Interleukin-6 in experimental endometriosis

Objective: To measure the concentration of interleukin-6 (IL-6) in peripheral serum and conditioned media (CM) of macrophages collected from the peritoneal cavity in rats before and after surgically inducing endometriosis. Design: Adult female rats (n = 50) underwent autotransplantation of adipose tissue or uterine squares. Peritoneal cavity macrophages were collected at the initial laparotomy. Rats were killed 4 or 8 weeks later, and peripheral serum and peritoneal cavity macrophages were collected. Macrophages were cultured for 48 hours, and the IL-6 concentrations in CM and serum were measured using the B9 hybridoma cell line bioassay. Results: Serum IL-6 levels were significantly increased at 4 weeks but not at 8 weeks in rats receiving endometrial implants. Interleukin-6 production by macrophages from rats with endometrial implants at 4 or 8 weeks was not significantly different from baseline or from rats receiving adipose tissue implants. Conclusion: The increased serum IL-6 levels at 4 but not 8 weeks after surgical induction of endometriosis suggest that IL-6 may be involved in the initial development of endometriosis in this experimental model.