Inflammatory manifestations of experimental lymphatic insufficiency

Fibrosis and secondary lymphedema: chicken or egg?

Secondary lymphedema is a common complication of cancer treatment resulting in progressive fibroadipose tissue deposition, increased risk of infections, and, in rare cases, secondary malignancies. Until recently, the pathophysiology of secondary lymphedema was thought to be related to impaired collateral lymphatic formation after surgical injury. However, more recent studies have shown that chronic inflammation-induced fibrosis plays a key role in the pathophysiology of this disease. In this review, we will discuss the evidence supporting this hypothesis and summarize recent publications demonstrating that lymphatic injury activates chronic immune responses that promote fibrosis and lymphatic leakiness, decrease collecting lymphatic pumping, and impair collateral lymphatic formation. We will review how chronic mixed T-helper cell inflammatory reactions regulate this process and how this response may be used to design novel therapies for lymphedema.

T helper 2 differentiation is necessary for development of lymphedema

T cells infiltrating lymphedematous tissues have a mixed T helper 1 (Th1) and Th2 differentiation profile. Treatment with neutralizing antibodies targeting cytokines that promote Th2 differentiation (interleukin 4 [IL-4] and IL-13) decreases the severity of lymphedema in preclinical models, suggesting that Th2 cells play a key role in the pathology of this disease. However, these previous studies do not address the contribution of Th1 cells and it remains unknown if IL-4 and IL-3 blockade acts primarily on T cells or decreases the pathological changes of lymphedema by other mechanisms. Therefore, this study sought to analyze the effect of lymphatic injury in transgenic mice with mutations that cause defects in Th1 and Th2 cell generation (T-bet knockout or T-betKO and STAT6 knockout or STAT6KO mice, respectively). Using both the mouse tail and popliteal lymph node dissection models of lymphedema, we show that Th2-deficient (STAT6KO) mice are protected from developing lymphedema, have decreased fibrosis, increased collateral vessel formation, and preserved collecting lymphatic vessel pumping function. In contrast, mice with defective Th1 cell generation (T-betKO) develop disease with the same severity as wild-type controls. Taken together, our results suggest that Th2 differentiation is necessary for development of lymphedema following lymphatic injury and that Th1 differentiation does not significantly contribute to the pathology of the disease. Such findings are important as immunotherapy directed at Th2 cells has been found to be effective in well-studied Th2-mediated diseases such as asthma and atopic dermatitis and may therefore be similarly useful for lymphedema management.

Cancer-associated secondary lymphoedema

Lymphoedema is an oedematous condition with a specific and complex tissue biology. In the clinical context of cancer, the pathogenesis of lymphoedema ensues most typically from the modalities employed to stage and treat the cancer (in particular, surgery and radiotherapy). Despite advances in cancer treatment, lifelong lymphoedema (limb swelling and the accompanying chronic inflammatory processes) affects approximately one in seven individuals treated for cancer, although estimates of lymphoedema prevalence following cancer treatment vary widely depending upon the diagnostic criteria used and the duration of follow-up. The natural history of cancer-associated lymphoedema is defined by increasing limb girth, fibrosis, inflammation, abnormal fat deposition and eventual marked cutaneous pathology, which also increases the risk of recurrent skin infections. Lymphoedema can substantially affect the daily quality of life of patients, as, in addition to aesthetic concerns, it can cause discomfort and affect the ability to carry out daily tasks. Clinical diagnosis is dependent on comparison of the affected region with the equivalent region on the unaffected side and, if available, with pre-surgical measurements. Surveillance is indicated in this high-risk population to facilitate disease detection at the early stages, when therapeutic interventions are most effective. Treatment modalities include conservative physical strategies that feature complex decongestive therapy (including compression garments) and intermittent pneumatic compression, as well as an emerging spectrum of surgical interventions, including liposuction for late-stage disease. The future application of pharmacological and microsurgical therapeutics for cancer-associated lymphoedema holds great promise.

Prioritization of genes involved in endothelial cell apoptosis by their implication in lymphedema using an analysis of associative gene networks with ANDSystem

BACKGROUND

Currently, more than 150 million people worldwide suffer from lymphedema. It is a chronic progressive disease characterized by high-protein edema of various parts of the body due to defects in lymphatic drainage. Molecular-genetic mechanisms of the disease are still poorly understood. Beginning of a clinical manifestation of primary lymphedema in middle age and the development of secondary lymphedema after treatment of breast cancer can be genetically determined. Disruption of endothelial cell apoptosis can be considered as one of the factors contributing to the development of lymphedema. However, a study of the relationship between genes associated with lymphedema and genes involved in endothelial apoptosis, in the associative gene network was not previously conducted.

METHODS

In the current work, we used well-known methods (ToppGene and Endeavour), as well as methods previously developed by us, to prioritize genes involved in endothelial apoptosis and to find potential participants of molecular-genetic mechanisms of lymphedema among them. Original methods of prioritization took into account the overrepresented Gene Ontology biological processes, the centrality of vertices in the associative gene network, describing the interactions of endothelial apoptosis genes with genes associated with lymphedema, and the association of the analyzed genes with diseases that are comorbid to lymphedema.

RESULTS

An assessment of the quality of prioritization was performed using criteria, which involved an analysis of the enrichment of the top-most priority genes by genes, which are known to have simultaneous interactions with lymphedema and endothelial cell apoptosis, as well as by genes differentially expressed in murine model of lymphedema. In particular, among genes involved in endothelial apoptosis, KDR, TNF, TEK, BMPR2, SERPINE1, IL10, CD40LG, CCL2, FASLG and ABL1 had the highest priority. The identified priority genes can be considered as candidates for genotyping in the studies involving the search for associations with lymphedema.

CONCLUSIONS

Analysis of interactions of these genes in the associative gene network of lymphedema can improve understanding of mechanisms of interaction between endothelial apoptosis and lymphangiogenesis, and shed light on the role of disturbance of these processes in the development of edema, chronic inflammation and connective tissue transformation during the progression of the disease.

Small Numbers of CD4+ T Cells Can Induce Development of Lymphedema

BACKGROUND

CD4 T cells have been implicated in the pathology of lymphedema. Interestingly, however, there have been case reports of lymphedema development in patients with low levels of CD4 T cells because of immunosuppression. In this study, the authors sought to delineate the effect of relative CD4 T-cell deficiency on the development of lymphedema in a mouse model.

