Capillary defects and exaggerated inflammatory response in the airways of EphA2-deficient mice

Mesenchymal stem cells overexpressing interleukin-10 prevent allergic airway inflammation

BACKGROUNDS

Allergic airway inflammation is prevalent worldwide and imposes a considerable burden on both society and affected individuals. This study aimed to investigate the therapeutic advantages of mesenchymal stem cells (MSCs) overexpressed interleukin-10 (IL-10) for the treatment of allergic airway inflammation, as both IL-10 and MSCs possess immunosuppressive properties.

METHODS

Induced pluripotent stem cell (iPSC)-derived MSCs were engineered to overexpress IL-10 via lentiviral transfection (designated as IL-10-MSCs). MSCs and IL-10-MSCs were administered intravenously to mice with allergic inflammation induced by ovalbumin (OVA), and the features of allergic inflammation including inflammatory cell infiltration, Th cells in the lungs, and T helper 2 cell (Th2) cytokine levels in bronchoalveolar lavage fluid (BALF) were examined. MSCs and IL-10-MSCs were co-cultured with CD4+ T cells from patients with allergic rhinitis (AR), and the levels of Th2 cells and corresponding type 2 cytokines were studied. RNA-sequence was performed to further investigate the potential effects of MSCs and IL-10-MSCs on CD4+ T cells.

RESULTS

Stable IL-10-MSCs were established and characterised by high IL-10 expression. IL-10-MSCs significantly reduced inflammatory cell infiltration and epithelial goblet cell numbers in the lung tissues of mice with allergic airway inflammation. Inflammatory cell and cytokine levels in BALF also decreased after the administration of IL-10-MSCs. Moreover, IL-10-MSCs showed a stronger capacity to inhibit the levels of Th2 after co-cultured with CD4+ T cells from patients with AR. Furthermore, we elucidated lower levels of IL-5 and IL-13 in IL-10-MSCs treated CD4+ T cells, and blockade of IL-10 significantly reversed the inhibitory effects of IL-10-MSCs. We also reported the mRNA profiles of CD4+ T cells treated with IL-10-MSCs and MSCs, in which IL-10 played an important role.

CONCLUSION

IL-10-MSCs showed positive effects in the treatment of allergic airway inflammation, providing solid support for the use of genetically engineered MSCs as a potential novel therapy for allergic airway inflammation.

Anatomy and function of the lymphatic vessels in the parietal pleura and their plasticity under inflammation in mice

Inflammatory pleuritis often causes pleural effusions, which are drained through lymphatic vessels (lymphatics) in the parietal pleura. The distribution of button- and zipper-like endothelial junctions can identify the subtypes of lymphatics, the initial, pre-collecting, and collecting lymphatics. Vascular endothelial growth factor receptor (VEGFR)-3 and its ligands VEGF-C/D are crucial lymphangiogenic factors. Currently, in the pleura covering the chest walls, the anatomy of the lymphatics and connecting networks of blood vessels are incompletely understood. Moreover, their pathological and functional plasticity under inflammation and the effects of VEGFR inhibition are unclear. This study aimed to learn the above-unanswered questions and immunostained mouse chest walls as whole-mount specimens. Confocal microscopic images and their 3-dimensional reconstruction analyzed the vasculatures. Repeated intra-pleural cavity lipopolysaccharide challenge induced pleuritis, which was also treated with VEGFR inhibition. Levels of vascular-related factors were evaluated by quantitative real-time polymerase chain reaction. We observed the initial lymphatics in the intercostals, collecting lymphatics under the ribs, and pre-collecting lymphatics connecting both. Arteries branched into capillaries and gathered into veins from the cranial to the caudal side. Lymphatics and blood vessels were in different layers with an adjacent distribution of the lymphatic layer to the pleural cavity. Inflammatory pleuritis elevated expression levels of VEGF-C/D and angiopoietin-2, induced lymphangiogenesis and blood vessel remodeling, and disorganized the lymphatic structures and subtypes. The disorganized lymphatics showed large sheet-like structures with many branches and holes inside. Such lymphatics were abundant in zipper-like endothelial junctions with some button-like junctions. The blood vessels were tortuous and had various diameters and complex networks. Stratified layers of lymphatics and blood vessels were disorganized, with impaired drainage function. VEGFR inhibition partially maintained their structures and drainage function. These findings demonstrate anatomy and pathological changes of the vasculatures in the parietal pleura and their potential as a novel therapeutic target.

Anatomy and pathology of lymphatic vessels under physiological and inflammatory conditions in the mouse diaphragm

The lymphatic vessels in the parietal pleura drain fluids. Impaired drainage function and excessive fluid entry in the pleural cavity accumulate effusion. The rat diaphragmatic lymphatics drain fluids from the pleura to the muscle layer. Lymphatic subtypes are characterized by the major distribution of discontinuous button-like endothelial junctions (buttons) in initial lymphatics and continuous zipper-like junctions (zippers) in the collecting lymphatics. Inflammation replaced buttons with zippers in tracheal lymphatics. In the mouse diaphragm, the structural relationship between the lymphatics and blood vessels, the presence of lymphatics in the muscle layer, and the distributions of initial and collecting lymphatics are unclear. Moreover, the endothelial junctional alterations and effects of vascular endothelial growth factor receptor (VEGFR) inhibition under pleural inflammation are unclear. We subjected the whole-mount mouse diaphragms to immunohistochemistry. The lymphatics and blood vessels were distributed in different layers of the pleural membrane. Major lymphatic subtypes were initial lymphatics in the pleura and collecting lymphatics in the muscle layer. Chronic pleural inflammation disorganized the stratified layers of the lymphatics and blood vessels and replaced buttons with zippers in the pleural lymphatics, which impaired drainage function. VEGFR inhibition under inflammation maintained the vascular structures and drainage function. In addition, VEGFR inhibition maintained the lymphatic endothelial junctions and reduced the blood vessel permeability under inflammation. These findings may provide new targets for managing pleural effusions caused by inflammation, such as pleuritis and empyema, which are common pneumonia comorbidities.

Alleviating experimental allergic eye disease by inhibiting pro-lymphangiogenic VEGFR3 signal

PURPOSE

Ocular allergy leads to acute and chronic inflammation that may deteriorate the conjunctiva and other ocular tissue. The conjunctiva is covered with abundant lymphatic vessels but how the conjunctival lymphatic system patriciates in the development of allergic eye disease (AED) remains to be elucidated.

