Human lymphatic pumping measured in healthy and lymphoedematous arms by lymphatic congestion lymphoscintigraphy

Lymphatic-draining nanoparticles deliver Bay K8644 payload to lymphatic vessels and enhance their pumping function

Dysfunction of collecting lymphatic vessel pumping is associated with an array of pathologies. S-(-)-Bay K8644 (BayK), a small-molecule agonist of L-type calcium channels, improves vessel contractility ex vivo but has been left unexplored in vivo because of poor lymphatic access and risk of deleterious off-target effects. When formulated within lymph-draining nanoparticles (NPs), BayK acutely improved lymphatic vessel function, effects not seen from treatment with BayK in its free form. By preventing rapid drug access to the circulation, NP formulation also reduced BayK's dose-limiting side effects. When applied to a mouse model of lymphedema, treatment with BayK formulated in lymph-draining NPs, but not free BayK, improved pumping pressure generated by intact lymphatic vessels and tissue remodeling associated with the pathology. This work reveals the utility of a lymph-targeting NP platform to pharmacologically enhance lymphatic pumping in vivo and highlights a promising approach to treating lymphatic dysfunction.

The Vicious Circle of Stasis, Inflammation, and Fibrosis in Lymphedema

SUMMARY

Lymphedema is a progressive disease of the lymphatic system arising from impaired lymphatic drainage, accumulation of interstitial fluid, and fibroadipose deposition. Secondary lymphedema resulting from cancer treatment is the most common form of the disease in developed countries, affecting 15% to 40% of patients with breast cancer after lymph node dissection. Despite recent advances in microsurgery, outcomes remain variable and, in some cases, inadequate. Thus, development of novel treatment strategies is an important goal. Research over the past decade suggests that lymphatic injury initiates a chronic inflammatory response that regulates the pathophysiology of lymphedema. T-cell inflammation plays a key role in this response. In this review, the authors highlight the cellular and molecular mechanisms of lymphedema and discuss promising preclinical therapies.

KATP channels in lymphatic function

KATP channels function as negative regulators of active lymphatic pumping and lymph transport. This review summarizes and critiques the evidence for the expression of specific KATP channel subunits in lymphatic smooth muscle and endothelium, the roles that they play in normal lymphatic function, and their possible involvement in multiple diseases, including metabolic syndrome, lymphedema, and Cantú syndrome. For each of these topics, suggestions are made for directions for future research.

Effect of Lymphaticovenous Anastomosis on Muscle Edema, Limb, and Subfascial Volume in Lower Limb Lymphedema: MRI Studies

BACKGROUND

Although satisfactory volume reduction in secondary unilateral lower limb lymphedema after lymphaticovenous anastomosis (LVA) in the affected limb has been well reported, alleviation of muscle edema and the impact of LVA on the contralateral limb have not been investigated.

STUDY DESIGN

This retrospective cohort study enrolled patients who underwent supermicrosurgical LVA between November 2015 and January 2017. Pre- and post-LVA muscle edema were assessed using fractional anisotropy (FA) and apparent diffusion coefficient (ADC). The primary endpoint was changes in limb/subfascial volume assessed with magnetic resonance volumetry at least 6 months after LVA.

RESULTS

Twenty-one patients were enrolled in this study. Significant percentage reductions in post-LVA muscle edema were found in the affected thigh (83.6% [interquartile range = range of Q1 to Q3; 29.8-137.1] [FA], 53.3% [27.0-78.4] [ADC]) as well as limb (21.7% [4.4-26.5]) and subfascial (18.7% [10.7-39.1]) volumes. Similar findings were noted in the affected lower leg: 71.8% [44.0-100.1] (FA), 59.1% [45.8-91.2] (ADC), 21.2% [6.8-38.2], and 28.2% [8.5-44.8], respectively (all p < 0.001). Significant alleviation of muscle edema was also evident in the contralateral limbs (thigh: 25.1% [20.4-57.5] [FA]; 10.7% [6.6-17.7] [ADC]; lower leg: 47.1% [35.0-62.8] [FA]; 14.6% [6.5-22.1] [ADC]; both p < 0.001), despite no statistically significant difference in limb and subfascial volumes.

CONCLUSIONS

Our study found significant reductions in muscle edema and limb/subfascial volumes in the affected limb after LVA. Our findings regarding edema in the contralateral limb were consistent with possible lymphedema-associated systemic influence on the unaffected limb, which could be surgically relieved.

Current Understanding of Pathological Mechanisms of Lymphedema

Significance: Lymphedema is a common disease that affects hundreds of millions of people worldwide with significant financial and social burdens. Despite increasing prevalence and associated morbidities, the mainstay treatment of lymphedema is largely palliative without an effective cure due to incomplete understanding of the disease. Recent Advances: Recent studies have described key histological and pathological processes that contribute to the progression of lymphedema, including lymphatic stasis, inflammation, adipose tissue deposition, and fibrosis. This review aims to highlight cellular and molecular mechanisms involved in each of these pathological processes. Critical Issues: Despite recent advances in the understanding of the pathophysiology of lymphedema, cellular and molecular mechanisms underlying the disease remains elusive due to its complex nature. Future Directions: Additional research is needed to gain a better insight into the cellular and molecular mechanisms underlying the pathophysiology of lymphedema, which will guide the development of therapeutic strategies that target specific pathology of the disease.

The effects of gravity and compression on interstitial fluid transport in the lower limb

Edema in the limbs can arise from pathologies such as elevated capillary pressures due to failure of venous valves, elevated capillary permeability from local inflammation, and insufficient fluid clearance by the lymphatic system. The most common treatments include elevation of the limb, compression wraps and manual lymphatic drainage therapy. To better understand these clinical situations, we have developed a comprehensive model of the solid and fluid mechanics of a lower limb that includes the effects of gravity. The local fluid balance in the interstitial space includes a source from the capillaries, a sink due to lymphatic clearance, and movement through the interstitial space due to both gravity and gradients in interstitial fluid pressure (IFP). From dimensional analysis and numerical solutions of the governing equations we have identified several parameter groups that determine the essential length and time scales involved. We find that gravity can have dramatic effects on the fluid balance in the limb with the possibility that a positive feedback loop can develop that facilitates chronic edema. This process involves localized tissue swelling which increases the hydraulic conductivity, thus allowing the movement of interstitial fluid vertically throughout the limb due to gravity and causing further swelling. The presence of a compression wrap can interrupt this feedback loop. We find that only by modeling the complex interplay between the solid and fluid mechanics can we adequately investigate edema development and treatment in a gravity dependent limb.