METHODS

A mouse model of relative CD4 T-cell deficiency was created through lethal total body irradiation of wild-type mice that then underwent bone marrow transplantation with progenitors harvested from CD4 knockout mice (wild-type/CD4 knockout). Irradiated CD4 knockout mice reconstituted with wild-type mouse-derived progenitors (CD4 knockout/wild-type), and unirradiated CD4 knockout and wild-type mice were used as controls. All mice underwent tail skin and lymphatic excision to induce lymphedema, and analysis was performed 6 weeks later.

RESULTS

Wild-type/CD4 knockout chimeras were not protected from developing lymphedema. Despite a global deficit in CD4 T cells, these mice had swelling, fibrosis, inflammation, and impaired lymphatic transport function indistinguishable from that in wild-type and CD4 knockout/wild-type mice. In contrast, unirradiated CD4 knockout mice had no features of lymphedema after lymphatic injury.

CONCLUSIONS

Relatively small numbers of bone marrow and peripheral CD4 T cells are sufficient to induce the development of lymphedema. These findings suggest that lymphatic injury results in expansion of CD4 T-cell populations in lymphedematous tissues.

Lymphatic Vessel Network Structure and Physiology

The lymphatic system is comprised of a network of vessels interrelated with lymphoid tissue, which has the holistic function to maintain the local physiologic environment for every cell in all tissues of the body. The lymphatic system maintains extracellular fluid homeostasis favorable for optimal tissue function, removing substances that arise due to metabolism or cell death, and optimizing immunity against bacteria, viruses, parasites, and other antigens. This article provides a comprehensive review of important findings over the past century along with recent advances in the understanding of the anatomy and physiology of lymphatic vessels, including tissue/organ specificity, development, mechanisms of lymph formation and transport, lymphangiogenesis, and the roles of lymphatics in disease. © 2019 American Physiological Society. Compr Physiol 9:207-299, 2019.

Biomarkers Associated with Lymphedema and Fibrosis in Patients with Cancer of the Head and Neck

BACKGROUND

This study examined interrelationships of selected interleukins (ILs), tumor growth factors, matrix metalloproteinases (MMPs), and C-reactive protein, interferon-gamma (IFN-γ), and tumor necrosis factor α (TNF-α) with lymphedema/fibrosis in patients with head and neck cancer (HNC).

METHODS AND RESULTS

Patients newly diagnosed with ≥Stage II HNC (N = 100) were assessed for external/internal lymphedema and/or fibrosis before treatment, end-of-treatment, and at regularly established intervals through 72 weeks posttreatment and blood was drawn. Data from 83 patients were analyzed. Group-based trajectory modeling generated patient groups with similar longitudinal biomarker and lymphedema-fibrosis trajectories. Area-under-the-curve (AUC) values were also generated for each biomarker and severity of lymphedema-fibrosis. Associations among and between biomarkers and lymphedema-fibrosis trajectories and AUCs were tested (log-likelihood chi-square, correlations). The strongest evidence for the association of biomarkers with the overall and trajectory patterns and severity of lymphedema-fibrosis was observed for IL-6, IL-1β, TNF-α, TGF-β1, and MMP-9 (all p < 0.05). Convergence of joint trajectory patterns and AUC were observed with IL-6 with all lymphedema-fibrosis trajectories and internal lymphedema AUC. IL-1β trajectories converged with external lymphedema trajectories and all lymphedema-fibrosis AUCs. TNF-α and TGF-β1 converged most strongly with fibrosis in terms of trajectory patterns. However TNF-α demonstrated stronger association with lymphedema-fibrosis AUC (fibrosis: rs = 0.49). MMP-9 demonstrated convergence with lymphedema-fibrosis AUCs (lymphedema: 0.43-0.42; fibrosis: 0.35).

CONCLUSION

Systemic levels of selected mediators of proinflammatory processes track with acute and chronic clinical phenotypes of lymphedema/fibrosis in HNC patients suggesting their potential role in the pathogenesis of these conditions.

Pilot studies demonstrate the potential benefits of antiinflammatory therapy in human lymphedema

BACKGROUND

Lymphedema is a common condition affecting millions around the world that still lacks approved medical therapy. Because ketoprofen, an NSAID, has been therapeutic in experimental lymphedema, we evaluated its efficacy in humans.

METHODS

We first performed an exploratory open-label trial. Patients with either primary or secondary lymphedema received ketoprofen 75 mg by mouth 3 times daily for 4 months. Subjects were evaluated for changes in histopathology, with skin thickness, limb volume, and tissue bioimpedance changes serving as secondary endpoints. Based on our encouraging findings, we next conducted a placebo-controlled trial, with the primary outcome defined as a change in skin thickness, as measured by skin calipers. Secondary endpoints for this second study included histopathology, limb volume, bioimpedance, and systemic inflammatory mediators.

RESULTS

We enrolled 21 lymphedema patients in the open-label trial, from November 2010 to July 2011. Histopathology and skin thickness were significantly improved at 4 months compared with baseline. In the follow-up, double-blind, placebo-controlled trial, we enrolled 34 patients from August 2011 to October 2015, with 16 ketoprofen recipients and 18 placebo-treated subjects. No serious adverse events occurred. The ketoprofen recipients demonstrated reduced skin thickness, as well as improved composite measures of histopathology and decreased plasma granulocyte CSF (G-CSF) expression.

CONCLUSION

These 2 exploratory studies together support the utility of targeted antiinflammatory therapy with ketoprofen in patients with lymphedema. Our results highlight the promise of such approaches to help restore a failing lymphatic circulation.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02257970.

CD4+ T cells are activated in regional lymph nodes and migrate to skin to initiate lymphedema

T cell-mediated responses have been implicated in the development of fibrosis, impaired lymphangiogenesis, and lymphatic dysfunction in secondary lymphedema. Here we show that CD4+ T cells are necessary for lymphedema pathogenesis by utilizing adoptive transfer techniques in CD4 knockout mice that have undergone tail skin and lymphatic excision or popliteal lymph node dissection. We also demonstrate that T cell activation following lymphatic injury occurs in regional skin-draining lymph nodes after interaction with antigen-presenting cells such as dendritic cells. CD4+ T cell activation is associated with differentiation into a mixed T helper type 1 and 2 phenotype, as well as upregulation of adhesion molecules and chemokines that promote migration to the skin. Most importantly, we find that blocking T cell release from lymph nodes using a sphingosine-1-phosphate receptor modulator prevents lymphedema, suggesting that this approach may have clinical utility.