METHODS AND RESULTS

By using ovalbumin (OVA)+pertussis toxin (PTX) as a sensitizer followed by daily OVA challenges, we induced optimized AED manifestations in mice. We show that conjunctival lymphatics underwent significant expansion after 28 days of chronic OVA challenge, and this process can be prevented by inducible genetic ablation of lymphatic Vegfr3. Through transcriptomic profile analysis in combination with histopathological examinations, we found that pro-lymphangiogenic VEGFR3 signal promoted allergy-induced activation of T helper 2 (Th2) type immune responses, including antigen presentation, and Th2 cells, B cells and mast cell-related pathways in the conjunctiva, thereby critically contributing to the immunoglobulin E (IgE) production and AED manifestations. As a result, ocular allergy can be alleviated by genetic inhibition of lymphatic Vegfr3. Interestingly, pro-lymphangiogenic VEGFR3 signal did not appear to affect the obstruction of meibomian glands (MGs) or the activation of Th17 type and neutrophil pathways that are associated with AED.

CONCLUSIONS

These data reveal the key role of pro-lymphangiogenic VEGFR3 signaling in the development of AED and provide experimental evidence that VEGFR3 inhibition may be useful in treating ocular allergy in patients.

EphrinA1-Fc Attenuates Ventricular Remodeling and Dysfunction in Chronically Nonreperfused WT but not EphA2-R-M mice

Background: EphrinA1-Fc abolishes acute I/R injury and attenuates nonreperfused cardiac injury 4 days after permanent occlusion in mice. The goal of this study was to assess the capacity of a single intramyocardial administration of ephrinA1-Fc at the time of coronary artery ligation, to determine the degree to which early salvage effects translate to reduced adverse remodeling after 4 weeks of nonreperfused myocardial infarction (MI) in wild-type B6 and EphA2-R-M (EphA2 receptor null) mice. Methods: At 4 weeks post-MI, echocardiography, histologic and immunohistochemical analyses of B6 mouse hearts were performed. Primary mouse cardiac fibroblasts (FBs) isolated from B6 mice cultured in the presence of low and high dose ephrinA1-Fc, both with and without pro-fibrotic TGF-β stimulation and Western blots, were probed for relative expression of remodeling proteins MMP-2, MMP-9 and TIMP-1, in addition to DDR2 and (p)SMAD2/3/totalSMAD2/3. Results: EphrinA1-Fc preserved a significant degree of contractile function, decreased adverse left ventricular remodeling, attenuated excessive compensatory hypertrophy, and decreased interstitial fibrosis in wild-type (WT) B6 mouse hearts. In contrast, most of these parameters were poorer in ephrinA1-Fc-treated EphA2-R-M mice. Of note, fibrosis was proportionately decreased, implying that other EphA receptor(s) are more important in regulating the pro-fibrotic response. Primary FBs showed disparate alteration of MMP-2, MMP-9 and TIMP-1, as well as DDR2 and p-SMAD2/3/totalSMAD2/3, which indicates that matrix remodeling and cardiac fibrosis in the injured heart are influenced by ephrinA1-Fc. Conclusion: This study demonstrates the capacity of a single administration of ephrinA1-Fc at the onset of injury to attenuate long-term nonreperfused post-MI ventricular remodeling that results in progressive heart failure, and the important role of EphA2 in mitigating the deleterious effects.

Tissue Engineering of Axially Vascularized Soft-Tissue Flaps with a Poly-(ɛ-Caprolactone) Nanofiber-Hydrogel Composite

Objective: To develop a novel approach for tissue engineering of soft-tissue flaps suitable for free microsurgical transfer, using an injectable nanofiber hydrogel composite (NHC) vascularized by an arteriovenous (AV) loop. Approach: A rat AV loop model was used for tissue engineering of vascularized soft-tissue flaps. NHC or collagen-elastin (CE) scaffolds were implanted into isolation chambers together with an AV loop and explanted after 15 days. Saphenous veins were implanted into the scaffolds as controls. Neoangiogenesis, ultrastructure, and protein expression of SYNJ2BP, EPHA2, and FOXC1 were analyzed by immunohistochemistry and compared between the groups. Rheological properties were compared between the two scaffolds and native human adipose tissue. Results: A functional neovascularization was evident in NHC flaps with its amount being comparable with CE flaps. Scanning electron microscopy revealed a strong mononuclear cell infiltration along the nanofibers in NHC flaps and a trend toward higher fiber alignment compared with CE flaps. SYNJ2BP and EPHA2 expression in endothelial cells (ECs) was lower in NHC flaps compared with CE flaps, whereas FOXC1 expression was increased in NHC flaps. Compared with the stiffer CE flaps, the NHC flaps showed similar rheological properties to native human adipose tissue. Innovation: This is the first study to demonstrate the feasibility of tissue engineering of soft-tissue flaps with similar rheological properties as human fat, suitable for microsurgical transfer using an injectable nanofiber hydrogel composite. Conclusions: The injectable NHC scaffold is suitable for tissue engineering of axially vascularized soft-tissue flaps with a solid neovascularization, strong cellular infiltration, and biomechanical properties similar to human fat. Our data indicate that SYNJ2BP, EPHA2, and FOXC1 are involved in AV loop-associated angiogenesis and that the scaffold material has an impact on protein expression in ECs.

EphA2 phosphorylates NLRP3 and inhibits inflammasomes in airway epithelial cells

Inflammasomes are intracellular complexes that form in the cytosol of inflammatory cells. NLRP3 is one of the sensor proteins in the complex that can recognize a wide variety of stimuli ranging from microbial components to environmental particulates. Here, we report that in mouse airway epithelial cells (AECs), inflammasome activation is inhibited by EphA2, a member of the transmembrane tyrosine kinase receptor family, via tyrosine phosphorylation of NLRP3 in a model of reovirus infection. We find that EphA2 depletion markedly enhances interleukin-1β (IL-1β) and interleukin-18 (IL-18) production in response to the virus. EphA2^-/- mice show stronger inflammatory infiltration and enhanced inflammasome activation upon viral infection, and aggravated asthma symptoms upon ovalbumin (ova) induction. Mechanistically, EphA2 binds to NLRP3 and induces its phosphorylation at Tyr132, thereby interfering with ASC speck formation and blocking the activation of the NLRP3-inflammasome. These data demonstrate that reovirus employs EphA2 to suppress inflammasome activation in AECs and that EphA2 deficiency causes a pathological exacerbation of asthma in an ova-induced asthma model.

