Contractile activity of lymphatic vessels is altered in the TNBS model of guinea pig ileitis

Not just fibrotic: endothelial-derived TGFβ maintains contractile function and lymphatic muscle phenotype during homeostasis

Cell-cell communication within the lymphatic vasculature during homeostasis is incompletely detailed. Although many discoveries highlight the pathological roles of transforming growth factor-beta (TGFβ) in chronic vascular inflammation and associated fibrosis, only a small amount is known surrounding the role of TGFβ-signaling in homeostatic lymphatic function. Here, we discovered that pharmacological blockade of TGFβ receptor 1 (TGFβR1) negatively impacts rat mesenteric lymphatic vessel pumping, significantly reducing vessel contractility and surrounding lymphatic muscle coverage. We have identified mesenteric lymphatic endothelial cells themselves as a source of endogenous vascular TGFβ and that TGFβ production is significantly increased in these cells via activation of a number of functional pattern recognition receptors they express. We show that a continuous supply of TGFβ is essential to maintain the contractile phenotype of neighboring lymphatic muscle cells and support this conclusion through in vitro analysis of primary isolated lymphatic muscle cells that undergo synthetic differentiation during 2-D cell culture, a phenomenon that could be effectively rescued by supplementation with recombinant TGFβ. Finally, we demonstrate that lymphatic endothelial production of TGFβ is regulated, in part, by nitric oxide in a manner we propose is essential to counteract the pathological over-production of TGFβ. Taken together, these data highlight the essential role of homeostatic TGFβ signaling in the maintenance of lymphatic vascular function and highlight possible deleterious consequences of its inhibition.NEW & NOTEWORTHY The growth factor TGFβ is commonly associated with its pathological overproduction during tissue fibrosis rather than its homeostatic functions. We expose the lymphatic endothelium as a source of endogenous TGFβ, the impact of its production on the maintenance of surrounding lymphatic muscle cell phenotype, and internally regulated mechanisms of its production. Overall, these results highlight the intricate balance of TGFβ-signaling as an essential component of maintaining lymphatic contractile function.

Increased contractile activity and dilation of popliteal lymphatic vessels in the TNF-α-overexpressing TNFΔARE/+ arthritic mouse

AIMS

TNF-α acute treatment has been found to disrupt lymphatic drainage in the setting of arthritis through the NF-kB-iNOS- signaling pathway. We examined whether popliteal lymphatic vessels (pLVs) contractile activity was altered in 12- and 24- week-old females of an arthritic mouse model overexpressing TNF-α (TNFΔARE/+).

MAIN METHODS

pLVs were prepared for intravital imaging to measure lymph flow speed, and ex vivo functional responses to a stepwise increase in transmural pressure in the absence or presence of the non-selective NOS inhibitor (L-NNA) or the selective iNOS inhibitor (1400W) were compared between TNFΔARE/+ and WT mice. Total eNOS (t-eNOS) and eNOS phosphorylated at ser1177 (p-eNOS) were evaluated by western blotting.

KEY FINDINGS

In vivo imaging revealed a significantly increase in lymph flow speed in TNFΔARE/+ mice in comparison to WT at both ages. Pressure myography showed an increase in contraction frequency, diameters and fractional pump flow at both ages, whereas amplitude and ejection fraction were significantly decreased in older TNFΔARE/+ mice. Additionally, contraction frequency was increased in the presence of 1400W, and systolic diameter was abolished with L-NNA in TNFΔARE/+ mice compared to WT. Significant increases in p-eNOS expression and neutrophil recruitment (MPO activity) were observed in TNFΔARE/+ mice compared to WT.

SIGNIFICANCE

Our data reveal functional changes in pLVs, especially in advanced stage of arthritis. These alterations may be related to eNOS and iNOS response, which can affect drainage of the inflammatory content from the joints.