Near-Infrared Fluorescence Imaging Directly Visualizes Lymphatic Drainage Pathways and Connections between Superficial and Deep Lymphatic Systems in the Mouse Hindlimb

Since lymphedema rarely develops in the mouse hindlimb, the underlying mechanisms remain unclear. We herein investigated the resolution of chronic hindlimb lymphedema in mice using a Near-Infrared Fluorescence (NIRF) imaging system. Nineteen 7–28-week-old BALB/c male and female mice were injected with two dyes for lymphography and dissection. Lymphadenectomy was performed on six male mice to completely obstruct lymph flow in the hindlimb. Edematous changes in both hindlimbs were compared until 60 days after surgery. The NIRF imaging system detected three lymphatic collecting systems in the mouse hindlimb: superficial lateral, superficial medial, and deep medial. It also showed connections between the superficial and deep lymphatic systems in the inguinal region. Lymphadenectomy of the iliac, inguinal, and popliteal lymph nodes caused edematous changes. However, lymph flow in these operated areas restarted within 60 days and the severity of lymphedema appeared to be low. NIRF imaging showed that the deep medial system and a connection between the superficial and deep lymphatic systems in the inguinal region drain lymph from the hindlimb. This is the one reasons why lymphedema does not develop in the mouse hindlimb. The stable obstruction of lymph flow in these three systems is desired to develop chronic lymphedema.

Leukotriene B4 antagonism ameliorates experimental lymphedema

Acquired lymphedema is a cancer sequela and a global health problem currently lacking pharmacologic therapy. We have previously demonstrated that ketoprofen, an anti-inflammatory agent with dual 5-lipoxygenase and cyclooxygenase inhibitory properties, effectively reverses histopathology in experimental lymphedema. We show that the therapeutic benefit of ketoprofen is specifically attributable to its inhibition of the 5-lipoxygenase metabolite leukotriene B₄ (LTB₄). LTB₄ antagonism reversed edema, improved lymphatic function, and restored lymphatic architecture in the murine tail model of lymphedema. In vitro, LTB₄ was functionally bimodal: Lower LTB₄ concentrations promoted human lymphatic endothelial cell sprouting and growth, but higher concentrations inhibited lymphangiogenesis and induced apoptosis. During lymphedema progression, lymphatic fluid LTB₄ concentrations rose from initial prolymphangiogenic concentrations into an antilymphangiogenic range. LTB₄ biosynthesis was similarly elevated in lymphedema patients. Low concentrations of LTB₄ stimulated, whereas high concentrations of LTB₄ inhibited, vascular endothelial growth factor receptor 3 and Notch pathways in cultured human lymphatic endothelial cells. Lymphatic-specific Notch1^-/- mice were refractory to the beneficial effects of LTB₄ antagonism, suggesting that LTB₄ suppression of Notch signaling is an important mechanism in disease maintenance. In summary, we found that LTB₄ was harmful to lymphatic repair at the concentrations observed in established disease. Our findings suggest that LTB₄ is a promising drug target for the treatment of acquired lymphedema.

Translation and adaptation to Brazilian Portuguese of the Lymphedema Rating Scale in Head and Neck Cancer

Objective

Translate to brazilian portuguese, culturally adapt and test the rating and classification scales of cervicofacial lymphedema of the MD Anderson Cancer Center Head and Neck Lymphedema Protocol (MDACC HNL) in patients undergoing treatment for head and neck cancer.

Methods

The process followed international guidelines and translation stages by two head and neck surgeons, and back translation independently by two native Americans. The test of final version was based on the evaluation of 18 patients by one speech pathologist and one physical therapist who applied the scales in Portuguese.

Results

The translation of the three scales was carried out independently and the translators reached a consensus for the final version. Minor modifications were made by translating two terms into the Assessment of the Face. Versions of back-translation were similar to each other. The instrument was successfully applied to patients independently.

Conclusion

The translation and cultural adaptation of the assessment and rating scale of the cervicofacial lymphedema of the MD Anderson Cancer Center Head and Neck Lymphedema Protocol to the Brazilian Portuguese were successful.

Lymphatic Dysfunction, Leukotrienes, and Lymphedema

The lymphatic system is essential for the maintenance of tissue fluid homeostasis, gastrointestinal lipid absorption, and immune trafficking. Whereas lymphatic regeneration occurs physiologically in wound healing and tissue repair, pathological lymphangiogenesis has been implicated in a number of chronic diseases such as lymphedema, atherosclerosis, and cancer. Insight into the regulatory mechanisms of lymphangiogenesis and the manner in which uncontrolled inflammation promotes lymphatic dysfunction is urgently needed to guide the development of novel therapeutics: These would be designed to reverse lymphatic dysfunction, either primary or acquired. Recent investigation has demonstrated the mechanistic role of leukotriene B₄ (LTB₄) in the molecular pathogenesis of lymphedema. LTB₄, a product of the innate immune response, is a constituent of the eicosanoid inflammatory mediator family of molecules that promote both physiological and pathological inflammation. Here we provide an overview of lymphatic development, the pathophysiology of lymphedema, and the role of leukotrienes in lymphedema pathogenesis.

Modified Mouse Models of Chronic Secondary Lymphedema: Tail and Hind Limb Models

BACKGROUND

Postsurgical secondary lymphedema is usually a progressive and lifelong condition lacking any curative treatment. The aim of this study was to develop new, simple surgical mouse models of chronic lymphedema, better simulating chronic nature of human postsurgical lymphedema.

METHODS

Two experimental mouse models of secondary lymphedema were created surgically without radiation by modifications of the previously described methods: the tail model and the hind limb model. Lymphedema formation was clinically assessed and quantitatively evaluated by measuring circumferences and limb volumes. Postmortem specimens were assessed histologically to examine the efficacy of the models.

RESULTS

In the tail models, although a substantial frequency of tail necrosis (30.0%) was noted and the increase in circumference was maintained for only limited times postoperatively depending on the particular tail model, the overall success rate was 65.0%. In the mouse hind limb model, the overall success rate was 88.9%, and the increased circumference and limb volume were maintained over the entire study period of 8 weeks. The overall success rate of the mouse hind limb model was significantly higher than that of the mouse tail model(s).

CONCLUSIONS

We have successfully established modified mouse tail and hind limb lymphedema models via only surgical techniques without radiation, which have characteristics of chronic secondary lymphedema. The mouse hind limb model has a higher success rate than the mouse tail model and has advantages of having the healthy contralateral hind limbs as an internal control.

Topical tacrolimus for the treatment of secondary lymphedema

Secondary lymphedema, a life-long complication of cancer treatment, currently has no cure. Lymphedema patients have decreased quality of life and recurrent infections with treatments limited to palliative measures. Accumulating evidence indicates that T cells play a key role in the pathology of lymphedema by promoting tissue fibrosis and inhibiting lymphangiogenesis. Here using mouse models, we show that topical therapy with tacrolimus, an anti-T-cell immunosuppressive drug, is highly effective in preventing lymphedema development and treating established lymphedema. This intervention markedly decreases swelling, T-cell infiltration and tissue fibrosis while significantly increasing formation of lymphatic collaterals with minimal systemic absorption. Animals treated with tacrolimus have markedly improved lymphatic function with increased collecting vessel contraction frequency and decreased dermal backflow. These results have profound implications for lymphedema treatment as topical tacrolimus is FDA-approved for other chronic skin conditions and has an established record of safety and tolerability.

