β-Sitosterol Inhibits The Proliferation of Endometrial Cells via Regulating Smad7-Mediated TGF-β/Smads Signaling Pathway

Objective: To investigate the effect of β-sitosterol on endometrial cells to understand the underlying mechanism.Materials and Methods: This is a laboratory-based experimental study conducted on animals and cells. Histologicalassays were performed to determine the effect of β-sitosterol on endometrial cells. The CCK-8 assay was used toassess the inhibitory effect of β-sitosterol on the proliferation of ectopic endometrial stromal cells (hEM15A). Flowcytometry was performed to evaluate the induction of apoptosis by β-sitosterol in hEM15A cells. The transwell invasionassay was conducted to measure the suppression of hEM15A cell migration by β-sitosterol. Western blot analyseswere performed to analyze the effect of β-sitosterol on the expression of Smad family member 7 (Smad7) and theactivity of transforming growth factor-β (TGF-β1), as well as the phosphorylation of Smad2 and Smad3.Results: Histological assays showed that β-sitosterol regulates histopathology and induces apoptosis of endometrialcells in vivo. The CCK-8 assay revealed that β-sitosterol could inhibit the proliferation of hEM15A in human endometriosispatients. Flow cytometry showed that apoptosis was triggered by β-sitosterol in hEM15A. The transwell invasion assayindicated that the hEM15A migration under the β-sitosterol treatment group was suppressed. Western blot analysessuggested that β-sitosterol increased the expression of Smad7, decreased the activity of TGF-β1, and reduced thephosphorylation of Smad2 and Smad3. The effect of β-sitosterol was weakened by the silence of Smad7.Conclusion: The results suggest that β-sitosterol can inhibit the proliferation of endometrial cells and relieveendometriosis by inhibiting TGF-β-induced phosphorylation of Smads through regulation of Smad7.