Development of a diffusion-weighed mathematical model for intradermal drainage quantification

The quantitative assessment of lymphatic dermal clearance using NIR fluorescent tracers is particularly important for the early diagnosis of several potential disabling diseases. Currently, half-life values are computed using a mono-exponential mathematical model, neglecting diffusion of the tracer within the dermis after injection. The size and position of the region of interest are subjectively manually selected around the point of injection on the skin surface where the fluorescence signal intensity is averaged, neglecting any spatial information contained in the image. In this study we present and test a novel mathematical model allowing the objective quantification of dermal clearance, taking into consideration potential dermal diffusion. With only two parameters, this "clearance-diffusion" model is simple enough to be applied in a variety of settings and requires almost no prior information about the system. We demonstrate that if dermal diffusion is low, the mono-exponential approach is suitable but still lacking objectivity. However, if dermal diffusion is substantial, the clearance-diffusion model is superior and allows the accurate calculation of half-life values.

Lymphoscintigraphy as an Outcome Measurement for Conservative Upper Limb Lymphedema Treatments: A Systematic Review

Introduction: The impact of conservative interventions on lymphatic function and the relationship to clinical outcomes is currently unknown. A systematic review was undertaken to evaluate studies that used lymphoscintigraphy to measure outcomes from conservative intervention for secondary arm lymphedema and to explore the relationship between changes in the lymphoscintigraphy and clinical outcomes. Methods and Results: Five databases were systematically searched using the selection criteria: randomized controlled trials (RCTs); quasi-RCTs; pre/post and cohort studies; upper limb secondary lymphedema; use of lymphoscintigraphy as an outcome measure; and conservative intervention. Seven articles met the inclusion criteria. Compression, exercise, hyperbaric oxygen therapy, and pharmacological interventions were evaluated using lymphoscintigraphy. There was heterogeneity with all aspects of the lymphoscintigraphy techniques, including radioisotope used, injection location, use of exercise, and imaging sequence between the studies as well as the outcome analysis. Also most studies did not show a relationship between the clinical and lymphoscintigraphy outcomes measured. Conclusions: Lymphoscintigraphy has not been used regularly or recently to evaluate conservative upper limb lymphedema treatment outcomes. Lack of standardization of lymphoscintigraphy protocols and lack of consensus and understanding of the lymphoscintigraphy analyses used to measure the outcomes of diverse conservative lymphedema interventions currently limit the use of lymphoscintigraphy as an outcome measure. Further research adopting recent guidelines to standardize lymphoscintigraphy and use of reliable analysis techniques that measure the physiological impact of the chosen conservative lymphedema intervention is recommended to evaluate the impact of conservative interventions on lymphatic function.

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

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

Lymphatic Function in the Arms of Breast Cancer Patients-A Prospective Cohort Study

Background:

Lymphedema is a highly feared complication of breast cancer treatment, but the underlying complex mechanisms are still unknown. Thus, we investigated the lymphatic morphology and contractility in the lymphatic vessels of arms of high-risk breast cancer patients treated for node-positive early breast cancer.

Methods:

In this prospective cohort study 32 women treated for unilateral node-positive breast cancer were enrolled and studied 36 ± 23 days after loco-regional radiotherapy. Near-infrared fluorescence imaging was used to assess morphology and function of the superficial lymphatic vessels. Strain-gauge plethysmography was performed to evaluate the capillary filtration of fluid.

Both arms were investigated, with the non-treated arm acting as control. The patients were questioned about the presence of lymphedema yearly and finally 574 ± 118 days after ended radiotherapy.

Results:

Morphologically, 25% of the treated arms expressed lymphatic vessel abnormalities compared to the control arms (p = 0.0048). No difference in functional parameters (maximal pumping pressure, p = 0.20; contraction frequency, p = 0.63; contraction velocity, p = 0.55) was found between the treated and control arms. Patients who later developed lymphedema had a difference in velocity compared to those who did not develop lymphedema (p = 0.02). The capillary filtration rate was similar between the two arms (p = 0.18).

Conclusions:

Peripheral lymphatic vessels were morphologically changed in the ipsilateral arm in 25% of the patients and patients who later developed lymphedema showed an early increase in velocity. Other functional parameters and capillary filtration were unchanged in this early phase. These discrete changes might be early indicators of later development of lymphedema.

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.

Breast Cancer-Related Lymphedema: Recent Updates on Diagnosis, Severity and Available Treatments

Breast cancer-related lymphedema (BCRL) represents a global healthcare issue affecting the emotional and life quality of breast cancer survivors significantly. The clinical presentation is characterized by swelling of the affected upper limb, that may be accompanied by atrophic skin findings, pain and recurrent cellulitis. Cardinal principles of lymphedema management are the use of complex decongestive therapy and patient education. Recently, new microsurgery procedures have been reported with interesting results, bringing in a new opportunity to care postmastectomy lymphedema. However, many aspects of the disease are still debated in the medical community, including clinical examination, imaging techniques, patient selection and proper treatment. Here we will review these aspects and the current literature.

Lymphatic injury alters the contractility and mechanosensitivity of collecting lymphatics to intermittent pneumatic compression

KEY POINTS

We present the first in vivo evidence that lymphatic contraction can entrain with an external oscillatory mechanical stimulus. Lymphatic injury can alter collecting lymphatic contractility, but not much is known about how its mechanosensitivity to external pressure is affected, which is crucial given the current pressure application methods for treating lymphoedema. We show that oscillatory pressure waves (OPW), akin to intermittent pneumatic compression (IPC) therapy, optimally entrain lymphatic contractility and modulate function depending on the frequency and propagation speed of the OPW. We show that the OPW-induced entrainment and contractile function in the intact collecting lymphatics are enhanced 28 days after a contralateral lymphatic ligation surgery. The results show that IPC efficacy can be improved through proper selection of OPW parameters, and that collecting lymphatics adapt their function and mechanosensitivity after a contralateral injury, switching their behaviour to a pump-like configuration that may be more suited to the altered microenvironment.

ABSTRACT

Intermittent pneumatic compression (IPC) is commonly used to control the swelling due to lymphoedema, possibly modulating the collecting lymphatic function. Lymphoedema causes lymphatic contractile dysfunction, but the consequent alterations in the mechanosensitivity of lymphatics to IPC is not known. In the present work, the spatiotemporally varying oscillatory pressure waves (OPW) generated during IPC were simulated to study the modulation of lymphatic function by OPW under physiological and pathological conditions. OPW with three temporal frequencies and three propagation speeds were applied to rat tail collecting lymphatics. The entrainment of the lymphatics to OPW was significantly higher at a frequency of 0.05 Hz compared with 0.1 Hz and 0.2 Hz (P = 0.0054 and P = 0.014, respectively), but did not depend on the OPW propagation speed. Lymphatic function was significantly higher at a frequency of 0.05 Hz and propagation speed of 2.55 mm/s (P = 0.015). Exogenous nitric oxide was not found to alter OPW-induced entrainment. A contralateral lymphatic ligation surgery was performed to simulate partial lymphatic injury in rat tails. The intact vessels showed a significant increase in entrainment to OPW, 28 days after ligation (compared with sham) (P = 0.016), with a similar increase in lymphatic transport function (P = 0.0029). The results suggest an enhanced mechanosensitivity of the lymphatics, along with a transition to a pump-like behaviour, in response to a lymphatic injury. These results enhance our fundamental understanding of how lymphatic mechanosensitivity assists the coordination of lymphatic contractility and how this might be leveraged in IPC therapy.

