Endometriotic epithelial cell response to macrophage-secreted factors is dependent on extracellular matrix context

Endometriosis is a chronic disease in which epithelial and stromal cells that resemble the eutopic endometrium are found in ectopic lesions. In order to examine how microenvironmental factors such as extracellular matrix (ECM) and macrophages influence disease progression, 12Z (an immortalized ectopic epithelial cell line) were cultured on tissue culture plastic or in gels of recombinant basement membrane (rBM) or collagen I. Unlike cells in other conditions, cells in rBM formed multi-cellular structures in a 67 kDa non-integrin laminin receptor (67LR)-dependent manner. To examine the impact of macrophage-secreted factors on cell behavior, 12Z cells on all three substrates were treated with conditioned media from differentiated THP-1 (an immortalized monocytic cell line). Significant proliferation and invasion was observed only with cells cultured in rBM, indicating that ECM cues help dictate cell response to soluble signals. Cells cultured on rBM were then treated with individual cytokines detected in the conditioned media, with increased proliferation observed following exposure to interleukin-8 (CXCL8/IL-8) and both increased proliferation and invasion following treatment with heparin-binding EGF-like growth factor (HB-EGF). This study suggests that rBM gels can be used to induce in vitro lesion formation in order to identify soluble factors that influence proliferation and invasion.