Stimulation of lymphangiogenesis via VEGFR-3 inhibits chronic skin inflammation

Therapeutically Induced Lymphangiogenesis Is Ineffective in Resolving Established Kidney Disease in Mice

Key Points

CKD is a state of unresolved kidney inflammation. Lymphatic vessels and lymphangiogenesis regulate inflammation, and thus, more lymphatics could potentially resolve inflammation and CKD progression. Induction of kidney-specific lymphangiogenesis in three mouse CKD models did not improve kidney function and has the potential to worsen CKD.

Background

CKD counts AKI as one of its many underlying causes. Lymphatic vessels are important in modulating inflammation postinjury. Manipulating lymphatic vessel expansion thus has the potential to alter CKD progression. Previously, we demonstrated that renal lymphatic expansion before injury reduced CKD progression after an AKI. Here, we test whether inducing lymphangiogenesis affects established CKD.

Methods

After CKD progression, kidney lymphatics were expanded by transgenic induction of kidney-specific overexpression of vascular endothelial growth factor-D in aristolochic acid (AA) nephropathy and cisplatin injury aggravated with chronic high phosphate diet (CisPi) models or by infusion of kidney-targeting nanoparticles loaded with the vascular endothelial growth factor receptor-3 specific ligand vascular endothelial growth factor-C C156S in a progressive proteinuria (POD) model. Renal fibrosis and lymphatic density were determined by picrosirius red staining and immunofluorescence, respectively. Renal function was assessed by creatinine clearance rate, serum creatinine, BUN, and urinary albumin-creatinine ratio. Renal proinflammatory and fibrotic markers expression were measured by quantitative RT-PCR.

Results

Kidney-specific overexpression of vascular endothelial growth factor-D+ mice demonstrated expanded renal lymphatics, while nanoparticles treatment minimally expanded lymphatics. In neither the AA nor POD model did lymphangiogenesis improve renal function or fibrosis. AA mice showed decreased Tgfb1 expression and POD mice showed increased Col4a1 expression. Expansion worsened function in CisPi CKD and increased fibrosis. CisPi kidneys also demonstrated increased expression of Mcp-1 , Il1b , Col1a1 , and Tgfb1 and increased macrophage numbers.

Conclusions

Therapeutically induced lymphatic expansion is ineffective in resolving established CKD and has the potential to further worsen CKD progression.

Mechanics of Lymphatic Pumping and Lymphatic Function

The lymphatic system plays a crucial role in maintaining tissue fluid balance, immune surveillance, and the transport of lipids and macromolecules. Lymph is absorbed by initial lymphatics and then driven through lymph nodes and to the blood circulation by the contraction of collecting lymphatic vessels. Intraluminal valves in collecting lymphatic vessels ensure the unidirectional flow of lymph centrally. The lymphatic muscle cells that invest in collecting lymphatic vessels impart energy to propel lymph against hydrostatic pressure gradients and gravity. A variety of mechanical and biochemical stimuli modulate the contractile activity of lymphatic vessels. This review focuses on the recent advances in our understanding of the mechanisms involved in regulating and collecting lymphatic vessel pumping in normal tissues and the association between lymphatic pumping, infection, inflammatory disease states, and lymphedema.

Mucocutaneous Adverse Events in Patients With Cancer Treated with the Highly Selective RET Kinase Inhibitor Selpercatinib (LOXO-292)

Introduction

Selective RET inhibitors are approved for the treatment of RET-dependent cancers. A comprehensive characterization of mucocutaneous adverse events (MAEs) has not been performed; therefore, we characterized MAEs associated with the selective RET inhibitor, selpercatinib.

Methods

We assessed 133 patients with RET-altered cancers treated with selpercatinib. The type, grade, cumulative incidence, and time to onset of MAEs were determined. Therapy interruptions, clinicopathologic findings, and management were described. Laboratory values were compared between patients with and without MAEs.

Results

A total of 73 patients with mostly NSCLC (n = 46, 63%), medullary thyroid (n = 19, 26%), and papillary thyroid (n = 6, 8%) cancers had 126 predominantly grade 1/2 (n = 124, 98%) MAEs, with 48% reporting greater than one MAE. Xerostomia (n = 49, 37%), rash (n = 24, 18%), periorbital edema (n = 16, 12%), and xerosis (n = 12, 9%) were the most common MAEs. The yearly cumulative incidence of all-grade MAEs was 55%, with a median time to onset of 57 (interquartile range: 15-166) days after initiation. Those with MAEs had a significantly higher percentage of lymphocytes (mean = 21.8, SD = 11.3, p = 0.005) compared with those without MAEs (16.9, SD = 10.0) and elevated immunoglobulin E (mean = 275, SD = 294.5 IU/mL). There were 18 (14%) MAE-related therapy interruptions, including the following: three (2%) rechallenged with dose maintained, 10 (7%) with a 50% dose reduction, 5 (4%) with a 25% dose reduction, and no drug discontinuations. A treatment algorithm was created for the most common MAEs: xerostomia managed with saliva and lubricants; mucositis with steroid rinses; rashes with topical steroids with or without topical ammonium lactate; periorbital edema with cold or caffeine compresses; and xerosis and pruritus with emollients.

Conclusions

Selective RET inhibition is associated with a unique MAE profile. Early recognition and management of MAEs may improve quality of life, minimize interruptions, and maximize therapeutic benefit.

Neutrophils in tumor- and inflammation-induced lymphangiogenesis

Lymphangiogenesis is the formation of new lymphatic vessels from preexisting vessels and occurs during embryonic lymphatic development and under pathological conditions induced by internal or external stimuli. Emerging evidence suggests that neutrophils contribute to the construction and remodeling of new lymphatic vessels. Neutrophils migrate to lymph nodes through the lymphatic vessels or high endothelial venules, and neutrophil migration may depend on the phenotype of the neutrophil. The presence of unique neutrophil phenotypes in individuals with lymphangiogenesis has been reported. Neutrophils promote lymphangiogenesis mainly by secreting lymphotropic factors or increasing their bioavailability and by collaborating with various immune cells. Neutrophils mediate lymphangiogenesis and exert complex effects on tumors and inflammation. The selective inhibition of specific neutrophil and neutrophil lymphangiogenic molecules may provide a novel approach for the prevention and treatment of associated diseases.

Negative regulation of lymphangiogenesis by Tenascin-C delays the resolution of inflammation

Lymphatic vessels are required for the clearance of excess fluid and immune cells from inflamed tissue, making the regulation of lymphangiogenesis an important area of research. Although the positive regulatory mechanisms of lymphangiogenesis are well known, the negative regulatory mechanisms observed during inflammation remain unclear. Here, we identify tenascin-C (TNC) as a spatiotemporal negative regulator of lymphangiogenesis during inflammation. We found an inverse correlation between lymphangiogenesis and TNC expression in a mouse lymphedema model. Genetic deletion of Tnc promotes lymphangiogenesis and improves lymphatic drainage function, thereby accelerating the resolution of inflammation. Conversely, the exogenous addition of TNC suppresses lymphangiogenesis and prolongs inflammation. TNC inhibits the proliferation and promotes apoptosis of lymphatic endothelial cells. Mechanistically, TNC facilitates integrin αvβ1 heterodimer formation, leading to the activation of non-canonical (TAK1/p38MAPK/ATF-2) TGFβ signaling to suppress lymphangiogenesis. Our study highlights the importance of negative regulation of lymphangiogenesis in modulating immune responses.