IP3R1 underlies diastolic ANO1 activation and pressure-dependent chronotropy in lymphatic collecting vessels

Pressure-dependent chronotropy of murine lymphatic collecting vessels relies on the activation of the Ca2+-activated chloride channel encoded by Anoctamin 1 (Ano1) in lymphatic muscle cells. Genetic ablation or pharmacological inhibition of ANO1 results in a significant reduction in basal contraction frequency and essentially complete loss of pressure-dependent frequency modulation by decreasing the rate of the diastolic depolarization phase of the ionic pacemaker in lymphatic muscle cells (LMCs). Oscillating Ca2+ release from sarcoendoplasmic reticulum Ca2+ channels has been hypothesized to drive ANO1 activity during diastole, but the source of Ca2+ for ANO1 activation in smooth muscle remains unclear. Here, we investigated the role of the inositol triphosphate receptor 1 (Itpr1; Ip3r1) in this process using pressure myography, Ca2+ imaging, and membrane potential recordings in LMCs of ex vivo pressurized inguinal-axillary lymphatic vessels from control or Myh11CreERT2;Ip3r1fl/fl (Ip3r1ismKO) mice. Ip3r1ismKO vessels had significant reductions in contraction frequency and tone but an increased contraction amplitude. Membrane potential recordings from LMCs of Ip3r1ismKO vessels revealed a depressed diastolic depolarization rate and an elongation of the plateau phase of the action potential (AP). Ca2+ imaging of LMCs using the genetically encoded Ca2+ sensor GCaMP6f demonstrated an elongation of the Ca2+ flash associated with an AP-driven contraction. Critically, diastolic subcellular Ca2+ transients were absent in LMCs of Ip3r1ismKO mice, demonstrating the necessity of IP3R1 activity in controlling ANO1-mediated diastolic depolarization. These findings indicate a critical role for IP3R1 in lymphatic vessel pressure-dependent chronotropy and contractile regulation.

The Enigmas of Lymphatic Muscle Cells: Where Do They Come From, How Are They Maintained, and Can They Regenerate?

Lymphatic muscle cell (LMC) contractility and coverage of collecting lymphatic vessels (CLVs) are integral to effective lymphatic drainage and tissue homeostasis. In fact, defects in lymphatic contractility have been identified in various conditions, including rheumatoid arthritis, inflammatory bowel disease, and obesity. However, the fundamental role of LMCs in these pathologic processes is limited, primarily due to the difficulty in directly investigating the enigmatic nature of this poorly characterized cell type. LMCs are a unique cell type that exhibit dual tonic and phasic contractility with hybrid structural features of both vascular smooth muscle cells (VSMCs) and cardiac myocytes. While advances have been made in recent years to better understand the biochemistry and function of LMCs, central questions regarding their origins, investiture into CLVs, and homeostasis remain unanswered. To summarize these discoveries, unexplained experimental results, and critical future directions, here we provide a focused review of current knowledge and open questions related to LMC progenitor cells, recruitment, maintenance, and regeneration. We also highlight the high-priority research goal of identifying LMC-specific genes towards genetic conditional- inducible in vivo gain and loss of function studies. While our interest in LMCs has been focused on understanding lymphatic dysfunction in an arthritic flare, these concepts are integral to the broader field of lymphatic biology, and have important potential for clinical translation through targeted therapeutics to control lymphatic contractility and drainage.

Intestinal Lymphatic Dysfunction in Kidney Disease

Kidney disease is associated with adverse consequences in many organs beyond the kidney, including the heart, lungs, brain, and intestines. The kidney-intestinal cross talk involves intestinal epithelial damage, dysbiosis, and generation of uremic toxins. Recent studies reveal that kidney injury expands the intestinal lymphatics, increases lymphatic flow, and alters the composition of mesenteric lymph. The intestinal lymphatics, like blood vessels, are a route for transporting potentially harmful substances generated by the intestines. The lymphatic architecture and actions are uniquely suited to take up and transport large macromolecules, functions that differentiate them from blood vessels, allowing them to play a distinct role in a variety of physiological and pathological processes. Here, we focus on the mechanisms by which kidney diseases result in deleterious changes in intestinal lymphatics and consider a novel paradigm of a vicious cycle of detrimental organ cross talk. This concept involves kidney injury-induced modulation of intestinal lymphatics that promotes production and distribution of harmful factors, which in turn contributes to disease progression in distant organ systems.

