Angiogenic properties of endometrial mesenchymal stromal cells in endothelial co-culture: an in vitro model of endometriosis.

Can endometrial mesenchymal stromal cells (E-MSCs) differentiate into endothelial cells in an in vitro co-culture system with human umbilical vein endothelial cells (HUVECs)? E-MSCs can acquire endothelial markers and function in a direct co-culture system with HUVECs. E-MSCs have been identified in the human endometrium as well as in endometriotic lesions. E-MSCs appear to be involved in formation of the endometrial stromal vascular tissue and the support of tissue growth and vascularization. The use of anti-angiogenic drugs appears as a possible therapeutic strategy against endometriosis. This is an in vitro study comprising patients receiving surgical treatment of ovarian endometriosis (n = 9). E-MSCs were isolated from eutopic and ectopic endometrial tissue and were characterized for the expression of mesenchymal and endothelial markers by FACS analysis and Real-Time PCR. CD31 acquisition was evaluated by FACS analysis and immunofluorescence after a 48 h-direct co-culture with green fluorescent protein +-HUVECs. A tube-forming assay was set up in order to analyze the functional potential of their interaction. Finally, co-cultures were treated with the anti-angiogenic agent Cabergoline. A subpopulation of E-MSCs acquired CD31 expression and integrated into tube-like structures when directly in contact with HUVECs, as observed by both FACS analysis and immunofluorescence. The isolation of CD31+ E-MSCs revealed significant increases in CD31, vascular endothelial growth factor receptor 2, TEK receptor tyrosine kinase and vascular endothelial-Cadherin mRNA expression levels with respect to basal and to CD31neg cells (P < 0.05). On the other hand, the expression of mesenchymal genes such as c-Myc, Vimentin, neuronal-Cadherin and sushi domain containing 2 remained unchanged. Cabergoline treatment induced a significant reduction of the E-MSC angiogenic potential (P < 0.05 versus control). Not applicable. Further studies are necessary to investigate the cellular and molecular mechanisms underlying the endothelial cell differentiation. E-MSCs may undergo endothelial differentiation, and be potentially involved in the development of endometriotic implants. Cell culture systems that more closely mimic the cellular complexity typical of endometriotic tissues in vivo are required to develop novel strategies for treatment. This study was supported by the 'Research Fund ex-60%', University of Turin, Turin, Italy. All authors declare that their participation in the study did not involve actual or potential conflicts of interests.

Canosa S ，Moggio A ，Brossa A ，Pittatore G ，Marchino GL ，Leoncini S ，Benedetto C ，Revelli A ，Bussolati B ... -  《-》

Synergistic effect of regulatory T cells and proinflammatory cytokines in angiogenesis in the endometriotic milieu.

