Objective: To investigate the influence of lipopolysaccharide, cytokines, growth factors, and progesterone on the synthesis of interleukin-8 by human lower uterine segment fibroblasts.
Methods: Fibroblasts derived from a lower uterine segment biopsy specimen obtained from a woman undergoing elective cesarean delivery at term were exposed to lipopolysaccharide, interleukin-1beta, transforming growth factor-beta(1), platelet-derived growth factor-AB, and combinations of these substances. All experiments were performed in the absence and presence of progesterone. The concentration of interleukin-8 in the culture medium was determined by enzyme immunoassay after 24 hours.
Results: Compared with controls (0.71 +/- 0.04 ng interleukin-8/10(6) cells), fibroblasts exposed to lipopolysaccharide, transforming growth factor-beta(1), or platelet-derived growth factor-AB exhibited no increase, or at most, only a minor but significant increase, in interleukin-8 secretion. Incubation with interleukin-1beta led to a moderate increase, whereas the combinations interleukin-1beta/transforming growth factor-beta(1) (105.0 +/- 7.5 ng interleukin-8/10(6) cells) and interleukin-1beta/platelet-derived growth factor-AB (387.3 +/- 25.6 ng interleukin-8/10(6) cells) increased interleukin-8 secretion dramatically. No further increase was observed with the combination interleukin-1beta/platelet-derived growth factor-AB/transforming growth factor-beta(1). When progesterone was added, interleukin-8 secretion decreased significantly by 16-34%, depending on the stimulator, or did not change.
Conclusion: The findings indicate that interleukin-8 secretion by human lower uterine segment fibroblasts in vitro is upregulated by interleukin-1beta, transforming growth factor-beta(1), and platelet-derived growth factor-AB in a synergistic fashion. Because interleukin-8 mediates the invasion of neutrophils into the cervical stroma, this may be an important mechanism controlling cervical dilatation during parturition.