Lymphatic Vessel Pumping

Anesthesia-induced Lymphatic Dysfunction

General anesthetics adversely alters the distribution of infused fluid between the plasma compartment and the extravascular space. This maldistribution occurs largely from the effects of anesthetic agents on lymphatic pumping, which can be demonstrated by macroscopic fluid kinetics studies in awake versus anesthetized patients. The magnitude of this effect can be appreciated as follows: a 30% reduction in lymph flow may result in a fivefold increase of fluid-induced volume expansion of the interstitial space relative to plasma volume. Anesthesia-induced lymphatic dysfunction is a key factor why anesthetized patients require greater than expected fluid administration than can be accounted for by blood loss, urine output, and insensible losses. Anesthesia also blunts the transvascular refill response to bleeding, an important compensatory mechanism during hemorrhagic hypovolemia, in part through lymphatic inhibition. Last, this study addresses how catecholamines and hypertonic and hyperoncotic fluids may mobilize interstitial fluid to mitigate anesthesia-induced lymphatic dysfunction.

Evaluation of the Superficial Collecting Lymph Vessels' Vasa Vasorum in Lymphoedematous Limbs Using Video Capillaroscopy

OBJECTIVE

The pre-collecting and collecting lymph vessels have smooth muscle cells, and sufficient perfusion is vital to maintain their function. Although the vasa vasorum of the collecting lymph vessels (VVCL) have been histologically investigated, little is known about their physiology. This study aimed to investigate the relationship between morphology and blood flow of the VVCL in lymphoedematous limbs.

METHODS

Medical records of lower extremity lymphoedema patients who underwent video capillaroscopy observation during supermicrosurgical lymphaticovenous anastomosis (LVA) surgery were reviewed. The collecting lymph vessels, dissected for LVA, were examined under video capillaroscopy (GOKO Bscan-ZD, GOKO Imaging Devices Co., Japan) with a magnification of 175x and 620x. Blood flow velocity of the VVCL was calculated by measuring the red blood cell movement using software (GOKO-VIP ver. 1.0.0.4, GOKO Imaging Devices Co., Japan). Based on the video capillaroscopy findings, the VVCL were grouped according to their morphology; the VVCL morphology types and blood flow velocity were then compared according to the lymphosclerosis severity grade.

RESULTS

Sixty-seven lymph vessels in 20 lower extremity lymphoedema patients were evaluated, including s0 in 19 (28.4%), s1 in 34 (50.7%), s2 in 10 (14.9%), and s3 in four (6.0%) lymph vessels. The VVCLs were grouped into four types: type 1 (n = 4), type 2 (n = 37), type 3 (n = 19), and type 4 (n = 7). Blood flow velocity of the VVCL ranged 0 - 189.3 μm/sec (average 26.40 μm/sec). There were statistically significant differences in VVCL morphology (p < .001) and blood flow velocity (p < .001) according to lymphosclerotic severity.

CONCLUSION

Vasa vasorum of the collecting lymph vessels could be grouped into four types with different characteristics. Morphological and physiological changes of the VVCL were related to sclerotic changes of the collecting lymph vessels.

Rapid lymphatic malformation expansion: Imaging, association with asymptomatic Streptococcus infection, multidisciplinary management, and therapeutic approach

Lymphatic malformations are congenital anomalies of the lymphatic system that can occur anywhere in the body and typically present in early childhood. They are often painless, slow-growing, and asymptomatic, but may lead to a wide range of symptoms depending on their size and location. Rarely, congenital malformations may not be diagnosed until later in childhood or adolescence, despite being present from birth. In some individuals, lymphatic malformations can expand quickly, especially in the setting of an inflammatory process. We present the case of an 8-year-old boy who had a rapidly enlarging, nonpainful mass on his right neck and a positive streptococcus throat swab. After evaluation by multiple specialists and imaging studies, he was diagnosed with a multilocular, multicystic lymphatic malformation. He was treated with fluoroscopy-guided doxycycline sclerotherapy, and has had near total resolution of neck swelling. This case report is significant because it highlights the potential benefits of a multidisciplinary approach to the diagnosis and management of lymphatic malformations. Additionally, it emphasizes the importance of considering congenital malformations in the differential diagnosis of neck masses, even in older children. Finally, it also adds to the growing body of evidence that hypothesizes that strep throat infections may trigger the sudden expansion of previously asymptomatic congenital lymphatic malformations.

