Estrogen-mediated activation of fibroblasts and its effects on the fibroid cell proliferation

In this study, we explored the role of estrogen-mediated activation of stromal fibroblasts in the pathogenesis of uterine fibroid in patients. We isolated uterine fibroids and surrounding smooth muscle from patients and separated fibroblasts using immunomagnetic beads. We also measured the expression levels of estrogen receptors in fibroblasts and examined cell proliferation, expressions of fibroblast activation protein (FAP), extracellular matrix (ECM) (fibronectin, laminin, collagen I), growth factors (transforming growth factor-β, insulin-like growth factor-1), and cell proliferation pathway stimulated by estrogen. We also silenced the expression of FAP by RNA interference and analyzed the expression levels of these markers before and after E2 stimulation. Finally, we also investigated the effect of activated fibroblast supernatant on cell proliferation of fibroblasts, smooth muscle cells, and fibroid cells. We found that fibroblasts in uterine fibroid were activated, and the expression levels of estrogen receptors from fibroid cells were higher than those from smooth muscle cells. After estrogen stimulation, the proliferation activity of fibroblast was enhanced, and the expression of FAP, ECM, and growth factors was increased; the signaling pathway involved in cell proliferation was also activated. Interestingly, the activated fibroblast supernatant stimulation can promote cell proliferation. Silencing of FAP expression could inhibit the E2-mediated biological effects. In conclusion, estrogen promotes proliferation of uterine fibroids through the activation of fibroblasts, thus, activated fibroblasts may play an important role in the pathogenesis of uterine fibroids, which could be targeted in future for the treatment of uterine fibroid.