[Expression of claudin-4 in eutopic and ectopic endometrium of women with endometriosis]

To investigate the expression of claudin-4 in the eutopic and ectopic endometrium of women with endometriosis and evaluate the role of claudin-4 in the pathogenesis of endometriosis.

Thirty-five women with endometriosis and 35 controls were studied. Expression of claudin-4 was investigated using immunohistochemistry, western blot and RT-PCR, respectively. Morphologic change of tight junction was also observed in different kinds of endometria

(1) Glandular epithelial cells of control endometrium and eutopic endometrium showed intact tight junctions in electron micrographs, whereas the morphology of tight junctions in ovarian endometriotic tissue was disrupted and collagen bundles could be easily detected. (2) The immunohistochemical staining of claudin-4 was localized to the glandular epithelial cell membrane. Deficient or weak staining was found in ovarian endometriotic tissues. In control endometrium, eutopic and ectopic endometrium of women with endometriosis, the expression of claudin-4 protein was 89 +/- 24, 84 +/- 22 and 27 +/- 14, respectively. Relative expression of claudin-4 mRNA was 14.5 +/- 6.8, 13.8 +/- 9.5 and 2.6 +/- 2.5, respectively. Expression of claudin-4 was significantly lower in the ectopic endometriotic tissue than in the eutopic endometrium and the control at both mRNA and protein levels (P<0.05). No significant difference was found between eutopic endometrium from women with endometriosis and control endometrium from women without endometriosis (P>0.05).

Down-regulated expression of claudin-4 might play a pathogenic role in the formation of endometriosis.