Intestinal Lymphatic Dysfunction in Kidney Disease

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

Dicarbonyl-modified lipoproteins contribute to proteinuric kidney injury

Lipoprotein modification by reactive dicarbonyls, including isolevuglandin (IsoLG), produces dysfunctional particles. Kidneys participate in lipoprotein metabolism, including tubular uptake. However, the process beyond the proximal tubule is unclear, as is the effect of kidney injury on this pathway. We found that patients and animals with proteinuric injury have increased urinary apolipoprotein AI (apoAI), IsoLG, and IsoLG adduct enrichment of the urinary apoAI fraction compared with other proteins. Proteinuric mice, induced by podocyte-specific injury, showed more tubular absorption of IsoLG-apoAI and increased expression of lipoprotein transporters in proximal tubular cells compared with uninjured animals. Renal lymph reflects composition of the interstitial compartment and showed increased apoAI and IsoLG in proteinuric animals, supporting a tubular cell-interstitium-lymph pathway for renal handling of lipoproteins. IsoLG-modified apoAI was not only a marker of renal injury but also directly damaged renal cells. IsoLG-apoAI increased inflammatory cytokines in cultured tubular epithelial cells (TECs), activated lymphatic endothelial cells (LECs), and caused greater contractility of renal lymphatic vessels than unmodified apoAI. In vivo, inhibition of IsoLG by a dicarbonyl scavenger reduced both albuminuria and urinary apoAI and decreased TEC and LEC injury, lymphangiogenesis, and interstitial fibrosis. Our results indicate that IsoLG-modified apoAI is, to our knowledge, a novel pathogenic mediator and therapeutic target in kidney disease.

Cadmium mediates pyroptosis of human dermal lymphatic endothelial cells in a NLRP3 inflammasome-dependent manner

Pyroptosis is a form of inflammasome-trigged programmed cell death in response to a variety of stimulators, including environmental cytotoxic pollutant Cadmium (Cd). Vascular endothelial cell is one of the first-line cell types of Cd cell toxicity. Studies report that Cd exposure causes pyroptosis in vascular endothelial cells. Vascular and lymphatic endothelial cells have many common properties, but these two cell types are distinguished in gene expression profile and the responsive behaviors to chemokine or physical stimulations. Whether Cd exposure also causes pyroptosis in lymphatic endothelial cells has not been investigated. Here, we found that Cd treatment significantly decreased the viability of human dermal lymphatic endothelial cells (HDLECs). Cd treatment induced inflammasome activation indicated by elevated cleavage of pro-caspase-1 into active form Casp1p20, elevated secretion of pro-inflammatory cytokines and production of reactive oxygen species (ROS). Flow cytometry showed that caspase-1 activity was significantly increased in Cd-treated cells. Moreover, knockdown of NLRP3 effectively rescued Cd-induced inflammasome activation and pyroptosis in HDLECs. Collectively, our results indicated that Cd induced pyroptosis in a NLRP3 inflammasome-dependent manner in lymphatic endothelial cells.

Draining the Pleural Space: Lymphatic Vessels Facing the Most Challenging Task

Simple Summary

Fluid drainage operated by lymphatic vessels is crucial for a proper volume homeostasis of body compartments. This role is particularly relevant for the pleural cavity, where the hydraulic pressure of the pleural liquid is very subatmospheric and fluid filtering from the blood capillaries into the pleural space must be continuously removed to keep the pleural space volume low and to prevent accumulation of liquid causing impairments of the respiratory mechanics. In order to accomplish this task, lymphatic vessels of the pleural side of the diaphragm and those lying on the pleural surface of the chest wall must possess a negative intraluminal pressure which has to vary during the respiratory cycle to follow the similar variations occurring to the pressure of pleural liquid. This review focuses on the in vivo pressure measurements performed in sedated animal models to understand how these lymphatic networks can accomplish this complex but pivotal role.