Secondary lymphedema is a debilitating disease with no cure. Here the authors show that topical application of an FDA-approved anti-T cell drug tacrolimus potently prevents development and alleviates pathologic changes of established lymphedema in mice, suggesting a new treatment for human patients.

Inflammatory Manifestations of Lymphedema

Lymphedema results from lymphatic insufficiency leading to a progressive inflammatory process that ultimately manifests as discomfort, recurrent infections, and, at times, secondary malignancy. Collectively, these morbidities contribute to an overall poor quality of life. Although there have been recent advances in microsurgical interventions, a conservative palliative approach remains the mainstay of treatment for this disabling disease. The absence of a cure is due to an incomplete understanding of the pathophysiological changes that result in lymphedema. A histological hallmark of lymphedema is inflammatory cell infiltration and recent studies with animal models and clinical biopsy specimens have suggested that this response plays a key role in the pathology of the disease. The purpose of this report is to provide an overview of the ongoing research in and the current understanding of the inflammatory manifestations of lymphedema.

Therapeutic effects of hyaluronidase on acquired lymphedema using a newly developed mouse limb model

Acquired lymphedema is one of the most dreaded side effects of cancer treatment, such as surgical treatment or irradiation. However, due to the lack of appropriate animal models, there is no effective therapeutic method to cure acquired lymphedema. To develop a reproducible acquired lymphedema animal model, we devised a mouse hind limb model by removing a superficial inguinal lymph node, a popliteal lymph node, a deep inguinal lymph node, and the femoral lymphatic vessel. We measured the volume of lymphedematous leg and observed the change in level of hyaluronic acid (HA) and lymphangiogenic factors after injecting hyaluronidase. Our model showed the distinguishable swelling and the reliable symptoms compared to previously reported models. In the lymphedematous regions of our model, we confirmed that HA, a major component of extracellular matrix, accumulated to higher levels than in a normal mouse. This lymphedema volume was rapidly reduced by treating hyaluronidase. Following hyaluronidase injection, the lymphedematous region of our model resembled a normal hind limb. Our findings indicated that hyaluronidase promoted lymphangiogenesis on the lymphedematous limb. Based on hyaluronidase treatment in the lymphedematous region, this could potentially be a new therapeutic approach for acquired lymphedema mediated through the modification of the size of HA fragments. Impact statement In this manuscript, the essence of the work described in this manuscript involves the development of (1) a mouse limb model showing acquired lymphedema and (2) a potent therapeutic treatment using hyaluronidase to remedy acquired lymphedema in our model. In order to develop a reproducible acquired lymphedema animal model that reflects the most common symptoms experienced by lymphedema patients, we devised a mouse hind limb model by removing lymph nodes and lymphatics. Our model showed the distinguishable swelling and the reliable symptoms compared to previously reported models. In the lymphedematous regions of our model, we confirmed that hyaluronic acid (HA) accumulated to higher levels than in a normal mouse. This lymphedema volume was rapidly reduced by treating the lymphedematous leg with hyaluronidase, which also degraded high molecular weight HA to low molecular weight HA. Immunohistochemical analysis, quantitative real-time PCR analysis and lymphangioscintigraphy showed that hyaluronidase enhanced lymphangiogenesis in the lymphedematous limb.

Obesity-induced lymphatic dysfunction is reversible with weight loss

KEY POINTS

Obesity induces lymphatic leakiness, decreases initial lymphatic vessel density, impairs collecting vessel pumping and decreases transport of macromolecules. Obesity results in perilymphatic inducible nitric oxide synthase (iNOS) expression and accumulation of T cells and macrophages. Deleterious effects of obesity on the lymphatic system correlate with weight gain. Weight loss restores lymphatic function in obese animals and decreases perilymphatic iNOS and inflammatory cell accumulation.

ABSTRACT

Although clinical and experimental studies have shown that obesity results in lymphatic dysfunction, it remains unknown whether these changes are permanent or reversible with weight loss. In the current study, we used a mouse model of diet-induced obesity to identify putative cellular mechanisms of obesity-induced lymphatic dysfunction, determine whether there is a correlation between these deleterious effects and increasing weight gain, and finally examine whether lymphatic dysfunction is reversible with diet-induced weight loss. We report that obesity is negatively correlated with cutaneous lymphatic collecting vessel pumping rate (r = -0.9812, P < 0.0005) and initial lymphatic vessel density (r = -0.9449, P < 0.005). In addition, we show a significant positive correlation between weight gain and accumulation of perilymphatic inflammatory cells (r = 0.9872, P < 0.0005) and expression of inducible nitric oxide synthase (iNOS; r = 0.9986, P < 0.0001). Weight loss resulting from conversion to a normal chow diet for 8 weeks resulted in more than a 25% decrease in body weight and normalized cutaneous lymphatic collecting vessel pumping rate, lymphatic vessel density, lymphatic leakiness, and lymphatic macromolecule clearance (all P < 0.05). In addition, weight loss markedly decreased perilymphatic inflammation and iNOS expression. Taken together, our findings show that obesity is linearly correlated with lymphatic dysfunction, perilymphatic inflammation and iNOS expression, and that weight loss via dietary modification effectively reverses these deleterious effects.

Regulatory T cell transfer ameliorates lymphedema and promotes lymphatic vessel function

Secondary lymphedema is a common postcancer treatment complication, but the underlying pathological processes are poorly understood and no curative treatment exists. To investigate lymphedema pathomechanisms, a top-down approach was applied, using genomic data and validating the role of a single target. RNA sequencing of lymphedematous mouse skin indicated upregulation of many T cell-related networks, and indeed depletion of CD4⁺ cells attenuated lymphedema. The significant upregulation of Foxp3, a transcription factor specifically expressed by regulatory T cells (Tregs), along with other Treg-related genes, implied a potential role of Tregs in lymphedema. Indeed, increased infiltration of Tregs was identified in mouse lymphedematous skin and in human lymphedema specimens. To investigate the role of Tregs during disease progression, loss-of-function and gain-of-function studies were performed. Depletion of Tregs in transgenic mice with Tregs expressing the primate diphtheria toxin receptor and green fluorescent protein (Foxp3-DTR-GFP) mice led to exacerbated edema, concomitant with increased infiltration of immune cells and a mixed T_H1/T_H2 cytokine profile. Conversely, expansion of Tregs using IL-2/anti-IL-2 mAb complexes significantly reduced lymphedema development. Therapeutic application of adoptively transferred Tregs upon lymphedema establishment reversed all of the major hallmarks of lymphedema, including edema, inflammation, and fibrosis, and also promoted lymphatic drainage function. Collectively, our results reveal that Treg application constitutes a potential new curative treatment modality for lymphedema.

