expressed by ESCs and EECs from women with and without endometriosis were v3, v6, v7, v8, v9, and v10. ESCs from women with endometriosis were more likely to express v6, v7, v8 or v9 than ESCs from controls (72% vs. 45%, P<0.04). Increased expression of these variants by EECs from women with endometriosis approached statistical significance when compared to controls (94% vs. 75%, P=0.06). The present study is the first to demonstrate that menstrual ESCs from women with endometriosis have increased adherence to PMCs when compared to ESCs from controls. The increased expression rates of v6, v7, v8, or v9 by ESCs from women with endometriosis suggest that qualitative differences in ESC CD44 isoform expression may contribute to the pathogenesis of endometriosis. Similar findings of increased adherence and CD44 isoform expression by EECs from women with endometriosis approached statistical significance. Studies are in progress to further clarify the role of variable CD44 isoform expression in the genesis of the early endometriotic lesion and its potential for future targeted therapies.