Imaging technology of the lymphatic system

The lymphatic system plays critical roles in tissue fluid homeostasis and immunity and has been implicated in the development of many different pathologies, ranging from lymphedema, the spread of cancer to chronic inflammation. In this review, we first summarize the state-of-the-art of lymphatic imaging in the clinic and the advantages and disadvantages of these existing techniques. We then detail recent progress on imaging technology, including advancements in tracer design and injection methods, that have allowed visualization of lymphatic vessels with excellent spatial and temporal resolution in preclinical models. Finally, we describe the different approaches to quantifying lymphatic function that are being developed and discuss some emerging topics for lymphatic imaging in the clinic. Continued advancements in lymphatic imaging technology will be critical for the optimization of diagnostic methods for lymphatic disorders and the evaluation of novel therapies targeting the lymphatic system.

Lymph Flow Before and After Lymphaticovenous Anastomosis Measured Using Transonic Transit-Time Ultrasound Microvascular Flowprobe

Background: Assessment of lymph flow has proven challenging. Transit-time ultrasound technique (TTUT) is the first technique that provides real-time quantitative lymphatic flow values. In cardiothoracic surgery and neurosurgery, this technique has tremendous clinical value in assessing surgery quality and predicting outcomes. The objective of this study was to measure lymph flow before and after lymphaticovenous anastomosis (LVA), using TTUT. Methods and Results: Consecutive patients with peripheral lymphedema undergoing LVA were included. Preoperative workup was performed using indocyanine green (ICG) lymphangiography. Perioperatively, the Transonic^® Microvascular Flowprobe was used to measure lymph flow before and after anastomosis. Twenty-five patients with International Society of Lymphology stage IIA (68%) and stage IIB (32%) peripheral lymphedema were included. Lymph flow velocities ranged from 0.02 to 0.80 mL/min (mean 0.25 ± 0.19) before anastomosis and from 0.02 to 0.86 mL/min (mean 0.27 ± 0.22) after anastomosis (p = 0.340). Mean flow values were significantly higher in the upper extremities compared with the lower extremities. Furthermore, there was a decrease in flow in patients with ICG stage IV in comparison with ICG stage III. Clinical outcomes could not be directly correlated with flow values in these individual cases. Conclusion: TTUT micro-flowprobe is a suitable instrument to measure real-time quantitative lymphatic flow in both lymphatics and LVA. It can confirm patency of lymphatic collectors and LVA peroperatively. Significantly higher lymph flow velocities were found in upper extremities in comparison with lower extremities, both before and after LVA. Further studies should be performed to evaluate lymph flow values and clinical correlation.

Lymphatic Valves and Lymph Flow in Cancer-Related Lymphedema

Lymphedema is a complex disease caused by the accumulation of fluid in the tissues resulting from a dysfunctional or damaged lymphatic vasculature. In developed countries, lymphedema most commonly occurs as a result of cancer treatment. Initially, impaired lymph flow causes edema, but over time this results in inflammation, fibrotic and fatty tissue deposition, limited mobility, and bacterial infections that can lead to sepsis. While chronically impaired lymph flow is generally believed to be the instigating factor, little is known about what pathophysiological changes occur in the lymphatic vessels to inhibit lymph flow. Lymphatic vessels not only regulate lymph flow through a variety of physiologic mechanisms, but also respond to lymph flow itself. One of the fascinating ways that lymphatic vessels respond to flow is by growing bicuspid valves that close to prevent the backward movement of lymph. However, lymphatic valves have not been investigated in cancer-related lymphedema patients, even though the mutations that cause congenital lymphedema regulate genes involved in valve development. Here, we review current knowledge of the regulation of lymphatic function and development by lymph flow, including newly identified genetic regulators of lymphatic valves, and provide evidence for lymphatic valve involvement in cancer-related lymphedema.

Simplified method to quantify valve back-leak uncovers severe mesenteric lymphatic valve dysfunction in mice deficient in connexins 43 and 37

KEY POINTS

Lymphatic valve defects are one of the major causes of lymph transport dysfunction; however, there are no accessible methods for quantitatively assessing valve function. This report describes a novel technique for quantifying lymphatic valve back-leak. Postnatal endothelial-specific deletion of connexin 43 (Cx43) in connexin 37 null (Cx37-/- ) mice results in rapid regression of valve leaflets and severe valve dysfunction. This method can also be used for assessing the function of venous and lymphatic valves from various species, including humans.

ABSTRACT

The lymphatic system relies on robust, spontaneous contractions of collecting lymphatic vessels and one-way secondary lymphatic valves to efficiently move lymph forward. Secondary valves prevent reflux and allow for the generation of propulsive pressure during each contraction cycle. Lymphatic valve defects are one of the major causes of lymph transport dysfunction. Genetic mutations in multiple genes have been associated with the development of primary lymphoedema in humans; and many of the same mutations in mice result in valve defects that subsequently lead to chylous ascites or chylothorax. At present the only experimental technique for the quantitative assessment of lymphatic valve function utilizes the servo-null micropressure system, which is highly accurate and precise, but relatively inaccessible and difficult to use. We developed a novel, simplified alternative method for quantifying valve function and determining the degree of pressure back-leak through an intact valve in pressurized, single-valve segments of isolated lymphatic vessels. With this diameter-based method, the competence of each lymphatic valve is challenged over a physiological range of pressures (e.g. 0.5-10cmH2 O) and pressure back-leak is extrapolated from calibrated, pressure-driven changes in diameter upstream from the valve. Using mesenteric lymphatic vessels from C57BL/6J, Ub-CreERT2 ;Rasa1fx/fx , Foxc2Cre/+ , Lyve1-Cre;Cx43fx/fx , and Prox1-CreERT2 ;Cx43fx/fx ;Cx37-/- mice, we tested our method on lymphatic valves displaying a wide range of dysfunction, from fully competent to completely incompetent. Our results were validated by simultaneous direct measurement of pressure back-leak using a servo-null micropressure system. Our diameter-based technique can be used to quantify valve function in isolated lymphatic valves from a variety of species. This method also revealed that haplodeficiency in Foxc2 (Foxc2Cre/+ ) is not sufficient to cause significant valve dysfunction; however, postnatal endothelial-specific deletion of Cx43 in Cx37-/- mice results in rapid regression of valve leaflets and severe valve dysfunction.