Diphtheria toxin-mediated ablation of lymphatic endothelial cells results in progressive lymphedema

Development of novel treatments for lymphedema has been limited by the fact that the pathophysiology of this disease is poorly understood. It remains unknown, for example, why limb swelling resulting from surgical injury resolves initially, but recurs in some cases months or years later. Finding answers for these basic questions has been hampered by the lack of adequate animal models. In the current study, we used Cre-lox mice that expressed the human diphtheria toxin receptor (DTR) driven by a lymphatic-specific promoter in order to noninvasively ablate the lymphatic system of the hind limb. Animals treated in this manner developed lymphedema that was indistinguishable from clinical lymphedema temporally, radiographically, and histologically. Using this model and clinical biopsy specimens, we show that the initial resolution of edema after injury is dependent on the formation of collateral capillary lymphatics and that this process is regulated by M2-polarized macrophages. In addition, we show that despite these initial improvements in lymphatic function, persistent accumulation of CD4⁺ cells inhibits lymphangiogenesis and promotes sclerosis of collecting lymphatics, resulting in late onset of edema and fibrosis. Our findings therefore provide strong evidence that inflammatory changes after lymphatic injury play a key role in the pathophysiology of lymphedema.

Sodium selenite and cancer related lymphedema: Biological and pharmacological effects

A significant percentage of cancer patients develop secondary lymphedema after surgery or radiotherapy. The preferred treatment of secondary lymphedema is complex physical therapy. Pharmacotherapy, for example with diuretics, has received little attention, because they were not effective and only offered short-term solutions. Sodium selenite showed promise as a cost-effective, nontoxic anti-inflammatory agent. Treatment with sodium selenite lowers reactive oxygen species (ROS) production, causes a spontaneous reduction in lymphedema volume, increases the efficacy of physical therapy for lymphedema, and reduces the incidence of erysipelas infections in patients with chronic lymphedema. Besides biological effects in reducing excessive production of ROS, sodium selenite also displays various pharmacological effects. So far the exact mechanisms of these pharmacological effects are mostly unknown, but probably include inhibition of adhesion protein expression.

Prominent Lymphatic Vessel Hyperplasia with Progressive Dysfunction and Distinct Immune Cell Infiltration in Lymphedema

Lymphedema is a common complication that occurs after breast cancer treatment in up to 30% of the patients undergoing surgical lymph node excision. It is associated with tissue swelling, fibrosis, increased risk of infection, and impaired wound healing. Despite the pronounced clinical manifestations of the disease, little is known about the morphological and functional characteristics of the lymphatic vasculature during the course of lymphedema progression. We used an experimental murine tail lymphedema model where sustained fluid stasis was generated on disruption of lymphatic flow, resulting in chronic edema formation with fibrosis and adipose tissue deposition. Morphological analysis of the lymphatic vessels revealed a dramatic expansion during the course of the disease, with active proliferation of lymphatic endothelial cells at the early stages of lymphedema. The lymphatic capillaries exhibited progressively impaired tracer filling and retrograde flow near the surgery site, whereas the collecting lymphatic vessels showed a gradually decreasing contraction amplitude with unchanged contraction frequency, leading to lymphatic contraction arrest at the later stages of the disease. Lymphedema onset was associated with pronounced infiltration by immune cells, predominantly Ly6G(+) and CD4(+) cells, which have been linked to impaired lymphatic vessel function.

Local inhibition of elastase reduces EMILIN1 cleavage reactivating lymphatic vessel function in a mouse lymphoedema model

Lymphatic vasculature critically depends on the connections of lymphatic endothelial cells with the extracellular matrix (ECM), which are mediated by anchoring filaments (AFs). The ECM protein EMILIN1 is a component of AFs and is involved in the regulation of lymphatic vessel functions: accordingly, Emilin1^−/− mice display lymphatic vascular morphological alterations, leading to functional defects such as mild lymphoedema, lymph leakage and compromised lymph drainage. In the present study, using a mouse post-surgical tail lymphoedema model, we show that the acute phase of acquired lymphoedema correlates with EMILIN1 degradation due to neutrophil elastase (NE) released by infiltrating neutrophils. As a consequence, the intercellular junctions of lymphatic endothelial cells are weakened and drainage to regional lymph nodes is severely affected. The local administration of sivelestat, a specific NE inhibitor, prevents EMILIN1 degradation and reduces lymphoedema, restoring a normal lymphatic functionality. The finding that, in human secondary lymphoedema samples, we also detected cleaved EMILIN1 with the typical bands of an NE-dependent pattern of fragmentation establishes a rationale for a powerful strategy that targets NE inhibition. In conclusion, the attempts to block EMILIN1 degradation locally represent the basis for a novel ‘ECM’ pharmacological approach to assessing new lymphoedema treatments.

Galectin-1 regulates tissue exit of specific dendritic cell populations

During inflammation, dendritic cells emigrate from inflamed tissue across the lymphatic endothelium into the lymphatic vasculature and travel to regional lymph nodes to initiate immune responses. However, the processes that regulate dendritic cell tissue egress and migration across the lymphatic endothelium are not well defined. The mammalian lectin galectin-1 is highly expressed by vascular endothelial cells in inflamed tissue and has been shown to regulate immune cell tissue entry into inflamed tissue. Here, we show that galectin-1 is also highly expressed by human lymphatic endothelial cells, and deposition of galectin-1 in extracellular matrix selectively regulates migration of specific human dendritic cell subsets. The presence of galectin-1 inhibits migration of immunogenic dendritic cells through the extracellular matrix and across lymphatic endothelial cells, but it has no effect on migration of tolerogenic dendritic cells. The major galectin-1 counter-receptor on both dendritic cell populations is the cell surface mucin CD43; differential core 2 O-glycosylation of CD43 between immunogenic dendritic cells and tolerogenic dendritic cells appears to contribute to the differential effect of galectin-1 on migration. Binding of galectin-1 to immunogenic dendritic cells reduces phosphorylation and activity of the protein-tyrosine kinase Pyk2, an effect that may also contribute to reduced migration of this subset. In a murine lymphedema model, galectin-1(-/-) animals had increased numbers of migratory dendritic cells in draining lymph nodes, specifically dendritic cells with an immunogenic phenotype. These findings define a novel role for galectin-1 in inhibiting tissue emigration of immunogenic, but not tolerogenic, dendritic cells, providing an additional mechanism by which galectin-1 can dampen immune responses.

