Menstrual cycle-specific inhibition of the proliferation of endometrial stromal cells by interleukin 6 and its soluble receptor

OBJECTIVE: This study investigated the possible roles of interleukin 6 and soluble interleukin 6 receptor in the growth of endometrial and endometriot ic cells. STUDY DESIGN: Endometrial and endometriotic stromal cells were collected fr om the uterus or from ovarian chocolate cysts. We examined the effects of i nterleukin 6, soluble interleukin 6 receptor, and a combination of both fac tors on the proliferation of endometrial and endometriotic stromal cells. T he action of sex steroids on the interleukin 6 regulation of the growth of stromal cells was also evaluated. The gene expressions of interleukin 6 rec eptor and glycoprotein 130 were examined in endometrial and endometriotic c ells by reverse transcription-polymerase chain reaction. RESULTS: Interleukin 6 had no effect on the growth of stromal cells in tiss ue from the proliferative phase. In contrast, the addition of concentration s of greater than or equal to 100 pg/mL interleukin 6 induced significant i nhibition of stromal cell proliferation in tissue from the secretory phase. Similarly, the addition of soluble interleukin 6 receptor caused significa nt suppression in the growth of endometrial stromal cells in tissue from th e secretory phase but not the proliferative phase. On the other hand, strom al cells of endometriotic tissues were resistant to interleukin 6, showing no inhibitory response. Although the combination treatment did not affect t he proliferation of stromal cells of the proliferative phase and of endomet riotic tissues, 10 pg/mL interleukin 6 inhibited proliferation of stromal c ells of the secretory phase in the presence of 1 ng/mL soluble interleukin 6 receptor. Treatment with estradiol and progesterone for 10 days newly ind uced the inhibitory response to interleukin 6 in the endometrial cells from the proliferative phase. Expressions of transcripts of Interleukin 6 recep tor and glycoprotein 130 were observed in the endometrial cells from the pr oliferative and secretory phases and in endometriotic cells. CONCLUSIONS: Interleukin 6 may play a central role in regulation of the gro wth of endometrial cells as a mediator of endocrine action. Endometriotic c ells may behave differently from their normal counterparts in terms of the inhibitory regulation exerted by interleukin 6.