An Update on the Role of Lymphatic Function in Skin Inflammatory Disorders: A Scoping Review

The lymphatic system is essential in maintaining skin health through coordinated immunological actions. This review explores the relationship between lymphatic function and skin health, as well as the impact of lymphatic dysfunction in the development and progression of inflammatory skin disorders. A systemic search was conducted in the Web of Science, Embase, and Ovid MEDLINE databases, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews (PRISMA-ScR) guidelines. Included studies were peer-reviewed human or animal research published in English from 2014 to 2024, focusing on inflammatory skin disorders, including skin cancer, autoimmune skin diseases, and infectious skin diseases. A total of 1232 citations were identified, with 37 studies meeting the eligibility criteria after assessment and critical appraisal. The review's findings highlight the essential role of lymphatics in maintaining skin health, mitigating inflammatory, infectious, and skin cancer-related processes, and delaying the effects of skin aging. The mechanisms underlying lymphatic function in these processes are complex, with some aspects needing further investigation. However, the evidence indicates that a well-functioning skin lymphatic system, supported by various cytokines, aids in reducing the inflammatory state, reduces inflammation, alleviates lymphedema, and prevents lymphatic stasis, which can increase infection risk. Several studies demonstrated that restoring lymphatic function through improved neutrophil migration and cytokine responses reduces the spread of infectious diseases.

Molecular Characterization and Interaction between Human VEGF-D and VEGFR-3

Angiogenesis and lymphangiogenesis are some of the routes that cause metastasis. Vascular Endothelial Growth Factors (VEGFs) stimulate angiogenesis and lymphangiogenesis through VEGF receptors. Especially, VEGF-D and its receptor, VEGFR-3, play a pivotal role in regulating cellular processes such as survival, proliferation, and migration, thereby influencing lymphangiogenesis. The aim of this research is to clarify the molecular characteristics of VEGF-D and VEGFR-3 proteins and identify the key residues that are essential for the interaction between VEGF-D and VEGFR-3. Experiments, including size exclusion chromatography and GST pull-down assay analysis, reveal that specific residues, particularly D103 and Q110, are essential for VEGF-D/VEGFR-3 binding. Mutations in these residues induce structural alterations, resulting in reduced binding affinity and impaired activation of VEGFR-3. Moreover, this study suggests that a synthesized peptide, designed based on key residues of VEGF-D involved in binding to VEGFR-3, may act as a metastasis suppressor by competitively inhibiting the interaction between VEGF-D and VEGFR-3. Understanding these molecular interactions is expected to have significant potential to develop therapeutic peptides that can inhibit cancer cell-induced lymphangiogenesis and resolve metastasis via lymphangiogenesis across various cancer types.

Prostanoids Regulate Angiogenesis and Lymphangiogenesis in Pathological Conditions

Angiogenesis, the formation of new blood vessels from the preexistent microvasculature, is an essential component of wound repair and tumor growth. Nonsteroidal anti-inflammatory drugs that suppress prostanoid biosynthesis are known to suppress the incidence and progression of malignancies including colorectal cancers, and also to delay the wound healing. However, the precise mechanisms are not fully elucidated. Accumulated results obtained from prostanoid receptor knockout mice indicate that a prostaglandin E-type receptor signaling EP3 in the host microenvironment is critical in tumor angiogenesis inducing vascular endothelial growth factor A (VEGF-A). Further, lymphangiogenesis was also enhanced by EP signaling via VEGF-C/D inductions in pathological settings. These indicate the importance of EP receptor to facilitate angiogenesis and lymphangiogenesis in vivo. Prostanoids act beyond their commonly understood activities in smooth muscle contraction and vasoactivity, both of which are quick responses elicited within several seconds on stimulations. Prostanoid receptor signaling will be a potential therapeutic target for disease conditions related to angiogenesis and lymphangiogenesis.

Lymphangiogenesis: novel strategies to promote cutaneous wound healing

The cutaneous lymphatic system regulates tissue inflammation, fluid balance and immunological responses. Lymphangiogenesis or lymphatic dysfunction may lead to lymphedema, immune deficiency, chronic inflammation etc. Tissue regeneration and healing depend on angiogenesis and lymphangiogenesis during wound healing. Tissue oedema and chronic inflammation can slow wound healing due to impaired lymphangiogenesis or lymphatic dysfunction. For example, impaired lymphangiogenesis or lymphatic dysfunction has been detected in nonhealing wounds such as diabetic ulcers, venous ulcers and bedsores. This review summarizes the structure and function of the cutaneous lymphatic vessel system and lymphangiogenesis in wounds. Furthermore, we review wound lymphangiogenesis processes and remodelling, especially the influence of the inflammatory phase. Finally, we outline how to control lymphangiogenesis to promote wound healing, assess the possibility of targeting lymphangiogenesis as a novel treatment strategy for chronic wounds and provide an analysis of the possible problems that need to be addressed.

Lymphatic endothelial cell-targeting lipid nanoparticles delivering VEGFC mRNA improve lymphatic function after injury

Dysfunction of the lymphatic system following injury, disease, or cancer treatment can lead to lymphedema, a debilitating condition with no cure. Advances in targeted therapy have shown promise for treating diseases where conventional therapies have been ineffective and lymphatic vessels have recently emerged as a new therapeutic target. Lipid nanoparticles (LNPs) have emerged as a promising strategy for tissue specific delivery of nucleic acids. Currently, there are no approaches to target LNPs to lymphatic endothelial cells, although it is well established that intradermal (ID) injection of nanoparticles will drain to lymphatics with remarkable efficiency. To design an LNP that would effectively deliver mRNA to LEC after ID delivery, we screened a library of 150 LNPs loaded with a reporter mRNA, for both self-assembly and delivery in vivo to lymphatic endothelial cells (LECs). We identified and validated several LNP formulations optimized for high LEC uptake when administered ID and compared their efficacy for delivery of functional mRNA with that of free mRNA and mRNA delivered with a commercially available MC3-based LNP (Onpattro™). The lead LEC-specific LNP was then loaded with VEGFC mRNA to test the therapeutic advantage of the LEC-specific LNP (namely, LNP7) for treating a mouse tail lymphatic injury model. A single dose of VEGFC mRNA delivered via LNP7 resulted in enhanced LEC proliferation at the site of injury, and an increase in lymphatic function up to 14-days post-surgery. Our results suggest a therapeutic potential of VEGFC mRNA lymphatic-specific targeted delivery in alleviating lymphatic dysfunction observed during lymphatic injury and could provide a promising approach for targeted, transient lymphangiogenic therapy.

VEGF-C prophylaxis favors lymphatic drainage and modulates neuroinflammation in a stroke model

Meningeal lymphatic vessels (MLVs) promote tissue clearance and immune surveillance in the central nervous system (CNS). Vascular endothelial growth factor-C (VEGF-C) regulates MLV development and maintenance and has therapeutic potential for treating neurological disorders. Herein, we investigated the effects of VEGF-C overexpression on brain fluid drainage and ischemic stroke outcomes in mice. Intracerebrospinal administration of an adeno-associated virus expressing mouse full-length VEGF-C (AAV-mVEGF-C) increased CSF drainage to the deep cervical lymph nodes (dCLNs) by enhancing lymphatic growth and upregulated neuroprotective signaling pathways identified by single nuclei RNA sequencing of brain cells. In a mouse model of ischemic stroke, AAV-mVEGF-C pretreatment reduced stroke injury and ameliorated motor performances in the subacute stage, associated with mitigated microglia-mediated inflammation and increased BDNF signaling in brain cells. Neuroprotective effects of VEGF-C were lost upon cauterization of the dCLN afferent lymphatics and not mimicked by acute post-stroke VEGF-C injection. We conclude that VEGF-C prophylaxis promotes multiple vascular, immune, and neural responses that culminate in a protection against neurological damage in acute ischemic stroke.