Animal models in surgical lymphedema research--a systematic review

BACKGROUND

Chronic secondary lymphedema is a well-known complication in oncologic surgery. Autologous lymph node transplantation, lymphovenous anastomosis, and other lymphatic surgeries have been developed in the last decades with rising clinical application. Animal models to explore the pathophysiology of lymphedema and microsurgical interventions have reached great popularity, although the induction of stable lymphedema in animals is still challenging. The aim of this review was to systematically assess lymphedema animal models and their potential use to study surgical interventions.

MATERIALS AND METHODS

A systematic review according to the PRISMA guidelines was performed without time or language restriction. Studies describing new or partially new models were included in chronological order. Models for primary and secondary lymphedema were assessed, and their potential for surgical procedures was evaluated.

RESULTS

The systematic search yielded 8590 discrete articles. Of 180 articles included on basis of title, 84 were excluded after abstract review. Ninety-six were included in the final analysis with 24 key articles.

CONCLUSIONS

No animal model is perfect, and many models show spontaneous lymphedema resolution. The rodent limb appears to be the most eligible animal model for experimental reconstruction of the lymphatic function as it is well accessible for vascularized tissue transfer. There is a need for standardized parameters in experimental lymphedema quantification. Also, more permanent models to study the effect of free vascularized lymph node transfer are needed.

Higher vascular endothelial growth factor-C concentration in plasma is associated with increased forearm capillary filtration capacity in breast cancer-related lymphedema

Breast cancer-related lymphedema (BCRL) is a frequent, chronic and debilitating swelling that mainly affects the ipsilateral arm and develops as a complication to breast cancer treatment. The pathophysiology is elusive opposing development of means for prediction and treatment. We have earlier shown that the forearm capillary filtration coefficient (CFC) is increased bilaterally in BCRL. In this study, we aimed to elucidate if increased CFC is associated with low-grade inflammation and/or vascular endothelial growth factor-c (VEGF-C) signaling. Fourteen patients with unilateral BCRL and nine matched breast cancer controls without BCRL participated. Forearm CFC was measured by venous congestion strain gauge plethysmography, and suction blisters were induced medially on the upper arms. Concentrations of 17 selected cytokines, VEGF-C, and total protein were measured in blister fluid and in plasma. Forearm CFC was higher bilaterally in BCRL subjects (P ≤ 0.036). No differences between forearms were found in either group. Plasma VEGF-C concentrations were significantly higher in the BCRL subjects (P < 0.001). In BCRL subjects, monocyte chemotactic protein 1 (MCP-1) (P = 0.009) and total protein (P = 0.035) concentrations were higher in blister fluid from edematous arms compared with nonedematous arms. No differences were found in interstitial cytokine or total protein concentrations between arms in control subjects. Higher plasma concentration of VEGF-C is a possible cause of bilaterally increased forearm CFC in BCRL subjects. Interstitially increased MCP-1 levels may augment local microvascular protein permeability in BCRL.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Lymphedema and subclinical lymphostasis (microlymphedema) facilitate cutaneous infection, inflammatory dermatoses, and neoplasia: A locus minoris resistentiae

Whether primary or secondary, lymphedema is caused by failure to drain protein-rich interstitial fluid. Typically affecting a whole limb, it has become apparent that lymphedema can also affect localized regions of the skin, or it can be clinically silent but histologically evident, denoted by dilated lymphangiectases (latent lymphedema). Chronic lymph stasis has numerous consequences, including lipogenesis, fibrosis, inflammation, lymphangiogenesis, and immunosuppression. For example, lymphedema's disruption of immune cell trafficking leads to localized immune suppression, predisposing the area affected to chronic inflammation, infection (cellulitis and verrucosis), and malignancy (angiosarcoma and nonmelanoma skin cancer). The pathogenesis of lymphedema is reviewed and exemplified by describing how a combination of lymph stasis-promoting factors such as trauma, obesity, infection, and inflammatory disorders produces localized elephantiasis; furthermore, the finding of lymphangiectases is found to be common in numerous dermatologic disorders and argued to play a role in their pathogenesis. Lastly, it is discussed how antigen burden, which is controlled by lymphatic clearance, affects the immune response, resulting in immune tolerance, immunopathology, or normal adaptive immunity.

Bridging the divide between pathogenesis and detection in lymphedema

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

Serum fibronectin 1 and ApoE levels increase with risk of lymphedema in Korean breast cancer survivors

PURPOSE

Lymphedema is an irreversible disorder often seen as a postoperative side effect in breast cancer survivors. We aimed to identify serum factors that are associated with lymphedema risk in breast cancer survivors.

METHODS

This study recruited 60 volunteer breast cancer survivors. Participants were classified into either a CTRL group who underwent sentinel lymph node biopsy (SLNB), a RISK group who underwent axillary lymph node dissection (ALND) with removal of fewer than five lymph nodes, or an LE group who underwent ALND with removal of more than five lymph nodes. Bioimpedance was measured to determine the ratio of extracellular water (ECW) to total cellular water (TCW) and single-frequency bioimpedance analysis (SFBIA) ratios. Serum lipid profiles were compared among the groups using label-free quantitative proteomics with the nano-liquid chromatography (LC)-tandem mass spectrometer (MS/MS) and emPAI method.

RESULTS

The CTRL, RISK, and LE groups had similar body weights and body mass indexes (BMIs) (<25 kg/m(2)). The LE group showed a higher grade of lymphedema severity compared to the RISK and CTRL groups. Lymphedema indices such as the ECW/TCW ratio and SFBIA ratio at 1 and 5 kHz were greatly increased in the LE group. Serum total cholesterol (total-C) level was higher in the LE group without affecting atherogenic index. Serum proteomics revealed that fibronectin 1 (FN1), apolipoprotein E (ApoE), antithrombin (ANT3), and complement C4 had different abundance values among the groups. ELISA confirmed that FN1 and ApoE were significantly elevated in both the RISK and LE groups compared to the CTRL group.

CONCLUSIONS

Changes in serum FN1 and ApoE levels were detected prior to changes in serum total-C level and lymphedema indices such as SFBIA ratio. Therefore, elevation in serum FN1 and ApoE concentrations could likely be used to monitor the risk of lymphedema in breast cancer survivors.

