Inflammatory mediators in parturition

Inflammatory mediators in the cervix, fetal membranes and myometrium play a crucial role in parturition. Each of the pro-inflammatory cytokines interleukin (IL)-1β, IL-6, IL-8 and Tumour Necrosis Factor (TNF)α has been identified in reproductive tissues during labour. The cellular origins of these cytokines is unclear. The aim of this study was to localise the above pro-inflammatory cytokines using immunocytochemistry and quantify pro-inflammatory cytokine expression using northern analysis. These protocols were carried out in cervix, fetal membranes and myometrium at term. Biopsies were taken from women undergoing caesarean section either before or after the onset of labour. The density of leukocytes in these tissues was also determined by immunolocalisation using the following antibodies, CD45 (leukocytes), CD3 (T-cells), CD20 (B-cells), CD68 (macrophages) and neutrophil elastase (neutrophils). In myometrium and cervix, immunostaining for IL-1β was predominantly in leukocytes. In fetal membranes, IL-1β localised to leukocytes and to the stromal cells of the decidua. In myometrium, IL-6, IL-8 and TNFα were restricted to leukocytes which were present in greater numbers in tissue obtained during labour. In cervix, IL-6, IL-8 and TNFα localized to leukocytes, glandular and surface epithelium. IL-8 also localised to cervical stromal cells. In fetal membranes, IL-6 and TNFα were expressed by decidual stromal cells, infiltrating leukocytes and extravillous trophoblast. In membranes, IL- 8 localized to leukocytes in the chorion but was not detected in the amnion. In fetal membranes collected in labour, IL-8 was expressed in decidual stromal cells. In northern analysis the ratio of IL-1β mRNA/GAPDH mRNA expression was significantly higher in amnion (p<0.02 [median 0.21 (interquartile range IQ 0.12-0.35)]), myometrium (p<0.02 [median 0.27 (IQ range 0.12-1.4)]) and cervix (p<0.02 [median 1.45 (IQ range 0.69- 2.43)]) following spontaneous labour compared to not in labour, amnion (median 0 [IQ range 0-0]), myometrium (median 0 [IQ range 0-0]) and cervix (median 0 [IQ range 0-0]). We found the ratio of IL-6 mRNA/GAPDH mRNA significantly increased in chorion (p<0.05 [median 1.42 (IQ range 1.10-2.06)]), myometrium (p<0.005 [median 1.34 (IQ range 1.23- 2.40)]) and cervix (p<0.05 [median 1.35 (IQ range 0.65-2.53)]) after the onset of spontaneous labour compared to not in labour, chorion (median 0.28 [IQ range 0.20-0.38]), myometrium (median 0.13 [IQ range 0.09-0.16]) and cervix (median 0.23 [IQ range 0.18-0.31]). The expression of IL-8 was significantly higher in amnion (p<0.01 [median 0.24 (IQ range 0.10- 0.40)]), chorion (p<0.005 [median 0.89 (IQ range 0.38-1.62)]), myometrium (p<0.005 [median 0.63 (IQ range 0.50-1.8)]) and cervix (p<0.02 [median 1.30 (IQ range 0.33-2.4)]) following spontaneous labour compared to not in labour, amnion (median 0 [IQ range 0-0]), chorion (median 0 [IQ range 0-0]), myometrium (median 0 [IQ range 0-0]) and cervix (median 0 [IQ range 0-0]). TNFα expression was below the limits of detection for our assay. The density of leukocytes and of the subfractions, neutrophils, macrophages, T-cells and B- cells in cervix and myometrium were significantly greater in tissues obtained during labour. The density of leukocytes and white cell subfractions were significantly greater in decidua than in either chorion and amnion, but there was no difference in tissues taken either before or after the onset of labour. Establishing which of the pro-inflammatory cyokines are expressed in uterine tissues before and after the onset of labour, and determining the leukocytes involved in this expression, could lead to the development of strategies which could be effectively employed to treat pre-term labour which is a major problem in obstetrics.