X-ray irradiation negatively affects immune responses in the lymphatic network

Immune checkpoint inhibitor therapy has been attracting attention as a new cancer treatment and is likely to be widely used in combination with radiotherapy. Therefore, examination of the effects of X-ray irradiation on sentinel lymph nodes and lymphatic vessels, which are involved in antigen presentation, is important for therapy. The hindlimbs of mice were irradiated with X-rays (total radiation doses: 2, 10, and 30 Gy), and X-ray computed tomography (CT) imaging was performed using 15-nm or 2-nm gold nanoparticles (AuNPs) as contrast agents on days 7, 14, and 28 after irradiation to evaluate the diameter of the collecting lymph vessels and lymph flow within the irradiated area. X-ray CT imaging data using 15-nm AuNPs on day 28 after irradiation showed that the diameter of the collecting lymph vessels was significantly larger in all irradiated groups compared to the control group (p ≤ 0.01). CT imaging with 2-nm AuNPs showed that lymphatic drainage was significantly reduced in the lymph nodes irradiated with 10 Gy and 30 Gy compared to the lymph nodes irradiated with 2 Gy (p ≤ 0.05). Additionally, immunohistochemical analyses were conducted to evaluate the area density and morphology of high endothelial venules (HEVs) in the lymph nodes, which are important vessels for naive T cells to enter the lymph nodes. The expression level of MECA-79, which specifically localized to HEVs, was significantly decreased in the 10 Gy and 30 Gy irradiation groups compared to the control group (p ≤ 0.05). There was a significant decrease in normal HEV morphology (p ≤ 0.05) and a significant increase in abnormal HEV morphology (p ≤ 0.05) in all irradiated groups. These results also showed that X-ray irradiation induced a time- and radiation dose-dependent increase in the diameter of the collecting lymph vessels, stagnation of intralymphatic lymph flow, and a reduction in the area density of HEVs and their abnormal morphology, demonstrating that X-ray irradiation affected the immune responses. Therefore, these findings suggest that X-ray irradiation to lymph nodes may impair the opportunity for antigen presentation in the lymph nodes, which is the key to cancer immunity, and that for this reason, it is important to carefully plan irradiation of sentinel lymph nodes and develop treatment strategies according to future treatment options.

Vmeasur: A software package for experimental and clinical measurement of mesenteric lymphatic contractile function over an extended vessel length

OBJECTIVE

Conventionally, in vivo mesenteric lymphatic contractile function is measured using a high magnification transmission microscope (field of view 0.3-1.5 mm), which precludes visualization of extended lengths of vessels embedded in mesenteric fat. Existing software is not optimized for imaging at a low magnification using a contrast agent. We aimed to develop a simple and clinically transferable method for in situ visualization, image analysis, and quantitative assessment of mesenteric lymphatic contractile function over an extended area.

METHODS

Subserosal injection of various blue dyes was taken up by mesenteric lymphatics and visualized under a stereomicroscope (25×), allowing for video recording of 1.4 × 1.1 cm of intact mesentery. A new R package ("vmeasur") that combines multiple high-performance image analyses into a single workflow was developed. The edges of each vessel were determined by applying an automated threshold to each frame (with real-time manual verification). The vessel width at every point in each frame was plotted to provide contractile parameters over time and along the lymphatic vessel length.

RESULTS

Contractile parameters and their differences along the length of the vessel were accurately calculated in a rodent model. In a human mesenteric lymphatic, the algorithm was also able to measure changes in diameter over length.

CONCLUSION

This software offers a low cost, rapid, and accessible method to measure lymphatic contractile function over a wide area, showing differences in contractility along the length of a vessel. Because the presence of mesenteric fat has less of an impact on imaging, due to the use of an exogenous contrast agent, there is potential for clinical application.