Abstract

Lymphatic vessels exploit the mechanical stresses of their surroundings together with intrinsic rhythmic contractions to drain lymph from interstitial spaces and serosal cavities to eventually empty into the blood venous stream. This task is more difficult when the liquid to be drained has a very subatmospheric pressure, as it occurs in the pleural cavity. This peculiar space must maintain a very low fluid volume at negative hydraulic pressure in order to guarantee a proper mechanical coupling between the chest wall and lungs. To better understand the potential for liquid drainage, the key parameter to be considered is the difference in hydraulic pressure between the pleural space and the lymphatic lumen. In this review we collected old and new findings from in vivo direct measurements of hydraulic pressures in anaesthetized animals with the aim to better frame the complex physiology of diaphragmatic and intercostal lymphatics which drain liquid from the pleural cavity.

From histo-anatomy to sonography in lymphedema: EURO-MUSCULUS/USPRM approach

Lymphedema is a disorder characterized by the accumulation of protein-rich lymphatic fluid in the cutaneous and subcutaneous tissue. Based on the underlying causes, it is classified into primary and secondary forms. The use of ultrasound has recently become widespread in the field of lymphedema - especially for its diagnosis and treatment planning. In this study, we briefly reviewed the anatomy and histology of the skin and subcutaneous tissue - to propose a standardized ultrasound assessment of the superficial tissues in patients with upper-/lower-limb lymphedema. We believe that identification of the sono-histological patterns of the dermo-epidermal complex and subcutaneous tissue has place to serve as a simple and reproducible strategy to evaluate their edema diseases that are often subject to an inaccurate diagnosis in daily clinical practice.

Association between intestinal lymphangiectasia and expression of inducible nitric oxide synthase in dogs with lymphoplasmacytic enteritis

Intestinal lymphangiectasia (IL) is a common complication in dogs. Since nitric oxide (NO) is known to relax the lymphatic vessel, we evaluated inducible NO synthase (iNOS) expression using immunohistochemistry in 13 dogs with lymphoplasmacytic enteritis (LPE) with or without IL. The duodenal iNOS expressing cells were significantly increased in dogs with IL-negative or IL-positive LPE dogs (P=0.025, P=0.007) compared with control dogs. However, there was no significant difference in iNOS expression between IL-positive and IL-negative tissues. Based on these results, there is no clear evidence for the NO overproduction in the pathogenesis of IL in dogs with LPE. Factors other than NO could, thus, contribute to IL in dogs with LPE.

Lymphotonic activity of Ruscus extract, hesperidin methyl chalcone and vitamin C in human lymphatic smooth muscle cells

OBJECTIVE

Besides actions including their venotonic, anti-inflammatory, and anti-oxidant effects, venoactive drugs are expected to act on edema via their action on lymphatics. The objective of this study was to evaluate the effect of the combination of Ruscus, hesperidin methyl chalcone and Vitamin C (Ruscus/HMC/Vit C) on intracellular calcium mobilization and contraction of human lymphatic smooth muscle cells (LSMCs) to better characterize the mechanism of its lymphotonic activity.

METHODS

Calcium mobilization was evidenced by videomicroscopy analysis of the fluorescence emitted by a specific Ca²⁺ sensitive dye and measured after injection of Ruscus/HMC/Vit C at 0.1, 0.3, 1.0, and 3.0 mg/mL into LSMCs.

RESULTS

Ruscus/HMC/Vit C induced a strong and reproducible concentration-dependent calcium mobilization in LSMCs. On the contrary, another venoactive drug used as comparator, micronized purified flavonoid fraction (MPFF), did not induce calcium mobilization whatever the tested concentration.

CONCLUSION

Although alternative mechanisms of action may result in potential lymphotonic effects, the efficacy of lymphotonic products is nonetheless related to their stimulating effect on the contractile activity of the smooth muscle cells surrounding lymphatic vessels. In the light of the results obtained in this study, the direct effect of Ruscus/HMC/Vit C on LSMC contraction may partially explain its clinical efficacy on lymphotonic activity, as has been observed in terms of objective signs of edema as reported in the recent guidelines on chronic venous disease.