Multi-Compartment 3D-Cultured Organ-on-a-Chip: Towards a Biomimetic Lymph Node for Drug Development

The interaction of immune cells with drugs and/or with other cell types should be mechanistically investigated in order to reduce attrition of new drug development. However, they are currently only limited technologies that address this need. In our work, we developed initial but significant building blocks that enable such immune-drug studies. We developed a novel microfluidic platform replicating the Lymph Node (LN) microenvironment called LN-on-a-chip, starting from design all the way to microfabrication, characterization and validation in terms of architectural features, fluidics, cytocompatibility, and usability. To prove the biomimetics of this microenvironment, we inserted different immune cell types in a microfluidic device, which showed an in-vivo-like spatial distribution. We demonstrated that the developed LN-on-a-chip incorporates key features of the native human LN, namely, (i) similarity in extracellular matrix composition, morphology, porosity, stiffness, and permeability, (ii) compartmentalization of immune cells within distinct structural domains, (iii) replication of the lymphatic fluid flow pattern, (iv) viability of encapsulated cells in collagen over the typical timeframe of immunotoxicity experiments, and (v) interaction among different cell types across chamber boundaries. Further studies with this platform may assess the immune cell function as a step forward to disclose the effects of pharmaceutics to downstream immunology in more physiologically relevant microenvironments.

A systematic review of magnetic resonance lymphography for the evaluation of peripheral lymphedema

OBJECTIVE

Visualization of the lymphatic system is necessary for both early diagnosis and associated treatments. A promising imaging modality is magnetic resonance lymphography (MRL). The aim of this review was to summarize different MRL protocols, to assess the clinical value in patients with peripheral lymphedema, and to define minimal requirements necessary for visualization of lymphatics.

METHODS

A systematic literature search was conducted in PubMed, Embase, and the Cochrane Library in December 2018. Studies performing MRL in patients with peripheral lymphedema or healthy participants were included. Study design, population, etiology, duration of lymphedema, clinical staging, contrast agent, dose, injection site, and technical magnetic resonance imaging details were analyzed. No meta-analyses were performed because of different study aims and heterogeneity of the study populations.

RESULTS

Twenty-five studies involving 1609 patients with both primary lymphedema (n = 669) and secondary lymphedema (n = 657) were included. Upper and lower limbs were examined in 296 and 602 patients, respectively. Twenty-two studies used a gadolinium-based contrast agent that was injected intracutaneously or subcutaneously in the interdigital web spaces. Contrast-enhanced T1-weighted combined with T2-weighted protocols were most frequently used. T1-weighted images showed lymphatics in 63.3% to 100%, even in vessels with a diameter of ≥0.5 mm. Dermal backflow and a honeycomb pattern were clearly recognized.

CONCLUSIONS

MRL identifies superficial lymphatic vessels with a diameter of ≥0.5 mm with high sensitivity and specificity and accurately shows abnormal lymphatics and lymphatic drainage patterns. Therefore, MRL could be of clinical value in both early and advanced stages of peripheral lymphedema. Minimum requirements of an MRL protocol should consist of a gadolinium-based contrast-enhanced T1-weighted gradient-recalled echo sequence combined with T2-weighted magnetic resonance imaging, with acquisition at least 30 minutes after injection of contrast material.

Examining Obesity in Lymphedema: A Retrospective Study of 178 New Patients with Suspected Lymphedema at a Canadian Hospital-Based Clinic

Purpose: Physiotherapists have an important role to play in the early detection and treatment of lymphedema, a chronic inflammatory condition characterized by excess interstitial protein-rich fluid, which is estimated to affect more than one million Canadians. Obesity has been identified both as an important cause of and as a risk factor for developing lymphedema of various aetiologies. Little is currently known about obesity in Canadians affected by lymphedema. The objective of this study was to report on the prevalence of overweight and obesity in a Canadian lymphedema clinic population and the relationships among BMI; demographic, medical, and lymphedema characteristics; and cellulitis history. Method: We conducted a retrospective electronic record review of the clinical data collected from new patients evaluated for suspected lymphedema at a specialized Canadian hospital-based clinic over a 2-year period. We used descriptive analyses to characterize the sample and one-way analysis of variance and χ2 tests for comparative analyses. Results: Of the 178 patients whose records were reviewed, 36.5% were classified as overweight and 39.3% as obese. Patients with non-cancer diagnoses had a higher mean BMI than those with cancer-related diagnoses (p < 0.001). A higher BMI was associated with a longer time since lymphedema onset (p < 0.001), bilateral lymphedema (p = 0.010), and history of cellulitis (p < 0.001). Conclusions: Obesity is prevalent in the Canadian population with lymphedema and is associated with delayed referral and increased cellulitis rates. Early detection and tailored management strategies are needed to address obesity in patients with lymphedema and the complexities associated with these two related conditions.

Characteristics and outcomes of lymphaticovenular anastomosis in older patients with bilateral involvement versus younger patients with unilateral involvement in lower extremity lymphedema

OBJECTIVE

We have previously reported that patients with idiopathic primary lymphedema of adult onset can be classified into an older group with bilateral involvement and a younger group with unilateral involvement and that there are significant differences in the characteristics of these groups. The aims of this study were to investigate the features of these two groups further by evaluating the lymphatics while performing lymphaticovenular anastomosis (LVA) and to compare the effectiveness of LVA between the two groups.

METHODS

This study enrolled 74 patients (136 edematous legs) in whom indocyanine green (ICG) lymphography and LVA were performed. The rate of detection and the diameter of the lymphatic vessels were recorded. The lower extremity lymphedema index (the total sum of the squares of the circumference for five areas in each leg divided by the body mass index) was obtained before and 6 months after LVA. The rate of improvement in the affected lower limbs after LVA was also calculated.

