Thrombin induces slug-mediated E-cadherin transcriptional repression and the parallel up-regulation of N-cadherin by a transcription-independent mechanism in RPE cells

PAK5 potentiates slug transactivation of N-cadherin to facilitate metastasis of renal cell carcinoma

Renal cell carcinoma (RCC) is an aggravating cancer with a poor prognosis and a high rate of metastasis. PAK5, a p21-activated kinases, has shown to be overexpressed in a variety of cancers, including RCC. In previous studies, we discovered that PAK5 regulates cell migration and invasion in RCC cell lines. However, the underlying mechanisms remain obscure. In this study, we consolidated that PAK5 confers a pro-metastatic phenotype RCC cells in vitro and exacerbates metastasis in vivo. High PAK5 expression was associated with an advanced TNM stage and a lower overall survival. Furthermore, PAK5 increases the expression level of N-cadherin. In terms of mechanism, PAK5 bound to Slug and phosphorylated it at serine 87. As a result, phosphorylated Slug transactivated N-cadherin, accelerating the epithelial-mesenchymal transition. Collectively, Slug is a novel PAK5 substrate, and PAK5-mediated phosphorylation of Slug-S87 increases N-cadherin and the pro-metastatic phenotype of RCC, implying that phosphorylated Slug-S87 could be a therapeutic target in progressive RCC.

METTL3-mediated m6A modification of HMGA2 mRNA promotes subretinal fibrosis and epithelial-mesenchymal transition

Subretinal fibrosis is a major cause of the poor visual prognosis for patients with neovascular age-related macular degeneration (nAMD). Myofibroblasts originated from retinal pigment epithelial (RPE) cells through epithelial-mesenchymal transition (EMT) contribute to the fibrosis formation. N6-Methyladenosine (m6A) modification has been implicated in the EMT process and multiple fibrotic diseases. The role of m6A modification in EMT-related subretinal fibrosis has not yet been elucidated. In this study, we found that during subretinal fibrosis in the mouse model of laser-induced choroidal neovascularization, METTL3 was upregulated in RPE cells. Through m6A epitranscriptomic microarray and further verification, high-mobility group AT-hook 2 (HMGA2) was identified as the key downstream target of METTL3, subsequently activating potent EMT-inducing transcription factor SNAIL. Finally, by subretinal injections of adeno-associated virus vectors, we confirmed that METTL3 deficiency in RPE cells could efficiently attenuate subretinal fibrosis in vivo. In conclusion, our present research identified an epigenetic mechanism of METTL3-m6A-HMGA2 in subretinal fibrosis and EMT of RPE cells, providing a novel therapeutic target for subretinal fibrosis secondary to nAMD.

Nintedanib prevents TGF-β2-induced epithelial-mesenchymal transition in retinal pigment epithelial cells

Epithelial-mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cells is a key fibrosis pathogenesis in proliferative vitreoretinopathy (PVR). However, few medicines can prevent proliferative membranes and cell proliferation in the clinic. Nintedanib, a tyrosine kinase inhibitor, has been shown to prevent fibrosis and be anti-inflammatory in multiple organ fibrosis. In our study, 0.1, 1, 10 μM nintedanib was added to 20 ng/mL transforming growth factor beta 2 (TGF-β2)-induced EMT in ARPE-19 cells. Western blot and immunofluorescence assay showed that 1 μM nintedanib suppressed TGF-β2-induced E-cadherin expression decreased and Fibronectin, N-cadherin, Vimentin, and α-SMA expression increased. Quantitative real-time PCR results showed that 1 μM nintedanib decreased TGF-β2-induced increase in SNAI1, Vimentin, and Fibronectin expression and increased TGF-β2-induced decrease in E-cadherin expression. In addition, the CCK-8 assay, wound healing assay, and collagen gel contraction assay also showed that 1 μM nintedanib ameliorated TGF-β2-induced cell proliferation, migration, and contraction, respectively. These results suggested that nintedanib inhibits TGF-β2-induced EMT in ARPE-19 cells, which may be a potential pharmacological treatment for PVR.

