Tolerance induction at the early maternal-placental interface through VIP production by first trimester trophoblast cells

LAURA FRACCAROLI; ESTEBAN GRASSO; VANESA HAUK; GIL MOR; CLAUDIA PÉREZ LEIRÓS; ROSANNA RAMHORST

Simposio; 11th International Symposium on VIP, PACAP and related peptides; 2013

Pregnancy challenges immune cells and immunomodulatory circuits of the mother and the developing fetus to dynamically adapt to each other in an homeostatic and tolerant environment for fetal growth. From an immunological standpoint, pregnancy was proposed to follow a temporal sequence with a predominantly pro-inflammatory first stage, an immunologically more quiescent, fetal growth promoting second period, and a final cut to a prominent inflammatory environment that precedes labor and delivery. In humans, between weeks 3 and 8 of gestation, a variety of cellular processes are encompassed to ensure proper trophoblast growth and invasion, uterine quiescence, vascularization and tissue remodeling in an immunotolerant microenvironment. The transition points imply redundant immunoregulatory mechanisms to tolerance maintenance. In this sense, the inducible regulatory T cells (iTreg) population is essential for maternal tolerance of the conceptus, performs its suppressive actions in the critical peri-implantation phase of pregnancy. On the other hand, the Vasoactive intestinal peptide (VIP) is synthesized and secreted by trophoblast cells and promotes anti-inflammatory and tolerogenic profiles through specific receptors VPAC1 and VPAC2 on immune cells. Here, we evaluated VIP contribution to the differentiation of maternal iTreg after the interaction with trophoblast cell lines obtained from different stages of human pregnany. We used an in vitro model of maternal leukocyte-trophoblast cell interaction represented by cocultures of fertile women PBMC with human trophoblast cell line from first trimestre (Swan71) and from third trimester (JEG3 and BeWo cell lines). We observed that VIP (10-7M) increased the frequency of maternal CD4+CD25+Foxp3+ cells after 48h of coculture with Swan cells (3.9±0.4 vs 8.3%±0.6) was prevented by VIP antagonist. This modulation was specific for the first trimester trophoblast cells since neither JEG3 or BeWo cells increased iTregs frequency. In addition, iTreg differentiated upon interaction with Swan cells in the presence of VIP, suppressed the maternal alloresponse and increased the frequency of CD4+IL10+ cells but did not modulate IFN or IL-17 production. Getting insight into the mechanisms involved in iTreg differentiation, VIP induced the expression of the three isoforms of TGFbeta in Swan cells with a peak at 12h and increased TGF1 and TG2 secretion (confirmed by RT-qPCR and Luminex assays). Finally, the increase in iTreg frequency was prevented by an antiTGF Ab and VIP antagonist. These results suggest that VIP could have an active role in the immunoregulatory processes operating during early stages of the maternal-placental interaction contributing to the induction of iTregs in a TGF dependent mechanism.