Inflammation induces lymphangiogenesis through up-regulation of VEGFR-3 mediated by NF-kappaB and Prox1. Blood. 2010;115:418-429. [PMID: 19901262 DOI: 10.1182/blood-2008-12-196840]

Increased Lymphangiogenesis and Lymphangiogenic Growth Factor Expression in Perivascular Adipose Tissue of Patients with Coronary Artery Disease

Experimental and human autopsy studies have associated adventitial lymphangiogenesis with atherosclerosis. An analysis of perivascular lymphangiogenesis in patients with coronary artery disease is lacking. Here, we examined lymphangiogenesis and its potential regulators in perivascular adipose tissue (PVAT) surrounding the heart (C-PVAT) and compared it with PVAT of the internal mammary artery (IMA-PVAT). Forty-six patients undergoing coronary artery bypass graft surgery were included. Perioperatively collected C-PVAT and IMA-PVAT were analyzed using histology, immunohistochemistry, real time PCR, and PVAT-conditioned medium using cytokine arrays. C-PVAT exhibited increased PECAM-1 (platelet endothelial cell adhesion molecule 1)-positive vessel density. The number of lymphatic vessels expressing lymphatic vessel endothelial hyaluronan receptor-1 or podoplanin was also elevated in C-PVAT and associated with higher inflammatory cell numbers, increased intercellular adhesion molecule 1 (ICAM1) expression, and fibrosis. Significantly higher expression of regulators of lymphangiogenesis such as vascular endothelial growth factor (VEGF)-C, VEGF-D, and VEGF receptor-3 was observed in C-PVAT compared to IMA-PVAT. Cytokine arrays identified angiopoietin-2 as more highly expressed in C-PVAT vs. IMA-PVAT. Findings were confirmed histologically and at the mRNA level. Stimulation of human lymphatic endothelial cells with recombinant angiopoietin-2 in combination with VEGF-C enhanced sprout formation. Our study shows that PVAT surrounding atherosclerotic arteries exhibits more extensive lymphangiogenesis, inflammation, and fibrosis compared to PVAT surrounding a non-diseased vessel, possibly due to local angiopoietin-2, VEGF-C, and VEGF-D overexpression.

Current understanding of lymphatic vessels in the central nervous system

Lymphangiogenesis is associated with some pathological conditions such as inflammation, tissue repair, and tumor growth. Recently, a paradigm shift occurred following the discovery of meningeal lymphatic structures in the human central nervous system (CNS); these structures may be a key drainage route for cerebrospinal fluid (CSF) into the peripheral blood and may also contribute to inflammatory reaction and immune surveillance of the CNS. Lymphatic vessels located along the dural sinuses absorb CSF from the adjacent subarachnoid space and brain interstitial fluid via the glymphatic system, which is composed of aquaporin-4 water channels expressed on perivascular astrocytic end-feet membranes. Magnetic resonance imaging (MRI) clearly visualized these lymphatic vessels in the human dura mater. The conception of some neurological disorders, such as multiple sclerosis and Alzheimer's disease, has been changed by this paradigm shift. Meningeal lymphatic vessels could be a promising therapeutic target for the prevention of neurological disorders. However, the involvement of meningeal lymphatic vessels in the pathophysiology has not been fully elucidated and is the subject of future investigations. In this article, to understand the involvement of meningeal lymphatic vessels in neurological disorders, we review the differences between lymphangiogenesis in the CNS and in other tissues during both developmental and adulthood stages, and pathological conditions that may be associated with meningeal lymphatic vessels in the CNS.

Three kinds of corneal host cells contribute differently to corneal neovascularization

Background

Corneal neovascularization (angiogenesis and lymphangiogenesis) compromises corneal transparency and transplant survival, however, the molecular mechanisms of corneal host epithelial and stromal cells in neovascularization have not yet been fully elucidated. Furthermore, the contribution and mechanism of corneal host endothelial cells involved in neovascularization are largely unexplored.

Methods

Liquid chromatography-mass spectrometry, immunoblotting, and ELISA were used to screen and identify potential neovascularization-related factors in human full-thickness vascularized corneal tissues. Lipopolysaccharide was used to induce inflammation in three kinds of corneal host cells in vitro, including corneal epithelial, stromal, and endothelial cells. Fungus was used to establish an animal model of corneal neovascularization in vivo. Tube formation and spheroid sprouting assays were used to evaluate the contribution of three kinds of corneal host cells to the degree of neovascularization under various stimuli. Matrix metalloproteinase (MMP)-2, alpha-crystallin A chain (CRYAA), galectin-8, Bcl-2, neuropilin-2, MMP-9 plasmids, and recombinant human fibronectin were used to identify the key proteins of corneal host cells involved in corneal inflammatory neovascularization.

Findings

All three kinds of corneal host cells influenced corneal neovascularization to varying degrees. MMP-9 in human corneal epithelial cells, MMP-2, and CRYAA in human corneal stromal cells, and MMP-2 and galectin-8 in human corneal endothelial cells are potential key proteins that participate in corneal inflammatory neovascularization.

Interpretation

Our data indicated that both the effects of key proteins and corneal host cells involved should be considered for the treatment of corneal inflammatory neovascularization.

Phomaketide A Inhibits Lymphangiogenesis in Human Lymphatic Endothelial Cells

Lymphangiogenesis is an important biological process associated with cancer metastasis. The development of new drugs that block lymphangiogenesis represents a promising therapeutic strategy. Marine fungus-derived compound phomaketide A, isolated from the fermented broth of Phoma sp. NTOU4195, has been reported to exhibit anti-angiogenic and anti-inflammatory effects. However, its anti-lymphangiogenic activity has not been clarified to date. In this study, we showed that phomaketide A inhibited cell growth, migration, and tube formation of lymphatic endothelial cells (LECs) without an evidence of cytotoxicity. Mechanistic investigations revealed that phomaketide A reduced LECs-induced lymphangiogenesis via vascular endothelial growth factor receptor-3 (VEGFR-3), protein kinase Cδ (PKCδ), and endothelial nitric oxide synthase (eNOS) signalings. Furthermore, human proteome array analysis indicated that phomaketide A significantly enhanced the protein levels of various protease inhibitors, including cystatin A, serpin B6, tissue factor pathway inhibitor (TFPI), and tissue inhibitor matrix metalloproteinase 1 (TIMP-1). Importantly, phomaketide A impeded tumor growth and lymphangiogenesis by decreasing the expression of LYVE-1, a specific marker for lymphatic vessels, in tumor xenograft animal model. These results suggest that phomaketide A may impair lymphangiogenesis by suppressing VEGFR-3, PKCδ, and eNOS signaling cascades, while simultaneously activating protease inhibitors in human LECs. We document for the first time that phomaketide A inhibits lymphangiogenesis both in vitro and in vivo, which suggests that this natural product could potentially treat cancer metastasis.