Effect of the snake venom component crotamine on lymphatic endothelial cell responses and lymph transport

OBJECTIVE

The pathology of snake envenomation is closely tied to the severity of edema in the tissue surrounding the area of the bite. Elucidating the mechanisms that promote the development of such severe edema is critical to a better understanding of how to treat this life-threatening injury. We focused on one of the most abundant venom components in North American viper venom, crotamine, and the effects it has on the cells and function of the lymphatic system.

METHODS

We used RT-PCR to identify the location and relative abundance of crotamine's cellular targets (Kvα channels) within the tissues and cells of the lymphatic system. We used calcium flux, nitrate production, and cell morphometry to determine the effects of crotamine on lymphatic endothelial cells. We used tracer transport, node morphometry, and node deposition to determine the effects of crotamine on lymph transport in vivo.

RESULTS

We found that genes that encode targets of crotamine are highly present in lymphatic tissues and cells and that there is a differential distribution of those genes that correlates with phasic contractile activity. We found that crotamine potentiates calcium flux in human dermal lymphatic endothelial cells in response to stimulation with histamine and sheer stress (but not alone) and that it alters the production of nitric oxide in response to shear as well as changes the level of F-actin polymerization of those same cells. Crotamine alters lymphatic transport of large molecular weight tracers to local lymph nodes and is deposited within the node mostly in the immediate subcapsular region.

CONCLUSION

This evidence suggests that snake venom components may have an impact on the function of the lymphatic system. This needs to be studied in greater detail as there are numerous venom components that may have effects on aspects of the lymphatic system. This would not only provide basic information on the pathobiology of snakebite but also provide targets for improved therapeutics to treat snakebite.

Lymphatic Collecting Vessel: New Perspectives on Mechanisms of Contractile Regulation and Potential Lymphatic Contractile Pathways to Target in Obesity and Metabolic Diseases

Obesity and metabolic syndrome pose a significant risk for developing cardiovascular disease and remain a critical healthcare challenge. Given the lymphatic system's role as a nexus for lipid absorption, immune cell trafficking, interstitial fluid and macromolecule homeostasis maintenance, the impact of obesity and metabolic disease on lymphatic function is a burgeoning field in lymphatic research. Work over the past decade has progressed from the association of an obese phenotype with Prox1 haploinsufficiency and the identification of obesity as a risk factor for lymphedema to consistent findings of lymphatic collecting vessel dysfunction across multiple metabolic disease models and organisms and characterization of obesity-induced lymphedema in the morbidly obese. Critically, recent findings have suggested that restoration of lymphatic function can also ameliorate obesity and insulin resistance, positing lymphatic targeted therapies as relevant pharmacological interventions. There remain, however, significant gaps in our understanding of lymphatic collecting vessel function, particularly the mechanisms that regulate the spontaneous contractile activity required for active lymph propulsion and lymph return in humans. In this article, we will review the current findings on lymphatic architecture and collecting vessel function, including recent advances in the ionic basis of lymphatic muscle contractile activity. We will then discuss lymphatic dysfunction observed with metabolic disruption and potential pathways to target with pharmacological approaches to improve lymphatic collecting vessel function.

The Role of the Lymphatic System in the Pathogenesis and Treatment of Inflammatory Bowel Disease

Although the number of therapeutic options for the treatment of inflammatory bowel disease (IBD) has increased in recent years, patients suffer from decreased quality of life due to non-response or loss of response to the currently available treatments. An increased understanding of the disease’s etiology could provide novel insights for treatment strategies in IBD. Lymphatic system components are generally linked to immune responses and presumably related to inflammatory diseases pathophysiology. This review aims to summarize findings on immune-mediated mechanisms in lymphoid tissues linked with IBD pathogenesis and (potential) novel treatments. Enhanced innate and adaptive immune responses were observed in mesenteric lymph nodes (MLNs) and other lymphoid structures, such as Peyer’s patches, in patients with IBD and in animal models. Furthermore, the phenomenon of lymphatic obstruction in the form of granulomas in MLNs and lymphatic vessels correlates with disease activity. There is also evidence that abnormalities in the lymphatic stromal components and lymph node microbiome are common in IBD and could be exploited therapeutically. Finally, novel agents targeting lymphocyte trafficking have been added to the treatment armamentarium in the field of IBD. Overall, gut-associated lymphoid tissue plays a key role in IBD immunopathogenesis, which could offer novel therapeutic targets.

