Endothelial Markers VE-cadherin Research Articles

Exercise may be a Novel Strategy to Reduce Vascular Toxicity of Immune Checkpoint Inhibitors in a Mouse Melanoma Model

Background: Immune checkpoint inhibitors (ICIs) are a cornerstone in advanced melanoma treatment. Unfortunately, ICI-associated cardiovascular toxicity, particularly atherosclerotic events, poses a significant challenge. Identifying interventions to mitigate the cardiovascular toxicity of ICI is critical for enhancing the quality and duration of life in cancer survivors. Given the established benefits of exercise in atherosclerosis prevention, this study explores its potential to reduce ICI-induced vascular toxicity in the context of melanoma. We hypothesized that aerobic exercise would decrease ICI's vascular toxicity in a mouse melanoma model. The primary experimental outcome was endothelial mesenchymal transition (EndMT), an early atherosclerosis indicator. Methods: C57BL/6 mice were subcutaneously injected with 0.8 x 106 BP melanoma cells ( BrafV600E/WT and Pten−/−). Upon tumor palpability, mice were assigned into four groups: IgG, Exercise, anti-PD-1, and anti-PD-1+Exercise. Mice were treated with bi-weekly administration of anti-PD-1 or IgG antibody (150 μg) for three weeks, combined with or without treadmill exercise (12 meters/minute for 45 min per day, five days/week). Body weight was monitored weekly. Following the final treatment, aortic tissues were collected and en face immunofluorescence staining for endothelial marker VE-cadherin (VE-Cad) and vimentin was performed to assess EndMT, then analyzed via confocal microscopy. Results: No significant weight differences were observed between groups. Notably, the EndMT marker vimentin expression was significantly higher in anti-PD-1 treated tumor-bearing mice compared to IgG controls (3.8% vs 0.6%, p=.03) in the atheroprotective laminar flow area. This was reduced by exercise; the anti-PD-1+Exercise group showed significantly reduced endothelial vimentin levels relative to the anti-PD-1 alone (0.8% vs 3.8%, p=.04). Disturbed flow areas did not exhibit notable differences between any group. Conclusions: Aerobic exercise may be protective against vascular toxicity in mice treated with ICIs by promoting atheroprotective flow and potentially inhibiting EndMT. Although these initial results are promising, comprehensive studies are required to ascertain the impact of exercise on preventing ICI-induced EndMT and subsequent atherosclerosis in this mouse melanoma model. Future research will aim to more deeply characterize the process of EndMT following ICI treatment and evaluate the preventive capacity of exercise against atherosclerosis in this context. MD Anderson Cancer Center Melanoma SPORE grant (NCI P50CA221703-05). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Abstract 2066: Relationship Between Stat3 And Endoplasmic Reticulum Stress Induces Lipopolysaccharide-induced Endothelial To Mesenchymal Transition In Vascular Endothelial Cell

Background: Endothelial to mesenchymal transition (EndMT) is a process that involves the loss of endothelial cell (EC) phenotype and induced plaque instability during the progression of atherosclerosis. Primarily, EC injury, caused by an accelerated inflammatory signaling pathway, plays a crucial role in activating EC dysfunction by inducing endoplasmic reticulum (ER) stress and disrupting EC junctions. In the present study, we investigated the molecular mechanisms between EndMT and ER stress on STAT3-mdeiated inflammation under LPS-treated human umbilical vein EC (HUVEC). Methods: To explore the EndMT progression under chronic inflammation, LPS-treated HUVEC were used. Western blot, siRNA transfection, and immunofluorescence assay were employed to evaluate signaling pathways and target proteins. The phenotypic switching of ECs on the endothelium of the mouse aorta after challenging 10 mg/kg LPS was assessed by en face staining. Results: Deactivation of STAT3 by stattic pretreatment abolished not only LPS-mediated STAT3 phosphorylation, but also VCAM-1 and ICAM-1. In addition, STAT3 inhibition surprisingly reversed LPS-induced mesenchymal markers, including SM22α and vimentin, and the suppression of endothelial marker VE-cadherin. Mechanistically, stattic treatment suppressed LPS-induced EndMT progression by inhibiting protein expression and nuclear translocation of Smad2/3. Furthermore, LPS-induced chronic inflammation disrupted EC homeostasis by PERK or IRE-1α/CHOP-mediated ER stress, whereas stattic abolished LPS-mediated PERK and CHOP expression. Interestingly, depletion of CHOP by siRNA transfection significantly abolished LPS-mediated EndMT progression (p<0.001. Figure 1). Notably, the absence of CHOP significantly suppressed phosphorylation of STAT3 and its nuclear expression as well. Consistent to in vitro data, STAT3 inhibition by stattic injection significantly suppressed LPS-mediated STAT3 activation as well as CHOP expression in the mouse endothelium. Conclusion: Collectively, the STAT3-CHOP axis may contribute to the loss of EC function and induce mesenchymal differentiation by aggravating chronic inflammation and EndMT.