Mechanisms underlying spontaneous phasic contractions and sympathetic control of smooth muscle in the rat caudal epididymis

Here we investigate mechanisms underlying spontaneous phasic contractions (SPCs) and sympathetic control of contractility in the rat epididymis, a long tubular duct involved in transportation and maturation of sperm. Longitudinal contractions of short segments (~ 1.5 mm) of rat proximal and distal caudal epididymal duct were measured + / - nerve stimulation. The extent of sympathetic innervation of these duct regions was determined by immunohistochemistry. Proximal caudal duct segments (150-300 μm dia.) exhibited SPCs, while distal segments (350-500 μm) were quiescent in ~ 80% of preparations. SPC amplitude and frequency were reduced by the L-type voltage-dependent Ca²⁺ channel (LVDCC) blocker nifedipine (1 μM), with the T-type voltage-dependent Ca²⁺ channel (TVDCC) blocker ML218 (1 μM) specifically decreasing SPC frequency. SPCs were inhibited upon blockade of the SR/ER Ca²⁺-ATPase (CPA 10 μM). SPCs were also inhibited by caffeine (1 μM), 2-APB (100 μM), niflumic acid (100 μM), or by lowering extracellular [Cl^-] from 134.4 to 12.4 mM but not by ryanodine (25 μM) or tetracaine (100 μM). Electrical field stimulation (EFS) at 2 Hz for 60 s caused a sustained α₁-adrenoceptor-sensitive contraction in distal segments and enhanced and/or induced α₂-adrenoceptor-sensitive oscillatory phasic contractions in proximal and distal segments, the latter mimicked by application of the α₂-adrenoceptor agonist clonidine. We hypothesise that SPCs in the proximal cauda are triggered by pacemaker mechanisms involving rhythmic IP₃ receptor-operated SR/ER store Ca²⁺ release and resultant activation of CaCC with TVDCCs and possibly LVDCCs subserving in this process. Sympathetic nerve-released noradrenaline induces α₂-adrenoceptor-mediated phasic contractions in the proximal and distal cauda. These findings provide new pharmacological targets for male infertility and contraception.

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.

Overcoming physiological barriers by nanoparticles for intravenous drug delivery to the lymph nodes

The lymph nodes are major sites of cancer metastasis and immune activity, and thus represent important clinical targets. Although not as well-studied compared to subcutaneous administration, intravenous drug delivery is advantageous for lymph node delivery as it is commonly practiced in the clinic and has the potential to deliver therapeutics systemically to all lymph nodes. However, rapid clearance by the mononuclear phagocyte system, tight junctions of the blood vascular endothelium, and the collagenous matrix of the interstitium can limit the efficiency of lymph node drug delivery, which has prompted research into the design of nanoparticle-based drug delivery systems. In this mini review, we describe the physiological and biological barriers to lymph node targeting, how they inform nanoparticle design, and discuss the future outlook of lymph node targeting.

Lymphatic Vasculature: An Emerging Therapeutic Target and Drug Delivery Route

The lymphatic system has received increasing scientific and clinical attention because a wide variety of diseases are linked to lymphatic pathologies and because the lymphatic system serves as an ideal conduit for drug delivery. Lymphatic vessels exert heterogeneous roles in different organs and vascular beds, and consequently, their dysfunction leads to distinct organ-specific outcomes. Although studies in animal model systems have led to the identification of crucial lymphatic genes with potential therapeutic benefit, effective lymphatic-targeted therapeutics are currently lacking for human lymphatic pathological conditions. Here, we focus on the therapeutic roles of lymphatic vessels in diseases and summarize the promising therapeutic targets for modulating lymphangiogenesis or lymphatic function in preclinical or clinical settings. We also discuss considerations for drug delivery or targeting of lymphatic vessels for treatment of lymphatic-related diseases. The lymphatic vasculature is rapidly emerging as a critical system for targeted modulation of its function and as a vehicle for innovative drug delivery.