Long Noncoding RNA Regulator of Reprogramming Regulates Cell Growth, Metastasis, and Cisplatin Resistance in Gastric Cancer via miR-519d-3p/HMGA2 Axis

Background: Gastric cancer (GC) is a common tumor found worldwide, and cisplatin is the first-line agent for the treatment of GC. However, the resistance to cisplatin is an obstacle. Here, we explored the biological mechanism of long noncoding RNA regulator of reprogramming (ROR) in the cisplatin resistance of GC. Materials and Methods: ROR, miR-519d-3p, and high mobility group protein A2 (HMGA2) expression in GC tissues and cells were measured by quantitative real-time polymerase chain reaction and Western blot. Cell viability, migration, invasion, and apoptosis were detected by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay, transwell assay, and flow cytometry, respectively. The relative protein expression was detected by Western blot. The interactions between miR-519d-3p and ROR, HMGA2 were predicted using miRcode and starBase v2.0 online database, and then verified by dual luciferase reporter assay and RNA immunoprecipitation assay. In addition, the xenograft tumor mouse model was constructed to verify the biological role of ROR in vivo. Results: The levels of ROR, HMGA2 were significantly upregulated, and miR-519d-3p was apparently downregulated in GC tissues and cells. The miRcode and starBase v2.0 online websites and dual luciferase reporter assay validated that miR-519d-3p directly interacted with ROR and HMGA2. Furthermore, ROR knockdown downregulated HMGA2 to restrain cell proliferation, migration, invasion, epithelial-mesenchymal transition (EMT), and cisplatin resistance in GC cells by targeting miR-519d-3p. In addition, the depletion of ROR repressed the xenograft tumor growth in vivo. Conclusion: In conclusion, we first found the ROR/miR-519d-3p/HMGA2 regulatory network to regulate cell proliferation, migration, invasion, EMT, and cisplatin resistance in GC, and this may shed light on the GC tumorigenesis.

MicroRNA-4516 suppresses proliferative vitreoretinopathy development via negatively regulating OTX1

Proliferative vitreoretinopathy (PVR) progression is associated with TGF-β2-induced epithelial–mesenchymal transition (EMT) in retinal pigment epithelial (RPE) cells. In cancer cells, miR-4516 downregulates orthodenticle homeobox 1 (OTX1)-mediated cell invasion. Moreover, OTX1 is shown to be involved in invasion and EMT. The purpose of this study was to assess whether microRNA (miR-4516) suppresses EMT in RPE cells. EMT features were assessed using Western blotting, immunocytochemical staining, scratch-wound healing, modified Boyden chamber assay, and collagen gel contraction assay. For in vivo testing, a rabbit model was used, which involved induction of PVR by injection of transfected spontaneously arising RPE (ARPE) cells into the vitreous chamber. The putative target of miR-4516 was identified by luciferase reporter assay. Results showed that TGF-β2-induced transdifferentiation and migration of RPE cells was inhibited by miR-4516 delivery. Overexpression of miR-4516 led to upregulation of zonula occludens-1, downregulation of α-smooth muscle actin and vimentin, and cell contractility—all EMT features—in the TGF-β2-treated ARPE-19 cells. MiR-4516 regulated OTX1 expression negatively by binding to its 3’-UTR. TGF-β2-induced phosphorylated ERK was inhibited in miR-4516-overexpressing ARPE-19 cells. MiR-4516 suppressed experimental PVR in vitro and in vivo. In conclusion, the overexpression of miR-4516 suppresses TGF-β2-induced EMT in a PVR model, and its role in PVR depends on OTX1/ERK. Further research is needed to develop a feasible treatment method to prevent and treat PVR.

Repression of Smad4 by MicroRNA-1285 moderates TGF-β-induced epithelial-mesenchymal transition in proliferative vitreoretinopathy

The purpose of this study was to assess whether microRNA (miR)-1285 can suppress the epithelial-mesenchymal transition (EMT) in retinal pigment epithelial cells. Expression of miR-1285 was evaluated using quantitative real-time polymerase chain reaction (RT-qPCR). The features of EMT were assessed using Western blotting, immunocytochemical staining, scratch wound healing tests, modified Boyden chamber assay, and collagen gel contraction assay. A rabbit model of proliferative vitreoretinopathy (PVR) was used for in vivo testing, which involved the induction of PVR by injection of transfected ARPE cells into the vitreous chamber. Luciferase reporter assay was performed to identify the putative target of miR-1285. The expression of miR-1285 was downregulated in ARPE-19 cells treated with transforming growth factor (TGF)-β. Overexpression of miR-1285 led to upregulation of zonula occludens-1, downregulation of α-smooth muscle actin and vimentin, cell migration and cell contractility-all EMT features-in the TGF-β2-treated ARPE-19 cells. The reporter assay indicated that the 3' untranslated region of Smad4 was the direct target of miR1285. PVR progression was alleviated in the miR-1285 transfected rabbits. In conclusion, overexpression of miR-1285 attenuates TGF-β2-induced EMT in a rabbit model of PVR, and the effect of miR-1285 in PVR is dependent on Smad4. Further research is warranted to develop a feasible therapeutic approach for the prevention and treatment of PVR.