Abstract 655: Protecting The Saphenous Vein Endothelium During Bypass Surgery

Coronary artery bypass graft surgeries commonly use saphenous vein grafts to revascularize diseased coronary arteries. Despite surgical and pharmacological advancements, graft failure rates remain high. Loss of endothelial cells (EC) during saphenous vein harvest and preservation likely contributes to the high incidence of graft failure. Standard methods of saphenous vein preparation and preservation during surgery include perfusion with heparinized saline solutions, a practice known to induce EC damage. As such, improved methods of saphenous vein storage may be the key to preserving EC and reducing graft failure rates. Here, we assessed the hypothesis that maintaining saphenous veins in autologous heparinized blood would preserve EC coverage and reduce cellular damage compared to standard of care, heparinized saline. To investigate this, saphenous vein tissues from 12 patients undergoing coronary artery bypass graft surgery were split into 2 treatment groups, 1) standard maintenance in heparin-saline (n=6) and 2) maintenance in heparin-blood (n=6). At the end of the surgeries, excess saphenous vein tissues were immediately fixed in 4% PFA to analyze endothelial coverage and DNA damage. In heparin-saline veins, histological analysis by H&E and Movat pentachrome staining revealed a broken or absent luminal layer and exposed lamina matrix, suggesting a loss of endothelial cell coverage. Luminal cell coverage was notably increased in heparin-blood samples. Immunofluorescent staining of endothelial markers VE-cadherin and endothelial nitric oxide identified a significant improvement in endothelial coverage in the heparin-blood group compared to heparin-saline. To determine the health of remaining endothelial cells, DNA damage was measured using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. Our data show that most of the endothelium (VE-cadherin positive) in heparin-saline tissues was TUNEL positive compared with heparin-blood. In conclusion, our data indicate that maintaining saphenous vein tissues in solutions containing autologous heparinized blood helps preserve the endothelium and maintains vein graft health which has the potential to improve vein graft patency rates in patients.

Dysregulation of cardiac endothelial lncRNA H19 in COVID19 patients induces endothelial dysfunction, which impairs cardiomyocyte function

Abstract Background COVID19 is accompanied by cardiac complications. Long non-coding RNAs (lncRNAs) have been implicated in the pathogenesis of cardiovascular diseases. However, their contribution to the cardiac manifestation of COVID19 is unknown. Methods and results We discovered that endothelial-enriched lncRNA H19 is downregulated in the heart of patients with COVID19 (∼2 fold, p<0.01). H19 was highly expressed in cardiac microvascular endothelial cells (CMEC) as compared to the other endothelial cell types (∼10 fold, p<0.05), suggesting its cardiac enrichment. H19 silencing in CMEC induced endothelial stress phenotype and a reduction in endothelial markers VE-cadherin and eNOS (∼1.5 fold, p<0.01), indicating its importance in endothelial physiology. Using the endothelial-cardiomyocyte co-culture system we previously developed, we showed that H19 silencing in CMEC reduced cardiomyocyte (CM) relaxation and contraction (∼1.5 fold, p<0.01). Interestingly, exposure to plasma from COVID19 patients decreased endothelial H19 level and impaired endothelial enhancement of CM function. Mechanistically, reduced level of H19 increased endothelial IL6 expression (∼1.5 fold, p<0.01). Further, exposure of CMs to IL6 also impaired CM relaxation and contraction, suggesting that endothelial cells devoid of H19 release IL6 which represses CM function. Interestingly, we found increased IL6 levels in the heart of COVID19 patients (∼2 fold, p<0.05). Indeed, the impairment of endothelial enhancement of CM function upon H19 silencing in CMEC was restored in the presence of tocilizumab, an IL6 receptor antagonist (∼1.5 fold, p<0.01). Furthermore, the impairment of the endothelial control on CM function upon exposure to COVID19 plasma was mitigated when the patients were treated with tocilizumab (∼1.5 fold, p<0.01). Conclusion COVID19 reduces cardiac endothelial H19 level and induces impairment of endothelial enhancement of CM function via increased release of endothelial-derived IL6, the effect that can be rescued in the presence of IL6 receptor blocker tocilizumab. Funding Acknowledgement Type of funding sources: Public grant(s) – EU funding. Main funding source(s): ERC

Fibrotic Changes to Schlemm's Canal Endothelial Cells in Glaucoma.