Refueling the Ischemic CNS: Guidance Molecules for Vascular Repair

Stroke patients have only limited therapeutic options and often remain with considerable disabilities. To promote neurological recovery, angiogenesis in the ischemic peri-infarct region has been recognized as an encouraging therapeutic target. Despite advances in mechanistic understanding of vascular growth and repair, effective and safe angiogenic treatments are currently missing. Besides the most intensively studied angiogenic growth factors, recent research has indicated that the process of vascular sprouting and migration also requires the participation of guidance molecules, many of which were initially identified as regulators of axonal growth. Here, we review the inhibitory and growth-promoting effects of guidance molecules on the vascular system and discuss their potential as novel angiogenic targets for neurovascular diseases.

MicroRNA-regulated pathways of flow-stimulated angiogenesis and vascular remodeling in vivo

BACKGROUND

Vascular shear stress promotes endothelial cell sprouting in vitro. The impact of hemodynamic forces on microRNA (miRNA) and gene expression within growing vascular networks in vivo, however, remain poorly investigated. Arteriovenous (AV) shunts are an established model for induction of neoangiogenesis in vivo and can serve as a tool for analysis of hemodynamic effects on miRNA and gene expression profiles over time.

METHODS

AV shunts were microsurgically created in rats and explanted on postoperative days 5, 10 and 15. Neoangiogenesis was confirmed by histologic analysis and micro-computed tomography. MiRNA and gene expression profiles were determined in tissue specimens from AV shunts by microarray analysis and quantitative real-time polymerase chain reaction and compared with sham-operated veins by bioinformatics analysis. Changes in protein expression within AV shunt endothelial cells were determined by immunohistochemistry.

RESULTS

Samples from AV shunts exhibited a strong overexpression of proangiogenic cytokines, oxygenation-associated genes (HIF1A, HMOX1), and angiopoetic growth factors. Significant inverse correlations of the expressions of miR-223-3p, miR-130b-3p, miR-19b-3p, miR-449a-5p, and miR-511-3p which were up-regulated in AV shunts, and miR-27b-3p, miR-10b-5p, let-7b-5p, and let-7c-5p, which were down-regulated in AV shunts, with their predicted interacting targets C-X-C chemokine receptor 2 (CXCR2), interleukin-1 alpha (IL1A), ephrin receptor kinase 2 (EPHA2), synaptojanin-2 binding protein (SYNJ2BP), forkhead box C1 (FOXC1) were present. CXCL2 and IL1A overexpression in AV shunt endothelium was confirmed at the protein level by immunohistochemistry.

CONCLUSIONS

Our data indicate that flow-stimulated angiogenesis is determined by an upregulation of cytokines, oxygenation associated genes and miRNA-dependent regulation of FOXC1, EPHA2 and SYNJ2BP.

Guidance Molecules in Vascular Smooth Muscle

Several highly conserved families of guidance molecules, including ephrins, Semaphorins, Netrins, and Slits, play conserved and distinct roles in tissue remodeling during tissue patterning and disease pathogenesis. Primarily, these guidance molecules function as either secreted or surface-bound ligands that interact with their receptors to activate a variety of downstream effects, including cell contractility, migration, adhesion, proliferation, and inflammation. Vascular smooth muscle cells, contractile cells comprising the medial layer of the vessel wall and deriving from the mural population, regulate vascular tone and blood pressure. While capillaries lack a medial layer of vascular smooth muscle, mural-derived pericytes contribute similarly to capillary tone to regulate blood flow in various tissues. Furthermore, pericyte coverage is critical in vascular development, as perturbations disrupt vascular permeability and viability. During cardiovascular disease, smooth muscle cells play a more dynamic role in which suppression of contractile markers, enhanced proliferation, and migration lead to the progression of aberrant vascular remodeling. Since many types of guidance molecules are expressed in vascular smooth muscle and pericytes, these may contribute to blood vessel formation and aberrant remodeling during vascular disease. While vascular development is a large focus of the existing literature, studies emerged to address post-developmental roles for guidance molecules in pathology and are of interest as novel therapeutic targets. In this review, we will discuss the roles of guidance molecules in vascular smooth muscle and pericyte function in development and disease.

A Novel EphA2 Inhibitor Exerts Beneficial Effects in PI-IBS in Vivo and in Vitro Models via Nrf2 and NF-κB Signaling Pathways

Though the detailed pathological mechanism of post-infectious irritable bowel syndrome (PI-IBS) remains unclear, accumulating evidence indicates that oxidative stress and inflammation are implicated in the process of PI-IBS. Oxidative stress and inflammation are regulated by Nrf2 and NF-κB signaling pathways, respectively. EphA2, a member of Eph receptor family, promotes oxidative stress and inflammatory responses via regulation of Nrf2 and NF-κB signaling pathways in various types of human diseases. Understanding the mechanisms by which EphA2 regulate oxidative stress and inflammation in PI-IBS is important for the development of new strategies to treat PI-IBS. However, the effects of ALW-II-41-27, a novel EphA2 inhibitor on PI-IBS and the underlying molecular mechanisms have never been studied. In the present study, we showed that ALW-II-41-27 decreased gastrointestinal motility and abdominal withdrawal reflex (AWR) scores, markedly reduced the levels of oxidative stress markers [4-hydroxy-2-nonenal (4-HNE), protein carbonyl, and 8-hydroxy-2-de-axyguanine (8-OHdG)] and proinflammatory cytokines (TNF-α, IL-6, IL-17, and ICAM-1), and remarkably increased the level of anti-inflammatory cytokine (IL-10) in serum and colon of Trichinella spiralis-infected mice. Moreover, ALW-II-41-27 was effective in suppressing oxidative stress and inflammation in LPS-treated NCM460 colonic cells. Treatment of ALW-II-41-27 reversed the activation of NF-κB and inactivation of Nrf2 in LPS-treated NCM460 cells. Importantly, these protective effects of ALW-II-41-27 were partially inhibited by EphA2 KO and abolished by EphA2 overexpression. In conclusion, EphA2 may represent a promising therapeutic target for patients with PI-IBS and ALW-II-41-27 might function as a novel therapeutic agent for PI-IBS.

MicroRNA-302b negatively regulates IL-1β production in response to MSU crystals by targeting IRAK4 and EphA2

Background

Interleukin-1β (IL-1β) is a pivotal proinflammatory cytokine that is strongly associated with the inflammation of gout. However, the underlying mechanism through which the production of IL-1β is regulated has not been fully elucidated. Our previous work identified that miR-302b had an important immune regulatory role in bacterial lung infections. This study was conducted to evaluate the function of miR-302b on monosodium urate (MSU) crystal-induced inflammation and its mechanism.

Methods

The expression pattern and the immune-regulatory role of miR-302b were evaluated both in vitro and in vivo. The functional targets of miR-302b were predicted by bioinformatics, and then validated by genetic approaches. In addition, the clinical feature of miR-302b was analyzed using serum samples of patients with gouty arthritis.