Inhibition of TGF-β2-induced migration and epithelial-mesenchymal transition in ARPE-19 by sulforaphane

AIM

To investigate the effects of sulforaphane (SFN) on transforming growth factor (TGF)-β2 stimulated migration and epithelial-mesenchymal transition (EMT) in ARPE-19 cells.

METHODS

ARPE-19 cells were cultured in the presence or absence of SFN or TGF-β2. SFN toxicity was assessed by performing a lactate dehydrogenase assay (LDH) and 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assays, and cell migration was evaluated by Transwell migration assay. Actin stress fiber formation in ARPE-19 cells was determined using immunofluorescence analysis. Immunoblotting analysis was used to determine fibronectin and α-smooth muscle actin expressions along with the degree of Smad and Akt phosphorylation.

RESULTS

SFN inhibited ARPE-19 migration. Additionally, SFN attenuated TGF-β2-induced appearance of actin stress fibers as well as fibronectin and α-smooth muscle actin expressions in these cells. SFN also hindered the TGF-β2-stimulated phosphorylation of Smad2, Smad3, and Akt. SFN showed no cytotoxicity towards ARPE-19 cells.

CONCLUSION

SFN inhibits TGF-β2-stimulated migration and EMT in ARPE-19 cells, probably by preventing the establishment of actin stress fibers and Akt and Smad2/3 signaling.

Endometrial epithelial-mesenchymal transition (EMT) by menstruation-related inflammatory factors during hypoxia

Endometriosis is characterised by inflammation and fibrotic changes. Our previous study using a mouse model showed that proinflammatory factors present in peritoneal haemorrhage exacerbated inflammation in endometriosis-like grafts, at least in part through the activation of prostaglandin (PG) E2 receptor and protease-activated receptor (PAR). In addition, hypoxia is a well-known inducer of fibrosis that may be associated with epithelial-mesenchymal transition (EMT). However, the complex molecular interactions between hypoxia and proinflammatory menstruation-related factors, PGE2 and thrombin, a PAR1 agonist, on EMT in endometriosis have not been fully characterised. To explore the effects of hypoxia and proinflammatory factors on EMT-like changes in endometrial cells, we determined the effects of PGE2 and thrombin (P/T) on EMT marker expression and cell migration in three dimensional cultured human endometrial epithelial cells (EECs) and endometrial stromal cells (ESCs). Treatment of EECs with P/T under hypoxia stimulated cell migration, increased the expression of mesenchymal N-cadherin, vimentin and C-X-C chemokine receptor type 4 (CXCR4), and reduced the expression of epithelial E-cadherin. Furthermore, treatment with C-X-C motif chemokine ligand 12 (CXCL12), a ligand for CXCR4, increased EMT marker expression and cell migration. In ESCs, P/T or oestrogen treatment under hypoxic conditions increased the expression and secretion of CXCL12. Taken together, our data show that hypoxic and proinflammatory stimuli induce EMT, cell migration and inflammation in EECs, which was increased by CXCL12 derived from ESCs. These data imply that inflammatory mediators in retrograde menstrual fluid contribute to ectopic endometrial EMT and migration in the presence of peritoneal hypoxia.

Polarity and epithelial-mesenchymal transition of retinal pigment epithelial cells in proliferative vitreoretinopathy

Under physiological conditions, retinal pigment epithelium (RPE) is a cellular monolayer composed of mitotically quiescent cells. Tight junctions and adherens junctions maintain the polarity of RPE cells, and are required for cellular functions. In proliferative vitreoretinopathy (PVR), upon retinal tear, RPE cells lose cell-cell contact, undergo epithelial-mesenchymal transition (EMT), and ultimately transform into myofibroblasts, leading to the formation of fibrocellular membranes on both surfaces of the detached retina and on the posterior hyaloids, which causes tractional retinal detachment. In PVR, RPE cells are crucial contributors, and multiple signaling pathways, including the SMAD-dependent pathway, Rho pathway, MAPK pathways, Jagged/Notch pathway, and the Wnt/β-catenin pathway are activated. These pathways mediate the EMT of RPE cells, which play a key role in the pathogenesis of PVR. This review summarizes the current body of knowledge on the polarized phenotype of RPE, the role of cell-cell contact, and the molecular mechanisms underlying the RPE EMT in PVR, emphasizing key insights into potential approaches to prevent PVR.