Adipose tissue microenvironments during aging: Effects on stimulated lipolysis

Adipose tissue is a critical organ for nutrient sensing, energy storage and maintaining metabolic health. The failure of adipose tissue homeostasis leads to metabolic disease that is seen during obesity or aging. Local metabolic processes are coordinated by interacting microenvironments that make up the complexity and heterogeneity of the adipose tissue. Catecholamine-induced lipolysis, a critical pathway in adipocytes that drives the release of stored triglyceride as free fatty acid after stimulation, is impaired during aging. The impairment of this pathway is associated with a failure to maintain a healthy body weight, core body-temperature during cold stress or mount an immune response. Along with impairments in aged adipocytes, aging is associated with an accumulation of inflammation, immune cell activation, and increased dysfunction in the nervous and lymphatic systems within the adipose tissue. Together these microenvironments support the initiation of stimulated lipolysis and the transport of free fatty acid under conditions of metabolic homeostasis. However, during aging, the defects in these cellular systems result in a reduction in ability to stimulate lipolysis. This review will focus on how the immune, nervous and lymphatic systems interact during tissue homeostasis, review areas that are impaired with aging and discuss areas of research that are currently unclear.

Proinflammatory mediators, TNFα, IFNγ, and thrombin, directly induce lymphatic capillary tube regression

In this work, we sought to investigate the direct effects of proinflammatory mediators on lymphatic endothelial cell (LEC) capillaries and whether they might induce regression. Our laboratory has developed novel in-vitro, serum-free, lymphatic tubulogenesis assay models whereby human LEC tube networks readily form in either three-dimensional collagen or fibrin matrices. These systems were initially conceptualized in the hopes of better understanding the influence of proinflammatory mediators on LEC capillaries. In this work, we have screened and identified proinflammatory mediators that cause regression of LEC tube networks, the most potent of which is TNFα (tumor necrosis factor alpha), followed by IFNγ (interferon gamma) and thrombin. When these mediators were combined, even greater and more rapid lymphatic capillary regression occurred. Surprisingly, IL-1β (interleukin-1 beta), one of the most potent and pathologic cytokines known, had no regressive effect on these tube networks. Finally, we identified new pharmacological drug combinations capable of rescuing LEC capillaries from regression in response to the potent combination of TNFα, IFNγ, and thrombin. We speculate that protecting lymphatic capillaries from regression may be an important step toward mitigating a wide variety of acute and chronic disease states, as lymphatics are believed to clear both proinflammatory cells and mediators from inflamed and damaged tissue beds. Overall, these studies identify key proinflammatory mediators, including TNFα, IFNγ, and thrombin, that induce regression of LEC tube networks, as well as identify potential therapeutic agents to diminish LEC capillary regression responses.

Dieckol Decreases Caloric Intake and Attenuates Nonalcoholic Fatty Liver Disease and Hepatic Lymphatic Vessel Dysfunction in High-Fat-Diet-Fed Mice

