Abstract
BackgroundSERPINE2, also known as protease nexin-1, belongs to the serine protease inhibitor (SERPIN) superfamily. It is one of the potent SERPINs that modulates the activity of plasminogen activators (PAs). PAs and their SERPIN inhibitors, such as SERPINB2 and SERPINE1, were expressed in the human endometrium and were implicated in implantation. However, expression data about SERPINE2 in the human endometrium is still unknown. Thus, we conducted an investigation to reveal the spatiotemporal and cellular expression of SERPINE2 in the human uterus during the menstrual cycle.MethodsSeven patients who underwent a hysterectomy and samples of 120 archived patients' endometrial curettage or parts of the uterus that were formalin-fixed and embedded in paraffin. Western blotting was performed to evaluate the specificity and sensitivity of the antibody. Immunohistochemistry was conducted to localize the SERPINE2 expression site. Quantitative analysis was conducted to evaluate expression levels of SERPINE2 in various sub-phases of the menstrual cycle.ResultsThe SERPINE2 protein was primarily detected in the uterine fluid during the mid- and late-secretory phases of the menstrual cycle. It was predominantly expressed in the luminal and glandular epithelium, less in the myometrium, and only dispersedly in certain stromal cells throughout the menstrual cycle. A quantitative analysis of expression levels of SERPINE2 in the glandular epithelium revealed that it was highly expressed in the endometrium during the secretory phase compared to the proliferative phase.ConclusionsThe SERPINE2 protein is highly expressed in the endometrium during the secretory phase, indicating that it may participate in tissue remodeling involved in implantation.
Highlights
SERPINE2, known as protease nexin-1, belongs to the serine protease inhibitor (SERPIN) superfamily
An apparent 44-kDa protein band corresponding to human SERPINE2 was immunodetected by our anti-mouse SERPINE2 antibody, while many non-specific crossedreacted protein bands were blotted by the commercial antibodies
To further evaluate the expression of the SERPINE2 protein in various sub-phases of the menstrual cycle, we examined endometrial slides prepared from early, mid, and late-proliferative as well as secretory phases by immunohistochemistry
Summary
SERPINE2, known as protease nexin-1, belongs to the serine protease inhibitor (SERPIN) superfamily. It is one of the potent SERPINs that modulates the activity of plasminogen activators (PAs). PAs and their SERPIN inhibitors, such as SERPINB2 and SERPINE1, were expressed in the human endometrium and were implicated in implantation. The system includes two forms of PA, tissue-type (PLAT or tPA) and urokinasetype (PLAU or uPA), and four forms of serine protease inhibitors (SERPIN), including SERPINA5 ( called protein C inhibitor, PCI), SERPINB2 ( called plasminogen activator inhibitor 2, PAI-2), SERPINE1 ( called plasminogen activator inhibitor 1, PAI-1), and SERPINE2 ( called protease nexin-1, PN-1) [2]. The classical substrate of plasmin is fibrin, but many other matrix proteins can be cleaved by this enzyme [1]
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