Effects of matrix stiffness on epithelial to mesenchymal transition-like processes of endometrial epithelial cells: Implications for the pathogenesis of endometriosis

Abstract

Endometriosis is defined as the presence of endometrial glands and stroma within extrauterine sites. Our previous study revealed an epithelial to mesenchymal transition (EMT)-like process in red peritoneal endometriosis, whereas membrane localization of E-cadherin was well maintained in epithelial cells of deep infiltrating endometriosis (DIE). Here we show that endometrial epithelial cells (EEE) grown on polyacrylamide gel substrates (PGS) of 2 kilopascal (kPa), a soft matrix, initiate a partial EMT-like process with transforming growth factor-β1 (TGF-β1) stimulation. Increasing matrix stiffness with TGF-β1 stimulation reduced the number of cell-cell contacts. Cells that retained cell-cell contacts showed decreased expression of E-cadherin and zonula occludens 1 (ZO-1) to cell-cell junctions. Few deep endometriotic epithelial cells (DEE) grown on 30-kPa PGS, which may mimic in vivo tissue compliance of DIE, retained localization of E-cadherin to cell-cell junctions with TGF-β1 treatment. Immunohistochemical analysis showed no phosphorylated Smad 2/3 nuclear localization in E-cadherin+ epithelial cells of DIE. We hypothesize that EEE may undergo an EMT-like process after attachment of endometrium to peritoneum in a TGF-β1–rich microenvironment. However, TGF-β1 signaling may be absent in DIE, resulting in a more epithelial cell-like phenotype in a rigid microenvironment.

TRPV4 regulates matrix stiffness and TGFβ1‐induced epithelial‐mesenchymal transition

“…The presence of TGFβ1 further augmented matrix stiffness‐induced EMT‐associated changes, suggesting functional crosstalk between physical and soluble factors. These results using NMEKs are consistent with recent studies in other cell types that have demonstrated increasing matrix stiffness as a crucial regulator of TGFβ1‐induced EMT . For example, it has been shown that matrix rigidity regulates a switch between TGFβ1‐induced apoptosis and EMT in murine mammary gland epithelial cells .…”

EGFR‐mediated matrix metalloproteinase‐7 up‐regulation promotes epithelial‐mesenchymal transitionviaERK1‐AP1 axis during ovarian endometriosis progression

“…The present study also found elevated collagen deposition in later stages of ovarian endometriosis. In addition to acting as a mesenchymal marker, collagen alleviates cellular invasiveness via mechanotransduction in cancer cells (33) as well as endometrial cells (27). Recently, fibroblast-to-myofibroblast transdifferentiation has been reported in a baboon model of endometriosis (34).…”

“…In addition, studies have identified an EMT-like phenomenon in deep-infiltrating pelvic endometriosis with elevated expression of vimentin and S00A4 and decreased expression of cytokeratin (25). Factors that reportedly promote EMT in endometriosis include hypoxia inducible factor 1a and matrix stiffness (26,27). MMPs involved in cleavage of ECM and non-ECM molecules also promote cellular invasiveness and transitions, especially MMP-3 and MMP-7, which are reported to cleave adherent junction proteins (28)(29)(30).…”

NEK4 kinase regulates EMT to promote lung cancer metastasis

“…ZO1 is an epithelial marker and the diffusion of ZO1 from cell-cell contacts results in the dissolution of tight junctions during EMT. 24 We propose that NEK4 may mainly contribute to the process of loss of epithelial characteristics.…”

“…In the meantime, we detected the up‐regulation of epithelial marker ZO1 and no obvious changes of the mesenchymal markers such as Vimentin and N‐cadherin in A549 cells transfected with siNEK4. ZO1 is an epithelial marker and the diffusion of ZO1 from cell‐cell contacts results in the dissolution of tight junctions during EMT . We propose that NEK4 may mainly contribute to the process of loss of epithelial characteristics.…”