Increased inflammation is the main pathophysiology of nonalcoholic fatty liver disease (NAFLD). Inflammation affects lymphatic vessel function that contributes to the removal of immune cells or macromolecules. Dysfunctional lymphatic vessels with decreased permeability are present in NAFLD. High-fat diet (HFD) is known to increase body weight, food intake, and inflammation in the liver. Previously, it was reported that Ecklonia cava extracts (ECE) decreased food intake or weight gain, and low-calorie diet and weight loss is known as a treatment for NAFLD. In this study, the effects of ECE and dieckol (DK)-which is one component of ECE that decreases inflammation and increases lymphangiogenesis and lymphatic drainage by controlling lymphatic permeability in high-fat diet (HFD)-fed mice-on weight gain and food intake were investigated. ECE and DK decreased weight gain and food intake in the HFD-fed mice. NAFLD activities such as steatosis, lobular inflammation, and ballooning were increased by HFD and attenuated by ECE and DK. The expression of inflammatory cytokines such as IL-6 and TNF-α and infiltration of M1 macrophages were increased by HFD, and they were decreased by ECE or DK. The signaling pathways of lymphangiogenesis, VEGFR-3, PI3K/pAKT, and pERK were decreased by HFD, and they were restored by either ECE or DK. The expression of VE-cadherin (which represents lymphatic junctional function) was increased by HFD, although it was restored by either ECE or DK. In conclusion, ECE and DK attenuated NAFLD by decreasing weight gain and food intake, decreasing inflammation, and increasing lymphangiogenesis, as well as modulating lymphatic vessel permeability.

Lymphatic Contractile Function: A Comprehensive Review of Drug Effects and Potential Clinical Application

BACKGROUND

The lymphatic system and the cardiovascular system work together to maintain body fluid homeostasis. Despite that, the lymphatic system has been relatively neglected as a potential drug target and a source of adverse effects from cardiovascular drugs. Like the heart, the lymphatic vessels undergo phasic contractions to promote lymph flow against a pressure gradient. Dysfunction or failure of the lymphatic pump results in fluid imbalance and tissue oedema. While this can due to drug effects, it is also a feature of breast cancer-associated lymphoedema, chronic venous insufficiency, congestive heart failure and acute systemic inflammation. There are currently no specific drug treatments for lymphatic pump dysfunction in clinical use despite the wealth of data from pre-clinical studies.

AIM

To identify (1) drugs with direct effects on lymphatic tonic and phasic contractions with potential for clinical application, and (2) drugs in current clinical use that have a positive or negative side effect on lymphatic function.

METHODS

We comprehensively reviewed all studies that tested the direct effect of a drug on the contractile function of lymphatic vessels.

RESULTS

Of the 208 drugs identified from 193 studies, about a quarter had only stimulatory effects on lymphatic tone, contraction frequency and/or contraction amplitude. Of FDA-approved drugs, there were 14 that increased lymphatic phasic contractile function. The most frequently used class of drug with inhibitory effects on lymphatic pump function were the calcium channels blockers.

CONCLUSION

This review highlights the opportunity for specific drug treatments of lymphatic dysfunction in various disease states and for avoiding adverse drug effects on lymphatic contractile function.

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.

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.

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.

Efficient aortic lymphatic drainage is necessary for atherosclerosis regression induced by ezetimibe

A functional lymphatic vasculature is essential for tissue fluid homeostasis, immunity, and lipid clearance. Although atherosclerosis has been linked to adventitial lymphangiogenesis, the functionality of aortic lymphatic vessels draining the diseased aorta has never been assessed and the role of lymphatic drainage in atherogenesis is not well understood. We develop a method to measure aortic lymphatic transport of macromolecules and show that it is impaired during atherosclerosis progression, whereas it is ameliorated during lesion regression induced by ezetimibe. Disruption of aortic lymph flow by lymphatic ligation promotes adventitial inflammation and development of atherosclerotic plaque in hypercholesterolemic mice and inhibits ezetimibe-induced atherosclerosis regression. Thus, progression of atherosclerotic plaques may result not only from increased entry of atherogenic factors into the arterial wall but also from reduced lymphatic clearance of these factors as a result of aortic lymph stasis. Our findings suggest that promoting lymphatic drainage might be effective for treating atherosclerosis.

