PROBLEM: Implantation of human embryo requires expression of inflammatory cytokines and local attraction of T cells and natural killer (NK) cells. Chemokines are chemoattractants for these cells in classical inflammation. We speculated that they could also be involved in implantation.
METHOD OF STUDY: We assessed by enzyme-linked immunosorbent assay (ELISA), reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry the presence of three classical β chemokines Macrophage Inflammatory Protein 1 (MIP1)α, MIP1β and Regulated upon activation, normal T cells expressed and secreted (RANTES) in cultures of placental villi or isolated trophoblasts derived from human first trimester and term placenta.
RESULTS: Explant culture assays were positive for these three chemokines, with important quantitative variations between individuals. Half of the highly purified trophoblasts cultures were found by ELISA and RT-PCR to secrete in vitro MIP1α and MIP1β. RANTES was never detected by ELISA in trophoblasts cultures, albeit we could detect a low amount of messenger RNA. Immunohistochemistry experiments show that Hofbauer cells and the trophoblast layer are a secretion site of MIP1β in term placenta, and that cytotrophoblasts are able to secrete this chemokine in early placenta.
CONCLUSION: Human placenta is a site of secretion of chemokines that could be involved in establishment of pregnancy.