Involvement of the Retinal Pigment Epithelium in the Development of Retinal Lattice Degeneration

Lattice degeneration involves thinning of the retina that occurs over time. Here we performed an immunohistological study of tissue sections of human peripheral retinal lattice degeneration to investigate if retinal pigment epithelium (RPE) cells are involved in the pathogenesis of this condition. In two cases of retinal detachment with a large tear that underwent vitreous surgery, retinal lattice degeneration tissue specimens were collected during surgery. In the obtained specimens, both whole mounts and horizontal section slices were prepared, and immunostaining was then performed with hematoxylin and antibodies against glial fibrillary acidic protein (GFAP), RPE-specific protein 65 kDa (RPE65), pan-cytokeratin (pan-CK), and CK18. Hematoxylin staining showed no nuclei in the center of the degenerative lesion, thus suggesting the possibility of the occurrence of apoptosis. In the degenerative lesion specimens, GFAP staining was observed in the center, RPE65 staining was observed in the slightly peripheral region, and pan-CK staining was observed in all areas. However, no obvious CK18 staining was observed. In a monkey retina used as the control specimen of a normal healthy retina, no RPE65 or pan-CK staining was observed in the neural retina. Our findings suggest that migration, proliferation, and differentiation of RPE cells might be involved in the repair of retinal lattice degeneration.

Loss-of-function mutations in FREM2 disrupt eye morphogenesis

Cryptophthalmos is a rare congenital disorder characterized by ocular dysplasia with eyelid malformation. Complete cryptophthalmos is characterized by the presence of continuous skin from the forehead over the eyes and onto the cheek, along with complete fusion of the eyelids. In the present study, we characterized the clinical manifestations of three patients with isolated bilateral cryptophthalmos. These patients shared the same c.6499C > T missense mutation in the FRAS1-related extracellular matrix protein 2 (FREM2) gene, while each individual presented an additional nonsense mutation in the same gene (Patient #1, c.2206C > T; Patient #2, c.5309G > A; and Patient #3, c.4063C > T). Then, we used CRISPR/Cas9 to generate mice carrying Frem2^R725X/R2156W compound heterozygous mutations, and showed that these mice recapitulated the human isolated cryptophthalmos phenotype. We detected FREM2 expression in the outer plexiform layer of the retina for the first time in the cryptophthalmic eyes, and the levels were comparable to the wild-type mice. Moreover, a set of different expressed genes that may contribute secondarily to the phenotypes were identified by performing RNA sequencing (RNA-seq) of the fetal Frem2 mutant mice. Our findings extend the spectrum of FREM2 mutations, and provide insights into opportunities for the prenatal diagnosis of isolated cryptophthalmos. Furthermore, our work highlights the importance of the FREM2 protein during the development of eyelids and the anterior segment of the eyeballs, establishes a suitable animal model for studying epithelial reopening during eyelid development and serves as a valuable reference for further mechanistic studies of the pathogenesis of isolated cryptophthalmos.

Utility of Induced Pluripotent Stem Cell-Derived Retinal Pigment Epithelium for an In Vitro Model of Proliferative Vitreoretinopathy

The advent of stem cell technology, including the technology to induce pluripotency in somatic cells, and direct differentiation of stem cells into specific somatic cell types, has created an exciting new field of scientific research. Much of the work with pluripotent stem (PS) cells has been focused on the exploration and exploitation of their potential as cells/tissue replacement therapies for personalized medicine. However, PS and stem cell-derived somatic cells are also proving to be valuable tools to study disease pathology and tissue-specific responses to injury. High-throughput drug screening assays using tissue-specific injury models have the potential to identify specific and effective treatments that will promote wound healing. Retinal pigment epithelium (RPE) derived from induced pluripotent stem cells (iPS-RPE) are well characterized cells that exhibit the phenotype and functions of in vivo RPE. In addition to their role as a source of cells to replace damaged or diseased RPE, iPS-RPE provide a robust platform for in vitro drug screening to identify novel therapeutics to promote healing and repair of ocular tissues after injury. Proliferative vitreoretinopathy (PVR) is an abnormal wound healing process that occurs after retinal tears or detachments. In this chapter, the role of iPS-RPE in the development of an in vitro model of PVR is described. Comprehensive analyses of the iPS-RPE response to injury suggests that these cells provide a physiologically relevant tool to investigate the cellular mechanisms of the three phases of PVR pathology: migration, proliferation, and contraction. This in vitro model will provide valuable information regarding cellular wound healing responses specific to RPE and enable the identification of effective therapeutics.