Do regulatory T cells (Tregs) contribute to angiogenesis in endometriosis? High levels of CCL17 and CCL22 cause the recruitment of Tregs, upregulate the immunosuppression of Tregs and, in turn, may promote angiogenesis in endometrial cells in synergy with proinflammatory cytokines. The peritoneal fluid of patients with endometriosis has a higher percentage of Tregs than that of normal individuals; however, the regulatory role of Tregs in the disease remains unclear. This study used primary human endometrial stromal cells (ESCs), monocytes (Mo), Tregs and human umbilical vein endothelial cells (HUVECs). All experiments were performed at least three times. The migration of Tregs was evaluated by the transwell migration assay. The activation of extracellular signal-regulated kinase (ERK)1/2, c-Jun N-terminal kinase and p38 signaling pathways was examined using the In-Cell WesternTM (LI-COR®) western blot analysis system, as well as by traditional western blot analysis. Changes in the expression of CCL22, CCL17, transforming growth factor-beta 1 (TGF-β1), Interleukin (IL)-1β, tumor necrosis factor alpha (TNF-α), IL-8 and vascular endothelial growth factor (VEGF) in cell-culture supernatant were detected by ELISA. We analyzed the Tregs by multicolor flow cytometry to directly test the expression of CCR4, CD4, CD25, Foxp3, CTLA-4, CD39 and CD73. Our results showed that ESCs-Mo co-culture produced significantly higher levels of CCL22 and CCL17 than ESCs or Mo cultured alone, and that estradiol (E2) or progesterone (P) further promoted this upregulation, demonstrating stronger chemotaxis on Tregs. The co-culture of ESCs with Mo stimulated TGF-β1 secretion by Tregs, which could be inhibited by anti-CCL22 or/and anti-CCL17 neutralizing antibodies (Abs). The expression of CCR4 by Tregs was upregulated in ESCs-Mo co-culture, especially by treatment with E2 and/or P, and this effect could be abolished by anti-CCL22 and/or anti-CCL17-neutralizing Abs. The Treg-ESCs-Mo co-culture treated with E2 (10-8 mol/l) and P (10-8 mol/l) could enhance the immunosuppression of Tregs, as proved by the elevated expression of Foxp3, CTLA-4, CD39 and CD73 on Tregs. ESCs-Mo co-culture could significantly promote the secretion of IL-1β and TNF-α. TGF-β1 from Tregs could activate p38/ERK1/2 signaling pathways in ESCs, and IL-1β and TNF-α produced by ESCs-Mo co-culture had synergistic roles with TGF-β1. TGF-β1 and the proinflammatory cytokines IL-1β or TNF-α could synergistically promote IL-8 and VEGF expression in ESCs via the p38/ERK1/2 signaling pathways. The high levels of IL-8 and VEGF in the supernatant of ESCs stimulated the angiogenesis of HUVECs. None. This study was only performed in vitro using eutopic ESCs, instead of ectopic cells, from endometriosis patients. Therefore, it is necessary to do further experiments to determine whether Tregs promote angiogenesis in the endometriotic milieu in synergy with proinflammatory cytokines in vivo. Co-targeting Tregs and proinflammatory cytokines may be an effective treatment for endometriosis. This study was supported by Ministry of Science and Technology of China 2015CB943300 to L.D.-J.; National Natural Science Foundation of China, item number 81200425 to  W.X.-Q.; National Natural Science Foundation of China, item number 81471548 to L.D.-J.; and The Research Fund for the Doctoral Program of Higher Education of China to W.X.-Q. (20110071120093). The authors have no conflicts of interest to declare.

Wang XQ ，Zhou WJ ，Luo XZ ，Tao Y ，Li DJ ... -  《-》

Suppression of COUP-TFII upregulates angiogenin and promotes angiogenesis in endometriosis.

How does hypoxia-mediated downregulation of chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) promote angiogenesis in endometriosis? Suppression of COUP-TFII by hypoxia stimulates angiogenesis through induction of angiogenin (ANG). The level of COUP-TFII is downregulated in endometriotic tissues, and downregulation of COUP-TFII contributes to the development of endometriosis. Twenty-seven patients of reproductive age with endometriosis were recruited in this study. Eutopic endometrial and ectopic endometriotic stromal cells were isolated, cultured and subjected to various treatments. Microarray hybridization, quantitative RT-PCR, and Western blot were used to detect gene expression in normal and endometriotic samples. A luciferase reporter assay and chromatin immunoprecipitation in normoxia- or hypoxia-treated primary cultures of human endometrial stromal cells were performed. Tube formation analysis was performed using primary human umbilical vein endothelial cells (HUVECs). Protein level of COUP-TFII was downregulated by hypoxia (P < 0.05, normoxia versus hypoxia). Loss of COUP-TFII increased the angiogenic capacity of endometrial stromal cells (P < 0.05, COUP-TFII knockdown versus knockdown control). A novel COUP-TFII target gene, ANG, was identified through microarray analysis. Chromatin immunoprecipitation and promoter activity assays demonstrated that the ANG promoter was bound and suppressed by COUP-TFII (P < 0.05, COUP-TFII overexpression versus empty vector). The levels of ANG mRNA and protein were elevated in ectopic endometriotic stromal cells and negatively correlated with COUP-TFII (P < 0.05, endometrial versus endometriotic tissues/stromal cells). Both knockdown and forced-expression of COUP-TFII further demonstrated that ANG expression and ANG-mediated angiogenic activity were negatively regulated by COUP-TFII (P < 0.05, COUP-TFII knockdown versus knockdown control, and COUP-TFII overexpression versus empty vector). This study was conducted in primary human endometrial stromal cell cultures and HUVECs, therefore, may not fully reflect the situation in vivo. The raw data were submitted to Gene Expression Omnibus (GSE107469). This is the first study to highlight that the aberrant expression of ANG in endometriotic lesions is mediated by hypoxia-suppressed COUP-TFII expression, which reveals an as yet unidentified molecular pathogenesis of endometriosis. This work was supported by research grants (MOST 105-2314-B-006-059-MY3 to M.H.W. and MOST 104-2320-B-006-036-MY3 to S.J.T.) from the Ministry of Science and Technology, Taiwan. The authors declare that there is no conflict of interest.

