Gene expression profiling of the paracrine effects of uterine natural killer cells on human endometrial epithelial cells

Abstract

The endometrium contains a population of immune cells that undergo changes during implantation and pregnancy. The majority of these cells are uterine natural killer (uNK) cells; however, it is unclear how these cells interact with endometrial epithelial cells. Therefore, we investigated the paracrine effects of the uNK cell-secretion medium on the gene expression profile of endometrial epithelial cells in vitro through microarray analysis. Our results, which were verified by qRT-PCR and western blot, revealed that soluble factors from uNK cells alter the gene expression profiles of epithelial cells. The upregulated genes included interleukin-15 (IL-15) and interleukin-15 receptor alpha (IL-15RA), which result in a loop that stimulates uNK cell proliferation. In addition, vascular endothelial growth factor C (VEGF-C) and chemokine (C-X-C motif) ligand 10 (CXCL-10) were also determined to be upregulated in epithelial cells, which suggests that uNK cells work synergistically with epithelial cells to support implantation and pregnancy. In addition, oriental herbal medicines have been used to treat infertility since ancient times; however, we failed to find that Zi Dan Yin can regulate these endometrial paracrine effects.

Figure 1

Transcription levels of (a) CXCL-10, (b) IL-15, (c) ICAM-1, (d) NLRC-5, and (e) IRF-1 determined by qRT-PCR. The relative fold changes are shown in Section 3. The qRT-PCR results were consistent with the microarray analysis. The data are expressed as means ± SEM. ^a P < 0.001 for the comparison between the uNK and control groups; ^b P < 0.001 for the comparison between the ZDY and control groups.

Figure 2

(a) Expression of endometrial ICAM-1 protein in endometrial epithelial cells. The GAPDH band was used as the internal loading control in each lane. (b) Comparison of the normalized expression intensity of endometrial ICAM-1 protein in the control, uNK, and ZDY groups. The data are expressed as means ± SEM. ^a P < 0.01 for the comparison between the uNK and control groups; ^b P < 0.01 for the comparison between the ZDY and control groups.

Figure 3

Model of the proliferation and function of uNK cells. During implantation and early pregnancy, the uNK paracrine signals stimulate endometrial epithelial cells to produce IL-15, VEGF, and other unidentified factors that may regulate uNK cell proliferation. The immune paracrine communication between uNK and endometrial epithelial cells may support implantation and trophoblast development.