Results

The extremely high expression of miR-302b was observed in both macrophages and mouse air membranes treated with MSU. Intriguingly, overexpression of miR-302b regulated NF-κB and caspase-1 signaling, leading to significantly attenuate MSU-induced IL-1β. By genetic analysis, miR-302b exhibited inhibitory function on IRAK4 and EphA2 by binding to their 3′-UTR regions. Corporately silencing IRAK4 and EphA2 largely impaired MSU-induced IL-1β protein production. Moreover, it was also found that miR-302b and EphA2 suppressed the migration of macrophages. Finally, it was observed that high expression of miR-302b was a general feature in patients with gouty arthritis.

Conclusions

These results suggest that miR-302b can regulate IL-1β production in MSU-induced inflammation by targeting NF-κB and caspase-1 signaling, and may be a potential therapeutic target for gouty arthritis.

Electronic supplementary material

The online version of this article (10.1186/s13075-018-1528-9) contains supplementary material, which is available to authorized users.

EPHA4-FC TREATMENT REDUCES ISCHEMIA/REPERFUSION-INDUCED INTESTINAL INJURY BY INHIBITING VASCULAR PERMEABILITY

The inflammatory response is characterized by increased endothelial permeability, which permits the passage of fluid and inflammatory cells into interstitial spaces. The Eph/ephrin receptor ligand system plays a role in inflammation through a signaling cascade, which modifies Rho-GTPase activity. We hypothesized that blocking Eph/ephrin signaling using an EphA4-Fc would result in decreased inflammation and tissue injury in a model of ischemia/reperfusion (I/R) injury. Mice undergoing intestinal I/R pretreated with the EphA4-Fc had significantly reduced intestinal injury compared to mice injected with the control Fc. This reduction in I/R injury was accompanied by significantly reduced neutrophil infiltration, but did not affect intestinal inflammatory cytokine generation. Using microdialysis, we identified that intestinal I/R induced a marked increase in systemic vascular leakage, which was completely abrogated in EphA4-Fc-treated mice. Finally, we confirmed the direct role of Eph/ephrin signaling in endothelial leakage by demonstrating that EphA4-Fc inhibited tumor necrosis factor-α-induced vascular permeability in human umbilical vein endothelial cells. This study identifies that Eph/ephrin interaction induces proinflammatory signaling in vivo by inducing vascular leak and neutrophil infiltration, which results in tissue injury in intestinal I/R. Therefore, therapeutic targeting of Eph/ephrin interaction using inhibitors, such as EphA4-Fc, may be a novel method to prevent tissue injury in acute inflammation by influencing endothelial integrity and by controlling vascular leak.

Eph Receptor Tyrosine Kinases in Tumor Immunity

The family of Eph receptor tyrosine kinases and their ephrin ligands regulate a diverse array of physiologic processes, such as axonal guidance, bone remodeling, and immune cell development and trafficking. Eph/ephrin interactions have also been implicated in various pathologic processes, including inflammation, cancer, and tumor angiogenesis. Because Eph receptors play prominent roles in both the immune system and cancer, they likely impact the tumor immune microenvironment, an area in which Eph receptors remain understudied. Here, we provide the first comprehensive review of Eph receptors in the context of tumor immunity. With the recent rise of cancer immunotherapies as promising therapeutic interventions, further elucidation of the roles of Eph receptors in the tumor immune microenvironment will be critical for understanding and developing novel targets against tumor immune evasion. Cancer Res; 76(22); 6452-7. ©2016 AACR.

Lymphangiogenesis in rat asthma model

Although bronchial angiogenesis has been well documented in allergic asthma, lymphangiogenesis has not been widely studied. Therefore, we evaluated changes in lung lymphatics in a rat model of allergen-induced asthma using house dust mite (Der p 1; 100 μg/challenge). Additionally, properties of isolated lung lymphatic endothelial cells (CD45^-, CD141⁺, LYVE-1⁺, Prox-1⁺) were studied in vitro. Three weeks after the onset of intranasal allergen exposure (twice-weekly), an increase in the number of lung lymphatic vessels was measured (34% increase) by lung morphometry. New lymphatic structures were seen predominantly in the peribronchial and periarterial interstitial space but also surrounding large airways. Isolated lymphatic endothelial cells from sensitized lungs showed enhanced proliferation (% Ki67⁺), chemotaxis, and tube formation (number and length) compared to lymphatic endothelial cells isolated from naive rat lungs. This hyper-proliferative lymphangiogenic phenotype was preserved through multiple cell passages (2-8). Lymphatic endothelial cells isolated from naive and HDM-sensitized rats produced similar in vitro levels of VEGF-C, VEGF-D, and VEGFR3 protein, each recognized as critical lymphangiogenic factors. Inhibition with anti-VEGFR (axitinib, 0.1 μM) blocked proliferation and chemotaxis. Results suggest that in vivo sensitization causes fundamental changes to lymphatic endothelium, which are retained in vitro, and may relate to VEGFR downstream signaling.

The endothelial adaptor molecule TSAd is required for VEGF-induced angiogenic sprouting through junctional c-Src activation

Activation of vascular endothelial growth factor (VEGF) receptor 2 (VEGFR2) by VEGF binding is critical for vascular morphogenesis. In addition, VEGF disrupts the endothelial barrier by triggering the phosphorylation and turnover of the junctional molecule VE-cadherin, a process mediated by the VEGFR2 downstream effectors T cell-specific adaptor (TSAd) and the tyrosine kinase c-Src. We investigated whether the VEGFR2-TSAd-c-Src pathway was required for angiogenic sprouting. Indeed, Tsad-deficient embryoid bodies failed to sprout in response to VEGF. Tsad-deficient mice displayed impaired angiogenesis specifically during tracheal vessel development, but not during retinal vasculogenesis, and in VEGF-loaded Matrigel plugs, but not in those loaded with FGF. The SH2 and proline-rich domains of TSAd bridged VEGFR2 and c-Src, and this bridging was critical for the localization of activated c-Src to endothelial junctions and elongation of the growing sprout, but not for selection of the tip cell. These results revealed that vascular sprouting and permeability are both controlled through the VEGFR2-TSAd-c-Src signaling pathway in a subset of tissues, which may be useful in developing strategies to control tissue-specific pathological angiogenesis.