Lymphatic-Dependent Modulation of the Sensitization and Elicitation Phases of Contact Hypersensitivity

Allergic contact dermatitis is a common inflammatory skin disease comprising 2 phases. During sensitization, immune cells are activated by exposure to various allergens, whereas repeated antigen exposure induces local inflammation during elicitation. In this study, we utilized mouse models lacking lymphatics in different skin regions to characterize the role of lymphatics separately in the 2 phases, using contact hypersensitivity as a model of human allergic inflammatory skin diseases. Lymphatic-deficient mice exhibited no major difference to single antigen exposure compared to controls. However, mice lacking lymphatics in both phases displayed reduced inflammation after repeated antigen exposure. Similarly, diminished immune response was observed in mice lacking lymphatics only in sensitization, whereas the absence of lymphatics only in the elicitation phase resulted in a more pronounced inflammatory immune response. This exaggerated inflammation is driven by neutrophils impacting regulatory T cell number. Collectively, our results demonstrate that skin lymphatics play an important but distinct role in the 2 phases of contact hypersensitivity. During sensitization, lymphatics contribute to the development of the antigen-specific immunization, whereas in elicitation, they moderate the inflammatory response and leukocyte infiltration in a neutrophil-dependent manner. These findings underscore the need for novel therapeutic strategies targeting the lymphatics in the context of allergic skin diseases.

Translational frontiers: insight from lymphatics in skin regeneration

The remarkable regenerative ability of the skin, governed by complex molecular mechanisms, offers profound insights into the skin repair processes and the pathogenesis of various dermatological conditions. This understanding, derived from studies in human skin and various model systems, has not only deepened our knowledge of skin regeneration but also facilitated the development of skin substitutes in clinical practice. Recent research highlights the crucial role of lymphatic vessels in skin regeneration. Traditionally associated with fluid dynamics and immune modulation, these vessels are now recognized for interacting with skin stem cells and coordinating regeneration. This Mini Review provides an overview of recent advancements in basic and translational research related to skin regeneration, focusing on the dynamic interplay between lymphatic vessels and skin biology. Key highlights include the critical role of stem cell-lymphatic vessel crosstalk in orchestrating skin regeneration, emerging translational approaches, and their implications for skin diseases. Additionally, the review identifies research gaps and proposes potential future directions, underscoring the significance of this rapidly evolving research arena.

Histological and biochemical changes in lymphatic vessels after skeletal muscle injury induced by lengthening contraction in male mice

Lymphatic vessels are actively involved in the recovery process of inflamed tissues. However, the changes in intramuscular lymphatic vessels during inflammation caused by skeletal muscle injury remain unclear. Therefore, the purpose of this study was to clarify the changes in lymphatic vessels after skeletal muscle injury. The left tibialis anterior muscles of male mice were subjected to lengthening contractions (LC) for inducing skeletal muscle injury, and samples were collected on Days 2, 4, and 7 for examining changes in both the skeletal muscles and intramuscular lymphatic vessels. With hematoxylin-eosin staining, the inflammatory response was observed in myofibers on Days 2 and 4 after LC, whereas regeneration of myofibers was found on Day 7 after LC. The number and area of intramuscular lymphatic vessels analyzed by immunohistochemical staining with an antibody against lymphatic vessel endothelial hyaluronan receptor 1 were significantly increased only on Day 4 after LC. Based on the abovementioned results, intramuscular lymphatic vessels undergo morphological changes such as increase under the state of muscle inflammation. This study demonstrated that the morphology of intramuscular lymphatic vessels undergoes significant changes during the initial recovery phase following skeletal muscle injury.

15-Lipoxygenase promotes resolution of inflammation in lymphedema by controlling Treg cell function through IFN-β

Lymphedema (LD) is characterized by the accumulation of interstitial fluid, lipids and inflammatory cell infiltrate in the limb. Here, we find that LD tissues from women who developed LD after breast cancer exhibit an inflamed gene expression profile. Lipidomic analysis reveals decrease in specialized pro-resolving mediators (SPM) generated by the 15-lipoxygenase (15-LO) in LD. In mice, the loss of SPM is associated with an increase in apoptotic regulatory T (Treg) cell number. In addition, the selective depletion of 15-LO in the lymphatic endothelium induces an aggravation of LD that can be rescued by Treg cell adoptive transfer or ALOX15-expressing lentivector injections. Mechanistically, exogenous injections of the pro-resolving cytokine IFN-β restores both 15-LO expression and Treg cell number in a mouse model of LD. These results provide evidence that lymphatic 15-LO may represent a therapeutic target for LD by serving as a mediator of Treg cell populations to resolve inflammation.

A human initial lymphatic chip reveals distinct mechanisms of primary lymphatic valve dysfunction in acute and chronic inflammation

Interstitial fluid uptake and retention by lymphatic vessels (LVs) play a role in maintaining interstitial fluid homeostasis. While it is well-established that intraluminal lymphatic valves in the collecting LVs prevent fluid backflow (secondary lymphatic valves), a separate valve system in the initial LVs that only permits interstitial fluid influx into the LVs, preventing fluid leakage back to the interstitium (primary lymphatic valves), remains incompletely understood. Although lymphatic dysfunction is commonly observed in inflammation and autoimmune diseases, how the primary lymphatic valves are affected by acute and chronic inflammation has scarcely been explored and even less so using in vitro lymphatic models. Here, we developed a human initial lymphatic vessel chip where interstitial fluid pressure and luminal fluid pressure are controlled to examine primary lymph valve function. In normal conditions, lymphatic drainage (fluid uptake) and permeability (fluid leakage) in engineered LVs were maintained high and low, respectively, which was consistent with our understanding of healthy primary lymph valves. Next, we examined the effects of acute and chronic inflammation. Under the acute inflammation condition with a TNF-α treatment (2 hours), degradation of fibrillin and impeded lymphatic drainage were observed, which were reversed by treatment with anti-inflammatory dexamethasone. Surprisingly, the chronic inflammation condition (repeated TNF-α treatments during 48 hours) deposited fibrillin to compensate for the fibrillin loss, showing no change in lymphatic drainage. Instead, the chronic inflammation condition led to cell death and disruption of lymphatic endothelial cell-cell junctions, increasing lymphatic permeability and fluid leakage. Our human lymphatic model shows two distinct mechanisms by which primary lymphatic valve dysfunction occurs in acute and chronic inflammation.

Progress on the pathological tissue microenvironment barrier-modulated nanomedicine

Imbalance in the tissue microenvironment is the main obstacle to drug delivery and distribution in the human body. Before penetrating the pathological tissue microenvironment to the target site, therapeutic agents are usually accompanied by three consumption steps: the first step is tissue physical barriers for prevention of their penetration, the second step is inactivation of them by biological molecules, and the third step is a cytoprotective mechanism for preventing them from functioning on specific subcellular organelles. However, recent studies in drug-hindering mainly focus on normal physiological rather than pathological microenvironment, and the repair of damaged physiological barriers is also rarely discussed. Actually, both the modulation of pathological barriers and the repair of damaged physiological barriers are essential in the disease treatment and the homeostasis maintenance. In this review, we present an overview describing the latest advances in the generality of these pathological barriers and barrier-modulated nanomedicine. Overall, this review holds considerable significance for guiding the design of nanomedicine to increase drug efficacy in the future.