Previous studies have shown that glaucomatous Schlemm’s canal endothelial cells (gSCECs) are stiffer and associated with reduced porosity and increased extracellular matrix (ECM) material compared to SCECs from healthy individuals. We hypothesised that Schlemm’s canal (SC) cell stiffening was a function of fibrotic changes occurring at the inner wall of SC in glaucoma. This study was performed in primary cell cultures isolated from the SC lumen of human donor eyes. RNA and protein quantification of both fibrotic and endothelial cell markers was carried out on both healthy and gSCECs. Functional assays to assess cell density, size, migration, proliferation, and mitochondrial function of these cells were also carried out. Indeed, we found that gSCECs deviate from typical endothelial cell characteristics and exhibit a more fibrotic phenotype. For example, gSCECs expressed significantly higher protein levels of the fibrotic markers α-SMA, collagen I-α1, and fibronectin, as well as significantly increased protein expression of TGFβ-2, the main driver of fibrosis, compared to healthy SCECs. Interestingly, we observed a significant increase in protein expression of endothelial marker VE-cadherin in gSCECs, compared to healthy SCECs. gSCECs also appeared to be significantly larger, and surprisingly proliferate and migrate at a significantly higher rate, as well as showing significantly reduced mitochondrial activity, compared to healthy SCECs.

Lymphatic Endothelial Cell Defects in Congenital Cardiac Patients With Postoperative Chylothorax

Objectives:Chylothorax following cardiac surgery for congenital cardiac anomalies is a complication associated with severe morbidities and mortality. We hypothesize that there are intrinsic defects in the lymphatics of congenital cardiac patients.Methods:Postsurgical chylothorax lymphatic endothelial cells (pcLECs) (n = 10) were isolated from the chylous fluid from congenital cardiac defect patients, and characterized by fluorescent-activated cell sorting, immunofluorescent staining, and quantitative RT-PCR. Results were compared to normal human dermal lymphatic endothelial cells (HdLECs). pcLECs (n = 3) and HdLECs were xenografted into immunocompromised mice. Implants and postoperative chylothorax patient’s pulmonary tissues were characterized by immunostaining for lymphatic endothelial proteins.Results:pcLECs expressed endothelial markers VECADHERIN, CD31, VEGFR2, lymphatic endothelial markers PROX1, podoplanin, VEGFR3, and progenitor endothelial markers CD90 and CD146. However, pcLECs had key differences relative to HdLECs, including altered expression and mislocalization of junctional proteins (VECADHERIN and CD31), and essential endothelial proteins, VEGFR2, VEGFR3, and PROX1. When xenografted in mice, pcLECs formed dilated lymphatic channels with poor cell–cell association. Similar to congenital lymphatic anomalies, the pulmonary lymphatics were dilated in a patient who developed postoperative chylothorax after cardiac surgery.Conclusions:Recent studies have shown that some postoperative chylothoraces in congenital cardiac anomalies are associated with anatomical lymphatic defects. We found that pcLECs have defects in expression and localization of proteins necessary to maintain lymphatic specification and function. This pcLEC phenotype is similar to that observed in lymphatic endothelial cells from congenital lymphatic anomalies. Co-existence of lymphatic anomalies should be considered as a feature of congenital cardiac anomalies.

Endothelial Notch1 Regulates High-dose Radiation Therapy (HDRT)-induced Endothelial-to-mesenchymal Transition (EbdMT)