Blood vessel crosstalk during organogenesis-focus on pancreas and endothelial cells

Blood vessels form a highly branched, interconnected, and largely stereotyped network of tubes that sustains every organ and tissue in vertebrates. How vessels come to take on their particular architecture, or how they are 'patterned,' and in turn, how they influence surrounding tissues are fundamental questions of organogenesis. Decades of work have begun to elucidate how endothelial progenitors arise and home to precise locations within tissues, integrating attractive and repulsive cues to build vessels where they are needed. Conversely, more recent findings have revealed an exciting facet of blood vessel interaction with tissues, where vascular cells provide signals to developing organs and progenitors therein. Here, we discuss the exchange of reciprocal signals between endothelial cells and neighboring tissues during embryogenesis, with a special focus on the developing pancreas. Understanding the mechanisms driving both sides of these interactions will be crucial to the development of therapies, from improving organ regeneration to efficient production of cell based therapies. Specifically, elucidating the interface of the vasculature with pancreatic lineages, including endocrine cells, will instruct approaches such as generation of replacement beta cells for Type I diabetes. WIREs Dev Biol 2016, 5:598-617. doi: 10.1002/wdev.240 For further resources related to this article, please visit the WIREs website.

Compensatory angiogenesis and tumor refractoriness

Since the establishment of tumor angiogenesis as a therapeutic target, an excitement in developing the anti-angiogenic agents was resulted in tailoring a humanized monoclonal antibody (Bevacizumab) against vascular endothelial growth factor (VEGF): a key factor in recruiting angiogenesis. The past three decades' research in the area of angiogenesis also invented a series of novel and effective anti-angiogenic agents targeting the VEGF signaling axis. Despite the demonstrable clinical benefits of anti-angiogenic therapy, the preclinical and clinical data of the current therapeutic settings clearly indicate the transient efficacy, restoration of tumor progression and aggressive recurrence of tumor invasion after the withdrawal of anti-angiogenic therapy. Therefore, the impact of this therapeutic regime on improving overall survival of patients has been disappointing in clinic. The recent advances in pathophysiology of tumor angiogenesis and related molecular and cellular underpinnings attributed the conspiracy of compensatory angiogenic pathways in conferring evasive and intrinsic tumor resistance to anti-angiogenic agents. The understandings of how these pathways functionally cross-talk for sustaining tumor angiogenesis during VEGF blockade is essential and perhaps may act as a basic prerequisite for designing novel therapeutic strategies to combat the growing arrogance of tumors toward anti-angiogenic agents. The present review offers a discourse on major compensatory angiogenic pathways operating at cellular and molecular levels and their attributes with resistance to anti-angiogenic agents along with strategic opinions on future setting in targeting tumor angiogenesis.

Chronic inflammation, lymphangiogenesis, and effect of an anti-VEGFR therapy in a mouse model and in human patients with aspiration pneumonia

Chronic inflammation induces lymphangiogenesis and blood vessel remodelling. Since aged pneumonia patients often have repeated episodes of aspiration pneumonia, the pathogenesis may involve chronic inflammation. For lymphangiogenesis, VEGFR-3 and its ligand VEGF-C are key factors. No previous studies have examined chronic inflammation or vascular changes in aspiration pneumonia or its mouse models. In lung inflammation, little is known about the effect of blocking VEGFR-3 on lung lymphangiogenesis and, moreover, its effect on the disease condition. This study aimed to establish a mouse model of aspiration pneumonia, examine the presence of chronic inflammation and vascular changes in the model and in patients, and evaluate the effect of inhibiting VEGFR-3 on the lymphangiogenesis and disease condition in this model. To induce aspiration pneumonia, we repeated inoculation of pepsin at low pH and LPS into mice for 21-28 days, durations in which bronchioalveolar lavage and plasma leakage in the lung suggested the presence of exaggerated inflammation. Conventional and immunohistochemical analysis of tracheal whole mounts suggested the presence of chronic inflammation, lymphangiogenesis, and blood vessel remodelling in the model. Quantitative RT-PCR of the trachea and lung suggested the involvement of lymphangiogenic factor VEGF-C, VEGFR-3, and pro-inflammatory cytokines. In the lung, the aspiration model showed the presence of chronic inflammation and exaggerated lymphangiogenesis. Treatment with the VEGFR inhibitor axitinib or the VEGFR-3 specific inhibitor SAR131675 impaired lymphangiogenesis in the lung and improved oxygen saturation in the aspiration model. Since the lung is the main site of aspiration pneumonia, the changes were intensive in the lung and mild in the trachea. Human lung samples also showed the presence of chronic inflammation and exaggerated lymphangiogenesis, suggesting the relevance of the model to the disease. These results suggest lymphatics in the lung as a new target of analysis and therapy in aspiration pneumonia.

Hypoxia-controlled EphA3 marks a human endometrium-derived multipotent mesenchymal stromal cell that supports vascular growth

Eph and ephrin proteins are essential cell guidance cues that orchestrate cell navigation and control cell-cell interactions during developmental tissue patterning, organogenesis and vasculogenesis. They have been extensively studied in animal models of embryogenesis and adult tissue regeneration, but less is known about their expression and function during human tissue and organ regeneration. We discovered the hypoxia inducible factor (HIF)-1α-controlled expression of EphA3, an Eph family member with critical functions during human tumour progression, in the vascularised tissue of regenerating human endometrium and on isolated human endometrial multipotent mesenchymal stromal cells (eMSCs), but not in other highly vascularised human organs. EphA3 affinity-isolation from human biopsy tissue yielded multipotent CD29⁺/CD73⁺/CD90⁺/CD146⁺ eMSCs that can be clonally propagated and respond to EphA3 agonists with EphA3 phosphorylation, cell contraction, cell-cell segregation and directed cell migration. EphA3 silencing significantly inhibited the ability of transplanted eMSCs to support neovascularisation in immunocompromised mice. In accord with established roles of Eph receptors in mediating interactions between endothelial and perivascular stromal cells during mouse development, our findings suggest that HIF-1α-controlled expression of EphA3 on human MSCs functions during the hypoxia-initiated early stages of adult blood vessel formation.

EphA2-receptor deficiency exacerbates myocardial infarction and reduces survival in hyperglycemic mice

Background

We have previously shown that EphrinA1/EphA expression profile changes in response to myocardial infarction (MI), exogenous EphrinA1-Fc administration following MI positively influences wound healing, and that deletion of the EphA2 Receptor (EphA2-R) exacerbates injury and remodeling. To determine whether or not ephrinA1-Fc would be of therapeutic value in the hyperglycemic infarcted heart, it is critical to evaluate how ephrinA1/EphA signaling changes in the hyperglycemic myocardium in response to MI.

