Research Article: Connective tissue growth factor mediates transforming growth factor β-induced collagen expression in human endometrial stromal cells

Date Published: January 29, 2019

Publisher: Public Library of Science

Author(s): Mei-Leng Cheong, Tsung-Hsuan Lai, Wen-Bin Wu, Chuen-Mao Yang.


Adenomyosis is a medical condition defined by the abnormal presence of endometrial tissue within the myometrium, in which fibrosis occurs with new collagen deposition and myofibroblast differentiation. In this study, the effect of several mediators and growth factors on collagen expression was investigated on human endometrial stromal cells (fibroblasts) derived from adenomyotic endometrium.

RT-PCR, Western blot analysis, pharmacological interventions and siRNA interference were applied to primary cultured human endometrial stromal cells (fibroblasts). Immunohistochemistry was used to analyze protein expression in adenomyotic endometrium tissue specimens.

Of the tested mediators, transforming growth factor β1 (TGFβ1) and its isoforms were effective to induce collagen and connective tissue growth factor (CTGF) expression. Collagen and CTGF induction by TGFβ1 could be reduced by the inhibitors targeting DNA transcription, protein translation, and Smad2/3 signaling. Interestingly, TGFβ1 induced Smad2/3 phosphorylation and CTGF mRNA expression, but not collagen mRNA expression, suggesting that TGFβ1 mediates collagen expression through CTGF induction and Smad2/3 activation. In parallel, TGFβ1 and CTGF also induced expression of heat shock protein (HSP) 47, a protein required for the synthesis of several types of collagens. However, only CTGF siRNA knockdown, could compromise TGFβ1-induced collagen expression. Finally, the immunohistochemistry revealed vimentin- and α-SMA-positive staining for (myo)fibroblasts, TGFβ1, collagen, and CTGF in the subepithelial stroma region of human adenomyotic endometria.

We reveal here that TGFβ1, collagen, and CTGF are expressed in the stroma of adenomyotic endometria and demonstrate that TGFβ1 can induce collagen production in endometrium-derived fibroblasts through cellular Smad2/3-dependent signaling pathway and CTGF expression, suggesting that endometrial TGFβ may take part in the pathogenesis of adenomyosis and ectopic endometrium may participate in uterine adenomyosis.

Partial Text

Uterine adenomyosis is a medical condition defined by the abnormal presence of endometrial tissue within the myometrium and the main mechanisms include sex hormone aberrations, inflammation and neuroangiogenesis, proliferation and fibrosis [1]. However, the exact etiology of adenomyosis remains unclear. Recently, by means of magnetic resonance imaging technology, it was reported that uterine adenomyosis can be further classified into four subtypes based on their localizations and all types usually have an aspect of fibrosis [2, 3].

An adenomyoma is a focal region of adenomyosis, which is a mass within uterine myometrium and is usually fibrotic. Although the exact etiology of adenomyosis is still elusive, all types of adenomyosis usually have a feature of fibrosis [2]. As described earlier, fibrosis is characterized by an excessive collagen and ECM deposition [26]. In this study, we found that TGFβ1 could induce collagen and CTGF expression in the HESCs (Fig 1B). IHC of the adenomyotic endometria demonstrates TGFβ1 and collagen expression in the endometrial subepithelial stroma (Fig 7), suggesting that they may be coexpressed in the pathological conditions. Interestingly, the inductory effect on collagen expression by TGFβ1 stimulation was not through directly affecting collagen gene expression but was mainly mediated via CTGF mRNA and protein expression. Although a previous study has shown that TGFβ1 can induce collagen, CTGF, α-SMA and fibronectin mRNA expression in endometriotic and endometrial stromal cells [27], this is the first time to elucidate the action mechanism that TGFβ1 is capable of inducing collagen expression mediated through induction of CTGF expression and cellular Smad2/3-dependent pathway in human adenomyotic endometrium-derived stromal fibroblasts. In addition, exogenous CTGF has been shown to induce collagen expression in human lung fibroblasts and CTGF participates in bleomycin-induced collagen expression and lung fibrosis [28, 29],




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