There is increasing evidence that high-dose radiation therapy (HDRT) induces endothelial-to-mesenchymal-transition (EdnMT) which promotes abnormal tumor vascularity and radioresistance. We have previously shown that HDRT induces Notch1 signaling in tumor endothelial cells. Here, we investigate if endothelial Notch1 regulates HDRT induced EdnMT. HUVEC monolayers, in vitro, were also treated with 0, 2, 8, and 12Gy and immunoblot was performed for Notch1, Jagged1, VE-Cadherin. HUVEC monolayers were also treated with a soluble Notch inhibitor, Notch1 decoy, to assess the effect of Notch inhibition on EdnMT. Human neuroblastoma cells NGP were engineered to express Fc(control) and Notch1 decoy. These cells were intrarenally injected to develop xenograft tumors. Tumors were treated with 0 Gy and 12 Gy single fraction doses of HDRT. Mice were sacked at 72 hr after HDRT. Tumor sections were subjected to double immunofluorescence staining for aSMA (mesenchymal marker) and endomucin (endothelial marker). We also assessed the effect of combining HDRT with Notch inhibition on macrophage infiltration into the tumor microenvironment by performing immunofluorescence staining for F480 (a marker for tumor associated macrophage), INOS (marker for M1 macrophage) and MRC1 (a marker for M2 macrophage). In HUVEC monolayers, HDRT doses of 8 Gy and 12 Gy profoundly increased Notch1 and Jagged1 protein levels after 72 hr. The increased level of Notch1 and Jagged1 was associated with the reduction of endothelial marker VE-Cadherin level. Notch1 decoy treatment inhibited reduction of VE-cadherin indicating Notch inhibition blocked EdnMT. In vivo in NGP xenograft mice model, increased colocalization of endomucin and αSMA was observed at 72 hr 12 Gy post-irradiation, when compared to nonirradiated tumors, indicating transition of ECs. Interestingly, Notch inhibition reduced colocalizing αSMA (+) endomucin (+) staining in Notch1decoy+12 Gy tumors. Quantification showed that while ∼4% and ∼3% of endomucin (+) vessels expressed αSMA, following Fc+0 Gy and Notch1decoy + 0 Gy treatments, respectively, ∼30% of the surviving vessels were αSMA (+) after Fc+12 Gy. Notch inhibition reduced αSMA staining in surviving vessels as ∼4% of the vessels were αSMA (+) in N11-24-decoy+12 Gy tumors. Increased F480 and MRC1 staining was observed in tumor treated with 12 Gy, compared to untreated tumors, while no change in INOS staining was noted. Notch1 decoy treatment significantly decreased F480 and MRC1 suggesting Notch blockade decreased HDRT induced M2 macrophage infiltration. Our data shows that Notch blockade inhibits HDRT-induced EdnMT. Our data further shows that HDRT increased tumor-promoting immune suppressive M2 macrophage infiltration. Combing HDRT with Notch blockade inhibits M2 macrophage infiltration into the tumor microenvironment and can be a potential therapeutic approach to minimize immunosuppressive immune response.

Roles of notch signaling pathway and endothelial-mesenchymal transition in vascular endothelial dysfunction and atherosclerosis.

To investigate the role of the Notch signaling pathway on the endothelial-mesenchymal transition (EndMT) during vascular endothelial dysfunction and atherosclerosis. Human coronary artery endothelial cells (HCAEC) were treated with the exogenous Notch homolog 1 (Notch1) factor to activate the Notch1 pathway, and cells were then observed under the microscope for morphologic changes. Changes in the expression of related proteins were detected by Western blot. In vivo experiments were performed using 18 Sprague Dawley® (SD) rats, and GSI factor was used to specifically inhibit Notch pathway activation. Rats were used and randomly divided into three groups: normal diet (ND) group, high-fat diet (HFD) group, and high-fat diet + GSI (HFD+GSI) group, 6 rats in each group. Hematoxylin and eosin (H&E) staining was used to examine the cardiac aortic morphology of the rats in each treatment group. Real-time polymerase chain reaction (RT-PCR) and Western blot were used to detect the expression of Notch1, Hes1, VE-cadherin and α-SMA in the aortic tissues of rats in each group at mRNA and protein levels, respectively. After HCAECs were treated with Notch1, endothelial protein levels of VE-cadherin were significantly decreased and levels of the interstitial protein α-SMA were significantly increased. In the animal model, the rats fed with high-fat diet for two months presented obvious atherosclerosis spots in their aorta, but those fed with the same diet and treated with GSI inhibitor of Notch pathway showed significantly fewer atherosclerosis signs. Compared with ND group, mRNA and protein expression levels of Notch1, Hes1 and α-SMA were significantly increased, and the expression levels of endothelial marker VE-cadherin were significantly decreased in aortas of rats in HFD group. Compared with the rats in HFD group, the rats in HFD+GSI group showed significantly reduced expression levels of Notch1, Hes1 and α-SMA. The activation of Notch signaling pathway can induce the EndMT progression and promote the development of atherosclerotic lesions.

The Roles of Matrix Stiffness and ß-Catenin Signaling in Endothelial-to-Mesenchymal Transition of Aortic Valve Endothelial Cells.

Valve stiffening is a hallmark of aortic valve stenosis caused by excess extracellular matrix accumulation by myofibroblasts. We aimed to elucidate whether matrix stiffness regulates endothelial-to-mesenchymal transition (EndMT) of adult valvular endothelial cells (VECs) to myofibroblasts as a mechanism to further promote valve fibrosis. In addition, we specifically examined the role of the Wnt/β-catenin signaling pathway in the development of myofibroblasts during EndMT, as Wnt/β-catenin signaling has been implicated in EndMT during heart development, is reactivated in valve disease, and is required for mechanically-regulated myofibrogenesis of valve interstitial cells. Clonally derived porcine VECs were cultured on soft (5kPa) or stiff (50kPa) silicone Sylgard 527 substrates and treated with transforming growth factor (TGF)-β1 to induce EndMT. Immunofluorescent staining revealed that TGF-β1 preferentially promoted EndMT in VECs on stiffer substrates, evidenced by a decrease in the endothelial marker VE-cadherin and an increase in the myofibroblast marker α-smooth muscle actin (α-SMA). These changes were accompanied by β-catenin nuclear localization both in vitro and in vivo, assessed by immunostaining. Degradation of β-catenin with endostatin reduced VEC myofibroblast transition, as indicated by decreased α-SMA fiber expression. We conclude that TGF-β1-induced EndMT in aortic VECs is dependent on matrix stiffness and Wnt/β-catenin signaling promotes myofibrogenesis during EndMT.