Local Adenoviral Delivery of Vascular Endothelial Growth Factor C Induces Lymphangiogenesis in the Conjunctiva in Rabbits

INTRODUCTION

The purpose of this study was to determine if conjunctival lymphangiogenesis can be induced using adenoviral delivery of vascular endothelial growth factor C (VEGF-C).

METHODS

Seventeen New Zealand white rabbits received a subconjunctival injection containing 3.5 × 107 plaque-forming units of an adenoviral vector containing the gene-encoding VEGF-C (Ad-VEGF-C). The contralateral eye was used for control experiment (the same volume of either saline or an empty vector). After 2 weeks, the animals were examined with trypan blue conjunctival lymphangiography, and the eyes were harvested for histology and immunohistochemistry (podoplanin and CD31).

RESULTS

Trypan blue conjunctival lymphangiography revealed significantly more extensive conjunctival vessel network in the Ad-VEGF-C group compared with control: 1.35 ± 0.67 versus 0.28 ± 0.17 vessel length/analysed area (p = <0.0001). This finding was confirmed with immunohistochemistry, where a significant increase in the number of lymphatic vessels was found compared to control; 34 ± 9 per mm2 versus 13 ± 8 per mm2 (p = 0.0019). Furthermore, there was a significant increase in lymphatic cross-sectional area; 32,500 ± 7,900 µm2 per mm2 versus 17,600 ± 9,700 µm2 per mm2 (p = 0.0149). Quantification of blood vessels revealed no significant difference in blood vessel density between Ad-VEGF-C and control; 19 ± 9 per mm2 versus 14 ± 8 per mm2 (p = 0.1971). There was no significant difference in total blood vessel area; 13,200 ± 7,600 µm2 per mm2 versus 7,100 ± 3,000 µm2 per mm2 (p = 0.0715). Eyes treated with an adenoviral vector (VEGF-C or empty vector) responded with a reactive cellular response, predominantly lymphocytes, towards the vector.

CONCLUSION

The study demonstrates the feasibility of inducing conjunctival lymphangiogenesis with a single subconjunctival injection of Ad-VEGF-C. Future studies will explore how this can be used with a therapeutic purpose.

Nanotechnologies for Physiology-Informed Drug Delivery to the Lymphatic System

Accompanying the increasing translational impact of immunotherapeutic strategies to treat and prevent disease has been a broadening interest across both bioscience and bioengineering in the lymphatic system. Herein, the lymphatic system physiology, ranging from its tissue structures to immune functions and effects, is described. Design principles and engineering approaches to analyze and manipulate this tissue system in nanoparticle-based drug delivery applications are also elaborated.

Hyperoxia Disrupts Lung Lymphatic Homeostasis in Neonatal Mice

Inflammation causes bronchopulmonary dysplasia (BPD), a common lung disease of preterm infants. One reason this disease lacks specific therapies is the paucity of information on the mechanisms regulating inflammation in developing lungs. We address this gap by characterizing the lymphatic phenotype in an experimental BPD model because lymphatics are major regulators of immune homeostasis. We hypothesized that hyperoxia (HO), a major risk factor for experimental and human BPD, disrupts lymphatic endothelial homeostasis using neonatal mice and human dermal lymphatic endothelial cells (HDLECs). Exposure to 70% O2 for 24-72 h decreased the expression of prospero homeobox 1 (Prox1) and vascular endothelial growth factor c (Vegf-c) and increased the expression of heme oxygenase 1 and NAD(P)H dehydrogenase [quinone]1 in HDLECs, and reduced their tubule formation ability. Next, we determined Prox1 and Vegf-c mRNA levels on postnatal days (P) 7 and 14 in neonatal murine lungs. The mRNA levels of these genes increased from P7 to P14, and 70% O2 exposure for 14 d (HO) attenuated this physiological increase in pro-lymphatic factors. Further, HO exposure decreased VEGFR3+ and podoplanin+ lymphatic vessel density and lymphatic function in neonatal murine lungs. Collectively, our results validate the hypothesis that HO disrupts lymphatic endothelial homeostasis.

Promotion of Lymphangiogenesis by Targeted Delivery of VEGF-C Improves Diabetic Wound Healing

Chronic wounds represent a major therapeutic challenge. Lymphatic vessel function is impaired in chronic ulcers but the role of lymphangiogenesis in wound healing has remained unclear. We found that lymphatic vessels are largely absent from chronic human wounds as evaluated in patient biopsies. Excisional wound healing studies were conducted using transgenic mice with or without an increased number of cutaneous lymphatic vessels, as well as antibody-mediated inhibition of lymphangiogenesis. We found that a lack of lymphatic vessels mediated a proinflammatory wound microenvironment and delayed wound closure, and that the VEGF-C/VEGFR3 signaling axis is required for wound lymphangiogenesis. Treatment of diabetic mice (db/db mice) with the F8-VEGF-C fusion protein that targets the alternatively spliced extra domain A (EDA) of fibronectin, expressed in remodeling tissue, promoted wound healing, and potently induced wound lymphangiogenesis. The treatment also reduced tissue inflammation and exerted beneficial effects on the wound microenvironment, including myofibroblast density and collagen deposition. These findings indicate that activating the lymphatic vasculature might represent a new therapeutic strategy for treating chronic non-healing wounds.

Intestinal dysbiosis exacerbates the pathogenesis of psoriasis-like phenotype through changes in fatty acid metabolism

The intestinal microbiota has been associated with host immunity as well as psoriasis; however, the mechanism of intestinal microbiota regulating psoriasis needs to be demonstrated systematically. Here, we sought to examine its role and mechanism of action in the pathogenesis of psoriasis. We found that the severity of psoriasis-like skin phenotype was accompanied by changes in the composition of the intestinal microbiota. We performed co-housing and fecal microbial transplantation (FMT) experiments using the K14-VEGF transgenic mouse model of psoriasis and demonstrated that the transfer of intestinal microbiota from mice with severe psoriasis-like skin phenotype exacerbated psoriasiform skin inflammation in mice with mild symptoms, including increasing the infiltration and differentiation of Th17, and increased the abundance of Prevotella, while decreasing that of Parabacteroides distasonis, in the colon. These alterations affected fatty acid metabolism, increasing the abundance of oleic and stearic acids. Meanwhile, gentamicin treatment significantly reduced the abundance of Prevotella and alleviated the psoriasis-like symptoms in both K14-VEGF mice and imiquimod (IMQ)-induced psoriasis-like mice. Indeed, administration of oleic and stearic acids exacerbated psoriasis-like symptoms and increased Th17 and monocyte-derived dendritic cell infiltration in the skin lesion areas in vivo, as well as increased the secretion of IL-23 by stimulating DCs in vitro. At last, we found that, treatment of PDE-4 inhibitor alleviated psoriasis-like phenotype of K14-VEGF mice accompanied by the recovery of intestinal microbiota, including the decrease of Prevotella and increase of Parabacteroides distasonis. Overall, our findings reveal that the intestinal microbiota modulates host metabolism and psoriasis-like skin inflammation in mice, suggesting a new target for the clinical diagnosis and treatment of psoriasis.