RESULTS

The clinical lymphedema pattern was determined to be bilateral in 62 patients and unilateral in 12. Patients with bilateral lymphedema were significantly older than those with unilateral lymphedema (77.1 ± 7.8 years vs 55.5 ± 12.77 years; P < .01). A linear pattern was seen in 23 patients (46 legs), a low enhancement (LE) pattern in 12 patients (24 legs), a distal dermal backflow (dDB) pattern in 20 patients (40 legs), and an extended dermal backflow (eDB) pattern in 7 patients (14 legs). The lymphedema was unilateral in 12 patients (12 legs). There were significant between-group differences in lymphatic diameter in relation to lower leg area: linear (0.9 ± 0.1 mm) vs dDB (0.7 ± 0.2 mm), linear vs eDB (0.7 ± 0.2 mm), linear vs unilateral (0.5 ± 0.1 mm), LE (0.9 ± 0.2 mm) vs dDB, LE vs eDB, LE vs unilateral, and dDB vs unilateral, P < .01; and eDB vs unilateral, P < .05. There were also significant between-group differences in the rate of improvement in the lower extremity lymphedema index according to the ICG lymphography pattern and laterality: linear (10.5% ± 2.4%) vs unilateral (6.7% ± 0.6%), LE (10.4% ± 1.5%) vs unilateral, dDB (11.0% ± 1.3%) vs eDB (8.9% ± 1.5%), and dDB vs unilateral, P < .01; linear vs eDB, P < .05; and eDB vs unilateral, P < .05.

CONCLUSIONS

The lymphatic vessel diameter tended to be greater in older patients with bilateral lymphedema than in younger patients with unilateral lymphedema. The rate of detection and improvement tended to decrease with worsening of the ICG lymphography pattern. LVA is thought to be more effective in older patients with early-stage bilateral lower leg lymphedema than in their younger counterparts with late-stage unilateral lymphedema.

Understanding Inter-Individual Variability in Monoclonal Antibody Disposition

Monoclonal antibodies (mAbs) are currently the largest and most dominant class of therapeutic proteins. Inter-individual variability has been observed for several mAbs; however, an understanding of the underlying mechanisms and factors contributing to inter-subject differences in mAb disposition is still lacking. In this review, we analyze the mechanisms of antibody disposition and the putative mechanistic determinants of inter-individual variability. Results from in vitro, preclinical, and clinical studies were reviewed evaluate the role of the neonatal Fc receptor and Fc gamma receptors (expression and polymorphism), target properties (expression, shedding, turnover, internalization, heterogeneity, polymorphism), and the influence of anti-drug antibodies. Particular attention is given to the influence of co-administered drugs and disease, and to the physiological relevance of covariates identified by population pharmacokinetic modeling, as determinants of variability in mAb pharmacokinetics.

Biomaterials for Modulating Lymphatic Function in Immunoengineering

Immunoengineering is a rapidly growing and interdisciplinary field focused on developing tools to study and understand the immune system, then employing that knowledge to modulate immune response for the treatment of disease. Because of its roles in housing a substantial fraction of the body's lymphocytes, in facilitating immune cell trafficking, and direct immune modulatory functions, among others, the lymphatic system plays multifaceted roles in immune regulation. In this review, the potential for biomaterials to be applied to regulate the lymphatic system and its functions to achieve immunomodulation and the treatment of disease are described. Three related processes-lymphangiogenesis, lymphatic vessel contraction, and lymph node remodeling-are specifically explored. The molecular regulation of each process and their roles in pathologies are briefly outlined, with putative therapeutic targets and the lymphatic remodeling that can result from disease highlighted. Applications of biomaterials that harness these pathways for the treatment of disease via immunomodulation are discussed.

Modeling of Transport Mechanisms in the Respiratory System: Validation via Congestive Heart Failure Patients

The heart and lungs are intricately related. For congestive heart failure patients, fluid (plasma) backs up into the pulmonary system. As a result, pulmonary capillary pressure increases, causing fluid to seep into the lungs (pulmonary edema) within minutes. This excess fluid induces extra stress during breathing that affects respiratory health. In this paper, we focus on the effect that high pulmonary capillary pressure has on the development of this extravascular lung water (EVLW). A mathematical model of pulmonary fluid and mass transport mechanisms is developed in order to quantitatively analyze the transport phenomena in the pulmonary system. The model is then validated on 15 male heart failure patients from published literature [1]. The model shows reasonable estimation of EVLW in heart failure patients, which is useful in assessing the severity of pulmonary edema.

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.

Regulation of Immune Function by the Lymphatic System in Lymphedema

The lymphatic vasculature has traditionally been thought to play a passive role in the regulation of immune responses by transporting antigen presenting cells and soluble antigens to regional lymph nodes. However, more recent studies have shown that lymphatic endothelial cells regulate immune responses more directly by modulating entry of immune cells into lymphatic capillaries, presenting antigens on major histocompatibility complex proteins, and modulating antigen presenting cells. Secondary lymphedema is a disease that develops when the lymphatic system is injured during surgical treatment of cancers or is damaged by infections. We have used mouse models of lymphedema in order to understand the effects of chronic lymphatic injury on immune responses and have shown that lymphedema results in a mixed T helper cell and T regulatory cell (Treg) inflammatory response. Prolonged T helper 2 biased immune responses in lymphedema regulate the pathology of this disease by promoting tissue fibrosis, inhibiting formation of collateral lymphatics, decreasing lymphatic vessel pumping capacity, and increasing lymphatic leakiness. Treg infiltration following lymphatic injury results from proliferation of natural Tregs and suppresses innate and adaptive immune responses. These studies have broad clinical relevance since understanding how lymphatic injury in lymphedema can modulate immune responses may provide a template with which we can study more subtle forms of lymphatic injury that may occur in physiologic conditions such as aging, obesity, metabolic tumors, and in the tumor microenvironment.

Minimally invasive method for the point-of-care quantification of lymphatic vessel function

Current clinical methods for the evaluation of lymphatic vessel function, crucial for early diagnosis and evaluation of treatment response of several pathological conditions, in particular of postsurgical lymphedema, are based on complex and mainly qualitative imaging techniques. To address this unmet medical need, we established a simple strategy for the painless and quantitative assessment of cutaneous lymphatic function. We prepared a lymphatic-specific tracer formulation, consisting of the clinically approved near-infrared fluorescent dye, indocyanine green, and the solubilizing surfactant Kolliphor HS15. The tracer was noninvasively delivered to the dermal layer of the skin using MicronJet600 hollow microneedles, and the fluorescence signal decay at the injection site was measured over time using a custom-made, portable detection device. The decay rate of fluorescence signal in the skin was used as a direct measure of lymphatic vessel drainage function. With this method, we could quantify impaired lymphatic clearance in transgenic mice lacking dermal lymphatics and distinguish distinct lymphatic clearance patterns in pigs in different body locations and under manual stimulus. Overall, this method has the potential for becoming a noninvasive and quantitative clinical "office test" for lymphatic function assessment.

Compression therapy in lymphedema: Between past and recent scientific data

Aim

To extrapolate and discuss the scientific data on compression in lymphedema treatment, so to review old and innovative concepts about pressure, stiffness and other interplaying factors related to its efficacy and comfort.

Material and methods

Narrative review based on search in Medline/Google Scholar through key-words related to compression in lymphedema.