Post-surgery fluids promote transition of cancer stem cell-to-endothelial and AKT/mTOR activity, contributing to relapse of giant cell tumors of bone.

Giant cell tumors of bone (GCTB) are rare sarcomas with a high rate of unpredictable local relapse. Studies suggest that surgical methods affect recurrence, supporting the idea that local disease develops from re-growth of residual cancer cells. To identify early prognostic markers of individual risk of recurrence, we evaluated the effect of post-surgery fluids from a cohort of GCTB patients on growth of primary and established sarcoma cell lines, and mice xenograph. Post-surgery fluids increased cell growth and enhanced expression of CD44++, the principal receptor for the extracellular matrix component hyaluronan and the mesenchymal stem marker CD117+. Cancer cells became highly invasive and tumorigenic, acquiring stemness properties, and activated AKT/mTOR pathway. Prolonged stimulation with post-surgery fluids down-regulated the mesenchymal gene TWIST1 and Vimentin protein, and transdifferentiated cells into tubule-like structures positive to the endothelial markers VE-Cadherin and CD31+. In mice, post-surgery fluids gave rise to larger and more vascularized tumors than control, while in patients AKT/mTOR pathway activation was associated with recurrence by logistic regression (Kaplan-Meier; P<0.001). These findings indicate that post-surgery fluids are an adjuvant in mechanisms of tumor regrowth, increasing stem cell growth and AKT/mTOR activity.

High glucose induced endothelial to mesenchymal transition in human umbilical vein endothelial cell

BackgroundStudies have shown that endothelial-to-mesenchymal transition (EndMT) could contribute to the progression of diabetic nephropathy, diabetic renal fibrosis, and cardiac fibrosis. The aim of this study was to investigate the influence of high glucose and related mechanism of MAPK inhibitor or specific antioxidant on the EndMT. MethodsIn vitro human umbilical vein endothelial cells (HUVEC) were cultured with 11mM, 30mM, 60mM and 120mM glucose for 0, 24, 48, 72 and 168h. Endothelial cell morphology was observed with microscope, and RT-PCR was used to detect mRNA expression of endothelial markers VE-cadherin and CD31, mesenchymal markers α-SMA and collagen I, and transforming growth factor TGF-β1. Immunofluorescence staining was performed to detect the expression of CD31 and α-SMA. The concentration of TGF-β1 in the supernatant was detected by ELISA. ERK1/2 phosphorylation level was detected by Western blot analysis. ResultsHigh glucose induced EndMT and increased the TGF-β1 level in HUVEC cells. Cells in high glucose for 7 days showed a significant decrease in mRNA expression of CD31 and VE-cadherin, and a significant increase in that of α-SMA and collagen I, while lost CD31 staining and acquired α-SMA staining. ERK signaling pathway blocker PD98059 significantly attenuated the high glucose-induced increase in the ERK1/2 phosphorylation level. PD98059 and NAC both inhibited high glucose-induced TGF-β1 expression and attenuated EndMT marker protein synthesis. ConclusionHigh glucose could induce HUVEC cells to undergo EndMT. NAC and ERK signaling pathway may play important role in the regulation of the TGF-β1 biosynthesis during high glucose-induced EndMT.

Disruption of the aortic wall by coelomic lining-derived mesenchymal cells accompanies the onset of aortic hematopoiesis.

In vertebrates, definitive hematopoietic stem cells (HSCs) first emerge in the ventral wall of the aorta in the Aorta-Gonad-Mesonephros (AGM) region of the embryo, where they differentiate from a specialized type of endothelium termed Hemogenic Endothelium (HE). While the transition from HE to hematopoietic tissue has received much experimental attention, much less is known regarding generation of HE itself. The current study investigates the emergence of the HE in the chick embryo aorta. Using the HE marker Runx1 as well as a new chicken-reactive antibody to the endothelial marker VE-Cadherin, we document the relationship between the emerging HE and surrounding tissues, particularly the coelomic epithelium (CE) and CE-derived sub-aortic mesenchyme. In addition, the fate of the CE cells was traced by electroporation of a GFP-expressing plasmid into the CE, followed by analysis using immunofluorescence and in situ hybridization. We make the novel observation that CE-derived mesenchyme transiently invades through the ventral wall of the aorta during the period of establishment of HE and just prior to the emergence of hematopoietic cell clusters in the ventral aortic wall. These observations emphasize a hitherto unappreciated dynamism in the aortic wall during the period of HE generation, and open the door to future studies regarding the role of invasive CE-derived cells during aortic hematopoiesis.