Shikonin Suppresses Lymphangiogenesis via NF-κB/HIF-1α Axis Inhibition

Lymphangiogenesis, the formation of lymphatic vessels from preexisting ones, promotes cancer growth and metastasis. Finding natural compounds with anti-lymphangiogenic activity will be useful for preventive treatment of lymphatic metastasis. Shikonin, an ingredient of a traditional Japanese and Chinese medicinal herb Lithospermum erythrorhizon, has been widely used in several pharmaceutical and cosmetic preparations, as well as in food colorants. Shikonin has been reported to inhibit lymphangiogenesis in vitro, but the mechanism of inhibition has not been determined. The aim of this study is to investigate the mechanism of anti-lymphangiogenesis of shikonin in primary human lymphatic endothelial cells (HMVEC-dLy). Shikonin, at non-toxic concentrations, significantly inhibited cord formation ability of lymphatic endothelial cells in a dose- and time-dependent manner. Western blotting analysis showed that shikonin decreased nuclear factor-kappaB (NF-κB) activation, as indicated by phosphorylation and nuclear translocation of NF-κB p65, and also reduced both mRNA and protein levels of hypoxia-inducible factor-1 (HIF-1)α. Use of an NF-κB inhibitor (BAY 11-7085) and HIF-1α small interfering RNA (siRNA) transfection revealed that NF-κB activation was upstream of HIF-1α expression, which controls cord formation by HMVEC-dLy. In addition, the reduction of vascular endothelial growth factor C (VEGF-C) and vascular endothelial growth factor receptor-3 (VEGFR-3) mRNA levels were also found in HMVEC-dLy that treated with shikonin. In conclusion, shikonin inhibits lymphangiogenesis in vitro by interfering the NF-κB/HIF-1α pathway and involves in suppression of VEGF-C and VEGFR-3 mRNA expression.

Tertiary Lymphoid Structures: Autoimmunity Goes Local

Tertiary lymphoid structures (TLS) are frequently observed in target organs of autoimmune diseases. TLS present features of secondary lymphoid organs such as segregated T and B cell zones, presence of follicular dendritic cell networks, high endothelial venules and specialized lymphoid fibroblasts and display the mechanisms to support local adaptive immune responses toward locally displayed antigens. TLS detection in the tissue is often associated with poor prognosis of disease, auto-antibody production and malignancy development. This review focuses on the contribution of TLS toward the persistence of the inflammatory drive, the survival of autoreactive lymphocyte clones and post-translational modifications, responsible for the pathogenicity of locally formed autoantibodies, during autoimmune disease development.

Immune cell trafficking, lymphatics and hypertension

Activated immune cell infiltration into organs contributes to the development and maintenance of hypertension. Studies targeting specific immune cell populations or reducing their inflammatory signalling have demonstrated a reduction in BP. Lymphatic vessels play a key role in immune cell trafficking and in resolving inflammation, but little is known about their role in hypertension. Studies from our laboratory and others suggest that inflammation-associated or induction of lymphangiogenesis is organ protective and anti-hypertensive. This review provides the basis for hypertension as a disease of chronic inflammation in various tissues and highlights how renal lymphangiogenesis is a novel regulator of kidney health and BP. LINKED ARTICLES: This article is part of a themed section on Immune Targets in Hypertension. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.12/issuetoc.

12(S)-HETE induces lymph endothelial cell retraction in vitro by upregulation of SOX18

Metastasising breast cancer cells communicate with adjacent lymph endothelia, intravasate and disseminate through lymphatic routes, colonise lymph nodes and finally metastasize to distant organs. Thus, understanding and blocking intravasation may attenuate the metastatic cascade at an early step. As a trigger factor, which causes the retraction of lymph endothelial cells (LECs) and opens entry ports for tumour cell intravasation, MDA-MB231 breast cancer cells secrete the pro-metastatic arachidonic acid metabolite, 12S-hydroxy-5Z,8Z,10E,14Z-eicosatetraenoic acid [12(S)-HETE]. In the current study, treatment of LECs with 12(S)-HETE upregulated the expression of the transcription factors SRY-related HMG-box 18 (SOX18) and prospero homeobox protein 1 (PROX1), which determine endothelial development. Thus, whether they have a role in LEC retraction was determined using a validated intravasation assay, small interfering RNA mediated knockdown of gene expression, and mRNA and protein expression analyses. Specific inhibition of SOX18 or PROX1 significantly attenuated in vitro intravasation of MDA-MB231 spheroids through the LEC barrier and 12(S)-HETE-triggered signals were transduced by the high and low affinity receptors, 12(S)-HETE receptor and leukotriene B4 receptor 2. In addition, the current findings indicate that there is crosstalk between SOX18 and nuclear factor κ-light-chain-enhancer of activated B cells, which was demonstrated to contribute to MDA-MB231/lymph endothelial intravasation. The present data demonstrate that the endothelial-specific and lymph endothelial-specific transcription factors SOX18 and PROX1 contribute to LEC retraction.

COMP-angiopoietin-1 ameliorates inflammation-induced lymphangiogenesis in dextran sulfate sodium (DSS)-induced colitis model

Alterations in the intestinal lymphatic network are pathological processes as related to inflammatory bowel disease (IBD). In this study, we demonstrated that reduction in inflammation-induced lymphangiogenesis ameliorates experimental acute colitis. A soluble and stable angiopoietin-1 (Ang1) variant, COMP-Ang1, possesses anti-inflammatory and angiogenic effects. We investigated the effects of COMP-Ang1 on an experimental colonic inflammation model. Experimental colitis was induced in mice by administering 3% dextran sulfate sodium (DSS) via drinking water. We determined body weight, disease activity indices, histopathological scores, lymphatic density, anti-ER-HR3 staining, and the expression of members of the vascular endothelial growth factor (VEGF) family and various inflammatory cytokines in the mice. The density of lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1) and VEGFR-3-positive lymphatic vessels increased in mice with DSS-induced colitis. We observed that COMP-Ang1-treated mice showed less weight loss, fewer clinical signs of colitis, and longer colons than Ade-DSS-treated mice. COMP-Ang1 also significantly reduced the density of LYVE-1-positive lymphatic vessels and the disruption of colonic architecture that is normally associated with colitis and repressed the immunoregulatory response. Further, COMP-Ang1 treatment reduced both M1 and M2 macrophage infiltration into the inflamed colon, which involved inhibition of VEGF-C and D expression. Thus, COMP-Ang1, which acts by reducing inflammation-induced lymphangiogenesis, may be used as a novel therapeutic for the treatment of IBD and other inflammatory diseases.

KEY MESSAGES

COMP-Ang1 decreases inflammatory-induced lymphangiogenesis in experimental acute colitis. COMP-Ang1 improves the symptom of DSS-induced inflammatory response. COMP-Ang1 reduces the expression of pro-inflammatory cytokines in inflamed colon. COMP-Ang1 reduces the expression of VEGFs in inflamed colon. COMP-Ang1 prevents infiltration of macrophages in a DSS-induced colitis model.

