The decidual expression of Interleukin-7 is upregulated in early pregnancy loss

Abstract

Background: Maternal immunological rejection of the semi-allogenic fetus is discussed as one of the significant factors involved in early pregnancy loss. An array of cytokines secreted by both maternal and fetal cells is involved in generating a delicate maternal immune tolerance. Interleukin-7 (IL-7) is discussed to play a key role in pro-inflammatory processes, but there is still limited insight into the pathophysiological input on placentation and embryonic development in early pregnancy loss.

Patients and methods: Cytokine level differences were identified with quantitative real-time PCR in placental tissue from spontaneous abortions (SA) (n = 18), recurrent spontaneous abortions (RSA) (n = 15), and healthy pregnancies (n = 15) at gestational weeks 7 to 14. Protein expression of IL-7 in the decidua was investigated by immunohistochemistry. IL-7-expressing cells were identified with double-immunofluorescence.

Results: Decidua of women with RSA expressed almost 51-times higher values of IL-7 in gene expression analysis. Immunohistochemistry identified a significant upregulation of IL-7 in the decidua of RSA specimens (p = .013) and in the decidua of women with SA (p = .004). Double-immunofluorescence confirmed decidual stroma cells as IL-7-expressing cells.

Conclusion: Significantly elevated IL-7 values in the decidua of spontaneous and recurrent miscarriages imply a crucial role of the cytokine in the signaling at the feto-maternal interface of the placenta. An overexpression of IL-7 could result in early pregnancy loss by inducing a pro-inflammatory environment. Proven to be valuable in other autoimmune diseases, targeting IL-7 signaling therapeutically may prove to be a very beneficial treatment option for RSA patients.

Keywords: first trimester placenta; interleukin-7; recurrent spontaneous abortion; spontaneous abortion.