CD44s expression is reduced in endometriotic lesions compared to eutopic endometrium in women with endometriosis

Immunohistochemical expression of the standard form of CD44 (CD44s) was exa mined in archival formalin-fixed endometriotic and matching eutopic endomet rial tissue obtained from 25 patients in proliferative (N = 16) and secreto ry (N = 9) stages of the cycle. CD44s was expressed in most eutopic endomet ria and endometriotic tissue. Its expression was significantly higher in se cretory than in proliferative phase endometrium. It was low but detectable in 13 of 16 proliferative phase biopsies. The majority of these endometria exhibited both glandular and stromal staining (63%). In the secretory phase , glandular cells exhibited a significantly greater intensity of staining c ompared to stromal cells. In endometriotic tissue, stromal cell CD44s expre ssion did not differ between tissue types in either stage of the cycle. In contrast, glandular expression in endometriotic tissue during the secretory phase was reduced (p < 0.05) compared to eutopic endometrium. It was absen t in 66% of cases and reduced in the remaining cases. Our results indicate a correlation between CD44s expression and secretory differentiation of end ometrial glands in the cycle, suggesting hormonal regulation of its express ion. This cyclic pattern of CD44s expression was lost in corresponding endo metriotic tissue. Reduced expression of CD44s in endometriotic tissue may p rovide insight into the pathophysiology of endometriosis.