Methods

Streptozotocin (STZ)-induced hyperglycemia in wild type (WT) and EphA2-receptor mutant (EphA2-R-M) mice was initiated by an intraperitoneal injection of STZ (150 mg/kg) 10 days before surgery. MI was induced by permanent ligation of the left anterior descending coronary artery and analyses were performed at 4 days post-MI. ANOVAs with Student-Newman Keuls multiple comparison post-hoc analysis illustrated which groups were significantly different, with significance of at least p < 0.05.

Results

Both WT and EphA2-R-M mice responded adversely to STZ, but only hyperglycemic EphA2-R-M mice had lower ejection fraction (EF) and fractional shortening (FS). At 4 days post-MI, we observed greater post-MI mortality in EphA2-R-M mice compared with WT and this was greater still in the EphA2-R-M hyperglycemic mice. Although infarct size was greater in hyperglycemic WT mice vs normoglycemic mice, there was no difference between hyperglycemic EphA2-R-M mice and normoglycemic EphA2-R-M mice. The hypertrophic response that normally occurs in viable myocardium remote to the infarct was noticeably absent in epicardial cardiomyocytes and cardiac dysfunction worsened in hyperglycemic EphA2-R-M hearts post-MI. The characteristic interstitial fibrotic response in the compensating myocardium remote to the infarct also did not occur in hyperglycemic EphA2-R-M mouse hearts to the same extent as that observed in the hyperglycemic WT mouse hearts. Differences in neutrophil and pan-leukocyte infiltration and serum cytokines implicate EphA2-R in modulation of injury and the differences in ephrinA1 and EphA6-R expression in governing this are discussed.

Conclusions

We conclude that EphA2-mutant mice are more prone to hyperglycemia-induced increased injury, decreased survival, and worsened LV remodeling due to impaired wound healing.

Deletion of the EphA2 receptor exacerbates myocardial injury and the progression of ischemic cardiomyopathy

EphrinA1-EphA-receptor signaling is protective during myocardial infarction (MI). The EphA2-receptor (EphA2-R) potentially mediates cardiomyocyte survival. To determine the role of the EphA2-R in acute non-reperfused myocardial injury in vivo, infarct size, inflammatory cell density, NF-κB, p-AKT/Akt, and MMP-2 protein levels, and changes in ephrinA1/EphA2-R gene expression profile were assessed 4 days post-MI in B6129 wild-type (WT) and EphA2-R-mutant (EphA2-R-M) mice lacking a functional EphA2-R. Fibrosis, capillary density, morphometry of left ventricular chamber and infarct dimensions, and cardiac function also were measured 4 weeks post-MI to determine the extent of ventricular remodeling. EphA2-R-M infarct size and area of residual necrosis were 31.7% and 113% greater than WT hearts, respectively. Neutrophil and macrophage infiltration were increased by 46% and 84% in EphA2-R-M hearts compared with WT, respectively. NF-κB protein expression was 1.9-fold greater in EphA2-R-M hearts at baseline and 56% less NF-κB after infarction compared with WT. EphA6 gene expression was 2.5-fold higher at baseline and increased 9.8-fold 4 days post-MI in EphA2-R-M hearts compared with WT. EphrinA1 gene expression in EphA2-R-M hearts was unchanged at baseline and decreased by 42% 4 days post-MI compared with WT hearts. EphA2-R-M hearts had 66.7% less expression of total Akt protein and 59% less p-Akt protein than WT hearts post-MI. EphA2-R-M hearts 4 weeks post-MI had increased chamber dilation and interstitial fibrosis and decreased MMP-2 expression and capillary density compared with WT. In conclusion, the EphA2-R is necessary to appropriately modulate the inflammatory response and severity of early injury during acute MI, thereby influencing the progression of ischemic cardiomyopathy.

Point mutations in dimerization motifs of the transmembrane domain stabilize active or inactive state of the EphA2 receptor tyrosine kinase

The EphA2 receptor tyrosine kinase plays a central role in the regulation of cell adhesion and guidance in many human tissues. The activation of EphA2 occurs after proper dimerization/oligomerization in the plasma membrane, which occurs with the participation of extracellular and cytoplasmic domains. Our study revealed that the isolated transmembrane domain (TMD) of EphA2 embedded into the lipid bicelle dimerized via the heptad repeat motif L(535)X3G(539)X2A(542)X3V(546)X2L(549) rather than through the alternative glycine zipper motif A(536)X3G(540)X3G(544) (typical for TMD dimerization in many proteins). To evaluate the significance of TMD interactions for full-length EphA2, we substituted key residues in the heptad repeat motif (HR variant: G539I, A542I, G553I) or in the glycine zipper motif (GZ variant: G540I, G544I) and expressed YFP-tagged EphA2 (WT, HR, and GZ variants) in HEK293T cells. Confocal microscopy revealed a similar distribution of all EphA2-YFP variants in cells. The expression of EphA2-YFP variants and their kinase activity (phosphorylation of Tyr(588) and/or Tyr(594)) and ephrin-A3 binding were analyzed with flow cytometry on a single cell basis. Activation of any EphA2 variant is found to occur even without ephrin stimulation when the EphA2 content in cells is sufficiently high. Ephrin-A3 binding is not affected in mutant variants. Mutations in the TMD have a significant effect on EphA2 activity. Both ligand-dependent and ligand-independent activities are enhanced for the HR variant and reduced for the GZ variant compared with the WT. These findings allow us to suggest TMD dimerization switching between the heptad repeat and glycine zipper motifs, corresponding to inactive and active receptor states, respectively, as a mechanism underlying EphA2 signal transduction.

Royal jelly prevents the progression of sarcopenia in aged mice in vivo and in vitro

Sarcopenia is characterized by the age-related loss of muscle mass and strength. One of the mechanisms of sarcopenia is the loss in the function and number of muscle satellite cells. Royal jelly (RJ) is a health food used worldwide. To obtain better digestion and absorption than RJ, protease-treated RJ (pRJ) has been developed. RJ and pRJ have been suggested to have potential pharmacological benefits such as prolonging the life span and reducing fatigue. Because these effects may improve sarcopenia and the functions of satellite cells, we examined the effects of RJ or pRJ treatment on the skeletal muscles in an animal model using aged mice. In vivo, RJ/pRJ treatment attenuated the decrease in the muscle weight and grip strength and increased the regenerating capacity of injured muscles and the serum insulin-like growth factor-1 levels compared with controls. In vitro, using isolated satellite cells from aged mice, pRJ treatment increased the cell proliferation rate, promoted cell differentiation, and activated Akt intracellular signaling pathway compared with controls. These findings suggest that RJ/pRJ treatment had a beneficial effect on age-related sarcopenia.

