Effects of interleukin-6 on extravillous trophoblast invasion in early human pregnancy

Invasion of uterine tissues by extravillous trophoblast cells (EVT) is essential for successful human pregnancy. EVT invasion is tightly regulated by a number of factors, including growth factors and cytokines, but the mechanisms that underlie their regulatory effect remain poorly understood. Interleukin (IL)-6 has been suggested to play a role in controlling EVT invasion. We hypothesized that IL-6 produced by cells in uterine decidua would regulate EVT invasiveness via IL-6R and gp130 receptors expressed by trophoblast cells. The effect of IL-6 on EVT signalling and cytokine production was also studied. Supernatants from disaggregated ototal' decidual cells, CD8 T cells, CD10 decidual stromal cells, CD14 macrophages, CD56 uterine natural killer cells, cytotrophoblast and EVT cells contained large quantities of IL-6 protein at both 810 and 1214 weeks gestational age. IL-6R and gp130 were immunolocalized to EVT in placental bed biopsies from 8 to 20 weeks gestation and IL-6R expression was confirmed by western blotting. IL-6 had no effect on the invasive potential of EVT from chorionic villi or the immortalized EVT cell line HTR-8/SVneo in a Matrigel invasion assay. IL-6 stimulated phosphorylation of several cell signalling proteins in EVT (814 weeks' gestation), although significance was lost after correction for multiple comparisons. Incubation with IL-6 decreased secretion of regulated upon activation, normal T-cell expressed and secreted (RANTES) by EVT cells. In conclusion, although IL-6 did not affect trophoblast cell invasion, it stimulated EVT cellular cascades and inhibited secretion of RANTES involved in a number of cellular processes.