MiR-199a/b-5p Inhibits Lymphangiogenesis by Targeting Discoidin Domain Receptor 1 in Corneal Injury

Discoidin domain receptor 1 (DDR1) is involved in tumorigenesis and angiogenesis. However, its role in lymphangiogenesis has been unknown. Here, we tested whether downregulation of DDR1 expression by miR-199a/b can suppress lymphangiogenesis. We also aimed to identify miRNA target site(s) in the 3' untranslated region (UTR) of DDR1. Transfection with miR-199a/b-5p mimics reduced expression of DDR1 and tube formation in primary human dermal lymphatic endothelial cells, whereas miR-199a/b-5p inhibitors showed the opposite effects. Critically, injection of miR-199a/b-5p mimics suppressed DDR1 expression and lymphangiogenesis in a corneal alkali-burn rat model. The three well-conserved seed matched sites for miR-199a/b-5p in the DDR1 3'-UTR were targeted, and miRNA binding to at least two sites was required for DDR1 inhibition. Our data suggest that DDR1 promotes enhanced lymphangiogenesis during eye injury, and miR-199a/b-5p suppresses this activity by inhibiting DDR1 expression. Thus, this miRNA may be useful for the treatment of lymphangiogenesis-related eye diseases.

Glucose transporter expression in the human colon

AIM

To investigate by immunostaining glucose transporter expression in human colorectal mucosa in controls and patients with inflammatory bowel disease (IBD).

METHODS

Colorectal samples were obtained from patients undergoing lower endoscopic colonoscopy or recto-sigmoidoscopy. Patients diagnosed with ulcerative colitis (n = 18) or Crohn’s disease (n = 10) and scheduled for diagnostic colonoscopy were enrolled. Patients who underwent colonoscopy for prevention screening of colorectal cancer or were followed-up after polypectomy or had a history of lower gastrointestinal symptoms were designated as the control group (CTRL, n = 16). Inflammatory status of the mucosa at the sampling site was evaluated histologically and/or endoscopically. A total of 147 biopsies of colorectal mucosa were collected and processed for immunohistochemistry analysis. The expression of GLUT2, SGLT1, and GLUT5 glucose transporters was investigated using immunoperoxidase labeling. To compare immunoreactivity of GLUT5 and LYVE-1, which is a marker for lymphatic vessel endothelium, double-labeled confocal microscopy was used.

RESULTS

Immunohistochemical analysis revealed that GLUT2, SGLT1, and GLUT5 were expressed only in short epithelial portions of the large intestinal mucosa. No important differences were observed in glucose transporter expression between the samples obtained from the different portions of the colorectal tract and between the different patient groups. Unexpectedly, GLUT5 expression was also identified in vessels, mainly concentrated in specific areas where the vessels were clustered. Immunostaining with LYVE-1 and GLUT5 antibodies revealed that GLUT5-immunoreactive (-IR) clusters of vessels were concentrated in areas internal to those that were LYVE-1 positive. GLUT5 and LYVE-1 did not appear to be colocalized but rather showed a close topographical relationship on the endothelium. Based on their LYVE-1 expression, GLUT5-IR vessels were identified as lymphatic. Both inflamed and non-inflamed mucosal colorectal tissue biopsies from the IBD and CTRL patients showed GLUT5-IR clusters of lymphatic vessels.

CONCLUSION

Glucose transporter immunoreactivity is present in colorectal mucosa in controls and IBD patients. GLUT5 expression is also associated with lymphatic vessels. This novel finding aids in the characterization of lymphatic vasculature in IBD patients.

Fucoidan inhibits lymphangiogenesis by downregulating the expression of VEGFR3 and PROX1 in human lymphatic endothelial cells

Lymphangiogenesis is one of the promoters of tumor lymphatic metastasis. Fucoidan which is a fucose-enriched sulfated polysaccharide has effect on various pharmacological activities including anti-metastasis activity. However, the inhibitory effect of fucoidan on lymphangiogenesis remains unclear. Here, fucoidan extracted from U. pinnatifida sporophylls suppressed HLECs proliferation, migration and tube-like structure formation, and had inhibitory effect of tumor-induced lymphangiogenesis in vitro. Additionally, we found that fucoidan had a dose-dependent depressive effect on the expressions of PROX1, vascular endothelial growth factor receptor 3 (VEGFR3), NF-κB, phospho-PI3K and phospho-Akt in HLECs. Moreover, anti-lymphangiogenesis effect of fucoidan was assessed by using mouse tumor model. In summary, fucoidan inhibit tumor lymphangiogenesis and lymphatic metastasis by suppressing the NF-κB/PI3K/Akt signaling pathway through reduced levels of PROX1 and VEGFR3.

Cellular and Vascular Components of Tertiary Lymphoid Structures

Inflammatory immune cells recruited at the site of chronic inflammation form structures that resemble secondary lymphoid organs (SLO). These are characterized by segregated areas of prevalent T- or B-cell aggregation, differentiation of high endothelial venules, and local activation of resident stromal cells, including lymphatic endothelial cells. B-cell proliferation and affinity maturation toward locally displayed autoantigens have been demonstrated at these sites, known as tertiary lymphoid structures (TLS). TLS formation during chronic inflammation has been associated with local disease persistence and progression, as well as increased systemic manifestations. While bearing a similar histological structure to SLO, the signals that regulate TLS and SLO formation can diverge and a series of pro-inflammatory cytokines have been ascribed as responsible for TLS formation at different anatomical sites. Moreover, for a long time the structural compartment that regulates TLS homeostasis, including survival and recirculation of leucocytes has been neglected. In this chapter, we summarize the novel data available on TLS formation, structural organization, and the functional and anatomical links connecting TLS and SLOs.

Congenital pulmonary lymphangiectasia

Congenital pulmonary lymphangiectasia (CPL) is a rare but fatal disease, usually having an onset from the first few hours to days after birth. Inconsistent nomenclatures were used for CPL in the past decades. Patients often present with intractable respiratory failure, hydrops fetalis and even sudden death. The etiologies of CPL remain unclear. Previous hypotheses suggested that CPL might be caused by conditions preventing normal regression of the lymphatics after the 18th-20th week of gestation. Up-to-date biological studies on lymphatic development, lymphatic valve formation and occurrence of hydrops fetalis revealed possible causative relations with mutations of genes of the vascular endothelial growth factor receptor (VEGFR), RAS/MAPK, PI3K/AKT and NF-κB signaling pathways. Lung biopsy with subsequent histological and immunohistochemical studies is a gold standard of CPL diagnosis. Apart from symptomatic and supportive treatments, novel regimens including sirolimus, a mammalian target of rapamycin (mTOR) inhibitor, one of the inhibitors of the pertinent signaling pathways and ethiodized oil lymphatic embolization under ultrasound-guided intranodal lymphangiography have shown encouraging short-term therapeutic effects for lymphatic anomalies. Surgical operations (lobectomy or pneumonectomy) can be the treatment of choice for patients with CPL confined to one lobe or one lung. Patients with CPL usually have a poor prognosis and often die during the neonatal period. Their prognoses are expected to improve with the development of modern therapeutic agents.