Results

Currently available literature lacks relevant details about data on protocol, devices, techniques, interface pressure, stiffness, as well as biases are represented by the different descriptions to present the outcomes. More recent evidence from adjustable wrap devices and elastic garments question the need for high pressure (especially for the upper limb) and stiffness in lymphedema treatment.

Conclusions

At present time a very strong compression pressure exerted by material with high stiffness seem to be questionable in lymphedema treatment. A low pressure provides the best outcomes in arm lymphedema, while a pressure in the range of 40–60 mm Hg seems to provide higher efficacy in lower limb lymphedema, provided it is maintained overtime. A high stiffness seems to be unnecessary to treat chronic edema. Future clinical trials, including proper description of treatment methodology and adequate investigating instrumental tools, are awaited to possibly corroborate the conclusive outcomes of our review.

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.

Mechanisms of Connexin-Related Lymphedema

RATIONALE

Mutations in GJC2 and GJA1, encoding Cxs (connexins) 47 and 43, respectively, are linked to lymphedema, but the underlying mechanisms are unknown. Because efficient lymph transport relies on the coordinated contractions of lymphatic muscle cells (LMCs) and their electrical coupling through Cxs, Cx-related lymphedema is proposed to result from dyssynchronous contractions of lymphatic vessels.

OBJECTIVE

To determine which Cx isoforms in LMCs and lymphatic endothelial cells are required for the entrainment of lymphatic contraction waves and efficient lymph transport.

METHODS AND RESULTS

We developed novel methods to quantify the spatiotemporal entrainment of lymphatic contraction waves and used optogenetic techniques to analyze calcium signaling within and between the LMC and the lymphatic endothelial cell layers. Genetic deletion of the major lymphatic endothelial cell Cxs (Cx43, Cx47, or Cx37) revealed that none were necessary for the synchronization of the global calcium events that triggered propagating contraction waves. We identified Cx45 in human and mouse LMCs as the critical Cx mediating the conduction of pacemaking signals and entrained contractions. Smooth muscle-specific Cx45 deficiency resulted in 10- to 18-fold reduction in conduction speed, partial-to-severe loss of contractile coordination, and impaired lymph pump function ex vivo and in vivo. Cx45 deficiency resulted in profound inhibition of lymph transport in vivo, but only under an imposed gravitational load.

CONCLUSIONS

Our results (1) identify Cx45 as the Cx isoform mediating the entrainment of the contraction waves in LMCs; (2) show that major endothelial Cxs are dispensable for the entrainment of contractions; (3) reveal a lack of coupling between lymphatic endothelial cells and LMCs, in contrast to arterioles; (4) point to lymphatic valve defects, rather than contraction dyssynchrony, as the mechanism underlying GJC2- or GJA1-related lymphedema; and (5) show that a gravitational load exacerbates lymphatic contractile defects in the intact mouse hindlimb, which is likely critical for the development of lymphedema in the adult mouse.

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.

A Descriptive Study of the Temporal Patterns of Volume and Contents Change in Human Acute Burn Edema: Application in Evidence-Based Intervention and Research Design

Edema after burn contributes significantly to burn wound depth conversion. In humans after burn injury, there is a lack of detailed understanding of the contents and temporal changes in volume of acute tissue edema. The novel findings of these studies relate to the collection of edema fluid after partial-thickness burn injury. Edema volume peaks on day 1 after burn without formal fluid resuscitation. The studies indicated that the peak was on day 2 for a resuscitated burn. In contrast, animal studies suggest that the peak of edema occurs by or before day 1 after injury. The findings confirm the pitfalls of evidence derived from animal models and assuming direct transference to humans. Postburn edema was demonstrated to be a high-protein fluid (ie, ≥10 g/L) for the duration of the inflammatory period. The presence of high-protein edema presents greater challenges to clinicians developing novel treatment options. The rate of volume change over time tapered to insignificant levels after day 4 following burn. Greater than 98% of the edema contents was fluid. However, the size of particulate matter did not preclude it passing through patent lymphatic collectors. The results indicate a necessity for urgent postburn intervention, which should incorporate the active stimulation of the lymphatic system to improve efficacy of edema removal.

Long term effects of manual lymphatic drainage and active exercises on physical morbidities, lymphoscintigraphy parameters and lymphedema formation in patients operated due to breast cancer: A clinical trial

PURPOSE

evaluate whether manual lymphatic drainage (MLD) or active exercise (AE) is associated with shoulder range of motion (ROM), wound complication and changes in the lymphatic parameters after breast cancer (BC) surgery and whether these parameters have an association with lymphedema formation in the long run.

METHODS

Clinical trial with 106 women undergoing radical BC surgery, in the Women's Integrated Healthcare Center-University of Campinas. Women were matched for staging, age and body mass index and were allocated to performed AE or MLD, 2 weekly sessions during one month after surgery. The wound was evaluated 2 months after surgery. ROM, upper limb circumference measurement and upper limb lymphoscintigraphy were performed before surgery, and 2 and 30 months after surgery.

RESULTS

The incidence of seroma, dehiscence and infection did not differ between groups. Both groups showed ROM deficit of flexion and abduction in the second month postoperative and partial recovery after 30 months. Cumulative incidence of lymphedema was 23.8% and did not differ between groups (p = 0.29). Concerning the lymphoscintigraphy parameters, there was a significant convergent trend between baseline degree uptake (p = 0.003) and velocity visualization of axillary lymph nodes (p = 0.001) with lymphedema formation. A reduced marker uptake before or after surgery predicted lymphedema formation in the long run (>2 years). None of the lymphoscintigraphy parameters were shown to be associated with the study group. Age ≤39 years was the factor with the greatest association with lymphedema (p = 0.009). In women with age ≤39 years, BMI >24Kg/m2 was significantly associated with lymphedema (p = 0.017). In women over 39 years old, women treated with MLD were at a significantly higher risk of developing lymphedema (p = 0.011).

CONCLUSION

Lymphatic abnormalities precede lymphedema formation in BC patients. In younger women, obesity seems to be the major player in lymphedema development and, in older women, improving muscle strength through AE can prevent lymphedema. In essence, MLD is as safe and effective as AE in rehabilitation after breast cancer surgery.

A vicious circle in chronic lymphoedema pathophysiology? An adipocentric view

Chronic lymphoedema is a disease caused by a congenital or acquired damage to the lymphatic system and characterized by complex chains of pathophysiologic events such as lymphatic fluid stasis, chronic inflammation, lymphatic vessels impairment, adipose tissue deposition and fibrosis. These events seem to maintain and reinforce themselves through a positive feedback loop: regardless of the initial cause of lymphatic stasis, the dysfunctional adipose tissue and its secretion products can worsen lymphatic vessels' function, aggravating lymph leakage and stagnation, which can promote further adipose tissue deposition and fibrosis, similar to what may happen in obesity. In addition to the current knowledge about the tight and ancestral interrelation between immunity system and metabolism, there is evidence for similarities between obesity-related and lymphatic damage-induced lymphoedema. Together, these observations indicate strong reciprocal relationship between lymphatics and adipose tissue and suggest a possible key role of the adipocyte in the pathophysiology of chronic lymphoedema's vicious circle.