Protease-activated receptor-1 contributes to renal injury and interstitial fibrosis during chronic obstructive nephropathy

End‐stage renal disease, the final stage of all chronic kidney disorders, is associated with renal fibrosis and inevitably leads to renal failure and death. Transition of tubular epithelial cells (TECs) into mesenchymal fibroblasts constitutes a proposed mechanism underlying the progression of renal fibrosis and here we assessed whether protease‐activated receptor (PAR)‐1, which recently emerged as an inducer of epithelial‐to‐mesenchymal transition (EMT), aggravates renal fibrosis. We show that PAR‐1 activation on TECs reduces the expression of epithelial markers and simultaneously induces mesenchymal marker expression reminiscent of EMT. We next show that kidney damage was reduced in PAR‐1‐deficient mice during unilateral ureter obstruction (UUO) and that PAR‐1‐deficient mice develop a diminished fibrotic response. Importantly, however, we did hardly observe any signs of mesenchymal transition in both wild‐type and PAR‐1‐deficient mice suggesting that diminished fibrosis in PAR‐1‐deficient mice is not due to reduced EMT. Instead, the accumulation of macrophages and fibroblasts was significantly reduced in PAR‐1‐deficient animals which were accompanied by diminished production of MCP‐1 and TGF‐β. Overall, we thus show that PAR‐1 drives EMT of TECs in vitro and aggravates UUO‐induced renal fibrosis although this is likely due to PAR‐1‐dependent pro‐fibrotic cytokine production rather than EMT.

Cypripedin diminishes an epithelial-to-mesenchymal transition in non-small cell lung cancer cells through suppression of Akt/GSK-3β signalling

Lung cancer appears to have the highest rate of mortality among cancers due to its metastasis capability. To achieve metastasis, cancer cells acquire the ability to undergo a switch from epithelial to mesenchymal behaviour, termed the epithelial-to-mesenchymal transition (EMT), which is associated with poor clinical outcomes. Drug discovery attempts have been made to find potent compounds that will suppress EMT. Cypripedin, a phenanthrenequinone isolated from Thai orchid, Dendrobium densiflorum, exhibits diverse pharmacological activities. In this study, we found that cypripedin attenuated typical mesenchymal phenotypes, including migratory behaviour, of non-small cell lung cancer H460 cells, with a significant reduction of actin stress fibres and focal adhesion and with weakened anchorage-independent growth. Western blot analysis revealed that the negative activity of this compound on EMT was a result of the down-regulation of the EMT markers Slug, N-Cadherin and Vimentin, which was due to ATP-dependent tyrosine kinase (Akt) inactivation. As a consequence, the increase in the Slug degradation rate via a ubiquitin-proteasomal mechanism was encouraged. The observation in another lung cancer H23 cell line also supported this finding, indicating that cypripedin exhibits a promising pharmacological action on lung cancer metastasis that could provide scientific evidence for the further development of this compound.

Novel NADPH oxidase inhibitor VAS2870 suppresses TGF‑β‑dependent epithelial‑to‑mesenchymal transition in retinal pigment epithelial cells

NADPH oxidases (NOXs) are important in the pathophysiology of fibrotic diseases. The expression and activity of NOXs are regulated by growth factors, including transforming growth factor (TGF-β). The proliferation of retinal pigment epithelial (RPE) cells following epithelial- to-mesenchymal transition (EMT) is a major pathological change involved in proliferative vitreoretinopathy (PVR). The aim of the present study was to determine the effects of the novel NOX inhibitor VAS2870 on the TGF-β-dependent expression of NOX4 and associated cellular events in RPE cells. Cell viability was examined using a Cell Counting Kit-8 assay and cell cycle progression was detected by flow cytometric analysis. Immunofluorescence analysis and western blot analysis were performed to assess EMT. It was found that TGF-β increased the expression of NOX4 and that pre-incubation with VAS2870 eliminated this effect. Additionally, TGF-β promoted RPE migration and increased EMT. Pre-incubation with VAS2870 significantly prevented TGF-β2-induced EMT by decreasing the levels of α-smooth muscle actin and E-cadherin, and also inhibited the migratory ability of the RPE cells, as demonstrated by scratch assays. Finally, VAS2870 suppressed the proliferation of RPE cells, and led to G₁-phase cell cycle arrest and a significant downregulation of the expression of cyclin D1. In conclusion, the pharmacological inhibition of NOX may be a promising tool for the treatment of PVR.