Mesenchymal Stromal Cells Inhibit Inflammatory Lymphangiogenesis in the Cornea by Suppressing Macrophage in a TSG-6-Dependent Manner

The cornea is a transparent tissue devoid of blood and lymphatic vessels. However, various inflammatory conditions can cause hemangiogenesis and lymphangiogenesis in the cornea, compromising transparency and visual acuity. Mesenchymal stem/stromal cells (MSCs) have therapeutic potentials in a variety of diseases because of anti-inflammatory properties. Herein, we investigated the effects of MSCs on corneal angiogenesis using a model of suture-induced inflammatory corneal neovascularization. Data demonstrated that an intravenous administration of MSCs suppressed corneal inflammation and neovascularization, inhibiting both hemangiogenesis and lymphangiogenesis. MSCs reduced the levels of vascular endothelial growth factor (VEGF)-C, VEGF-D, Tek, MRC1, and MRC2 in the cornea, which are expressed by pro-angiogenic macrophages. Moreover, the number of CD11b⁺ monocytes/macrophages in the cornea, spleen, peripheral blood, and draining lymph nodes was decreased by MSCs. Depletion of circulating CD11b⁺ monocytes by blocking antibodies replicated the effects of MSCs. Importantly, knockdown of tumor necrosis factor alpha (TNF-α)-stimulated gene/protein 6 (TSG-6) in MSCs abrogated the effects of MSCs in inhibiting corneal hemangiogenesis and lymphangiogenesis and monocyte/macrophage infiltration. Together, the results suggest that MSCs inhibit inflammatory neovascularization in the cornea by suppressing pro-angiogenic monocyte/macrophage recruitment in a TSG-6-dependent manner.

S1P Provokes Tumor Lymphangiogenesis via Macrophage-Derived Mediators Such as IL-1β or Lipocalin-2

A pleiotropic signaling lipid, sphingosine-1-phosphate (S1P), has been implicated in various pathophysiological processes supporting tumor growth and metastasis. However, there are only a few descriptive studies suggesting a role of S1P in tumor lymphangiogenesis, which is critical for tumor growth and dissemination. Corroborating own data, the literature suggests that apoptotic tumor cell-derived S1P alters the phenotype of tumor-associated macrophages (TAMs) to gain protumor functions. However, mechanistically, the role of TAM-induced lymphangiogenesis has only been poorly described, mostly linked to the production of lymphangiogenic factors such as vascular endothelial growth factor C (VEGF-C) and VEGF-D, or transdifferentiation into lymphatic endothelial cells. Recent findings highlight a rather underappreciated role of S1P in tumor lymphangiogenesis, referring to the production of interleukin-1β (IL-1β) and lipocalin-2 (LCN2) by a tumor-promoting macrophage phenotype. In this review, we aim to provide to the readers with the current understanding of the molecular mechanism how apoptotic cell-derived S1P triggers TAMs to promote lymphangiogenesis.

Lymphatic endothelial progenitors originate from plastic myeloid cells activated by toll-like receptor-4

BACKGROUND

Myeloid-derived lymphatic endothelial cells (M-LECP) are induced by inflammation and play an important role in adult lymphangiogenesis. However, the mechanisms driving M-LECP differentiation are currently unclear. We previously showed that activation of Toll-like receptor-4 (TLR4) induces myeloid-lymphatic transition (MLT) of immortalized mouse myeloid cells. Here the goals were to assess the potential of different TLR4 ligands to induce pro-lymphatic reprogramming in human and mouse primary myeloid cells and to identify transcriptional changes regulating this process.

METHODOLOGY/PRINCIPAL FINDINGS

Human and mouse myeloid cells were reprogrammed to the lymphatic phenotype by TLR4 ligands including lipopolysaccharide (LPS), recombinant high mobility group box 1 protein (HMGB1), and paclitaxel. TLR4 induced similar MLT in cells from mice of different strains and immune status. Commonly induced genes were detected by transcriptional profiling in human and mouse myeloid cells from either immunocompetent or immunodeficient mice. Shared trends included: (1) novel expression of lymphatic-specific markers vascular endothelial growth factor receptor-3 (VEGFR-3), lymphatic vessel endothelial hyaluronan receptor-1 (LYVE-1) and podoplanin (PDPN) largely absent prior to induction; (2) lack of notable changes in blood vessel-specific markers; (3) transient expression of VEGFR-3, but sustained increase of vascular endothelial growth factor-C (VEGF-C) and a variety of inflammatory cytokines; (4) dependency of VEGFR-3 upregulation and other LEC genes on NF-κB; and (5) novel expression of lymphatic-specific (e.g., PROX1) and stem/progenitor (e.g., E2F1) transcription factors known for their roles in adult and embryonic vascular formation. M-LECP generated by TLR4 ligands in vitro were functional in vivo as demonstrated by significantly increased lymphatic vessel density and lymphatic metastasis detected in orthotopic breast cancer models.

CONCLUSIONS/SIGNIFICANCE

We established a novel TLR4-dependent protocol for in vitro production of functionally competent M-LECP from primary human or mouse myeloid cells and identified many potential regulators of this process. This information can be further exploited for research and therapeutic purposes.

Longitudinal monitoring of the head and neck lymphatics in response to surgery and radiation

BACKGROUND

The lymphatic vasculature provides a route for cancer metastases, and its dysfunction after cancer treatment can result in lymphedema. However, changes in the lymphatics before, during, and after surgery and radiation remain unclear.

METHODS

Near-infrared fluorescence lymphatic imaging was performed before and after lymph node dissection and fractionated radiotherapy to assess changes in external lymphatic function.

RESULTS

Patients who underwent both lymph node dissection and radiotherapy developed lymphatic dermal backflow on treated sides ranging from days after the start of radiotherapy to weeks after its completion, whereas contralateral regions that were not associated with lymph node dissection but also treated with radiotherapy experienced no such changes in external lymphatic anatomies.

CONCLUSION

The external lymphatics undergo transient changes during and weeks after lymph node dissection and radiotherapy. © 2017 Wiley Periodicals, Inc. Head Neck 39: 1177-1188, 2017.

microRNAs in the Lymphatic Endothelium: Master Regulators of Lineage Plasticity and Inflammation

microRNAs (miRNAs) are highly conserved, small non-coding RNAs that regulate gene expression at the posttranscriptional level. They have crucial roles in organismal development, homeostasis, and cellular responses to pathological stress. The lymphatic system is a large vascular network that actively regulates the immune response through antigen trafficking, cytokine secretion, and inducing peripheral tolerance. Here, we review the role of miRNAs in the lymphatic endothelium with a particular focus on their role in lymphatic endothelial cell (LEC) plasticity, inflammation, and regulatory function. We highlight the lineage plasticity of LECs during inflammation and the importance of understanding the regulatory role of miRNAs in these processes. We propose that targeting miRNA expression in lymphatic endothelium can be a novel strategy in treating human pathologies associated with lymphatic dysfunction.