The relationship between lymphangion chain length and maximum pressure generation established through in vivo imaging and computational modeling

The intrinsic contraction of collecting lymphatic vessels serves as a pumping system to propel lymph against hydrostatic pressure gradients as it returns interstitial fluid to the venous circulation. In the present study, we proposed and validated that the maximum opposing outflow pressure along a chain of lymphangions at which flow can be achieved increases with the length of chain. Using minimally invasive near-infrared imaging to measure the effective pumping pressure at various locations in the rat tail, we demonstrated increases in pumping pressure along the length of the tail. Computational simulations based on a microstructurally motivated model of a chain of lymphangions informed from biaxial testing of isolated vessels was used to provide insights into the pumping mechanisms responsible for the pressure increases observed in vivo. These models suggest that the number of lymphangions in the chain and smooth muscle cell force generation play a significant role in determining the maximum outflow pressure, whereas the frequency of contraction has no effect. In vivo administration of nitric oxide attenuated lymphatic contraction, subsequently lowering the effective pumping pressure. Computational simulations suggest that the reduction in contractile strength of smooth muscle cells in the presence of nitric oxide can account for the reductions in outflow pressure observed along the lymphangion chain in vivo. Thus, combining modeling with multiple measurements of lymphatic pumping pressure provides a method for approximating intrinsic lymphatic muscle activity noninvasively in vivo while also providing insights into factors that determine the extent that a lymphangion chain can transport fluid against an adverse pressure gradient. NEW & NOTEWORTHY Here, we report the first minimally invasive in vivo measurements of the relationship between lymphangion chain length and lymphatic pumping pressure. We also provide the first in vivo validation of lumped parameter models of lymphangion chains previously developed through data obtained from isolated vessel testing.

Evaluation of Stiffness in Postmastectomy Lymphedema Using Acoustic Radiation Force Impulse Imaging: A Prospective Randomized Controlled Study for Identifying the Optimal Pneumatic Compression Pressure to Reduce Stiffness

PURPOSE

We aimed to assess the improvement in stiffness in patients with postmastectomy lymphedema (PMLE) after intermittent pneumatic compression (IPC) using acoustic radiation force impulse (ARFI) imaging and evaluate the effects of different IPC pressures.

METHODS

We randomly assigned 45 patients with PMLE (stage II) to three groups based on the IPC pressure: 25, 35, and 45 mmHg. Patients received a single session of IPC for 30 minutes. We recorded the subcutaneous tissue thickness of the proximal upper limbs using ultrasonography and circumference of the upper limbs and stiffness using ARFI before and immediately after IPC.

RESULTS

Arm circumference and subcutaneous tissue thickness were significantly decreased after IPC in all groups. The shear wave velocity (SWV) decreased after IPC in all groups, but significantly decreased only in the 35 mmHg group. The subcutaneous tissue thickness and SWV in the 35 mmHg group were significantly decreased compared to the other groups.

CONCLUSION

IPC can reduce stiffness and subcutaneous tissue thickness of the proximal upper arm in patients with PMLE. A pressure of 35 mmHg yields the largest improvement of stiffness; higher compression pressure did not yield any additional improvement.

Preoperative Lymphedema-Related Risk Factors in Early-Stage Breast Cancer

BACKGROUND

Prolongation of survival in patients with breast cancer due to early diagnosis and modern methods of treatment has turned the attention on lymphedema, which is the most important morbidity secondary to the treatment of the disease. Determination of lymphedema and related risk factors in patients before a surgical intervention may provide protection for patients and early treatment. The aim of this study was to determine the presence of lymphedema before surgery by bioimpedance analysis in patients with breast cancer and to establish risk factors associated with lymphedema.

PATIENTS AND METHODS

A total of 277 patients who were diagnosed as having breast cancer, were planned to undergo a surgical intervention, and had no clinical lymphedema were included in the study. The presence of lymphedema was evaluated with clinical examination, measurement of arm circumference, and bioimpedance analysis.

RESULTS

Lymphedema was found in 59 (21.3%) patients with no detected differences in arm circumferences. A significant relationship was found between the presence of lymphedema and body mass index (BMI), number of positive lymph nodes, and capsule invasion of the tumor (p = 0.001, p = 0.003, p = 0.002, respectively). Multiple regression analysis revealed that BMI and the number of positive lymph nodes were independent variables (p = 0.024, p = 0.002). ROC curve analysis resulted in an increased risk of preoperative lymphedema when the number of positive lymph nodes was ≥8. Correlation analysis revealed a positive correlation between the number of positive lymph nodes and L-dex score (p = 0.001, r = 0.219).

CONCLUSION

Preoperative bioimpedance analysis demonstrated that ∼1/5 of the patients had subclinical lymphedema. Preoperative subclinical lymphedema is associated with obesity and the number of positive lymph nodes, and thus, treatment of the axilla in patients who are preoperatively detected to have subclinical lymphedema should be revised.

Lymphedema evaluation using noninvasive 3T MR lymphangiography

PURPOSE

To exploit the long 3.0T relaxation times and low flow velocity of lymphatic fluid to develop a noninvasive 3.0T lymphangiography sequence and evaluate its relevance in patients with lymphedema.

MATERIALS AND METHODS

A 3.0T turbo-spin-echo (TSE) pulse train with long echo time (TE_effective  = 600 msec; shot-duration = 13.2 msec) and TSE-factor (TSE-factor = 90) was developed and signal evolution simulated. The method was evaluated in healthy adults (n = 11) and patients with unilateral breast cancer treatment-related lymphedema (BCRL; n = 25), with a subgroup (n = 5) of BCRL participants scanned before and after manual lymphatic drainage (MLD) therapy. Maximal lymphatic vessel cross-sectional area, signal-to-noise-ratio (SNR), and results from a five-point categorical scoring system were recorded. Nonparametric tests were applied to evaluate study parameter differences between controls and patients, as well as between affected and contralateral sides in patients (significance criteria: two-sided P < 0.05).