Effects of bradykinin on TGF‑β1‑induced epithelial‑mesenchymal transition in ARPE‑19 cells

The aim of the present study was to investigate the effects of bradykinin (BK) on an epithelial-mesenchymal transition (EMT) model in retinal pigment epithelium (RPE) cells through exposure to transforming growth factor‑β1 (TGF‑β1). The aim was to improve the effect of BK on proliferative vitreoretinopathy (PVR) progression, and to find a novel method of clinical prevention and treatment for PVR. The morphology of ARPE‑19 cells was observed using an inverted phase‑contrast microscope. A Cell Counting Kit‑8 was used to assess the effects of TGF‑β1 on the proliferation of ARPE‑19 cells. Western blotting and immunofluorescence were used to detect the expression levels of the epithelial marker E‑cadherin, mesenchymal markers α‑smooth muscle actin (SMA) and vimentin, and phosphorylated (p) mothers against decapentaplegic homolog (Smad)3 and Smad7 of the TGF/Smad signaling pathway. Wound healing tests and Transwell assays were performed to detect cell migration ability. Reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) analysis was performed to detect the expression levels of pSmad3 and Smad7 in the TGF/Smad signaling pathway. The results revealed that the addition of 10 ng/ml TGF‑β1 resulted in the expression of factors associated with EMT in ARPE‑19 cells. BK decreased the expression levels of the mesenchymal markers α‑SMA and vimentin, and increased the expression of the epithelial marker E‑cadherin. BK decreased cell migration in TGF‑β1‑induced EMT. These effects were reversed by HOE‑140, a specific BK 2 receptor antagonist. BK significantly downregulated the expression of pSmad3 and upregulated the expression of Smad7 in TGF‑β1‑treated ARPE‑19 cells, and the protective alterations produced by BK were inhibited by HOE‑140. In conclusion, 10 ng/ml TGF‑β1 resulted in EMT in ARPE‑19 cells and BK served a negative role in TGF‑β1‑induced EMT. BK had effects in TGF‑β1‑induced EMT by upregulating the expression of Smad7 and downregulating the expression of pSmad3 in TGF‑β/Smad signaling pathway, indicating that BK may be a novel and effective therapy for PVR.

The interplay between TGF-β/SMAD and BMP/SMAD signaling pathways in the epithelial mesenchymal transition of A549 cells induced by silica

The epithelial-mesenchymal transition (EMT) is a phenotype transdifferentiation of epithelial into mesenchymal cells and contributes to pulmonary fibrotic disease. SMAD-dependent pathway has been reported to play a key role in the multiple fibrotic diseases. We hypothesized that TGF-β/SMAD signaling could cross-interact with BMP/SMAD signaling pathways in silica-induced EMT in A549 cells. We investigated that the ability of silica-induced EMT in A549 cells, and this process was significantly inhibited by SB431542 through up-regulation of Vimentin, α-SMA and collagen type I expression and down-regulation of E-cadherin expression. Whereas BMP/SMAD inhibition using LDN193189 enhanced EMT. In addition, we also demonstrated that SB431542 could enhance BMP/SMAD signaling pathways in silica-induced EMT and vice versa. Therefore, our study provides evidence that the TGF-β/SMAD pathway was a crucial regulator in silica-induced EMT and that SB431542 could prevent the EMT. More importantly, we have identified that the interplay of TGF-β/SMAD and BMP/SMAD pathways in silica-induced EMT in A549 cells.

SphK1 modulates cell migration and EMT-related marker expression by regulating the expression of p-FAK in colorectal cancer cells

Sphingosine kinase 1 (SphK1) plays an important role in colorectal carcinoma metastasis. However, whether SphK1 modulates epithelial-mesenchymal transition (EMT)-related marker expression and the underlying mechanisms remain unclear. In this study, in order to clarify this issue, we used various colorectal cancer (CRC) cell lines, Caco2, HT29, RKO and HCT116. Each of the cell lines was divided into 3 groups as follows: the control group, SKI-Ⅱ (SphK1 inhibitor) group and PF-562271 [focal adhesion kinase (FAK) inhibitor] group. The migratory ability of the cells was examined by Transwell chamber assay. The mRNA and protein expression levels of SphK1, FAK (p-FAK), Slug, vimentin, N-cadherin and E-cadherin were detected by PCR and western blot analysis, respectively. The results revealed that the suppression of SphK1 reduced the cell migratory ability, and decreased the expression of Slug, vimentin and N-cadherin; however, the expression of E-cadherin was increased. Moreover, the inhibition of SphK1 reduced the expression of p-FAK. The inhibition of FAK (p-FAK) also decreased the cell migratory ability, and decreased the expression of Slug, vimentin and N-cadherin, whereas the expression of E-cadherin was increased. Thus, our data suggest that SphK1 modulates the expression of EMT-related markers and cell migration by regulating the expression of p-FAK in CRC cells. Thus, SphK1 may play a functional role in mediating the EMT process in CRC.