Renal lymphatic vessel dynamics

Similar to other organs, renal lymphatics remove excess fluid, solutes, and macromolecules from the renal interstitium. Given the kidney's unique role in maintaining body fluid homeostasis, renal lymphatics may be critical in this process. However, little is known regarding the pathways involved in renal lymphatic vessel function, and there are no studies on the effects of drugs targeting impaired interstitial clearance, such as diuretics. Using pressure myography, we showed that renal lymphatic collecting vessels are sensitive to changes in transmural pressure and have an optimal range of effective pumping. In addition, they are responsive to vasoactive factors known to regulate tone in other lymphatic vessels including prostaglandin E₂ and nitric oxide, and their spontaneous contractility requires Ca²⁺ and Cl^-. We also demonstrated that Na⁺-K⁺-2Cl^- cotransporter Nkcc1, but not Nkcc2, is expressed in extrarenal lymphatic vessels. Furosemide, a loop diuretic that inhibits Na⁺-K⁺-2Cl^- cotransporters, induced a dose-dependent dilation in lymphatic vessels and decreased the magnitude and frequency of spontaneous contractions, thereby reducing the ability of these vessels to propel lymph. Ethacrynic acid, another loop diuretic, had no effect on vessel tone. These data represent a significant step forward in our understanding of the mechanisms underlying renal lymphatic vessel function and highlight potential off-target effects of furosemide that may exacerbate fluid accumulation in edema-forming conditions.

Endogenous Specialized Proresolving Mediator Profiles in a Novel Experimental Model of Lymphatic Obstruction and Intestinal Inflammation in African Green Monkeys

Changes in the intestinal lymphatic vascular system, such as lymphatic obstruction, are characteristic features of inflammatory bowel diseases. The lymphatic vasculature forms a conduit to enable resolution of inflammation; this process is driven by specialized endogenous proresolving mediators (SPMs). To evaluate contributions of lymphatic obstruction to intestinal inflammation and to study profiles of SPMs, we generated a novel animal model of lymphatic obstruction using African green monkeys. Follow-up studies were performed at 7, 21, and 61 days. Inflammation was determined by histology. Luminex assays were performed to evaluate chemokine and cytokine levels. In addition, lipid mediator metabololipidomic profiling was performed to identify SPMs. After 7 days, lymphatic obstruction resulted in a localized inflammatory state, paralleled by an increase in inflammatory chemokines and cytokines, which were found to be up-regulated after 7 days but returned to baseline after 21 and 61 days. At the same time, a distinct pattern of SPMs was profiled, with an increase for D-series resolvins, protectins, maresins, and lipoxins at 61 days. These results indicate that intestinal lymphatic obstruction can lead to an acute inflammatory state, accompanied by an increase in proinflammatory mediators, followed by a phase of resolution, paralleled by an increase and decrease of respective SPMs.

Mesenteric Lymphatic Vessel Density Is Associated with Disease Behavior and Postoperative Recurrence in Crohn's Disease

PURPOSE

The aims of the present study were to examine the density of lymphatic vessels in the mesentery and to assess the predictive value of the mesenteric lymphatic vessel density for postoperative clinical recurrence.

METHODS

Ileocolonic resection specimens were obtained from 53 patients with Crohn's disease and 10 non-inflammatory bowel disease control subjects. Mesentery adipose tissues adjacent to the bowel wall were used for the histological quantification of lymphatic vessels using immunohistochemistry with the D2-40 antibody. The relationships between lymphatic vessel density and disease behavior, the presence of granulomas, the presence of creeping fat, and postoperative clinical recurrence were assessed.

RESULTS

Median lymphatic vessel density in the mesentery adjacent to inflamed or non-inflamed intestine was lower in control subjects than in Crohn's disease patients (2.13‰; interquartile range [IQR], 1.83-2.61; 8.34‰; IQR, 6.39-10.22; 4.43‰; IQR, 3.32-5.78; P ˂ 0.001). Increased mesenteric lymphatic vessel density was significantly associated with stricturing behavior, the presence of intestinal granulomas, the presence of creeping fat, and bowel thickness. Interestingly, patients with disease recurrence had an increased mesenteric lymphatic vessel density of the proximal mesenteric margin at the time of resection compared with those who did not have disease recurrence (6.23‰; IQR, 5.43-6.75 vs. 3.28‰; IQR, 2.93-4.29; P ˂ 0.001).