RESULTS

Patient volunteers demonstrated larger lymphatic cross-sectional areas in the affected (arm = 12.9 ± 6.3 mm² ; torso = 17.2 ± 15.6 mm² ) vs. contralateral (arm = 9.4 ± 3.9 mm² ; torso = 9.1 ± 4.6 mm² ) side; this difference was significant both for the arm (P = 0.014) and torso (P = 0.025). Affected (arm: P = 0.010; torso: P = 0.016) but not contralateral (arm: P = 0.42; torso: P = 0.71) vessel areas were significantly elevated compared with control values. Lymphatic cross-sectional areas reduced following MLD on the affected side (pre-MLD: arm = 8.8 ± 1.8 mm² ; torso = 31.4 ± 26.0 mm² ; post-MLD: arm = 6.6 ± 1.8 mm² ; torso = 23.1 ± 24.3 mm² ). This change was significant in the torso (P = 0.036). The categorical scoring was found to be less specific for detecting lateralizing disease compared to lymphatic-vessel areas.

CONCLUSION

A 3.0T lymphangiography sequence is proposed, which allows for upper extremity lymph stasis to be detected in ∼10 minutes without exogenous contrast agents.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2017;46:1349-1360.

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.

Multi-center rater-blinded study of early intervention with the Hand Incubator for breast cancer-related lymphedema (the BEAT-EDEMA trial): Proposal of a research protocol

Postoperative lymphedema is considered irreversible once it has developed, and significantly lowers the patient's quality of life. However, lymphatic function has recently been clarified, and it is possible that lymphedema can be cured if early treatment is started. This two-arm randomized clinical trial (UMIN000026124) will prospectively evaluate 24 patients with early-stage breast cancer-related lymphedema at the Nagoya University Hospital and Aichi Cancer Center Hospital. The eligibility criteria will be patients who are diagnosed with stage 0-1 breast cancer-related lymphedema, as defined by the International Society of Lymphology, within 12 weeks after breast cancer surgery. The diagnosis of lymphedema will be confirmed using a bioimpedance spectroscopy device (L-Dex®). Participants will be randomized 1:1 into the intervention and control groups. The physicians and patients will be aware of their group assignment, although treatment efficacy will be evaluated by raters who are blinded to the group assignments. The intervention group will complete grasping exercises in the Hand Incubator device for 4 weeks. The primary outcome will be the change in the affected upper limb's volume after the intervention, as measured using the water displacement method. This study may help establish a standard treatment for postoperative lymphedema.

Comparisons Between Cancer-Related and Noncancer-Related Lymphedema: An Overview of New Patients Referred to a Specialized Hospital-Based Center in Canada

BACKGROUND

Lymphedema is an irreversible inflammatory condition caused by accumulated lymph fluid and is associated with chronic swelling and increased risk of cellulitis. Our objectives were to: (1) describe the patient population referred to a Canadian lymphedema center and (2) compare lymphedema characteristics between patients with cancer and patients with noncancer diagnoses.

METHODS AND RESULTS

A retrospective cohort study was conducted of new patients referred for suspected lymphedema to a hospital-based center over a 2-year period. The mean age of the patients (n = 429) was 61.4 years; 85% were female and 81% had a history of cancer. Lymphedema characteristics were primary (7%) versus secondary (92%); upper body (51%) versus lower body (45%); unilateral (74%) versus bilateral (25%); and history of cellulitis (22%). Patients with noncancer diagnoses (n = 82) were more likely than patients with cancer diagnoses (n = 347) to have a history of cellulitis (44% vs. 17%), to have bilateral (61% vs. 16%) and lower limb (89% vs. 37%) lymphedema, and to experience a long delay between symptom onset and referral (14.0 vs. 3.5 years) (p < 0.001).

CONCLUSION

Most patients referred to our lymphedema center were female with a history of cancer. However, patients with noncancer diagnoses were more likely to have bilateral lower body lymphedema with an important history of cellulitis; this subgroup is at great risk of missed and delayed diagnoses in the medical setting and of experiencing long-term issues with mobility, recurrent hospitalizations, and poor quality of life.

Lymphatic pumping: mechanics, mechanisms and malfunction

A combination of extrinsic (passive) and intrinsic (active) forces move lymph against a hydrostatic pressure gradient in most regions of the body. The effectiveness of the lymph pump system impacts not only interstitial fluid balance but other aspects of overall homeostasis. This review focuses on the mechanisms that regulate the intrinsic, active contractions of collecting lymphatic vessels in relation to their ability to actively transport lymph. Lymph propulsion requires not only robust contractions of lymphatic muscle cells, but contraction waves that are synchronized over the length of a lymphangion as well as properly functioning intraluminal valves. Normal lymphatic pump function is determined by the intrinsic properties of lymphatic muscle and the regulation of pumping by lymphatic preload, afterload, spontaneous contraction rate, contractility and neural influences. Lymphatic contractile dysfunction, barrier dysfunction and valve defects are common themes among pathologies that directly involve the lymphatic system, such as inherited and acquired forms of lymphoedema, and pathologies that indirectly involve the lymphatic system, such as inflammation, obesity and metabolic syndrome, and inflammatory bowel disease.

Near-infrared indocyanine dye permits real-time characterization of both venous and lymphatic circulation

We investigated the optical properties of a near-infrared (NIR) fluorochrome, di-β-cyclodextrin-binding indocyanine derivative (TK-1), and its pharmacokinetic differences with indocyanine green (ICG). TK-1 was designed to have hydrophilic cyclodextrin molecules and, thus, for higher water solubility and smaller particle sizes than the plasma protein-bound ICG. We compared optical properties such as the absorption and fluorescence spectra, quantum yield, and photostability between both dyes in vitro. In addition, we subcutaneously injected a 1 mM solution of TK-1 or ICG into the hind footpad of rats and observed real-time NIR fluorescence intensities in their femoral veins and accompanying lymphatics at the exposed groin site to analyze the dye pharmacokinetics. These optical experiments demonstrated that TK-1 has high water solubility, a low self-aggregation tendency, and high optical and chemical stabilities. Our in vivo imaging showed that TK-1 was transported via peripheral venous flow and lymphatic flow, whereas ICG was drained only through lymphatics. The results of this study showed that lymphatic and venous transport can be differentially regulated and is most likely influenced primarily by particle size, and that TK-1 can enable real-time NIR fluorescence imaging of whole fluids and solute movement via both microvessels and lymphatics, which conventional ICG cannot achieve.

Vascularized Lymph Node Transfer: A Review of the Current Evidence

Over the past decade, lymph node transfer has rapidly gained popularity among plastic surgeons for the treatment of chronic lymphedema because of the initial promising results and its unique technical advantages compared with the other reconstructive options. However, its functional mechanism is still a matter of great debate, and some concerning reports have emerged regarding the safety of this procedure in patients with chronic lymphedema. The authors review the literature on the experimental and clinical evidence for lymph node transfer, discuss its proposed functional mechanisms, review the potential risk of iatrogenic lymphedema following this procedure, and discuss the suggested strategies to avoid this complication.