Turning the fate of reprogramming cells from retinal disorder to regeneration by Pax6 in newts

The newt, a urodele amphibian, has an outstanding ability– even as an adult –to regenerate a functional retina through reprogramming and proliferation of the retinal pigment epithelium (RPE) cells, even though the neural retina is completely removed from the eye by surgery. It remains unknown how the newt invented such a superior mechanism. Here we show that disability of RPE cells to regenerate the retina brings about a symptom of proliferative vitreoretinopathy (PVR), even in the newt. When Pax6, a transcription factor that is re-expressed in reprogramming RPE cells, is knocked down in transgenic juvenile newts, these cells proliferate but eventually give rise to cell aggregates that uniformly express alpha smooth muscle actin, Vimentin and N-cadherin, the markers of myofibroblasts which are a major component of the sub-/epi-retinal membranes in PVR. Our current study demonstrates that Pax6 is an essential factor that directs the fate of reprogramming RPE cells toward the retinal regeneration. The newt may have evolved the ability of retinal regeneration by modifying a mechanism that underlies the RPE-mediated retinal disorders.

Resveratrol inhibits epithelial-mesenchymal transition of retinal pigment epithelium and development of proliferative vitreoretinopathy

Proliferative vitreoretinopathy (PVR) is a serious complication of retinal detachment and ocular trauma, and its recurrence may lead to irreversible vision loss. Epithelial to mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cells is a critical step in the pathogenesis of PVR, which is characterized by fibrotic membrane formation and traction retinal detachment. In this study, we investigated the potential impact of resveratrol (RESV) on EMT and the fibrotic process in cultured RPE cells and further examined the preventive effect of RESV on PVR development using a rabbit model of PVR. We found that RESV induces mesenchymal to epithelial transition (MET) and inhibits transforming growth factor-β2(TGF-β2)-induced EMT of RPE cells by deacetylating SMAD4. The effect of RESV on MET was dependent on sirtuin1 activation. RESV suppressed proliferation, migration and fibronectin synthesis induced by platelet-derived growth factor-BB or TGF-β2. In vivo, RESV inhibited the progression of experimental PVR in rabbit eyes. Histological findings showed that RESV reduced fibrotic membrane formation and decreased α-SMA expression in the epiretinal membranes. These results suggest the potential use of RESV as a therapeutic agent to prevent the development of PVR by targeting EMT of RPE.

Combined silencing of TGF-β2 and Snail genes inhibit epithelial-mesenchymal transition of retinal pigment epithelial cells under hypoxia

BACKGROUND

The formation of scar-like fibrous tissue in age-related macular degeneration (AMD) is associated with hypoxia. Under hypoxia, retinal pigment epithelial (RPE) cells can secret more transforming growth factor-β2 (TGF-β2), which is determined to induce epithelial-mesenchymal transition (EMT) at certain concentrations. Whether hypoxia can induce EMT by stimulating RPE cell line secrets TGF-β2 or not remains unknown. To gain a better understanding of the signaling mechanisms of fibrosis in AMD under hypoxic conditions, we investigated EMT in retinal pigment epithelial (RPE) cells and the effect of TGF-β2 and Snail in this process.

METHODS

Human RPE cell line (ARPE-19) was incubated with 5 % O2 for different periods of time. The expression of N-cadherin, α-smooth muscle actin (α-SMA), TGF-β2 , and Snail were determined by Western blot and real-time PCR. Cell proliferation was assessed by CCK8 kit. RNA interference was used for multi-gene silencing of TGF-β2 and Snail genes.

RESULTS

N-cadherin was decreased and mesenchymal cell marker α-SMA was increased after the ARPE-19 cell line was incubated with 5 % O2. Meanwhile, the proliferation capability of the cell line was increased. TGF-β2 and Snail expression were increased in a time-dependent manner under hypoxia. After multi-silencing TGF-β2 and Snail genes, N-cadherin was increased and α-SMA was reduced. Meanwhile, the proliferation of the cell line was suppressed.

CONCLUSIONS

Under hypoxic conditions, RPE cells undergo EMT. Endogenic TGF-β2 and Snail are involved in this process. Furthermore, knockdown of both TGF-β2 and Snail inhibited EMT to a greater extent than knockdown of either gene individually.

