Abstract
BackgroundEndometriosis, which shares certain characteristics with cancers, may cause abnormal expression of proteins involved in cell migration. Endometrial epithelial cells (EECs) are believed to play an important role in endometriotic migration. The aim of this study was to investigate the relationship between the expression of osteopontin (OPN) and matrix metalloproteinase-9 (MMP-9) in endometriotic migration.MethodsWe performed primary culture of EECs and investigated the expression of OPN and MMP-9 in EECs regulated by 17beta-estradiol (E2). OPN-specific siRNA interference was used to down-regulate OPN and to explore the corresponding change in MMP-9 expression. Real-time RT-PCR, western blot analysis and flow cytometry were used to determine the expression levels of OPN and MMP-9. Gelatin zymography was performed to observe the enzymatic activity of MMP-9 in conditioned media. Transwell and wound scratch assays were performed to investigate the migration ability of EECs.ResultsThe expression levels of OPN and MMP-9 in normal EECs (NEECs) were inferior to those in EECs from patients with endometriosis (EEECs). The expression levels of OPN and MMP-9 from stage III/IV EEECs and secretory-phase EECs were higher than those of stage I/II EEECs or proliferative-phase EECs. The expression levels of OPN and MMP-9 in EEECs were increased by E2 treatment and remarkably decreased by siRNA interference. Active MMP-9 expression increased with E2 treatment and decreased with siRNA treatment in EEECs compared with the same treatments in NEECs. The migratory abilities of EEECs were enhanced after cells were treated with E2; in contrast, these abilities were reduced by siRNA interference. In NEECs, active MMP-9 and cellular migration abilities were only minimally influenced by E2 and siRNA treatment.ConclusionsThe present study suggests that the up-regulation of MMP-9 via activation of OPN induced by estrogen may correlate with the migration of endometrial epithelial cells in patients with endometriosis.
Highlights
Endometriosis is a common chronic gynecological disease affecting 10 % of women of child-bearing age
We found that the expression of OPN in Eutopic endometrial epithelial cell (EEEC) was significantly higher than that in the Normal endometrial epithelial cell (NEEC)
We found that Matrix metalloproteinase (MMP)-9 expression increased in synchrony with increased OPN expression in NEECs and EEECs, which is in agreement with previous reports [11, 14]
Summary
Endometriosis is a common chronic gynecological disease affecting 10 % of women of child-bearing age. Individual susceptibility to endometriosis includes a complex interaction of genetic, hormonal and environmental factors [1]. Several theories, such as retrograde menstruation, coelomic metaplasia and Müllerianosis, have been proposed to explain its etiology, the molecular mechanisms of this disease remain unclear. Endometriosis shares some similar characteristics with cancers [2]. Many proteins have been found to play roles in the invasion and metastasis of cancer cells; whether these proteins exert a similar influence on endometrial cells in endometriosis has not yet been fully investigated. Endometriosis, which shares certain characteristics with cancers, may cause abnormal expression of proteins involved in cell migration. The aim of this study was to investigate the relationship between the expression of osteopontin (OPN) and matrix metalloproteinase-9 (MMP-9) in endometriotic migration
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