Aspirin-Triggered Resolvin D1 Inhibits TGF-β1-Induced EndMT through Increasing the Expression of Smad7 and Is Closely Related to Oxidative Stress

The endothelial-mesenchymal transition (EndMT) is known to be involved in the transformation of vascular endothelial cells to mesenchymal cells. EndMT has been confirmed that occur in various pathologic conditions. Transforming growth factor β1 (TGF-β1) is a potent stimulator of the vascular endothelial to mesenchymal transition (EMT). Aspirin-triggered resolvin D1 (ATRvD1) has been known to be involved in the resolution of inflammation, but whether it has effects on TGF-β1-induced EndMT is not yet clear. Therefore, we investigated the effects of AT-RvD1 on the EndMT of human umbilical vein vascular endothelial cells line (HUVECs). Treatment with TGF-β1 reduced the expression of Nrf2 and enhanced the level of F-actin, which is associated with paracellular permeability. The expression of endothelial marker VE-cadherin in HUVEC cells was reduced, and the expression of mesenchymal marker vimentin was enhanced. AT-RvD1 restored the expression of Nrf2 and vimentin and enhanced the expression of VE-cadherin. AT-RvD1 did also affect the migration of HUVEC cells. Inhibitory κB kinase 16 (IKK 16), which is known to inhibit the NF-κB pathway, had an ability to increase the expression of Nrf2 and was associated with the inhibition effect of AT-RvD1 on TGF-β1-induced EndMT, but it had no effect on TGF-β1-induced EndMT alone. Smad7, which is a key regulator of TGF-β/Smads signaling by negative feedback loops, was significantly increased with the treatment of AT-RvD1. These results suggest the possibility that AT-RvD1 suppresses the TGF-β1-induced EndMT through increasing the expression of Smad7 and is closely related to oxidative stress.

Endotoxin-induced endothelial fibrosis is dependent on expression of transforming growth factors β1 and β2.

During endotoxemia-induced inflammatory disease, bacterial endotoxins circulate in the bloodstream and interact with endothelial cells (ECs), inducing dysfunction of the ECs. We previously reported that endotoxins induce the conversion of ECs into activated fibroblasts. Through endotoxin-induced endothelial fibrosis, ECs change their morphology and their protein expression pattern, thereby suppressing endothelial markers and upregulating fibrotic proteins. The most commonly used fibrotic inducers are transforming growth factor β1 (TGF-β1) and TGF-β2. However, whether TGF-β1 and TGF-β2 participate in endotoxin-induced endothelial fibrosis remains unknown. We have shown that the endotoxin-induced endothelial fibrosis process is dependent on the TGF-β receptor, ALK5, and the activation of Smad3, a protein that is activated by ALK5 activation, thus suggesting that endotoxin elicits TGF-β production to mediate endotoxin-induced endothelial fibrosis. Therefore, we investigated the dependence of endotoxin-induced endothelial fibrosis on the expression of TGF-β1 and TGF-β2. Endotoxin-treated ECs induced the expression and secretion of TGF-β1 and TGF-β2. TGF-β1 and TGF-β2 downregulation inhibited the endotoxin-induced changes in the endothelial marker VE-cadherin and in the fibrotic proteins α-SMA and fibronectin. Thus, endotoxin induces the production of TGF-β1 and TGF-β2 as a mechanism to promote endotoxin-induced endothelial fibrosis. To the best of our knowledge, this is the first report showing that endotoxin induces endothelial fibrosis via TGF-β secretion, which represents an emerging source of vascular dysfunction. These findings contribute to understanding the molecular mechanism of endotoxin-induced endothelial fibrosis, which could be useful in the treatment of inflammatory diseases.

Platelets induce endothelial tissue factor expression in a mouse model of acid-induced lung injury

Although the lung expresses procoagulant proteins under inflammatory conditions, underlying mechanisms remain unclear. Here, we addressed lung endothelial expression of tissue factor (TF), which initiates the coagulation cascade and expression of which signifies development of a procoagulant phenotype in the vasculature. To establish the model of acid-induced acute lung injury (ALI), we intranasally instilled anesthetized mice with saline or acid. Then 2 h later, we isolated pulmonary vascular cells for flow cytometry and confocal microscopy to detect the leukocyte antigen, CD45 and the endothelial markers VE-cadherin and von Willebrand factor (vWf). Acid increased both the number of vWf-expressing cells as well as TF and P-selectin expressions on these cells. All of these effects were markedly inhibited by treating mice with antiplatelet serum, suggesting the involvement of platelets. The increased expressions of TF, vWf, and P-selectin in response to acid also occurred in platelets. Moreover, the effects were replicated in endothelial cells derived from isolated, blood-perfused lungs. However, the effect was inhibited completely in lungs perfused with platelet-depleted and, to a lesser extent, with leukocyte-depleted blood. Acid injury increased endothelial expressions of the platelet proteins, CD41 and CD42b, providing evidence that platelet proteins were transferred to the vascular surface. Reactive oxygen species (ROS) were implicated in these responses, in that the endothelial and platelet protein expressions were inhibited. We conclude that acid-induced ALI causes NOX2-mediated ROS generation that activates platelets, which then generate a procoagulant endothelial surface.

