CXCL12/CXCR4 signal involved in the regulation of trophoblasts on peripheral NK cells leading to Th2 bias at the maternal-fetal interface

OBJECTIVE

In the early pregnancy, large number of decidual natural killer (dNK) cells are present in decidua, which exhibit distinctive phenotype and functions from peripheral blood NK cells (pNK)1. Unlike the cytotoxic pNK cells, dNK cells display more pronounced characteristics of immune tolerance, which contribute the Th2 bias at the maternal-fetal interface and ensure successful pregnancy2. However, the origin and the differentiation program of dNK still remain unknown.

MATERIALS AND METHODS

Our previous study has demonstrated that the CXCL12/CXCR4 signal axis is involved in the shaping of Th2 bias at the maternal-fetal interface3,4.

RESULTS

In this study, we demonstrated the first-trimester human trophoblast cells secrete chemokine CXCL12 that can recruit pNK cells to the decidua. We've also found that the pNK cells differentiate locally under the influence of trophablast cells. After co-culture with trophoblast cells, pNK cells could acquire dNK characteristics phenotypically while compared to the dNK cells; however, the blocking of CXCL12/CXCR4 signal of pNK cells has abrogated the modulation of trophoblast cells on the pNK cells. We've also found that JNK1/2/MAPK and ERK/MAPK signal pathways were required for the modulation of trophoblast cells on the pNK cells. MAPK signal pathway is involved in the functional modulation of human first-trimester trophoblast cells and decidual stromal cells on pNK and dNK cells.

CONCLUSIONS

Our study has elucidated that CXCL12/CXCR4 can recruit pNK cells to the decidua, then positively modulate pNK cells differentiation into the dNK cells, which thus results in Th2 bias and maternal-fetal immune tolerance.

Hyaluronan up-regulates growth and invasion of trophoblasts in an autocrine manner via PI3K/AKT and MAPK/ERK1/2 pathways in early human pregnancy

INTRODUCTION

As one of the key molecules in the extracellular matrix in human conceptus, hyaluronan (HA) has been receiving particular attention. Here, we have investigated the expression and regulation of different molecular weight HA on the biological behaviors of primary human trophoblasts during the first trimester of pregnancy.

METHODS

The expression of HA and HA synthetase (HAS) by human first trimester trophoblasts was analyzed in placentae from normal pregnancy or miscarriage by immunochemistry and real-time RT-PCR, respectively. ELISA was used to measure the secretion of HA by primary trophoblasts. The effects of HA on the proliferation, apoptosis and invasiveness of trophoblasts were examined. We also investigated the signaling pathways involved in HA activation in human trophoblasts.

RESULTS

The higher HAS2 expression and HA secretion were observed in normal villi than that of miscarriage, and the primary trophoblasts secreted HA continuously. High molecular weight HA (HMW-HA) and medium molecular weight HA (MMW-HA) promoted proliferation and invasiveness while inhibited apoptosis of trophoblasts. However, low molecular weight HA (LMW-HA) had no obvious effect on the growth or invasiveness of human trophoblasts. In addition, HMW-HA showed more efficiently than MMW-HA on the growth while MMW-HA displayed a more obvious effect on the invasiveness of trophoblasts than HMW-HA. HMW-HA activated PI3K/AKT and MAPK/ERK1/2 signaling pathways in trophoblasts. Blocking PI3K/AKT or MAPK/ERK1/2 signaling inhibited the HA-upregulated growth and invasiveness of human trophoblasts.

CONCLUSION

Our results suggest that higher level and greater molecular mass of HA can promote trophoblast growth and invasion in an autocrine manner, which was beneficial to placentation and maintenance of human early pregnancy.

RANKL promotes the growth of decidual stromal cells in an autocrine manner via CCL2/CCR2 interaction in human early pregnancy

OBJECTIVE

Receptor-activator of NF-κB ligand (TNFSF11, also known as RANKL) and its receptor RANK are essential regulators on bone remodeling, mammary gland development and hormone-associated breast cancer development. However, the expression pattern and role of RANKL/RANK axis in decidual stromal cells (DSCs) are unclear in human early pregnancy.

STUDY DESIGN

We analyzed RANKL/RANK expression in DSCs by real-time PCR, immunhistochemistry, enzyme-linked immunosorbent assay (ELISA) and flow cytometry, respectively. Then BrdU cell proliferation assay, flow cytometry assay and ELISA were performed to investigate the effect of recombinant human RANKL and DSCs-derived RANKL on the proliferation, apoptosis, chemokine (C-C motif) ligand 2 (CCL2) secretion, C-C chemokine receptor type 2 (CCR2) and other target proteins expression in DSCs in vitro, respectively.

RESULTS

Here we show that DSCs co-express RANKL/RANK. Not only recombinant human (rh) RANKL but also the DSC-secreted RANKL stimulate proliferation and anti-apoptosis, and elevate CCL2 secretion and CCR2 expression of DSCs. Furthermore, the stimulatory effects on the proliferation, anti-apoptosis and the expression of Bcl-2 and Ki67 and inhibitory signaling on Fas ligand (FasL) in DSCs induced by RANKL can be partly reversed by the way of blocking CCL2 and or CCR2.

CONCLUSIONS

Our results have revealed that RANKL/RANK signal promotes Bcl-2 and Ki67 and decreases FasL expression, and further as a positive regulator for stimulating the proliferation and growth of DSCs through up-regulating CCL2/CCR2 signal, which finally contributes to the establishment and maintenance of physiological pregnancy.