Involvement of Transcription Factor 21 in the Pathogenesis of Fibrosis in Endometriosis

Repeated tissue injury and repair and fibrosis play a pivotal role in endometriosis. Fibrotic tissue consists of extracellular matrix proteins, regulated by transcriptional factors promoting cell proliferation and survival. Periostin is one of the putative key extracellular matrix proteins. This study aimed to determine whether transcription factor 21 (TCF21) is involved in the development of endometriosis as an upstream regulatory gene of periostin. Formalin-fixed, paraffin-embedded tissue samples [normal endometrium of women without endometriosis; eutopic endometrium of women with endometriosis; ovarian endometriosis (OE); and deep infiltrating endometriosis (DIE)] and respective cells were analyzed. Basal, transiently stimulated, and knocked down periostin and TCF21 concentrations in stromal cells of women with or without endometriosis were examined. Periostin and TCF21 expressions were undetected in normal endometrium of women without endometriosis, weakly positive in eutopic endometrium of women with endometriosis, moderately positive in OE, and strongly positive in DIE. Type 2 helper T-cell cytokines (IL-4, IL-13, and transforming growth factor-β1) increased the mRNA expression of periostin and TCF21. These cytokines, periostin, and TCF21 colocalized in the stroma of OE and DIE. siRNA against human TCF21 gene suppressed periostin expression. Transfection of TCF21 plasmid vector into stromal cells of women without endometriosis, which originally expressed neither periostin nor TCF21, resulted in TCF21 and periostin expression. TCF21 and periostin are involved in the regulation of fibrosis in endometriosis. TCF21 may be a promising therapeutic target and biomarker in endometriosis.