Ephrin-Eph signaling as a potential therapeutic target for the treatment of myocardial infarction

Although numerous strategies have been developed to reduce the initial ischemic insult and cellular injury that occurs during myocardial infarction (MI), few have progressed into the clinical arena. The epidemiologic and economic impact of MI necessitates the development of innovative therapies to rapidly and effectively reduce the initial injury and subsequent cardiac dysfunction. The Eph receptors and their cognate ligands, the ephrins, are the largest family of receptor tyrosine kinases, and their signaling has been shown to play a diverse role in various cellular processes. The recent advances in the study of ephrin-Eph signaling have shown promising progress in many fields of medicine. They have been implicated in the pathophysiology of various cancers and in the regulation of inflammation and apoptosis. Recent studies have shown that manipulation of ephrin-Eph cell signaling can favorably influence cardiomyocyte viability and ultimately preserve cardiac function post-MI. In this article, we explore the hypothesis that manipulation of ephrin-Eph signaling may potentially be a novel therapeutic target in the treatment of MI through alteration of the cellular processes that govern injury and wound healing.

EphrinB2 reverse signaling protects against capillary rarefaction and fibrosis after kidney injury

Microvascular disease, a characteristic of acute and chronic kidney diseases, leads to rarefaction of peritubular capillaries (PTCs), promoting secondary ischemic injury, which may be central to disease progression. Bidirectional signaling by EphB4 receptor and ephrinB2 ligand is critical for angiogenesis during murine development, suggesting that ephrinB2 reverse signaling may have a role in renal angiogenesis induced by injury or fibrosis. Here, we found that ephrinB2 reverse signaling is activated in the kidney only after injury. In mice lacking the PDZ intracellular signaling domain of ephrinB2 (ephrinB2 ΔV), angiogenesis was impaired and kidney injury led to increased PTC rarefaction and fibrosis. EphrinB2 ΔV primary kidney pericytes migrated more than wild-type pericytes and were less able to stabilize capillary tubes in three-dimensional culture and less able to stimulate synthesis of capillary basement membrane. EphrinB2 ΔV primary kidney microvascular endothelial cells migrated and proliferated less than wild-type microvascular endothelial cells in response to vascular endothelial growth factor A and showed less internalization and activation of vascular endothelial growth factor receptor-2. Taken together, these results suggest that PDZ domain-dependent ephrinB2 reverse signaling protects against PTC rarefaction by regulating angiogenesis and vascular stability during kidney injury. Furthermore, this signaling in kidney pericytes protects against pericyte-to-myofibroblast transition and myofibroblast activation, thereby limiting fibrogenesis.

Eph/Ephrin signaling in injury and inflammation

The Eph/ephrin receptor-ligand system plays an important role in embryogenesis and adult life, principally by influencing cell behavior through signaling pathways, resulting in modification of the cell cytoskeleton and cell adhesion. There are 10 EphA receptors, and six EphB receptors, distinguished on sequence difference and binding preferences, that interact with the six glycosylphosphatidylinositol-linked ephrin-A ligands and the three transmembrane ephrin-B ligands, respectively. The Eph/ephrin proteins, originally described as developmental regulators that are expressed at low levels postembryonically, are re-expressed after injury to the optic nerve, spinal cord, and brain in fish, amphibians, rodents, and humans. In rodent spinal cord injury, the up-regulation of EphA4 prevents recovery by inhibiting axons from crossing the injury site. Eph/ephrin proteins may be partly responsible for the phenotypic changes to the vascular endothelium in inflammation, which allows fluid and inflammatory cells to pass from the vascular space into the interstitial tissues. Specifically, EphA2/ephrin-A1 signaling in the lung may be responsible for pulmonary inflammation in acute lung injury. A role in T-cell maturation and chronic inflammation (heart failure, inflammatory bowel disease, and rheumatoid arthritis) is also reported. Although there remains much to learn about Eph/ephrin signaling in human disease, and specifically in injury and inflammation, this area of research raises the exciting prospect that novel therapies will be developed that precisely target these pathways.

Pericytes on the tumor vasculature: jekyll or hyde?

The induction of tumor vasculature, known as the 'angiogenic switch', is a rate-limiting step in tumor progression. Normal blood vessels are composed of two distinct cell types: endothelial cells which form the channel through which blood flows, and mural cells, the pericytes and smooth muscle cells which serve to support and stabilize the endothelium. Most functional studies have focused on the responses of endothelial cells to pro-angiogenic stimuli; however, there is mounting evidence that the supporting mural cells, particularly pericytes, may play key regulatory roles in both promoting vessel growth as well as terminating vessel growth to generate a mature, quiescent vasculature. Tumor vessels are characterized by numerous structural and functional abnormalities, including altered association between endothelial cells and pericytes. These dysfunctional, unstable vessels contribute to hypoxia, interstitial fluid pressure, and enhanced susceptibility to metastatic invasion. Increasing evidence points to the pericyte as a critical regulator of endothelial activation and subsequent vessel development, stability, and function. Here we discuss both the stimulatory and inhibitory effects of pericytes on the vasculature and the possible utilization of vessel normalization as a therapeutic strategy to combat cancer.

EphA2 activation promotes the endothelial cell inflammatory response: a potential role in atherosclerosis

OBJECTIVE

Endothelial cell activation results in altered cell-cell interactions with adjacent endothelial cells and with infiltrating leukocytes. Eph receptors and their ephrin ligands regulate cell-cell interactions during tissue remodeling, and multiple proinflammatory mediators induce endothelial EphA receptor and ephrinA ligand expression. Therefore, we sought to elucidate the role of EphA receptors and ephrinA ligands in endothelial cell activation and atherosclerosis.

METHODS AND RESULTS

Quantitative reverse transcription-polymerase chain reaction screening for EphA/ephrinA expression in atherosclerosis-prone macrovascular endothelium identified EphA2, EphA4, and ephrinA1 as the dominant isoforms. Endothelial activation with oxidized low-density lipoprotein and proinflammatory cytokines induced EphA2 and ephrinA1 expression and sustained EphA2 activation, whereas EphA4 expression was unaffected. Atherosclerotic plaques from mice and humans showed enhanced EphA2 and ephrinA1 expression colocalizing in the endothelial cell layer. EphA2 activation with recombinant Fc-ephrinA1 induced proinflammatory gene expression (eg vascular cell adhesion molecule-1, E-selectin) and stimulated monocyte adhesion, whereas inhibiting EphA2 (small interfering RNA, pharmacological inhibitors) abrogated both ephrinA1-induced and oxidized low-density lipoprotein-induced vascular cell adhesion molecule-1 expression.

