# Effects of Interleukin-6 (IL-6) on In Vitro Cultured Equine Chorionic Girdle Cells

## TL;DR

This study shows that IL-6 affects gene expression and invasiveness in equine chorionic girdle cells, but not their morphology or migration.

## Contribution

The study is the first to investigate the effects of IL-6 on equine chorionic girdle cells and their gene expression profiles.

## Key findings

- IL-6 increased eCG-related gene expression at 30 ng/mL but reduced it at 70 ng/mL.
- IL-6 enhanced cell invasion and upregulated MMP2 and MMP9 genes.
- IL-6 influenced genes in the NOD-like receptor and JAK–STAT pathways.

## Abstract

This study investigated the effects of IL-6 on equine chorionic girdle cells. IL-6 did not significantly affect cell morphology, proliferation, or eCG secretion. However, 30 ng/mL IL-6 increased eCG-related gene expression, while 70 ng/mL IL-6 reduced it. IL-6 enhanced cell invasion and upregulated invasion-related genes (MMP2, MMP9), but did not impact migration. Transcriptomic analysis showed that IL-6 influenced genes in the NOD-like receptor and JAK–STAT pathways, which are involved in immune and inflammatory responses. Overall, IL-6 positively affected cytokine secretion and invasiveness in these cells.

Introduction: Equine chorionic girdle cells can give rise to the endometrial cup, a structure that secretes equine chorionic gonadotropin (eCG). To date, the mechanisms underlying the proliferation, differentiation, invasion, and hormone secretion of equine chorionic girdle cells are not fully understood. During human pregnancy, interleukin-6 (IL-6) is maternally expressed to stimulate the invasion and migration of human syncytiotrophoblast cells and influence the synthesis of human chorionic gonadotropin. Although many previous studies reported the same upregulation of IL-6 during equine placentation, its effects on equine chorionic girdle cells have never been tested. Methods: In this study, we tested the effects of different concentrations of IL-6 on the morphology, differentiation, proliferation, hormone production, invasion, migration, and gene expression profiles of equine chorionic girdle cells. Results: We found that, with respect to morphology and proliferation, IL-6 had no significant effect; with respect to eCG production, 30 ng/mL IL-6 significantly increased the expression of genes related to eCG production, whereas treatment with 70 ng/mL IL-6 downregulated these genes. However, no significant increase in intracellular protein levels or eCG secretion was observed following treatment with any concentration of IL-6. Regarding cell migration and invasion, we found that IL-6 treatment had no significant effect on the migration capability of equine chorionic girdle cells but did enhance the invasion capability of equine chorionic girdle cells and upregulated the expression of the invasion-related genes, Mmp2 and Mmp9. Finally, our transcriptomic study revealed that in equine chorionic girdle cells, IL-6 treatment mainly affected the expression of genes related to the NOD-like receptor signaling pathway and the JAK–STAT signaling pathways, which are involved in immune and inflammatory responses. Conclusions: In summary, this study demonstrates the positive effects of IL-6 on the cytokine secretion and invasive ability of equine chorionic girdle cells.