Spatio-temporal changes of lymphatic contractility and drainage patterns following lymphadenectomy in mice

Objective

To investigate the redirection of lymphatic drainage post-lymphadenectomy using non-invasive near-infrared fluorescence (NIRF) imaging, and to subsequently assess impact on metastasis.

Background

Cancer-acquired lymphedema arises from dysfunctional fluid transport after lymphadenectomy performed for staging and to disrupt drainage pathways for regional control of disease. However, little is known about the normal regenerative processes of the lymphatics in response to lymphadenectomy and how these responses can be accelerated, delayed, or can impact metastasis.

Methods

Changes in lymphatic “pumping” function and drainage patterns were non-invasively and longitudinally imaged using NIRF lymphatic imaging after popliteal lymphadenectomy in mice. In a cohort of mice, B16F10 melanoma was inoculated on the dorsal aspect of the paw 27 days after lymphadenectomy to assess how drainage patterns affect metastasis.

Results

NIRF imaging demonstrates that, although lymphatic function and drainage patterns change significantly in early response to popliteal lymph node (PLN) removal in mice, these changes are transient and regress dramatically due to a high regenerative capacity of the lymphatics and co-opting of collateral lymphatic pathways around the site of obstruction. Metastases followed the pattern of collateral pathways and could be detected proximal to the site of lymphadenectomy.

Conclusions

Both lymphatic vessel regeneration and co-opting of contralateral vessels occur following lymphadenectomy, with contractile function restored within 13 days, providing a basis for preclinical and clinical investigations to hasten lymphatic repair and restore contractile lymphatic function after surgery to prevent cancer-acquired lymphedema. Patterns of cancer metastasis after lymphadenectomy were altered, consistent with patterns of re-directed lymphatic drainage.

Obesity increases inflammation and impairs lymphatic function in a mouse model of lymphedema

Although obesity is a major clinical risk factor for lymphedema, the mechanisms that regulate this effect remain unknown. Recent reports have demonstrated that obesity is associated with acquired lymphatic dysfunction. The purpose of this study was to determine how obesity-induced lymphatic dysfunction modulates the pathological effects of lymphatic injury in a mouse model. We used a diet-induced model of obesity in adult male C57BL/6J mice in which experimental animals were fed a high-fat diet and control animals were fed a normal chow diet for 8-10 wk. We then surgically ablated the superficial and deep lymphatics of the midportion of the tail. Six weeks postoperatively, we analyzed changes in lymphatic function, adipose deposition, inflammation, and fibrosis. We also compared responses to acute inflammatory stimuli in obese and lean mice. Compared with lean control mice, obese mice had baseline decreased lymphatic function. Lymphedema in obese mice further impaired lymphatic function and resulted in increased subcutaneous adipose deposition, increased CD45(+) and CD4(+) cell inflammation (P < 0.01), and increased fibrosis, but caused no change in the number of lymphatic vessels. Interestingly, obese mice had a significantly increased acute inflammatory reaction to croton oil application. In conclusion, obese mice have impaired lymphatic function at baseline that is amplified by lymphatic injury. This effect is associated with increased chronic inflammation, fibrosis, and adipose deposition. These findings suggest that obese patients are at higher risk for lymphedema due to impaired baseline lymphatic clearance and an increased propensity for inflammation in response to injury.

An immunological fingerprint differentiates muscular lymphatics from arteries and veins

The principal function of the lymphatic system is to transport lymph from the interstitium to the nodes and then from the nodes to the blood. In doing so lymphatics play important roles in fluid homeostasis, macromolecular/antigen transport and immune cell trafficking. To better understand the genes that contribute to their unique physiology, we compared the transcriptional profile of muscular lymphatics (prenodal mesenteric microlymphatics and large, postnodal thoracic duct) to axillary and mesenteric arteries and veins isolated from rats. Clustering of the differentially expressed genes demonstrated that the lymph versus blood vessel differences were more profound than between blood vessels, particularly the microvessels. Gene ontology functional category analysis indicated that microlymphatics were enriched in antigen processing/presentation, IgE receptor signaling, catabolic processes, translation and ribosome; while they were diminished in oxygen transport, regulation of cell proliferation, glycolysis and inhibition of adenylate cyclase activity by G-proteins. We evaluated the differentially expressed microarray genes/products by qPCR and/or immunofluorescence. Immunofluorescence documented that multiple MHC class II antigen presentation proteins were highly expressed by an antigen-presenting cell (APC) type found resident within the lymphatic wall. These APCs also expressed CD86, a co-stimulatory protein necessary for T-cell activation. We evaluated the distribution and phenotype of APCs within the pre and postnodal lymphatic network. This study documents a novel population of APCs resident within the walls of muscular, prenodal lymphatics that indicates novel roles in antigen sampling and immune responses. In conclusion, these prenodal lymphatics exhibit a unique profile that distinguishes them from blood vessels and highlights the role of the lymphatic system as an immunovascular system linking the parenchymal interstitium, lymph nodes and the blood.

IL-6 regulates adipose deposition and homeostasis in lymphedema

Lymphedema (LE) is a morbid disease characterized by chronic limb swelling and adipose deposition. Although it is clear that lymphatic injury is necessary for this pathology, the mechanisms that underlie lymphedema remain unknown. IL-6 is a known regulator of adipose homeostasis in obesity and has been shown to be increased in primary and secondary models of lymphedema. Therefore, the purpose of this study was to determine the role of IL-6 in adipose deposition in lymphedema. The expression of IL-6 was analyzed in clinical tissue specimens and serum from patients with or without LE, as well as in two mouse models of lymphatic injury. In addition, we analyzed IL-6 expression/adipose deposition in mice deficient in CD4(+) cells (CD4KO) or IL-6 expression (IL-6KO) or mice treated with a small molecule inhibitor of IL-6 or CD4 depleting antibodies to determine how IL-6 expression is regulated and the effect of changes in IL-6 expression on adipose deposition after lymphatic injury. Patients with LE and mice treated with lymphatic excision of the tail had significantly elevated tissue and serum expression of IL-6 and its downstream mediator. The expression of IL-6 was associated with adipose deposition and CD4(+) inflammation and was markedly decreased in CD4KO mice. Loss of IL-6 function resulted in significantly increased adipose deposition after tail lymphatic injury. Our findings suggest that IL-6 is increased as a result of adipose deposition and CD4(+) cell inflammation in lymphedema. In addition, our study suggests that IL-6 expression in lymphedema acts to limit adipose accumulation.