CONCLUSION

The current data suggest that enhanced EphA2 signaling during endothelial cell activation perpetuates proinflammatory gene expression. Coupled with EphA2 expression in mouse and human atherosclerotic plaques, these data implicate EphA2 as a novel proinflammatory mediator and potential regulator of atherosclerotic plaque development.

Brain pericytes: emerging concepts and functional roles in brain homeostasis

Brain pericytes are an important constituent of neurovascular unit. They encircle endothelial cells and contribute to the maturation and stabilization of the capillaries in the brain. Recent studies have revealed that brain pericytes play pivotal roles in a variety of brain functions, such as regulation of capillary flow, angiogenesis, blood brain barrier, immune responses, and hemostasis. In addition, brain pericytes are pluripotent and can differentiate into different lineages similar to mesenchymal stem cells. The brain pericytes are revisited as a key player to maintain brain function and repair brain damage.

The small molecule specific EphB4 kinase inhibitor NVP-BHG712 inhibits VEGF driven angiogenesis

EphB4 and its cognitive ligand ephrinB2 play an important role in embryonic vessel development and vascular remodeling. In addition, several reports suggest that this receptor ligand pair is also involved in pathologic vessel formation in adults including tumor angiogenesis. Eph/ephrin signaling is a complex phenomena characterized by receptor forward signaling through the tyrosine kinase of the receptor and ephrin reverse signaling through various protein–protein interaction domains and phosphorylation motifs of the ephrin ligands. Therefore, interfering with EphR/ephrin signaling by the means of targeted gene ablation, soluble receptors, dominant negative mutants or antisense molecules often does not allow to discriminate between inhibition of Eph/ephrin forward and reverse signaling. We developed a specific small molecular weight kinase inhibitor of the EphB4 kinase, NVP-BHG712, which inhibits EphB4 kinase activity in the low nanomolar range in cellular assays showed high selectivity for targeting the EphB4 kinase when profiled against other kinases in biochemical as well as in cell based assays. Furthermore, NVP-BHG712 shows excellent pharmacokinetic properties and potently inhibits EphB4 autophosphorylation in tissues after oral administration. In vivo, NVP-BHG712 inhibits VEGF driven vessel formation, while it has only little effects on VEGF receptor (VEGFR) activity in vitro or in cellular assays. The data shown here suggest a close cross talk between the VEGFR and EphR signaling during vessel formation. In addition to its established function in vascular remodeling and endothelial arterio-venous differentiation, EphB4 forward signaling appears to be an important mediator of VEGF induced angiogenesis since inhibition of EphB4 forward signaling is sufficient to inhibit VEGF induced angiogenesis.

Eph receptors and ephrins in cancer: bidirectional signalling and beyond

The Eph receptor tyrosine kinases and their ephrin ligands have intriguing expression patterns in cancer cells and tumour blood vessels, which suggest important roles for their bidirectional signals in many aspects of cancer development and progression. Eph gene mutations probably also contribute to cancer pathogenesis. Eph receptors and ephrins have been shown to affect the growth, migration and invasion of cancer cells in culture as well as tumour growth, invasiveness, angiogenesis and metastasis in vivo. However, Eph signalling activities in cancer seem to be complex, and are characterized by puzzling dichotomies. Nevertheless, the Eph receptors are promising new therapeutic targets in cancer.

Steroid-resistant lymphatic remodeling in chronically inflamed mouse airways

Angiogenesis and lymphangiogenesis participate in many inflammatory diseases, and their reversal is thought to be beneficial. However, the extent of reversibility of vessel remodeling is poorly understood. We exploited the potent anti-inflammatory effects of the corticosteroid dexamethasone to test the preventability and reversibility of vessel remodeling in Mycoplasma pulmonis-infected mice using immunohistochemistry and quantitative RT-PCR. In this model robust immune responses drive rapid and sustained changes in blood vessels and lymphatics. In infected mice not treated with dexamethasone, capillaries enlarged into venules expressing leukocyte adhesion molecules, sprouting angiogenesis and lymphangiogenesis occurred, and the inflammatory cytokines tumor necrosis factor and interleukin-1 increased. Concurrent dexamethasone treatment largely prevented the remodeling of blood vessels and lymphatics. Dexamethasone also significantly reduced cytokine expression, bacterial burden, and leukocyte influx into airways and lungs over 4 weeks of infection. In contrast, when infection was allowed to proceed untreated for 2 weeks and then was treated with dexamethasone for 4 weeks, most blood vessel changes reversed but lymphangiogenesis did not, suggesting that different survival mechanisms apply. Furthermore, dexamethasone significantly reduced the bacterial burden and influx of lymphocytes but not of neutrophils or macrophages or cytokine expression. These findings show that lymphatic remodeling is more resistant than blood vessel remodeling to corticosteroid-induced reversal. We suggest that lymphatic remodeling that persists after the initial inflammatory response has resolved may influence subsequent inflammatory episodes in clinical situations.

Immature blood vessels in rheumatoid synovium are selectively depleted in response to anti-TNF therapy

Background

Angiogenesis is considered an important factor in the pathogenesis of Rheumatoid Arthritis (RA) where it has been proposed as a therapeutic target. In other settings, active angiogenesis is characterized by pathologic, immature vessels that lack periendothelial cells. We searched for the presence of immature vessels in RA synovium and analyzed the dynamics of synovial vasculature along the course of the disease, particularly after therapeutic response to TNF antagonists.

Methodology/Principal Findings

Synovial arthroscopic biopsies from RA, osteoarthritis (OA) and normal controls were analyzed by double labeling of endothelium and pericytes/smooth muscle mural cells to identify and quantify mature/immature blood vessels. To analyze clinicopathological correlations, a cross-sectional study on 82 synovial biopsies from RA patients with variable disease duration and severity was performed. A longitudinal analysis was performed in 25 patients with active disease rebiopsied after anti-TNF-α therapy. We found that most RA synovial tissues contained a significant fraction of immature blood vessels lacking periendothelial coverage, whereas they were rare in OA, and inexistent in normal synovial tissues. Immature vessels were observed from the earliest phases of the disease but their presence or density was significantly increased in patients with longer disease duration, higher activity and severity, and stronger inflammatory cell infiltration. In patients that responded to anti-TNF-α therapy, immature vessels were selectively depleted. The mature vasculature was similarly expanded in early or late disease and unchanged by therapy.

Conclusion/Significance

RA synovium contains a significant fraction of neoangiogenic, immature blood vessels. Progression of the disease increases the presence and density of immature but not mature vessels and only immature vessels are depleted in response to anti-TNFα therapy. The different dynamics of the mature and immature vascular fractions has important implications for the development of anti-angiogenic interventions in RA.