Heterogeneic nature of adult cardiac side population cells

Side population cells have been found in various types of adult tissue including heart and are presumed to be tissue-specific stem/progenitor cells. In the present study, we confirmed the presence of cardiac side population (cSP) cells, which showed both the Hoechst 33342 efflux ability and ABCG2 expression, in adult murine heart. Flow cytometric analysis showed that more than half of cSP cells expressed the endothelial marker VE-cadherin or the smooth muscle markers, α-smooth muscle actin and desmin. In addition, immunohistochemical analysis demonstrated that ABCG2 + cells were mainly localized within vascular walls. Quantitative RT-PCR analysis demonstrated that VE-cadherin − cSP cells progressively expressed Nkx2.5 and cardiac troponin T with time in culture. VE-cadherin − cSP cells also expressed mesodermal–mesenchymal-associated markers and differentiated into osteocytes and adipocytes. These results highlight the heterogeneic nature of cSP cells, consisting of vascular endothelial cells, smooth muscle cells, and mesenchymal stem/progenitor cells including potential cardiomyogenic cells.

Isolation of cardiac cells from E8.5 yolk sac by ALCAM (CD166) expression

It is known that the adhesion molecule ALCAM (CD166) mediates metastasis of malignant cells and organogenesis in embryos. We show here that embryonic day 8.5 (E8.5) murine yolk sac cells express ALCAM protein and that ALCAM expression can be used to define endothelial and cardiac precursors from hematopoietic precursors in E8.5 yolk sacs. ALCAM high+ cells exclusively give rise to endothelial and cardiac cells in matrigel assays but generate no hematopoietic colonies in methylcellulose assays. ALCAM low+ and ALCAM− populations predominantly give rise to hematopoietic cells in methylcellulose, but do not generate any cell clusters in matrigel. The ALCAM high+ population contains both Flk-1+ and Flk-1− cells. The former population exclusively contains endothelial cells whereas the latter give rise to cardiac cells when cultured on OP9 stromal cells. We also show that cardiac lineage marker genes such as Nkx-2.5, and the endothelial marker VE-cadherin are expressed in the ALCAM high+ fraction, whereas the hematopoietic marker GATA1 and Runx1 are expressed in the ALCAM low+/− fraction. However, we did not detect expression of the cardiac structural protein cTn-T in cells from yolk sac cells until these had had been differentiated on OP9 for 5 days. Altogether, these results indicate that cells retaining a potential to differentiate to the cardiac lineage are present in E8.5 yolk sacs and can be isolated as ALCAM high+, Flk-1− cells. Our report provides novel insights into the origin and differentiation process of cardiac cells in the formation of the circulatory system.

Characterization of GATA-1+ hemangioblastic cells in the mouse embryo

Hemangioblasts are thought to be one of the sources of hematopoietic progenitors, yet little is known about their localization and fate in the mouse embryo. We show here that a subset of cells co-expressing the hematopoietic marker GATA-1 and the endothelial marker VE-cadherin localize on the yolk sac blood islands at embryonic day 7.5. Clonal analysis demonstrated that GATA-1(+) cells isolated from E7.0-7.5 embryos include a common precursor for hematopoietic and endothelial cells. Moreover, this precursor possesses primitive and definitive hematopoietic bipotential. By using a transgenic complementation rescue approach, GATA-1(+) cell-derived progenitors were selectively restored in Runx1-deficient mice. In the rescued mice, definitive erythropoiesis was recovered but the rescued progenitors did not display multilineage hematopoiesis or intra-aortic hematopoietic clusters. These results provide evidence of the presence of GATA-1(+) hemangioblastic cells in the extra-embryonic region and also their functional contribution to hematopoiesis in the embryo.

Stromal-Derived Factor and Vascular Endothelial Growth Factor Synergistically Induce Mesenchymal Stem Cells To Differentiate into Endothelial Cells in Hypoxia Condition, which Incorporated Tumor Vasculogenesis and Angiogenesis.