N-cadherin mediates the migration of MCF-10A cells undergoing bone morphogenetic protein 4-mediated epithelial mesenchymal transition

Epithelial-mesenchymal transition (EMT) of mammary epithelial cells is important in both normal morphogenesis of mammary glands and metastasis of breast cancer. Cadherin switching from E-cadherin to N-cadherin plays important roles in EMT. We found that cadherin switching is important in bone morphogenetic protein 4 (BMP4)-induced EMT in MCF-10A cells. BMP4 increased the phosphorylation of SMAD proteins in MCF-10A cells. Canonical BMP4 signaling decreased the expression of E-cadherin and disrupted the polarity of the tight junction protein ZO-1 in MCF-10A cells. However, the expression of N-cadherin and SNAI2 was up-regulated in BMP4-treated MCF-10A cells. MCF-10A cells that expressed N-cadherin migrated into type I collagen gels in response to BMP4 when evaluated using three-dimensional culture assays. Thus, active canonical BMP4 signaling is important for the migration and EMT of mammary epithelial cells. Moreover, the decrease in E-cadherin and/or increase in N-cadherin may be required for BMP4-induced migration and EMT.

Bleomycin induces endothelial mesenchymal transition through activation of mTOR pathway: a possible mechanism contributing to the sclerotherapy of venous malformations

BACKGROUND AND PURPOSE

Bleomycin (BLM), one of the most common sclerosants, is often used to treat venous malformations (VMs). The present study was designed to investigate whether endothelial mesenchymal transition (EndoMT) contributes to the therapeutic effects of BLM.

EXPERIMENTAL APPROACH

Endothelial and mesenchymal markers of HUVECs were measured by immunofluorescence, real-time quantitative PCR and Western blot analysis. Cell migration and tube formation assays were performed to evaluate endothelial cell function. Slug small-interfering RNA and specific inhibitors [Z-VAD-FMK for pan caspases, rapamycin for mammalian target of rapamycin (mTOR)] were used to investigate the mechanism.

KEY RESULTS

Long term (48 h or longer) treatment with BLM (0.1 mU·mL(-1) ) induced EndoMT in HUVECs, as manifested by a reduction in the expression of vascular endothelial-cadherin and an up-regulation in the expression of α-smooth muscle actin and fibroblast specific protein-1, as well as activation of the transcription factor Slug. The size and protein content of the transformed cells were increased. BLM also enhanced the migration of HUVECs but diminished their tube formation. By employing rapamycin, we demonstrated that activation of the mTOR pathway is involved in BLM-induced EndoMT in HUVECs.

CONCLUSIONS AND IMPLICATIONS

Our results show that a Slug-dependent EndoMT process is involved in BLM-induced therapeutic effects on endothelial cells and, more importantly, indicate the potential role of this process in the sclerotherapy of VMs.

Thrombin promotes epithelial ovarian cancer cell invasion by inducing epithelial-mesenchymal transition

OBJECTIVE

Over-expression of thrombin in ovarian cancer cells is associated with poor prognosis. In this study, we investigated the role of thrombin in inducing epithelial-mesenchymal transition (EMT) in SKOV3 epithelial ovarian cancer cells.

METHODS

After thrombin treatment SKOV3 cells were subjected to western blots, reverse-transcription PCR, and enzyme-linked immunosorbent assay to quantify EMT-related proteins, mRNA expression of SMAD2, DKK1, and sFRP1, and the secretion of matrix metalloproteinases (MMPs) and cytokines. Meanwhile, invasion ability was evaluated using transwell assays.

RESULTS

The results indicated a dose- and time-dependent down-regulation of E-cadherin and upregulation of N-cadherin and vimentin in thrombin-treated SKOV3 cells, compared with the thrombin-free control group (p<0.05). There was a dose- and time-dependent increase in the levels of SMAD2 and DKK1 mRNAs and a decrease in the levels of sFRP1 mRNA in thrombin-treated SKOV3 cells compared to control cells (p<0.05). Thrombin-treated SKOV3 cells exhibited increased secretion of MMP-9, MMP-2, interleukin (IL)-8, and IL-6 and increased invasion compared to untreated cells (p<0.05). Thrombin altered the morphology of SKOV3 cells to a spindle-like phenotype. Addition of hirudin to thrombin-treated cells reversed the effects of thrombin.

CONCLUSION

Thrombin induced EMT and promoted the invasion of SKOV3 cells, possibly via distinct signaling pathways. Hirudin inhibited the effects of thrombin, suggesting that anticoagulant therapy could be a novel therapeutic strategy for ovarian carcinoma.