Antibody-Mediated Delivery of VEGF-C Promotes Long-Lasting Lymphatic Expansion That Reduces Recurrent Inflammation

The lymphatic vascular system plays a fundamental role in inflammation by draining interstitial fluid, immune cells, antigens, and inflammatory mediators from peripheral tissues. Site-specific delivery of the lymphangiogenic growth factor VEGF-C alleviates acute inflammation in mouse models of psoriasis and chronic colitis by enhancing local drainage. However, it is unclear whether therapeutically induced lymphangiogenesis is transient or long-lasting and whether it might prevent relapses of inflammation. Here, we investigated the long-term effects of targeted VEGF-C delivery in a chronic dermatitis model in mice. Congruent with our previous results, intravenous injection with a VEGF-C fusion protein targeted to the EDA domain of fibronectin initially resulted in reduced inflammation. Importantly, we found that targeted VEGF-C-mediated expansion of lymphatic vessels in the skin persisted for more than 170 days, long after primary inflammation had resolved. Furthermore, the treatment markedly decreased tissue swelling upon inflammatory re-challenge at the same site. Simultaneously, infiltration of leukocytes, including CD4+ T cells, macrophages, and dendritic cells, was significantly reduced in the previously treated group. In conclusion, our data show that targeted delivery of VEGF-C leads to long-lasting lymphatic expansion and long-term protection against repeated inflammatory challenge, suggesting that it is a promising new approach for the treatment of chronic, recurrent inflammatory diseases.

Mediators of Capillary-to-Venule Conversion in the Chronic Inflammatory Skin Disease Psoriasis

Psoriasis is a chronic inflammatory skin disease characterized by epidermal hyperplasia and hyperkeratosis, immune cell infiltration and vascular remodeling. Despite the emerging recognition of vascular normalization as a potential strategy for managing psoriasis, an in-depth delineation of the remodeled dermal vasculature has been missing. In this study, we exploited 5' single-cell RNA sequencing to investigate the transcriptomic alterations in different subpopulations of blood vascular and lymphatic endothelial cells directly isolated from psoriatic and healthy human skin. Individual subtypes of endothelial cells underwent specific molecular repatterning associated with cell adhesion and extracellular matrix organization. Blood capillaries, in particular, showed upregulation of the melanoma cell adhesion molecule as well as its binding partners and adopted postcapillary venule‒like characteristics during chronic inflammation that are more permissive to leukocyte transmigration. We also identified psoriasis-specific interactions between cis-regulatory enhancers and promoters for each endothelial cell subtype, revealing the dysregulated gene regulatory networks in psoriasis. Together, our results provide more insights into the specific transcriptional responses and epigenetic signatures of endothelial cells lining different vessel compartments in chronic skin inflammation.

Genetic Engineering of Lymphangiogenesis in Skin Does Not Affect Blood Pressure in Mouse Models of Salt-Sensitive Hypertension

Background:

Recent studies have indicated that sodium storage is influenced by macrophages that secrete VEGF-C (vascular endothelial growth factor) during salt stress thus stimulating lymphangiogenesis, thereby acting as a buffer against increased blood pressure (BP). We aimed to explore the role of dermal lymphatics in BP and sodium homeostasis. Our hypothesis was that mice with reduced dermal lymphatic vessels were more prone to develop salt-sensitive hypertension, and that mice with hyperplastic vessels were protected.

Methods:

Mice with either hypoplastic (Chy), absent (K14-VEGFR3 [vascular endothelial growth factor receptor 3]-Ig), or hyperplastic (K14-VEGF-C) dermal lymphatic vessels and littermate controls were given high-salt diet (4% NaCl in the chow), deoxycorticosterone acetate (DOCA)-salt diet and 1% saline to drink or nitric oxide blocker diet L-N G -nitro arginine methyl ester (followed by high salt diet). BP was measured by telemetric recording, and tissue sodium content by ion chromatography.

Results:

In contrast to previous studies, high salt diet did not induce an increase in BP or sodium storage in any of the mouse strains investigated. DOCA-salt, on the other hand, gave an increase in BP in Chy and K14-VEGFR3-Ig not different from their corresponding WT controls. DOCA induced salt storage in skin and muscle, but to the same extent in mice with dysfunctional lymphatic vessels and WT controls. Lymph flow as assessed by tracer washout was not affected by the diet in any of the mouse strains.

Conclusions:

Our results suggest that dermal lymphatic vessels are not involved in salt storage or blood pressure regulation in these mouse models of salt-sensitive hypertension.

The regulatory effect of pulmonary lymphatic drainage on silicosis fibrosis

Silicosis is a fibrotic disease caused by long-term inhalation of SiO₂ particles that currently has no effective treatment. Earlier studies have suggested that pulmonary lymphatic vessels play a key role in the transport of silica but have not address the long-term effects of altered pulmonary lymphatic drainage on silicosis. Here, we investigated the impact of impaired pulmonary lymphatic drainage on silicosis. In the past, lymphatic drainage disorders were established mainly through the use of VEGF inhibitors. For the first time, we established a model of pulmonary lymphatic drainage disorder by ligating the thoracic duct in rats. Impaired pulmonary lymphatic drainage was found to aggravate inflammation and oxidative damage in silicosis rats and accelerate silicosis progression. Next, we investigated the effect of pulmonary lymphatic drainage on silicosis. We have demonstrated the effect of sodium tanshinone IIA sulfonate(STS) on lymphangiogenesis, which revealed that STS promotes lymphangiogenesis and can delay inflammation, oxidative damage, and fibrosis progression in silicosis rats by promoting the pulmonary lymphatic drainage response, and this effect is mediated by the VEGFR-3/PI3K/AKT signaling pathway. These findings suggest that pulmonary lymphogenesis plays an important role in silicosis pathogenesis, and targeted intervention in pulmonary lymphangiogenesis may be a potential strategy for treating of silicosis in the future.

Use of Early Donated COVID-19 Convalescent Plasma Is Optimal to Preserve the Integrity of Lymphatic Endothelial Cells

Convalescent plasma therapy (CPT) has gained significant attention since the onset of the coronavirus disease 2019 (COVID-19) pandemic. However, clinical trials designed to study the efficacy of CPT based on antibody concentrations were inconclusive. Lymphatic transport is at the interplay between the immune response and the resolution of inflammation from peripheral tissues, including the artery wall. As vascular complications are a key pathogenic mechanism in COVID-19, leading to inflammation and multiple organ failure, we believe that sustaining lymphatic vessel function should be considered to define optimal CPT. We herein sought to determine what specific COVID-19 convalescent plasma (CCP) characteristics should be considered to limit inflammation-driven lymphatic endothelial cells (LEC) dysfunction. CCP donated 16 to 100 days after the last day of symptoms was characterized and incubated on inflammation-elicited adult human dermal LEC (aHDLEC). Plasma analysis revealed that late donation correlates with higher concentration of circulating pro-inflammatory cytokines. Conversely, extracellular vesicles (EVs) derived from LEC are more abundant in early donated plasma (r = −0.413, p = 0.004). Thus, secretion of LEC-EVs by an impaired endothelium could be an alarm signal that instigate the self-defense of peripheral lymphatic vessels against an excessive inflammation. Indeed, in vitro experiments suggest that CCP obtained rapidly following the onset of symptoms does not damage the aHDLEC junctions as much as late-donated plasma. We identified a particular signature of CCP that would counteract the effects of an excessive inflammation on the lymphatic endothelium. Accordingly, an easy and efficient selection of convalescent plasma based on time of donation would be essential to promote the preservation of the lymphatic and immune system of infected patients.