Fu JL ，Hsiao KY ，Lee HC ，Li WN ，Chang N ，Wu MH ，Tsai SJ ... -  《-》

Endometriotic mesenchymal stem cells significantly promote fibrogenesis in ovarian endometrioma through the Wnt/β-catenin pathway by paracrine production of TGF-β1 and Wnt1.

Are endometriotic mesenchymal stem cells (Ecto-MSCs) involved in the fibrosis of ovarian endometrioma? Ecto-MSCs enhanced the fibrotic behavior of stromal cells in ovarian endometrioma through the Wnt/β-catenin pathway by paracrine production of transforming growth factor-β1 (TGF-β1) and Wnt1. Endometriosis is characterized by ectopic outgrowth of endometrial stroma and glands surrounded by dense fibrous tissues. The pathogenesis of endometriosis, especially ovarian endometrioma-associated fibrosis, is still unknown. We analyzed endometrial samples from 15 patients of reproductive age with ovarian endometrioma and normal menstrual cycles. A total of 54 nude mice received a single injection of proliferative endometrial fragments from 14 individuals without endometriosis. Conditioned medium (CM) was collected from endometrial mesenchymal stem cells (Euto-MSCs) and Ecto-MSCs. The effects of CM on cell proliferation, migration, invasion and collagen gel contraction of endometrial and endometriotic stromal cells (Euto- and Ecto-ESCs) in ovarian endometrioma were evaluated by cell counting kit-8, transwell and collagen gel contraction assays. Effects of CM on fibrotic markers' expression [including α-smooth muscle actin, Type I collagen, connective tissue growth factor and fibronectin (FN)] in Euto- and Ecto-ESCs were determined by real-time reverse-transcription-polymerase chain reaction and western blotting. Additionally, fibrogenic effects of Ecto-MSC CM treatment on endometriotic implants were analyzed using a xenograft model of endometriosis in immunodeficient nude mice. Our results demonstrated that Ecto-MSC CM significantly promoted cell proliferation, migration, invasion and collagen gel contraction of Euto- and Ecto-ESCs from patients with ovarian endometrioma compared with control and Euto-MSC CM. Expression levels of fibrotic markers in Euto- and Ecto-ESCs were dramatically elevated after treatment with Ecto-MSC CM. Ecto-MSCs secreted higher levels of TGF-β1 and Wnt1 compared with Euto-MSCs. Furthermore, both TGF-β1 and Wnt1 significantly increased expression of fibrotic markers in Euto- and Ecto-ESCs, which was reversed by an anti-TGF-β1 antibody or Wnt1 negative regulator, Dickkopf-related protein 1 (Dkk1). Mechanistic studies demonstrated that Wnt/β-catenin signaling pathways in stromal cells were activated by Ecto-MSC CM. Animal experiments showed that TGF-β1 and Wnt1 as well as Ecto-MSC CM markedly increased the expression of FN and collagen I, which enhanced the progression of fibrosis in endometriosis. To our knowledge, this is the first study to identify the role of Ecto-MSCs in the pathogenesis of fibrosis in ovarian endometrioma. However, numerous other growth factors and cell types may also be involved in the pathogenesis. Therefore, further studies are required to elucidate the paracrine effects of cells in ovarian endometrioma. Ecto-MSCs may be involved in the pathogenesis of fibrosis in ovarian endometrioma. This study was supported in part by the National Natural Science Foundation of China (81471505 and 81270657). No competing interests are declared.