The Role of Lymphatic Endothelial Cells in Liver Injury and Tumor Development

Lymphatics and lymphatic endothelial cells (LECs) possess multiple immunological functions besides affecting immune cell migration, such as inhibiting T cell proliferation and antigen presentation by dendritic cells. Moreover, they control the trans-endothelial transport of multiple molecules and antigens. Emerging evidence suggest their active involvements in immunregulation, tumor, and metastases formation. In the liver, increased lymphangiogenesis, specifically at the portal area has been associated with multiple liver diseases in particular primary biliary cirrhosis, idiopathic portal hypertension, and liver malignancies. Nevertheless, the exact role and contribution of LECs to liver diseases are poorly understood. The review summarizes the current understanding of LECs in liver diseases.

Effect of Oral Administration of 3,3'-Diindolylmethane on Dextran Sodium Sulfate-Induced Acute Colitis in Mice

In patients with inflammatory bowel disease (IBD), inflammation is induced and maintained by lymphangiogenesis and angiogenesis. 3,3'-Diindolylmethane (DIM) is a natural product formed in acidic conditions from indole-3-carbinol in cruciferous vegetables, and it is known for its chemotherapeutic activity. This study evaluated DIM's effects on angiogenesis, lymphangiogenesis, and inflammation in a mouse colitis model. Experimental colitis was induced in mice by administering 3% dextran sulfate sodium (DSS) via drinking water. DIM remarkably attenuated the clinical signs and histological characteristics in mice with DSS-induced colitis. DIM suppressed neutrophil infiltration and pro-inflammatory cytokines. Moreover, it significantly suppressed the expression of vascular endothelial growth factor (VEGF)-A and VEGF receptor (VEGFR)-2, indicating that the mechanism may be related to the repression of pro-angiogenesis activity. DIM also remarkably suppressed the expression of VEGF-C, VEGF-D, VEGFR-3, and angiopoietin-2; thus, the mechanism may also be related to the suppression of lymphangiogenesis. Therefore, DIM is a possible treatment option for inflammation of the intestine and associated angiogenesis and lymphangiogenesis.

VEGF Pathways in the Lymphatics of Healthy and Diseased Heart

Cardiac lymphatic system is a rare focus of the modern cardiovascular research. Nevertheless, the growing body of evidence is depicting lymphatic endothelium as an important functional unit in healthy and diseased myocardium. Since the discovery of angiogenic VEGF-A in 1983 and lymphangiogenic VEGF-C in 1997, an increasing amount of knowledge has accumulated on the essential roles of VEGF ligands and receptors in physiological and pathological angiogenesis and lymphangiogenesis. Tissue adaptation to several stimuli such as hypoxia, pathogen invasion, degenerative process and inflammation often involves coordinated changes in both blood and lymphatic vessels. As lymphatic vessels are involved in the initiation and resolution of inflammation and regulation of tissue edema, VEGF family members may have important roles in myocardial lymphatics in healthy and in cardiac disease. We will review the properties of VEGF ligands and receptors concentrating on their lymphatic vessel effects first in normal myocardium and then in cardiac disease.

Du-Huo-Ji-Sheng-Tang Attenuates Inflammation of TNF-Tg Mice Related to Promoting Lymphatic Drainage Function

To investigate whether Du-Huo-Ji-Sheng-Tang (DHJST) attenuate inflammation of RA related to lymphatic drainage function in vivo, we treated eight 3-month-old TNF-Tg mice with DHJST (12 g/kg) or the same volume of physiological saline once every day for 12 weeks, and 3-month-old WT littermates were used as negative control. After twelve weeks, we performed NIR-ICG imaging and found that DHJST increased the ICG clearance at the footpad and the pulse of efferent lymphatic vessel between popliteal lymph node and footpad. Histology staining at ankle joints showed that DHJST decreases synovial inflammation, bone erosion, cartilage erosion, and TRAP+ osteoclast area in TNF-Tg mice. Immunohistochemical staining by using anti-Lyve-1 and anti-podoplanin antibody showed that DHJST stimulated lymphangiogenesis in ankle joints of TNF-Tg mice. And zebrafish study suggested that DHJST promoted the formation of lymphatic thoracic duct. In conclusion, DHJST inhibits inflammation severity and promotes lymphangiogenesis and lymphatic drainage function of TNF-Tg mice.

High Mobility Group Box-1 Promotes Inflammation-Induced Lymphangiogenesis via Toll-Like Receptor 4-Dependent Signalling Pathway

Lymphangiogenesis in inflammation has received considerable attention in recent years. Administration of modulating lymphangiogenesis provides more possibilities of treating inflammation-associated diseases. However, the main mediators and factors governing inflammation-induced lymphangiogenesis (ILA) are yet to be defined. Here, we explored the role of HMGB1-TLR4 signalling pathway in modulating inflammation-induced lymphangiogenesis and its underlying mechanisms using an ILA mouse model and 2 cell lines. Our results show that HMGB1 promoted VEGF-C-induced HDLECs proliferation in a dose-dependent manner and TLR4 mediates HMGB1-induced LECs proliferation and tube formation in vitro. And in vivo, rHMGB1 treatment significantly promoted ILA, and the promoting effects was inhibited notably when HMGB1-TLR4 was blocked. HMGB1-associated ILA is primarily dependent on TLR4 but not on TLR2. In mechanisms, the recruitment and activation of CD11b+ cells are important cellular mechanisms in HMGB1-TLR4 associated ILA, and multiple key pro-lymphangiogenesis molecules mediates HMGB1-TLR4 associated ILA, including VEGF-C/VEGFR3, inflammatory factors IL-1β and TNF-α, MMP-2 and MMP-9 and NF-κB p65. In conclusion, HMGB1-associated ILA is primarily dependent on TLR4, and CD11b+ cells and multiple molecular mechanisms mediate HMGB1-TLR4 associated ILA. Furthermore, the ILA can be effectively modulated by HMGB1-TLR4 signalling. Consequently, administration of modulating ILA through HMGB1-TLR4 pathway may provide us more possibilities of treating inflammation and lymphangiogenesis associated diseases.

Ischemia-Reperfusion Injury Enhances Lymphatic Endothelial VEGFR3 and Rejection in Cardiac Allografts

Organ damage and innate immunity during heart transplantation may evoke adaptive immunity with serious consequences. Because lymphatic vessels bridge innate and adaptive immunity, they are critical in immune surveillance; however, their role in ischemia-reperfusion injury (IRI) in allotransplantation remains unknown. We investigated whether the lymphangiogenic VEGF-C/VEGFR3 pathway during cardiac allograft IRI regulates organ damage and subsequent interplay between innate and adaptive immunity. We found that cardiac allograft IRI, within hours, increased graft VEGF-C expression and lymphatic vessel activation in the form of increased lymphatic VEGFR3 and adhesion protein expression. Pharmacological VEGF-C/VEGFR3 stimulation resulted in early lymphatic activation and later increase in allograft inflammation. In contrast, pharmacological VEGF-C/VEGFR3 inhibition during cardiac allograft IRI decreased early lymphatic vessel activation with subsequent dampening of acute and chronic rejection. Genetic deletion of VEGFR3 specifically in the lymphatics of the transplanted heart recapitulated the survival effect achieved by pharmacological VEGF-C/VEGFR3 inhibition. Our results suggest that tissue damage rapidly changes lymphatic vessel phenotype, which, in turn, may shape the interplay of innate and adaptive immunity. Importantly, VEGF-C/VEGFR3 inhibition during solid organ transplant IRI could be used as lymphatic-targeted immunomodulatory therapy to prevent acute and chronic rejection.