Cerium-Containing Bioactive Glasses Promote In Vitro Lymphangiogenesis

The lymphatic system is crucial for the regeneration of many tissues due to its fundamental role in immune cell trafficking, protein transport, and tissue homeostasis maintenance. Strategies stimulating lymphangiogenesis can provide new therapeutic approaches for tissue repair and regeneration (e.g., chronic wound healing). Here, we explored the effects of cerium-containing mesoporous bioactive glass nanoparticles (Ce-MBGNs) on lymphangiogenesis. The results showed that the extracts of Ce-MBGNs (1, 5, or 10 wt/v%) were non-cytotoxic toward lymphatic endothelial cells (LECs), while they enhanced the proliferation of LECs. Moreover, as evidenced by the scratch wound healing and Transwell migration assays, conditioned media containing the extract of Ce-MBGNs (1 wt/v%) could enhance the migration of LECs in comparison to the blank control and the media containing vascular endothelial growth factor-C (VEGF-C, 50 ng/mL). Additionally, a tube-formation assay using LECs showed that the extract of Ce-MBGNs (1 wt/v%) promoted lymphatic vascular network formation. Western blot results suggested that Ce-MBGNs could induce lymphangiogenesis probably through the HIF-1α/VEGFR-3 pathway. Our study for the first time showed the effects of Ce-MBGNs on stimulating lymphangiogenesis in vitro, highlighting the potential of Ce-MBGNs for wound healing.

Radiofrequency Irradiation Mitigated UV-B-Induced Skin Pigmentation by Increasing Lymphangiogenesis

Dermal macrophages containing melanin increase skin pigmentation since dermal melanin removal is slower than epidermal melanin removal. Lymphatic vessels are also involved in melanin clearance. We evaluated whether radiofrequency (RF) irradiation induced an increase in HSP90, which promotes lymphangiogenesis by activating the BRAF/MEK/ERK pathway and decreasing tyrosinase activity, in the UV-B exposed animal model. The HSP90/BRAF/MEK/ERK pathway was upregulated by RF. Tyrosinase activity and the VEGF-C/VEGFR 3/PI3K/pAKT1/2/pERK1/2 pathway, which increase lymphangiogenesis, as well as the expression of the lymphatic endothelial marker LYVE-1, were increased by RF. Additionally, the number of melanin-containing dermal macrophages, the melanin content in the lymph nodes, and melanin deposition in the skin were decreased by RF. In conclusion, RF increased HSP90/BRAF/MEK/ERK expression, which decreased tyrosinase activity and increased lymphangiogenesis to eventually promote the clearance of dermal melanin-containing macrophages, thereby decreasing skin pigmentation.

Lymphatic Reconstruction in Kidney Allograft Aggravates Chronic Rejection by Promoting Alloantigen Presentation

Chronic rejection of the renal allograft remains a major cause of graft loss. Here, we demonstrated that the remodeling of lymphatic vessels (LVs) after their broken during transplantation contributes to the antigen presenting and lymph nodes activating. Our studies observed a rebuilt of interrupted lymph draining one week after mouse kidney transplantation, involving preexisting lymphatic endothelial cells (LECs) from both the donor and recipient. These expanding LVs also release C-C chemokine ligand 21 (CCL21) and recruit CCR7⁺ cells, mainly dendritic cells (DCs), toward lymph nodes and spleen, evoking the adaptive response. This rejection could be relieved by LYVE-1 specific LVs knockout or CCR7 migration inhibition in mouse model. Moreover, in retrospective analysis, posttransplant patients exhibiting higher area density of LVs presented with lower eGFR, severe serum creatinine and proteinuria, and greater interstitial fibrosis. These results reveal a rebuilt pathway for alloantigen trafficking and lymphocytes activation, providing strategies to alleviate chronic transplantation rejection.

A novel personalised treatment approach for psoriasis: anti-VEGF-A therapy

Chronic plaque psoriasis is an inflammatory skin disease in which genetic predisposition along with environmental factors lead to the development of the disease, which affects 2% of the UK’s population and is associated with extracutaneous morbidities and a reduced quality of life. A complex crosstalk between innate and adaptive immunity, the epithelia and the vasculature maintain the inflammatory milieu in psoriasis. Despite the development of promising treatment strategies, mostly targeting the immune system, treatments fail to fulfil every patient’s goals. Vascular endothelial growth factor‐A (VEGF‐A) mediates angiogenesis and is upregulated in the plaques and plasma of patients with psoriasis. Transgenic expression of VEGF‐A in experimental models led to the development of skin lesions that share many psoriasis features. Targeting VEGF‐A in in vivo models of psoriasis‐like inflammation resulted in disease clearance. Anti‐angiogenesis treatments are widely used for cancer and eye disease and there are clinical reports of patients treated with VEGF‐A inhibitors who have experienced Psoriasis Area and Severity Index improvement. Existing psoriasis treatments downregulate VEGF‐A and angiogenesis as part of their therapeutic effect. Pharmacogenetics studies suggest the existence of different genetic signatures within patients with psoriasis that correspond with different treatment responsiveness and disease severity. There is a subset of patients with psoriasis with an increased predisposition to produce high levels of VEGF‐A, who may be most likely to benefit from anti‐VEGF‐A therapy, offering an opportunity to personalize treatment in psoriasis. Anti‐VEGF‐A therapies may offer an alternative to existing anticytokine strategies or be complementary to standard treatments for the management of psoriasis.

Effect of Total Glucosides of Paeony on Imiquimod-Induced Psoriatic Skin Lesions by Regulating VEGF

Purpose

The purpose of this study was to use a murine model of psoriasis to examine the effect of total glycosides of paeony (TGP) on psoriatic skin lesions and on the expression of vascular endothelial growth factor (VEGF) in skin lesions and blood.

Methods

A murine model of psoriasis was produced by shaving the backs of the mice and applying 5% imiquimod cream, 50 mg, to the backs of the mice once a day. Mice were killed on day 8, and skin and blood samples were obtained for histopathological examination and analysis of VEGF mRNA expression.

Results

By day 8 of the application of imiquimod cream, skin lesions characteristic of psoriasis were evident, and histopathological examination of skin sections showed changes consistent with psoriasis (corneum thickening and parakeratosis, attenuation of the stratum granulosum, thickening of the stratum spinosum, and lengthening of the epidermal ridge). In the treatment group, 7 days of treatment with TGP resulted in resolution of the skin lesions, and histopathological examination showed the epidermis and dermis are approximately normal, without corneum thickening, hyperkeratosis, and parakeratosis. On day 7 of treatment, skin expression of VEGF mRNA was significantly lower in the treatment group than in the group that did not receive treatment (p < 0.05). Blood VEGF mRNA expression was not different between the groups.

Conclusion

TGP is effective for the treatment of psoriasis and may act by decreasing lesion VEGF mRNA expression.

Immunological perspectives on spatial and temporal vaccine delivery

The so-called rational design of vaccines has been a very attractive concept and also an important direction for vaccine research and development. However, the underlying rationales, especially on the immunological aspect, remain less systemically and deeply understood. Given the critical role of lymph nodes (LNs) in the induction of B and T cell responses upon vaccination, LN targeting has been a popular strategy in vaccine design. The LN is a highly organized structure; induction of adaptive immune response is highly orchestrated by various types of LN stromal cells and hematopoietic immune cells both spatially and temporally. Thus, not only LN targeting, but also cellular targeting and even subcellular compartment targeting should be considered for specifically enhanced vaccine efficacy. Moreover, temporal control of vaccine antigen and adjuvant delivery may also optimize the immune response.