Li J ，Dai Y ，Zhu H ，Jiang Y ，Zhang S ... -  《-》

Human endometrial perivascular stem cells exhibit a limited potential to regenerate endometrium after xenotransplantation.

What are the localization, characteristics and potential for tissue regeneration of two perivascular stem cells, namely CD34+ adventitial cells and CD146+ pericytes, in human endometrium? Human endometrial CD34+ adventitial cells (located in the outermost layer of blood vessels and mainly in the basal layer) and CD146+ pericytes showed mesenchymal stem cell (MSC) phenotypes in in vitro culture, but presented limited potential to regenerate endometrium. Periodic endometrial regeneration is considered to be maintained by MSCs. Blood vessel wall, regarded as stem cell niche, harbors a large reserve of progenitor cells that may be integral to the origin of MSCs. However, a lack of validated markers has hampered the isolation of putative endometrial MSCs. Currently, CD146+ pericytes and Sushi Domain Containing 2 (SUSD2) positive cells have been identified in the endometrial perivascular region as sharing MSCs characteristics. The locations of adventitial cells and pericytes in the human endometrium were identified by immunofluorescence staining (n = 4). After CD34+CD146-CD45-CD56-CD144- adventitial cells and CD146+CD34-CD45-CD56-CD144- pericytes were isolated from the endometrium of normal women (n = 6) by fluorescence-activated cell sorting, their characteristics were investigated in culture. Adventitial cells and pericytes were induced to differentiate, respectively, into vascular endothelial-like cells or endometrial stromal-like cells in vitro, with their potential explored by in vivo xenotransplantation (n = 2 in each group) and eutopic transplantation (n = 2 in each group). CD34+ adventitial cells and CD146+ pericytes were cultured in the inducing medium to differentiate into endothelial-like cells in vitro, and then analyzed for CD31, von Willebrand factor immunofluorescent staining and tube formation. They were also cultured to differentiate into endometrial stromal cells in vitro, with the expression of vimentin and CD13 being detected by western blot before and after induction, and the expression of prolactin and insulin-like growth factor-binding protein 1 being determined as well. Single dispersed CD34+ adventitial cells and CD146+ pericytes were respectively transplanted under the kidney capsule of NOG mice to investigate their differentiation potential in vivo. A eutopic transplantation model was constructed by grafting recellularized uterine matrix loaded up with CM-Dil labeled adventitial cells or pericytes into the injury region of nude rat's uterus. CD34+ adventitial cells were mainly located at the outmost layer of endometrial large vessels, while CD146+ pericytes were found surrounding the inner endothelial cells of microvessels. A small proportion of CD34+ adventitial cells expressed SUSD2. The number of adventitial cells was ∼40 times higher than that of pericytes in the endometrium. Both adventitial cells and pericytes showed MSC phenotypes after in vitro culture. After in vitro induction into endometrial endothelial-like cells and stromal-like cells, adventitial cells showed higher plasticity than pericytes and a closer correlation with stromal-like cells. In the mouse xenotransplantation model, vimentin+ cells, CD31+ endothelial-like cells and CD146+ pericyte-like cells could be observed after adventitial cells were transplanted. CM-Dil-labeled adventitial cells or pericytes could survive in the immunocompromised nude rats after eutopic transplantation, and vimentin+ cells were detected. In addition, CM-Dil-labeled adventitial cells or pericytes did not express α-smooth muscle actin or E-cadherin after transplantation. N/A. CD34 was chosen as a novel marker to isolate adventitial cells from human endometrium according to previous literature. The association of endometrial CD34+ adventitial cells and SUSD2+ MSCs should be further investigated. The decellularized uterine matrix model might be useful in endometrial stem cell therapy. L.D. is supported by grants from National Key Research and Development Program of China (2018YFC1004700), Nature Science Foundation of China (81871128, 81571391) and Nanjing Medical Science Development Project (ZKX16042). H.S. is supported by a grant from Jiangsu Province Social Development Project (BE2018602). X.Z. was supported by grants from the Postgraduate Innovative Project of Jiangsu Province (KYCX19-1177). The authors declare no conflict of interest.

Zhu X ，Yu F ，Yan G ，Hu Y ，Sun H ，Ding L ... -  《-》