Activation of Dll4/Notch Signaling and Hypoxia-Inducible Factor-1 Alpha Facilitates Lymphangiogenesis in Lacrimal Glands in Dry Eye

PURPOSE

By using hypoxia-inducible factor-1 alpha conditional knockout (HIF-1α CKO) mice and a dry eye (DE) mouse model, we aimed to determine the role played by delta-like ligand 4 (Dll4)/Notch signaling and HIF-1α in the lymphangiogenesis of lacrimal glands (LGs).

METHODS

C57BL/6 mice were housed in a controlled-environment chamber for DE induction. During DE induction, the expression level of Dll4/Notch signaling and lymphangiogenesis in LGs was measured by quantitative RT-PCR, immunoblot, and immunofluorescence staining. Next, lymphangiogenesis was measured after Dll4/Notch signal inhibition by anti-Dll4 antibody or γ-secretase inhibitor. Using HIF-1α CKO mice, the expression of Dll4/Notch signaling and lymphangiogenesis in LGs of DE-induced HIF-1α CKO mice were assessed. Additionally, the infiltration of CD45+ cells in LGs was assessed by immunohistochemical (IHC) staining and flow cytometry for each condition.

RESULTS

DE significantly upregulated Dll4/Notch and lymphangiogenesis in LGs. Inhibition of Dll4/Notch significantly suppressed lymphangiogenesis in LGs. Compared to wild-type (WT) mice, DE induced HIF-1α CKO mice showed markedly low levels of Dll4/Notch and lymphangiogenesis. Inhibition of lymphangiogenesis by Dll4/Notch suppression resulted in increased CD45+ cell infiltration in LGs. Likewise, CD45+ cells infiltrated more in the LGs of HIF-1α CKO DE mice than in non-DE HIF-1α CKO mice.

CONCLUSIONS

Dll4/Notch signaling and HIF-1α are closely related to lymphangiogenesis in DE-induced LGs. Lymphangiogenesis stimulated by Dll4/Notch and HIF-1α may play a role in protecting LGs from DE-induced inflammation by aiding the clearance of immune cells from LGs.

Lymphangiogenesis and Inflammation-Looking for the "Missing Pieces" of the Puzzle

Several papers about lymphangiogenesis and inflammation focused on the detailed and complicated descriptions of the molecular pathways accompanying both non-tumor and tumor inflammatory-induced lymphatic vessel development. Many authors are tempted to present inflammatory-induced lymphangiogenesis in pathologic conditions neglecting the role of inflammatory cells during embryonic lymphatic vessel development. Some of the inflammatory cells are largely characterized in inflammatory-induced lymphangiogenesis, while others as mast cells, eosinophils, or plasma cells are less studied. No phenotypic characterization of inflammation-activated lymphatic endothelial cell is available in this moment. Another paradox is related to the existence of few papers regarding lymphangiogenesis inside lymphoid organs and for their related pathology. There are still several "missing pieces of such a big puzzle" of lymphangiogenesis and inflammation, with a direct impact on the ineffectiveness of the anti-inflammatory therapy as lymphangiogenesis inhibitors. The present paper will focus on the controversial issues of lymphangiogenesis and inflammation.

Three-dimensional biomimetic model to reconstitute sprouting lymphangiogenesis in vitro

Formation of new lymphatic vessels, termed lymphangiogenesis, is central for diverse biological processes during development, inflammation and tumor metastasis. However, reliable in vitro model is still under demand for detailed elucidation of how sprouting lymphangiogenesis is initiated and coordinated. Here, we describe a microfluidic platform optimized for close reconstitution of lymphangiogenesis, achieved by on-chip integration of salient constituents of lymphatic microenvironment found in vivo. With flexible and precise control over the factors that include biochemical cues, interstitial flow (IF), and endothelial-stromal interactions, we found that orchestrated efforts of multiple environmental factors are necessary for robust lymphatic sprouting in 3D extracellular matrix. Especially, we demonstrate that IF serves as a central regulatory cue which defines lymphangiogenic responses and phenotypes of lymphatic endothelial cells. When synergized with pro-lymphangiogenic factors, IF significantly augmented initiation and outgrowth of lymphatic sprouts toward upstream of the flow while suppressing downstream-directed sprouting. In an appropriate synergism, lymphatic sprouts exhibited structural, molecular signatures and cellular phenotypes that closely approximate sprouting lymphatic neovessels in vivo, and precisely reflected the modulatory effects of pro- and anti-lymphangiogenic stimuli. Our study not only reveals critical but unappreciated role of mechanical cue that regulates lymphangiogenic sprouting, but also provides a novel biomimetic model that may leverage further biological studies as well as phenotypic drug screening.

Neuropilin-2 contributes to LPS-induced corneal inflammatory lymphangiogenesis

Neuropilin-2 (NP2), a high-affinity kinase-deficient co-receptor for vascular endothelial growth factor (VEGF)-C, is involved in embryonic vessel development, tumor growth, tumor lymphangiogenesis and metastasis. However, the pathological role of NP2 in other disorders, particularly under inflammatory lymphangiogenic conditions, remains largely unknown. In this study, we investigated the role of NP2 in inflammation-induced lymphangiogenesis in vivo using a lipopolysaccharide (LPS)-induced corneal neovascularization mouse model and in vitro using a macrophage-mouse lymphatic endothelial cell (mLEC) co-culture system. In the mouse model of LPS-induced inflammatory corneal neovascularization, NP2 and VEGFR-3 expression were rapidly up-regulated after LPS stimulation, and microRNA-mediated knockdown of NP2 significantly inhibited the up-regulation of VEGFR-3. Moreover, NP2 knockdown specifically inhibited the increase in the number of corneal lymphatic vessels but did not influence the increase in the number of blood vessels or macrophage recruitment induced by LPS. In a macrophage-LEC co-culture system, LPS up-regulated VEGFR-3 expression and induced mLEC migration and proliferation, and NP2 knockdown inhibited the up-regulation of VEGFR-3 expression and mLEC migration but not proliferation. Taken together, these results suggested that NP2 might be involved in the regulation of lymphangiogenesis via the regulation of VEGFR-3 expression during corneal inflammation. Therefore, NP2-targeted therapy might be a promising strategy for selective inhibition of inflammatory lymphangiogenesis in corneal inflammatory diseases, transplant immunology and oncology.