Development and Clinical Validation of the LymphMonitor Technology to Quantitatively Assess Lymphatic Function

Current diagnostic methods for evaluating the functionality of the lymphatic vascular system usually do not provide quantitative data and suffer from many limitations including high costs, complexity, and the need to perform them in hospital settings. In this work, we present a quantitative, simple outpatient technology named LymphMonitor to quantitatively assess lymphatic function. This method is based on the painless injection of the lymphatic-specific near-infrared fluorescent tracer indocyanine green complexed with human serum albumin, using MicronJet600^TM microneedles, and monitoring the disappearance of the fluorescence signal at the injection site over time using a portable detection device named LymphMeter. This technology was investigated in 10 patients with unilateral leg or arm lymphedema. After injection of a tracer solution into each limb, the signal was measured over 3 h and the area under the normalized clearance curve was calculated to quantify the lymphatic function. A statistically significant difference in lymphatic clearance in the healthy versus the lymphedema extremities was found, based on the obtained area under curves of the normalized clearance curves. This study provides the first evidence that the LymphMonitor technology has the potential to diagnose and monitor the lymphatic function in patients.

Biologically active lipids in the regulation of lymphangiogenesis in disease states

Lymphatic vessels have crucial roles in the regulation of interstitial fluids, immune surveillance, and the absorption of dietary fat in the intestine. Lymphatic function is also closely related to the pathogenesis of various disease states such as inflammation, lymphedema, endometriosis, liver dysfunction, and tumor metastasis. Lymphangiogenesis, the formation of new lymphatic vessels from pre-existing lymphatic vessels, is a critical determinant in the above conditions. Although the effect of growth factors on lymphangiogenesis is well-characterized, and biologically active lipids are known to affect smooth muscle contractility and vasoaction, there is accumulating evidence that biologically active lipids are also important inducers of growth factors and cytokines that regulate lymphangiogenesis. This review discusses recent advances in our understanding of biologically active lipids, including arachidonic acid metabolites, sphingosine 1-phosphate, and lysophosphatidic acid, as regulators of lymphangiogenesis, and the emerging importance of the lymphangiogenesis as a therapeutic target.

The lymphatics in kidney health and disease

The mammalian vascular system consists of two networks: the blood vascular system and the lymphatic vascular system. Throughout the body, the lymphatic system contributes to homeostatic mechanisms by draining extravasated interstitial fluid and facilitating the trafficking and activation of immune cells. In the kidney, lymphatic vessels exist mainly in the kidney cortex. In the medulla, the ascending vasa recta represent a hybrid lymphatic-like vessel that performs lymphatic-like roles in interstitial fluid reabsorption. Although the lymphatic network is mainly derived from the venous system, evidence supports the existence of lymphatic beds that are of non-venous origin. Following their development and maturation, lymphatic vessel density remains relatively stable; however, these vessels undergo dynamic functional changes to meet tissue demands. Additionally, new lymphatic growth, or lymphangiogenesis, can be induced by pathological conditions such as tissue injury, interstitial fluid overload, hyperglycaemia and inflammation. Lymphangiogenesis is also associated with conditions such as polycystic kidney disease, hypertension, ultrafiltration failure and transplant rejection. Although lymphangiogenesis has protective functions in clearing accumulated fluid and immune cells, the kidney lymphatics may also propagate an inflammatory feedback loop, exacerbating inflammation and fibrosis. Greater understanding of lymphatic biology, including the developmental origin and function of the lymphatics and their response to pathogenic stimuli, may aid the development of new therapeutic agents that target the lymphatic system.

Genomic Approach to the Assessment of Adverse Effects of Particulate Matters on Skin Cancer and Other Disorders and Underlying Molecular Mechanisms

Air pollutants are in the spotlight because the human body can easily be exposed to them. Among air pollutants, the particulate matter (PM) represents one of the most serious toxicants that can enter the human body through various exposure routes. PMs have various adverse effects and classified as severe carcinogen by International Agency for Research on Cancer. Their physical and chemical characteristics are distinguished by their size. In this review, we summarized the published information on the physicochemical characteristics and adverse effects of PMs on the skin, including carcinogenicity. Through comparisons of biological networks constructed from relationships discussed in the previous scientific publications, we show it is possible to predict skin cancers and other disorders from particle-size-specific signaling alterations of PM-responsive genes. Our review not only helps to grasp the biological association between ambient PMs and skin diseases including cancer, but also provides new approaches to interpret chemical-gene-disease associations regarding the adverse effects of these heterogeneous particles.

The role of lymphatics in intestinal inflammation

The lymphatic vasculature returns filtered interstitial arterial fluid and tissue metabolites to the blood circulation. It also plays a major role in lipid absorption and immune cell trafficking. Lymphatic vascular defects have been revealed in inflammatory diseases, Crohn's disease, obesity, cardiovascular disease, hypertension, atherosclerosis, and Alzheimer's disease. In this review, we discuss lymphatic structure and function within the gut, such as dietary lipid absorption, the transport of antigens and immune cells to lymph nodes, peripheral tolerance, and lymphocyte migration from secondary lymphoid tissues to the lymphatics and the immune systems. We also discuss the potential roles of these lymphatics on the pathophysiology of inflammatory bowel disease and as new targets for therapeutic management.

The role of lymphatics in intestinal inflammation

The lymphatic vasculature returns filtered interstitial arterial fluid and tissue metabolites to the blood circulation. It also plays a major role in lipid absorption and immune cell trafficking. Lymphatic vascular defects have been revealed in inflammatory diseases, Crohn's disease, obesity, cardiovascular disease, hypertension, atherosclerosis, and Alzheimer's disease. In this review, we discuss lymphatic structure and function within the gut, such as dietary lipid absorption, the transport of antigens and immune cells to lymph nodes, peripheral tolerance, and lymphocyte migration from secondary lymphoid tissues to the lymphatics and the immune systems. We also discuss the potential roles of these lymphatics on the pathophysiology of inflammatory bowel disease and as new targets for therapeutic management.

The role of lymphatics in intestinal inflammation

The lymphatic vasculature returns filtered interstitial arterial fluid and tissue metabolites to the blood circulation. It also plays a major role in lipid absorption and immune cell trafficking. Lymphatic vascular defects have been revealed in inflammatory diseases, Crohn's disease, obesity, cardiovascular disease, hypertension, atherosclerosis, and Alzheimer's disease. In this review, we discuss lymphatic structure and function within the gut, such as dietary lipid absorption, the transport of antigens and immune cells to lymph nodes, peripheral tolerance, and lymphocyte migration from secondary lymphoid tissues to the lymphatics and the immune systems. We also discuss the potential roles of these lymphatics on the pathophysiology of inflammatory bowel disease and as new targets for therapeutic management.