CONCLUSIONS

In addition to its correlation with disease behavior, bowel thickness, and the presence of intestinal granulomas and creeping fat, increased mesenteric lymphatic vessel density in the proximal margin is predictive of early clinical recurrence after surgery in patients with Crohn's disease.

IL-1β reduces cardiac lymphatic muscle contraction via COX-2 and PGE2 induction: Potential role in myocarditis

The role of lymphatic vessels in myocarditis is largely unknown, while it has been shown to play a key role in other inflammatory diseases. We aimed to investigate the role of lymphatic vessels in myocarditis using in vivo model induced with Theiler's murine encephalomyelitis virus (TMEV) and in vitro model with rat cardiac lymphatic muscle cells (RCLMC). In the TMEV model, we found that upregulation of a set of inflammatory mediator genes, including interleukin (IL)-1β, tumor necrosis factor (TNF)-αand COX-2 were associated with disease activity. Thus, using in vitro collagen gel contraction assays, we decided to clarify the role(s) of these mediators by testing contractility of RCLMC in response to IL-1β and TNF-α individually and in combination, in the presence or absence of: IL-1 receptor antagonist (Anakinra); cyclooxygenase (COX) inhibitors inhibitors (TFAP, diclofenac and DuP-697). IL-1β impaired RCLMC contractility dose-dependently, while co-incubation with both IL-1β and TNF-α exhibited synergistic effects in decreasing RCLMC contractility with increased COX-2 expression. Anakinra maintained RCLMC contractility; Anakinra blocked the mobilization of COX-2 induced by IL-1β with or without TNF-α. COX-2 inhibition blocked the IL-1β-mediated decrease in RCLMC contractility. Mechanistically, we found that IL-1β increased prostaglandin (PG) E₂ release dose-dependently, while Anakinra blocked IL-1β mediated PGE₂ release. Using prostaglandin E receptor 4 (EP4) receptor antagonist, we demonstrated that EP4 receptor blockade maintained RCLMC contractility following IL-1β exposure. Our results indicate that IL-1β reduces RCLMC contractility via COX-2/PGE₂ signaling with synergistic cooperation by TNF-α. These pathways may help provoke inflammatory mediator accumulation within the heart, driving progression from acute myocarditis into dilated cardiomyopathy.

Obstructive Lymphangitis Precedes Colitis in Murine Norovirus-Infected Stat1-Deficient Mice

Murine norovirus (MNV) is an RNA virus that can prove lethal in mice with impaired innate immunity. We found that MNV-4 infection of Stat1-/- mice was not lethal, but produced a 100% penetrant, previously undescribed lymphatic phenotype characterized by chronic-active lymphangitis with hepatitis, splenitis, and chronic cecal and colonic inflammation. Lesion pathogenesis progressed from early ileal enteritis and regional dilated lymphatics to lymphangitis, granulomatous changes in the liver and spleen, and, ultimately, typhlocolitis. Lesion development was neither affected by antibiotics nor reproduced by infection with another enteric RNA virus, rotavirus. MNV-4 infection in Stat1-/- mice decreased expression of vascular endothelial growth factor (Vegf) receptor 3, Vegf-c, and Vegf-d and increased interferon (Ifn)-γ, tumor necrosis factor-α, and inducible nitric oxide synthase. However, anti-IFN-γ and anti-tumor necrosis factor-α antibody treatment did not attenuate the histologic lesions. Studies in Ifnαβγr-/- mice suggested that canonical signaling via interferon receptors did not cause MNV-4-induced disease. Infected Stat1-/- mice had increased STAT3 phosphorylation and expressed many STAT3-regulated genes, consistent with our findings of increased myeloid cell subsets and serum granulocyte colony-stimulating factor, which are also associated with increased STAT3 activity. In conclusion, in Stat1-/- mice, MNV-4 induces lymphatic lesions similar to those seen in Crohn disease as well as hepatitis, splenitis, and typhlocolitis. MNV-4-infected Stat1-/- mice may be a useful model to study mechanistic associations between viral infections, lymphatic dysfunction, and intestinal inflammation in a genetically susceptible host.