Characterization of ticlopidine-induced developmental and teratogenic defects in Xenopus embryos and human endothelial cells

Ticlopidine is an anti-platelet drug that inhibits platelet aggregation via the functional alteration of platelet membranes. However, the mechanism underlying the adverse developmental effects of ticlopidine has not been clearly demonstrated. In this study, we evaluated the developmental toxicity and teratogenicity of ticlopidine on Xenopus laevis embryos and in human umbilical vein endothelial cells (HUVECs) using a frog embryo teratogenesis assay-Xenopus (FETAX) and blood and lymph vessel formation assays. Ticlopidine induced teratogenicity and inhibited growth, as evidenced by mortality rates and embryo lengths, respectively. Moreover, ticlopidine induced severe hemorrhages and inhibited both blood and lymph vessel formation by modulating the expression of xMsr and Prox1 in Xenopus embryos. Additionally, Nkx2.5 and Cyl104 levels were perturbed by ticlopidine exposure, and more extensive aberrations were observed in the liver and heart using whole-mount in situ hybridization. In addition, ticlopidine reduced branching in HUVECs by blocking the effect of the angiogenic vascular endothelial growth factor (VEGF). Results from this study suggest that ticlopidine is a developmental toxicant and teratogen and therefore this is a step forward in our understanding of the effects of ticlopidine during developmental processes.

MicroRNA signature of inflamed lymphatic endothelium and role of miR-9 in lymphangiogenesis and inflammation

The lymphatics have emerged as critical players in the progression and resolution of inflammation. The goal of this study was to identify specific microRNAs (miRNAs) that regulate lymphatic inflammatory processes. Rat mesenteric lymphatic endothelial cells (LECs) were exposed to the proinflammatory cytokine tumor necrosis factor-α for 2, 24, and 96 h, and miRNA profiling was carried out by real-time PCR arrays. Our data demonstrate a specific set of miRNAs that are differentially expressed (>1.8-fold and/or P < 0.05) in LECs in response to tumor necrosis factor-α and are involved in inflammation, angiogenesis, endothelial-mesenchymal transition, and cell proliferation and senescence. We further characterized the expression of miRNA 9 (miR-9) that was induced in LECs and in inflamed rat mesenteric lymphatics. Our results showed that miR-9 overexpression significantly repressed NF-κB expression and, thereby, suppressed inflammation but promoted LEC tube formation, as well as expression of the prolymphangiogenic molecules endothelial nitric oxide synthase and VEGF receptor type 3. LEC viability and proliferation and endothelial-mesenchymal transition were also significantly induced by miR-9. This study provides the first evidence of a distinct profile of miRNAs associated with LECs during inflammation. It also identifies the critical dual role of miR-9 in fine-tuning the balance between lymphatic inflammatory and lymphangiogenic pathways.

Nuclear PROX1 is Associated with Hypoxia-Inducible Factor 1α Expression and Cancer Progression in Esophageal Squamous Cell Carcinoma

BACKGROUND

Transcription factor prospero homeobox 1 (PROX1) has been identified as a master regulator of lymphangiogenesis associated with metastasis. Although PROX1 expression has been investigated in several cancers, its clinical significance remains controversial and needs further validation. In this study, we investigated the clinical and functional significance of PROX1 and PROX1 regulator hypoxia-inducible factor 1α (HIF1α) in esophageal squamous cell carcinoma (ESCC).

METHODS

A total of 117 samples from ESCC patients were analyzed for PROX1, HIF1α, and E-cadherin expression by immunohistochemistry; correlation with clinicopathological characteristics was determined. PROX1 function was evaluated in PROX1 small interfering RNA (siRNA)-transfected human ESCC cells in vitro by assessing cell proliferation and migration.

RESULTS

PROX1 expression was higher in ESCC than in normal tissues. Patients with higher PROX1 expression (n = 26) had increased nuclear accumulation of HIF1α (p = 0.004) and more advanced metastasis, both lymph node (N factor; p = 0.09) and hematogenous (M factor; p = 0.04), than those with lower PROX1 expression (n = 91). In addition, high PROX1 and HIF1α expression correlated with low levels of E-cadherin, an epithelial cell marker. Analysis of overall and cancer-specific survival indicated that elevated PROX1 expression was significantly correlated with poor prognosis (p = 0.0064). PROX1 downregulation in ESCC cells inhibited cellular proliferation and migration (p < 0.05). Hypoxia restored PROX1 levels that were reduced by PROX1-specific siRNA.

CONCLUSION

Our data suggest that high expression of PROX1 in ESCC could be used as an indicator of poor prognosis, and that PROX1 is a promising candidate molecular target for ESCC treatment.

Neutrophils promote Alzheimer's disease-like pathology and cognitive decline via LFA-1 integrin

Inflammation is a pathological hallmark of Alzheimer's disease, and innate immune cells have been shown to contribute to disease pathogenesis. In two transgenic models of Alzheimer's disease (5xFAD and 3xTg-AD mice), neutrophils extravasated and were present in areas with amyloid-β (Aβ) deposits, where they released neutrophil extracellular traps (NETs) and IL-17. Aβ42 peptide triggered the LFA-1 integrin high-affinity state and rapid neutrophil adhesion to integrin ligands. In vivo, LFA-1 integrin controlled neutrophil extravasation into the CNS and intraparenchymal motility. In transgenic Alzheimer's disease models, neutrophil depletion or inhibition of neutrophil trafficking via LFA-1 blockade reduced Alzheimer's disease-like neuropathology and improved memory in mice already showing cognitive dysfunction. Temporary depletion of neutrophils for 1 month at early stages of disease led to sustained improvements in memory. Transgenic Alzheimer's disease model mice lacking LFA-1 were protected from cognitive decline and had reduced gliosis. In humans with Alzheimer's disease, neutrophils adhered to and spread inside brain venules and were present in the parenchyma, along with NETs. Our results demonstrate that neutrophils contribute to Alzheimer's disease pathogenesis and cognitive impairment and suggest that the inhibition of neutrophil trafficking may be beneficial in Alzheimer's disease.

Endothelial Snail Regulates Capillary Branching Morphogenesis via Vascular Endothelial Growth Factor Receptor 3 Expression

Vascular branching morphogenesis is activated and maintained by several signaling pathways. Among them, vascular endothelial growth factor receptor 2 (VEGFR2) signaling is largely presented in arteries, and VEGFR3 signaling is in veins and capillaries. Recent reports have documented that Snail, a well-known epithelial-to-mesenchymal transition protein, is expressed in endothelial cells, where it regulates sprouting angiogenesis and embryonic vascular development. Here, we identified Snail as a regulator of VEGFR3 expression during capillary branching morphogenesis. Snail was dramatically upregulated in sprouting vessels in the developing retinal vasculature, including the leading-edged vessels and vertical sprouting vessels for capillary extension toward the deep retina. Results from in vitro functional studies demonstrate that Snail expression colocalized with VEGFR3 and upregulated VEGFR3 mRNA by directly binding to the VEGFR3 promoter via cooperating with early growth response protein-1. Snail knockdown in postnatal mice attenuated the formation of the deep capillary plexus, not only by impairing vertical sprouting vessels but also by downregulating VEGFR3 expression. Collectively, these data suggest that the Snail-VEGFR3 axis controls capillary extension, especially in vessels expressing VEGFR2 at low levels.

Downregulation of FoxC2 Increased Susceptibility to Experimental Colitis: Influence of Lymphatic Drainage Function?