Neutrophil Interactions with the Lymphatic System

The lymphatic system is a complex network of lymphatic vessels and lymph nodes designed to balance fluid homeostasis and facilitate host immune defence. Neutrophils are rapidly recruited to sites of inflammation to provide the first line of protection against microbial infections. The traditional view of neutrophils as short-lived cells, whose role is restricted to providing sterilizing immunity at sites of infection, is rapidly evolving to include additional functions at the interface between the innate and adaptive immune systems. Neutrophils travel via the lymphatics from the site of inflammation to transport antigens to lymph nodes. They can also enter lymph nodes from the blood by crossing high endothelial venules. Neutrophil functions in draining lymph nodes include pathogen control and modulation of adaptive immunity. Another facet of neutrophil interactions with the lymphatic system is their ability to promote lymphangiogenesis in draining lymph nodes and inflamed tissues. In this review, we discuss the significance of neutrophil migration to secondary lymphoid organs and within the lymphatic vasculature and highlight emerging evidence of the neutrophils’ role in lymphangiogenesis.

The role of lymphatics in intestinal inflammation

The lymphatic vasculature returns filtered interstitial arterial fluid and tissue metabolites to the blood circulation. It also plays a major role in lipid absorption and immune cell trafficking. Lymphatic vascular defects have been revealed in inflammatory diseases, Crohn's disease, obesity, cardiovascular disease, hypertension, atherosclerosis, and Alzheimer's disease. In this review, we discuss lymphatic structure and function within the gut, such as dietary lipid absorption, the transport of antigens and immune cells to lymph nodes, peripheral tolerance, and lymphocyte migration from secondary lymphoid tissues to the lymphatics and the immune systems. We also discuss the potential roles of these lymphatics on the pathophysiology of inflammatory bowel disease and as new targets for therapeutic management.

The role of lymphatics in intestinal inflammation

The lymphatic vasculature returns filtered interstitial arterial fluid and tissue metabolites to the blood circulation. It also plays a major role in lipid absorption and immune cell trafficking. Lymphatic vascular defects have been revealed in inflammatory diseases, Crohn's disease, obesity, cardiovascular disease, hypertension, atherosclerosis, and Alzheimer's disease. In this review, we discuss lymphatic structure and function within the gut, such as dietary lipid absorption, the transport of antigens and immune cells to lymph nodes, peripheral tolerance, and lymphocyte migration from secondary lymphoid tissues to the lymphatics and the immune systems. We also discuss the potential roles of these lymphatics on the pathophysiology of inflammatory bowel disease and as new targets for therapeutic management.

The role of lymphatics in intestinal inflammation

The lymphatic vasculature returns filtered interstitial arterial fluid and tissue metabolites to the blood circulation. It also plays a major role in lipid absorption and immune cell trafficking. Lymphatic vascular defects have been revealed in inflammatory diseases, Crohn's disease, obesity, cardiovascular disease, hypertension, atherosclerosis, and Alzheimer's disease. In this review, we discuss lymphatic structure and function within the gut, such as dietary lipid absorption, the transport of antigens and immune cells to lymph nodes, peripheral tolerance, and lymphocyte migration from secondary lymphoid tissues to the lymphatics and the immune systems. We also discuss the potential roles of these lymphatics on the pathophysiology of inflammatory bowel disease and as new targets for therapeutic management.

The role of lymphatics in intestinal inflammation

The lymphatic vasculature returns filtered interstitial arterial fluid and tissue metabolites to the blood circulation. It also plays a major role in lipid absorption and immune cell trafficking. Lymphatic vascular defects have been revealed in inflammatory diseases, Crohn's disease, obesity, cardiovascular disease, hypertension, atherosclerosis, and Alzheimer's disease. In this review, we discuss lymphatic structure and function within the gut, such as dietary lipid absorption, the transport of antigens and immune cells to lymph nodes, peripheral tolerance, and lymphocyte migration from secondary lymphoid tissues to the lymphatics and the immune systems. We also discuss the potential roles of these lymphatics on the pathophysiology of inflammatory bowel disease and as new targets for therapeutic management.

The role of lymphatics in intestinal inflammation

The lymphatic vasculature returns filtered interstitial arterial fluid and tissue metabolites to the blood circulation. It also plays a major role in lipid absorption and immune cell trafficking. Lymphatic vascular defects have been revealed in inflammatory diseases, Crohn's disease, obesity, cardiovascular disease, hypertension, atherosclerosis, and Alzheimer's disease. In this review, we discuss lymphatic structure and function within the gut, such as dietary lipid absorption, the transport of antigens and immune cells to lymph nodes, peripheral tolerance, and lymphocyte migration from secondary lymphoid tissues to the lymphatics and the immune systems. We also discuss the potential roles of these lymphatics on the pathophysiology of inflammatory bowel disease and as new targets for therapeutic management.

The role of lymphatics in intestinal inflammation

The lymphatic vasculature returns filtered interstitial arterial fluid and tissue metabolites to the blood circulation. It also plays a major role in lipid absorption and immune cell trafficking. Lymphatic vascular defects have been revealed in inflammatory diseases, Crohn's disease, obesity, cardiovascular disease, hypertension, atherosclerosis, and Alzheimer's disease. In this review, we discuss lymphatic structure and function within the gut, such as dietary lipid absorption, the transport of antigens and immune cells to lymph nodes, peripheral tolerance, and lymphocyte migration from secondary lymphoid tissues to the lymphatics and the immune systems. We also discuss the potential roles of these lymphatics on the pathophysiology of inflammatory bowel disease and as new targets for therapeutic management.

The role of lymphatics in intestinal inflammation

The lymphatic vasculature returns filtered interstitial arterial fluid and tissue metabolites to the blood circulation. It also plays a major role in lipid absorption and immune cell trafficking. Lymphatic vascular defects have been revealed in inflammatory diseases, Crohn's disease, obesity, cardiovascular disease, hypertension, atherosclerosis, and Alzheimer's disease. In this review, we discuss lymphatic structure and function within the gut, such as dietary lipid absorption, the transport of antigens and immune cells to lymph nodes, peripheral tolerance, and lymphocyte migration from secondary lymphoid tissues to the lymphatics and the immune systems. We also discuss the potential roles of these lymphatics on the pathophysiology of inflammatory bowel disease and as new targets for therapeutic management.

The role of lymphatics in intestinal inflammation

The lymphatic vasculature returns filtered interstitial arterial fluid and tissue metabolites to the blood circulation. It also plays a major role in lipid absorption and immune cell trafficking. Lymphatic vascular defects have been revealed in inflammatory diseases, Crohn’s disease, obesity, cardiovascular disease, hypertension, atherosclerosis, and Alzheimer’s disease. In this review, we discuss lymphatic structure and function within the gut, such as dietary lipid absorption, the transport of antigens and immune cells to lymph nodes, peripheral tolerance, and lymphocyte migration from secondary lymphoid tissues to the lymphatics and the immune systems. We also discuss the potential roles of these lymphatics on the pathophysiology of inflammatory bowel disease and as new targets for therapeutic management.

The role of lymphatics in intestinal inflammation

The lymphatic vasculature returns filtered interstitial arterial fluid and tissue metabolites to the blood circulation. It also plays a major role in lipid absorption and immune cell trafficking. Lymphatic vascular defects have been revealed in inflammatory diseases, Crohn's disease, obesity, cardiovascular disease, hypertension, atherosclerosis, and Alzheimer's disease. In this review, we discuss lymphatic structure and function within the gut, such as dietary lipid absorption, the transport of antigens and immune cells to lymph nodes, peripheral tolerance, and lymphocyte migration from secondary lymphoid tissues to the lymphatics and the immune systems. We also discuss the potential roles of these lymphatics on the pathophysiology of inflammatory bowel disease and as new targets for therapeutic management.