In vitro expression of soluble and cell surface‐associated CD44 on endometrial cells from women with and without endometriosis

Background Endometriosis is one of the most common benign gynaecological diseases, and attachment of retrogradely shed viable endometrial cells is considered to be important in its development. CD44 is a multifunctional adhesion molecule that undergoes alternative splicing, giving rise to different isoforms. Methods The expression of cell surface-associated CD44 std, v4, v5, v6 and v10 variants before and after cytokine treatment was investigated in endometrial cultures derived from 10 endometriosis patients and 22 women without the disease using immunocytochemistry. The immunoreactivity of soluble CD44 std, v5 and v6 variants was measured in culture medium using an enzyme immunoassay kit. Results We report on the presence of soluble CD44 in endometrial culture supernatants. In particular, circulating CD44 standard form levels were significantly higher than levels of splice variants. We also found that both epithelial and stromal cells express surface-associated CD44 molecules in a distinct pattern and that this expression is not modulated by tumour necrosis factor (TNF)-α or/and interleukin 1 (IL-1) α/β. Finally, cell surface-associated as well as soluble CD44 expression was similar in the two groups. Conclusion Our results indicate that endometrial cells can serve as a source of circulating CD44, but a direct role in the pathogenesis of endometriosis is rather improbable.