BACKGROUND

Although inflammation-induced expansion of the intestinal lymphatic vasculature (lymphangiogenesis) is known to be a crucial event in limiting inflammatory processes, through clearance of interstitial fluid and immune cells, considerably less is known about the impact of an impaired lymphatic clearance function (as seen in inflammatory bowel diseases) on this cascade. We aimed to investigate whether the impaired intestinal lymphatic drainage function observed in FoxC2 mice would influence the course of disease in a model of experimental colitis.

METHODS

Acute dextran sodium sulfate colitis was induced in wild-type and haploinsufficient FoxC2 mice, and survival, disease activity, colonic histopathological injury, neutrophil, T-cell, and macrophage infiltration were evaluated. Functional and structural changes in the intestinal lymphatic vessel network were analyzed, including submucosal edema, vessel morphology, and lymphatic vessel density.

RESULTS

We found that FoxC2 downregulation in FoxC2 mice significantly increased the severity and susceptibility to experimental colitis, as displayed by lower survival rates, increased disease activity, greater histopathological injury, and elevated colonic neutrophil, T-cell, and macrophage infiltration. These findings were accompanied by structural (dilated torturous lymphatic vessels) and functional (greater submucosal edema, higher immune cell burden) changes in the intestinal lymphatic vasculature.

CONCLUSIONS

These results indicate that sufficient lymphatic clearance plays a crucial role in limiting the initiation and perpetuation of experimental colitis and those disturbances in the integrity of the intestinal lymphatic vessel network could intensify intestinal inflammation. Future therapies might be able to exploit these processes to restore and maintain adequate lymphatic clearance function in inflammatory bowel disease.

The mRNA expressions and immunohistochemistry of factors involved in angiogenesis and lymphangiogenesis in the early stage of rat skin incision wounds

Wound healing evaluation is important in forensic pathology, in which angiogenesis plays an important role. We have already shown that vascular endothelial growth factor A (VEGF) is produced in the rat skin incision wounds by neutrophils, endothelial cells, and fibroblasts. In this study, we assessed the changes in the mRNA expressions of various factors possibly involved in angiogenesis including angiopoietin (ANGPT) 1 and 2, cadherin 5 (CDH5), granulocyte-macrophage colony stimulating factor (CSF2/GM-CSF), granulocyte colony stimulating factor (CSF3/G-CSF), chemokine (C-X-C motif) ligand 2 (CXCL2), chemokine (C-X-C motif) ligand12 (CXCL12/SDF1), endothelin 1 (ET1), fibroblast growth factor 1 (FGF 1), hepatocyte growth factor (HGF), hypoxia inducible factor 1 alpha (HIF1a), leptin, matrix metallopepitidase 9 (MMP9), serpine/plasminogen activator inhibitor1 (PAI1), platelet-derived growth factor-A (PDGF-A), transforming growth factor alpha and beta 1 (TGFa and b1), tenomodulin (TNMD), and troponin I type 2 (TNNI2) in the early stage of the rat skin incision wounds by real time RT-PCR. Factors reported to be involved in lymphangiogenesis such as fibroblast growth factor 2 (FGF 2), c-fos induced growth factor (FIGF/VEGF-D), forkhead box C2 (FOXC2), and prospero homeobox 1 (PROX1) were also studied. One and 3 days after the dorsal skin incisions, wounds on male Sprague-Dawley rats showed the statistically significant increases in the mRNA expressions for CXCL2, CSF3, MMP9, PAI1, and CSF2, whereas TGFa, TNNI2, FGF1, TNMD, leptin, and CXCL12 showed the statistically significant decreases. Interestingly, lymphgangiogenic factors FOXC2, PROX1, and FGF2 also showed the statistically significant decreases. In situ hybridization and immunohistochemistry showed the mRNA and protein positivity in endothelial cells, fibroblasts, and some leukocytes at the bottom of the wound tissue for PAI1, CSF3, and MMP9, 1 day after the skin incisions. Our novel findings show the possible involvement of several factors involved in angiogenesis and lymphangiogenesis in the early stage of wound healing process, which may be useful for forensic wound evaluations.

Bridging the divide between pathogenesis and detection in lymphedema

While our understanding of the lymphatic system has improved substantially in the past few decades, the translation of this knowledge into improved healthcare solutions for patients suffering from secondary lymphedema has been severely limited. The challenge facing clinicians is two-fold. First, there is no reliable, affordable, diagnostic capable of detecting the disease before symptoms of the lymphedema develop and the efficacy of treatment options becomes limited. Second, our understanding of the disease pathogenesis, its risk factors, and the underlying physiologic mechanisms is still in its infancy. These two challenges go hand in hand as limited diagnostic options have hindered our ability to understand lymphedema progression, and the lack of known underlying mechanisms involved in the disease prohibits the development of new diagnostic targets. This review serves to discuss the recent developments in clinical and lab research settings of both lymphedema diagnostic technologies and our understanding of the mechanisms driving disease risk and progression. We will show how these two lines of research are synergistically working with the ultimate goal of improving patient outcomes for those suffering from this horrible disease, identifying key areas of further research that are warranted to move the field forward and provide clinical relief for this neglected patient population.

SH2B3 Is a Genetic Determinant of Cardiac Inflammation and Fibrosis

BACKGROUND

Genome-wide association studies are powerful tools for nominating pathogenic variants, but offer little insight as to how candidate genes affect disease outcome. Such is the case for SH2B adaptor protein 3 (SH2B3), which is a negative regulator of multiple cytokine signaling pathways and is associated with increased risk of myocardial infarction (MI), but its role in post-MI inflammation and fibrosis is completely unknown.

METHODS AND RESULTS

Using an experimental model of MI (left anterior descending artery occlusion/reperfusion injury) in wild-type and Sh2b3 knockout rats (Sh2b3(em2Mcwi)), we assessed the role of Sh2b3 in post-MI fibrosis, leukocyte infiltration, angiogenesis, left ventricle contractility, and inflammatory gene expression. Compared with wild-type, Sh2b3(em2Mcwi) rats had significantly increased fibrosis (2.2-fold; P<0.05) and elevated leukocyte infiltration (>2-fold; P<0.05), which coincided with decreased left ventricle fractional shortening (-Δ11%; P<0.05) at 7 days post left anterior descending artery occlusion/reperfusion injury. Despite an increased angiogenic potential in Sh2b3(em2Mcwi) rats (1.7-fold; P<0.05), we observed no significant differences in left ventricle capillary density between wild-type and Sh2b3(em2Mcwi) rats. In total, 12 genes were significantly elevated in the post left anterior descending artery occluded/reperfused hearts of Sh2b3(em2Mcwi) rats relative to wild-type, of which 3 (NLRP12, CCR2, and IFNγ) were significantly elevated in the left ventricle of heart failure patients carrying the MI-associated rs3184504 [T] SH2B3 risk allele.

CONCLUSIONS

These data demonstrate for the first time that SH2B3 is a crucial mediator of post-MI inflammation and fibrosis.

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.