New developments in clinical aspects of lymphatic disease

The lymphatic system is fundamentally important to cardiovascular disease, infection and immunity, cancer, and probably obesity--the four major challenges in healthcare in the 21st century. This Review will consider the manner in which new knowledge of lymphatic genes and molecular mechanisms has demonstrated that lymphatic dysfunction should no longer be considered a passive bystander in disease but rather an active player in many pathological processes and, therefore, a genuine target for future therapeutic developments. The specific roles of the lymphatic system in edema, genetic aspects of primary lymphedema, infection (cellulitis/erysipelas), Crohn's disease, obesity, cancer, and cancer-related lymphedema are highlighted.

Minimally invasive method for determining the effective lymphatic pumping pressure in rats using near-infrared imaging

The ability to quantify collecting vessel function in a minimally invasive fashion is crucial to the study of lymphatic physiology and the role of lymphatic pump function in disease progression. Therefore, we developed a highly sensitive, minimally invasive research platform for quantifying the pumping capacity of collecting lymphatic vessels in the rodent tail and forelimb. To achieve this, we have integrated a near-infrared lymphatic imaging system with a feedback-controlled pressure cuff to modulate lymph flow. After occluding lymphatic flow by inflating a pressure cuff on the limb or tail, we gradually deflate the cuff while imaging flow restoration proximal to the cuff. Using prescribed pressure applications and automated image processing of fluorescence intensity levels in the vessels, we were able to noninvasively quantify the effective pumping pressure (P(eff), pressure at which flow is restored after occlusion) and vessel emptying rate (rate of fluorescence clearance during flow occlusion) of lymphatics in the rat. To demonstrate the sensitivity of this system to changes in lymphatic function, a nitric oxide (NO) donor cream, glyceryl trinitrate ointment (GTNO), was applied to the tails. GTNO decreased P(eff) of the vessels by nearly 50% and the average emptying rate by more than 60%. We also demonstrate the suitability of this approach for acquiring measurements on the rat forelimb. Thus, this novel research platform provides the first minimally invasive measurements of P(eff) and emptying rate in rodents. This experimental platform holds strong potential for future in vivo studies that seek to evaluate changes in lymphatic health and disease.

Lymphatic filariasis: perspectives on lymphatic remodeling and contractile dysfunction in filarial disease pathogenesis

Lymphatic filariasis, one of the most debilitating diseases associated with the lymphatic system, affects over a hundred million people worldwide and manifests itself in a variety of severe clinical pathologies. The filarial parasites specifically target the lymphatics and impair lymph flow, which is critical for the normal functions of the lymphatic system in maintenance of body fluid balance and physiological interstitial fluid transport. The resultant contractile dysfunction of the lymphatics causes fluid accumulation and lymphedema, one of the major pathologies associated with filarial infection. In this review, we take a closer look at the contractile mechanisms of the lymphatics, its altered functions, and remodeling during an inflammatory state and how it relates to the severe pathogenesis underlying a filarial infection. We further elaborate on the complex host-parasite interactions, and molecular mechanisms contributing to the disease pathogenesis. The overall emphasis is on elucidating some of the emerging concepts and new directions that aim to harness the process of lymphangiogenesis or enhance contractility in a dysfunctional lymphatics, thereby restoring the fluid imbalance and mitigating the pathological conditions of lymphatic filariasis.

Minimally invasive method for determining the effective lymphatic pumping pressure in rats using near-infrared imaging

The ability to quantify collecting vessel function in a minimally invasive fashion is crucial to the study of lymphatic physiology and the role of lymphatic pump function in disease progression. Therefore, we developed a highly sensitive, minimally invasive research platform for quantifying the pumping capacity of collecting lymphatic vessels in the rodent tail and forelimb. To achieve this, we have integrated a near-infrared lymphatic imaging system with a feedback-controlled pressure cuff to modulate lymph flow. After occluding lymphatic flow by inflating a pressure cuff on the limb or tail, we gradually deflate the cuff while imaging flow restoration proximal to the cuff. Using prescribed pressure applications and automated image processing of fluorescence intensity levels in the vessels, we were able to noninvasively quantify the effective pumping pressure (P(eff), pressure at which flow is restored after occlusion) and vessel emptying rate (rate of fluorescence clearance during flow occlusion) of lymphatics in the rat. To demonstrate the sensitivity of this system to changes in lymphatic function, a nitric oxide (NO) donor cream, glyceryl trinitrate ointment (GTNO), was applied to the tails. GTNO decreased P(eff) of the vessels by nearly 50% and the average emptying rate by more than 60%. We also demonstrate the suitability of this approach for acquiring measurements on the rat forelimb. Thus, this novel research platform provides the first minimally invasive measurements of P(eff) and emptying rate in rodents. This experimental platform holds strong potential for future in vivo studies that seek to evaluate changes in lymphatic health and disease.

Systemic and global toxicities of head and neck treatment

The increased use of aggressive, combined modality therapy for the treatment of head and neck cancer has resulted in a marked increase in acute and late adverse effects. The acute effects of therapy have long been appreciated; however, it is now being recognized that the late effects of therapy result in a significant symptom burden, diminished functional capacity and decreased quality of survivorship. Furthermore, head and neck cancer has historically been considered a locoregional disease that is treated predominantly with locoregional therapy. It is now recognized that there are systemic effects of therapy that need to be considered. Potential systemic effects of therapy include: fatigue, weight loss, nutritional deficiencies, altered physical functioning and mood disorders. It is important for clinicians to be aware of these late effects in order to provide patients with appropriate support services and referrals. This paper examines the global and systemic effects of therapy.

Modification of a rodent hindlimb model of secondary lymphedema: surgical radicality versus radiotherapeutic ablation

Secondary lymphedema is an intractable disease mainly caused by damage of the lymphatic system during surgery, yet studies are limited by the lack of suitable animal models. The purpose of this study was to create an improved model of secondary lymphedema in the hindlimbs of rodents with sustained effects and able to mimic human lymphedema. This was achieved by combining previously reported surgical methods and radiation to induce chronic lymphedema. Despite more radical surgical destruction of superficial and deep lymphatic vessels, surgery alone was not enough to sustain increased hindlimb volume. Radiotherapy was necessary to prolong these effects, with decreased lymphatic flow on lymphoscintigraphy, but hindlimb necrosis occurred after 4 weeks due to radiation toxicity. The applicability of this model for studies of therapeutic lymphangiogenesis was subsequently tested by injecting muscle-derived stem cells previously cocultured with the supernatant of human lymphatic endothelial cells in vitro. There was a tendency for increased lymphatic flow which significantly increased lymphatic vessel formation after cell injection, but attenuation of hindlimb volume was not observed. These results suggest that further refinement of the rodent hindlimb model is needed by titration of adequate radiation dosage, while stem cell lymphangiogenesis seems to be a promising approach.