Lower Extremity Lymphatic Function in Nonambulatory Patients with Neuromuscular Disease

Background: Lymphedema results from inadequate lymphatic function causing swelling in subcutaneous tissues. Lymph is transported proximally through valved lymphatic channels and muscle contraction. The purpose of this study was to determine lymphatic function in nonambulatory patients with lower extremity neuromuscular disease. Methods and Results: Our Lymphedema Program database of 700 patients was reviewed for nonambulatory patients with lower extremity neuromuscular disease. Patient age, gender, disease, body mass index (BMI), and lymphoscintigram result were recorded. Eight patients were included in the study: myelomeningocele (n = 6), spinal muscle atrophy type 2 (n = 1), Charcot Marie Tooth (n = 1). Patient ages were between 15 and 36 years; five were female. BMI range for patients without swelling or a normal lymphoscintigram (n = 4) was 22-27. Four subjects with lymphatic dysfunction by lymphoscintigram all were obese (BMI 36-74; p = 0.03). Conclusions: Nonambulatory patients with lower extremity neuromuscular dysfunction and swelling can exhibit normal lymphatic function. Obesity is associated with abnormal lymphoscintigram result and lymphedema in this patient population. Individuals should be advised to maintain a normal BMI.

TRPV4 channels' dominant role in the temperature modulation of intrinsic contractility and lymph flow of rat diaphragmatic lymphatics

The lymphatic system drains and propels lymph by extrinsic and intrinsic mechanisms. Intrinsic propulsion depends upon spontaneous rhythmic contractions of lymphatic muscles in the vessel walls and is critically affected by changes in the surrounding tissue like osmolarity and temperature. Lymphatics of the diaphragm display a steep change in contraction frequency in response to changes in temperature, and this, in turn, affects lymph flow. In the present work, we demonstrated in an ex vivo diaphragmatic tissue rat model that diaphragmatic lymphatics express transient receptor potential channels of the vanilloid 4 subfamily (TRPV4) and that their blockade by both the nonselective antagonist Ruthenium Red and the selective antagonist HC-067047 abolished the response of lymphatics to temperature changes. Moreover, the selective activation of TRPV4 channels by means of GSK1016790A mirrored the behavior of vessels exposed to increasing temperatures, pointing out the critical role played by these channels in sensing the temperature of the lymphatic vessels' environment and thus inducing a change in contraction frequency and lymph flow.NEW & NOTEWORTHY The present work addresses the putative receptor system that enables diaphragmatic lymphatics to change intrinsic contraction frequency and thus lymph flow according to the changes in temperature of the surrounding environment, showing that this role can be sustained by TRPV4 channels alone.

Immunological Implications of Physical Inactivity among Older Adults during the COVID-19 Pandemic

Social distancing has been adopted worldwide to control severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission. Social isolation is likely to lead to a decline in physical activity, which could result in immune system dysfunction, thereby increasing infection susceptibility and exacerbating the pathophysiology of conditions that are common among older adults, including cardiovascular disease, cancer, and inflammatory disorders. Older adults and people living with these comorbidities are at a greater risk for complications during coronavirus disease 2019 (COVID-19). In this review, we discuss the negative impact of physical inactivity on immune function and showcase evidence that regular physical activity may be an effective strategy to counter some of the deleterious effects of social isolation. Furthermore, we briefly highlight key research questions in exercise immunology, with a focus on older adults in the context of COVID-19. Although it is worth emphasizing that there is no direct evidence that physical activity can prevent or treat ­COVID-19, promoting an active lifestyle is a key intervention to counteract the effects of social isolation, especially in older adults and other at-risk individuals, such as those living with chronic diseases associated with ageing and lifestyle.

Lymphatic Vasculature in Energy Homeostasis and Obesity

Obesity is a leading cause of cardiovascular diseases and cancer. Body mass is regulated by the balance between energy uptake and energy expenditure. The etiology of obesity is determined by multiple factors including genetics, nutrient absorption, and inflammation. Lymphatic vasculature is starting to be appreciated as a critical modulator of metabolism and obesity. The primary function of lymphatic vasculature is to maintain interstitial fluid homeostasis. Lymphatic vessels absorb fluids that extravasate from blood vessels and return them to blood circulation. In addition, lymphatic vessels absorb digested lipids from the intestine and regulate inflammation. Hence, lymphatic vessels could be an exciting target for treating obesity. In this article, we will review our current understanding regarding the relationship between lymphatic vasculature and obesity, and highlight some open questions.