Dysregulation of interleukin-6 responses in ectopic endometrial stromal cells: correlation with decreased soluble receptor levels in peritoneal fluid of women with endometriosis.

Abstract

Endometriosis (EM) is characterized by the aberrant growth of endometrial cells at sites outside the uterus. We showed previously that peritoneal leukocyte interleukin-6 (IL-6) production is altered in women with EM relative to that in normal control women. Because studies suggest that IL-6 may be growth regulatory for endometrial cells, we examined IL-6 and IL-6 soluble receptor (IL-6sR) in the peritoneal fluid of 40 women. In addition, the growth responsiveness of ectopic endometrial stromal cells to IL-6 was evaluated. The severity of EM correlated with increased levels of IL-6 accompanied by decreased IL-6sR in peritoneal fluid (controls, 1.0 +/- 0.1 and 525.4 +/- 53; stage I-II EM, 1.4 +/- 0.2 and 274.6 +/- 26; stage III-IV EM, 19.3 +/- 4.6 and 319.4 +/- 26; adhesions, 1.9 +/- 0.4 and 324.7 +/- 26 pmol/L IL-6 and IL-6sR, respectively). Additional studies revealed that unstimulated endometrial stromal cells from ectopic implants secreted this cytokine in vitro. Furthermore, these cells were resistant to growth inhibition induced by exposure to additional IL-6; this response correlated with weak expression of IL-6 receptor. Taken together, these findings lend further support to the hypothesis that dysregulation of IL-6 responses plays a role in the pathophysiology of EM.