INTRODUCTION: High level of vascular endothelial growth factor (VEGF) and stromal-derived factor (SDF-1) are often expressed in many carcinoma tissues that are accompanied by intense neovascularization. VEGF is a key regulator of blood vessel formation during both vasculogenesis and angiogenesis. Mesenchymal stem cells (MSCs) in peripheral blood that are released from the bone marrow can be strongly attracted by SDF-1. Low oxygen tension is thought to be an integral component of the tumor microenvironment. To examine tumor angiogenesis in the tumor microenvironment, we studied that SDF-1 and VEGF both can induce MSCs to differentiate into endothelial cells (ECs) in hypoxia condition.METHODS: Adult Sprague-Dawley rat bone marrow MSCs were purified and maintained in DMEM/F12 containing 10% FBS, and were characterized by high expression of CD44, the lack of CD45 and CD11b molecules, their typical spindle-shaped morphology, together with their ability to differentiate into osteogenic, chondrogenic, and adipogenic cells. Subconfluent MSCs were used, were maintained with DMEM/F12 containing 10% FBS in hypoxia condition (93% N2 + 2% O2 +5% CO2), and were treated with or without VEGF and/or SDF-1. During induction, cell morphology, the vascular endothelial markers VE-cadherin and von Willebrand factor (vWF), and mesenchymal cell marker CD44 were observed. After induction, functions of cells were examined.RESULTS: MSCs treated with both VEGF and SDF-1 for 7 days in hypoxic condition changed morphologically and adopted a caudate appearance with rod-shaped microtubulated structures resembling Weibel-Palade bodies, and formed mature endothelial cell tubules in Matrigel(R) cultures after 15 days. Almost every cell expressed VE-cadherin and vWF [(98.32±1.39)%], but CD44 expression was markedly down-regulated. Functional characteristics of vWF release upon histamine stimulation in response to hypoxia were indistinguishable between the MSC-derived endothelial-like cells and cultured mature ECs. The best condition for the differentiation was the combination of 0.3 nM VEGF and 100 ng/ml SDF-1 at a culture duration of 10 to 15 days. However, the positive ratio of both VE-cadherin and vWF in cells induced by different concentration of SDF-1 alone or VEGF alone was lower [(8.35±2.89)% and (27.33±3.26)%, respectively]. The positive ratio of both VE-cadherin and vWF in cells induced by the best combination of 0.3 nM VEGF and 100 ng/ml SDF-1 in normoxic culture condition was (34.91±3.47)%. Finally, in xenogenic transplantation studies using a SCID mouse model, non-small cell lung cancer cells were injected subcutaneously with the MSC-derived endothelial-like cells induced by the best condition. As a result, co-transplantation of the cells promoted the formation of blood vessels. Immunohistochemistry and FISH analysis showed that the MSC-derived cells incorporated tumor vasculogenesis and angiogenesis.CONCLUSION: Stromal-derived factor and vascular endothelial growth factor synergistically induce bone marrow-derived mesenchymal stem cells to differentiate into endothelial cells in hypoxia condition, which incorporated tumor vasculogenesis and angiogenesis. These results suggest that targeting MSCs-derived angiogenesis might be a novel efficient antiangiogenesis strategy to treat cancer.

The Origin and in Vivo Significance of Murine and Human Culture-Expanded Endothelial Progenitor Cells

In adults highly purified populations of early hematopoietic progenitors or cells derived from ex vivo expanded unmobilized human peripheral blood mononuclear cells contribute to new blood vessel formation. However, the source of these culture-expanded endothelial progenitor cells (CE-EPCs) remains controversial. We demonstrate that ex vivo expansion of unmobilized human peripheral blood generated CE-EPCs with similar numbers, kinetics, and antigen expression profile as compared to plating unfractionated CD34(+)/lin(-)-enriched bone marrow mononuclear cells. Both CE-EPC populations uniformly co-expressed myeloid and endothelial markers, suggesting that peripheral blood progenitor enumeration does not correlate with the numbers of early outgrowth CE-EPCs. Using purified myeloid subpopulations obtained from mice harboring the lacZ transgene driven by an endothelial-specific promoter, we showed that the immature myeloid lineage marker CD31(+) cells generated CE-EPCs with fourfold greater frequency than mature myeloid populations. Biphenotypic cells co-expressing myeloid/endothelial antigens were not detected in circulating human or murine peripheral blood or bone marrow but were associated with murine tumors. Unlike CE-EPCs, CD14(+) leukocytes admixed within tumors did not generate vWF-positive blood vessels during a similarly defined period of tumor growth, but some leukocytes up-regulated the endothelial marker VE-cadherin. Taken together, the data suggest that the local neovascular microenvironment may facilitate vasculogenesis by promoting endothelial differentiation and that CE-EPCs may accelerate such vasculo-genesis.