New Insights into the Molecular Control of the Lymphatic Vascular System and its Role in Disease

Complex lymphatic anomalies: Molecular landscape and medical management

The lymphatic system is one of the most essential and complex systems in the human body. Disorders that affect the development or function of the lymphatic system can lead to multi-system complications and life-long morbidity. The past two decades have seen remarkable progress in our knowledge of the basic biology and function of the lymphatic system, the molecular regulators of lymphatic development, and description of disorders associated with disrupted lymphangiogensis. In this chapter we will touch on the clinical features of complex lymphatic anomalies, new molecular knowledge of the drivers of these disorders, and novel developmental therapeutics for lymphatic disease.

The discriminative role of PROX-1 immunohistochemistry between venous malformation and lymphatic malformation of the deep type with no visible diagnostic surface skin lesion

BACKGROUND

Venous malformations (VMs) are distinguished from lymphatic malformations (LMs) when specific diagnostic skin lesions are present. In the deep type, this is difficult by clinico-radiologic evaluation alone. We aimed to investigate the usefulness of lymphatic vessel endothelial cell (LEC) markers for the differential diagnosis of the deep VMs and LMs.

METHODS

A retrospective study was conducted based on the medical records of patients with VMs and LMs who underwent biopsy with both D2-40 and PROX-1 immunohistochemistry. We compared the initial clinico-radiological diagnosis with the final pathological diagnosis and identified which ones showed a difference.

RESULTS

From 261 patients who had VMs and LMs, 111 remained after the exclusion of those who showed definite surface diagnostic features. After pathological diagnosis with the expressions of D2-40 and PROX-1, 38 of 111 (34.2%) patients' final diagnoses were changed. Among these 38 cases, diagnosis was not changed by D2-40 positivity alone, but changed by PROX-1 positivity alone (52.6%) or by both (47.4%). The diagnostic changes were more frequent in the deep category (43.7%) than in the superficial category.

CONCLUSIONS

Identifying the expression of D2-40, and especially PROX-1, in the differential diagnosis of VMs and LMs may provide important treatment guidelines and understanding their natural course.

A new lymphedema treatment using pyro-drive jet injection

Lymphedema, resulting from impaired lymphatic drainage, causes inflammation, fibrosis and tissue damage leading to symptoms such as limb swelling and restricted mobility. Despite various treatments under exploration, no standard effective therapy exists. Here a novel technique using the pyro-drive jet injection (PJI) was used to create artificial clefts between collagen fibers, which facilitated the removal of excess interstitial fluid. The PJI was used to deliver a mixture of lactated Ringer's solution and air into the tail of animals with secondary skin edema. Edema levels were assessed using micro-CT scanning. Histopathological changes and neovascularization were evaluated on the injury-induced regenerative tissue. Regarding tissue remodeling, we focused on connective tissue growth factor (CTGF) and vascular endothelial growth factor (VEGF)-C. PJI markedly diminished soft tissue volume in the experimental lymphedema animals compared to the non-injected counterparts. The PJI groups exhibited a significantly reduced proportion of inflammatory granulation tissue and an enhanced density of lymphatic vessels and α-smooth muscle actin (αSMA)-positive small vessels in the fibrous granulation tissue compared to the controls. In addition, PJI curtailed the prevalence of CTGF- and VEGF-C-positive cells in regenerative tissue. In a lymphedema animal model, PJI notably ameliorated interstitial edema, promoted lymphatic vessel growth, and bolstered αSMA-positive capillaries in fibrous granulation tissue. PJI's minimal tissue impact post-lymph node dissection indicates significant potential as an early, standard preventative measure. Easily applied in general clinics without requiring specialized training, it offers a cost-effective and highly versatile solution to the management of lymphedema.

Size-Dependent In Vivo Transport of Nanoparticles: Implications for Delivery, Targeting, and Clearance

Understanding the in vivo transport of nanoparticles provides guidelines for designing nanomedicines with higher efficacy and fewer side effects. Among many factors, the size of nanoparticles plays a key role in controlling their in vivo transport behaviors due to the existence of various physiological size thresholds within the body and size-dependent nano-bio interactions. Encouraged by the evolving discoveries of nanoparticle-size-dependent biological effects, we believe that it is necessary to systematically summarize the size-scaling laws of nanoparticle transport in vivo. In this review, we summarized the size effect of nanoparticles on their in vivo transport along their journey in the body: begin with the administration of nanoparticles via different delivery routes, followed by the targeting of nanoparticles to intended tissues including tumors and other organs, and eventually clearance of nanoparticles through the liver or kidneys. We outlined the tools for investigating the in vivo transport of nanoparticles as well. Finally, we discussed how we may leverage the size-dependent transport to tackle some of the key challenges in nanomedicine translation and also raised important size-related questions that remain to be answered in the future.

Tacrolimus loaded nanostructured lipid carriers using Moringa oleifera seed oil: design, optimization and in-vitro evaluations

The proposed research aims to develop Tacrolimus-loaded nanostructured lipid carriers (TAC-loaded NLCs) to overcome poor aqueous solubility and dissolution rate to enhance its oral absorption. A central composite design was used to optimise the amount of Poloxamer 188 and D-α-Tocopherol-polyethylene-glycol-succinate (TPGS). The optimised TAC-loaded NLCs contain stearic acid (250 mg), Moringa oleifera (MO) seed oil (50 mg), TAC (Tacrolimus: 10 mg), TPGS (60 mg), and Poloxamer 188 (1% w/v) with a mean diameter of 393.3 ± 29.68 nm, a zeta potential of -18.3 ± 6.19 mV, high entrapment efficiency (92.12 ± 1.14% w/w), and desirability (0.989). TAC-loaded NLCs showed ∼12 times higher drug dissolution efficiency, while in-vitro anti-inflammatory studies showed ∼1.8 times lower IC50 (half-maximal inhibitory concentration) than TAC suspension. The lyophilised TAC-loaded NLCs were found to be stable after 3 months. Thus, the present study concludes the successful encapsulation of TAC in NLCs made of stearic acid and MO seed oil.

The Lymphatic Endothelial Cell Secretome Inhibits Osteoblast Differentiation and Bone Formation

Complex lymphatic anomalies (CLAs) are a set of rare diseases with unique osteopathic profiles. Recent efforts have identified how lymphatic-specific somatic activating mutations can induce abnormal lymphatic formations that are capable of invading bone and inducing bone resorption. The abnormal bone resorption in CLA patients has been linked to overactive osteoclasts in areas with lymphatic invasions. Despite these findings, the mechanism associated with progressive bone loss in CLAs remains to be elucidated. In order to determine the role of osteoblasts in CLAs, we sought to assess osteoblast differentiation and bone formation when exposed to the lymphatic endothelial cell secretome. When treated with lymphatic endothelial cell conditioned medium (L-CM), osteoblasts exhibited a significant decrease in proliferation, differentiation, and function. Additionally, L-CM treatment also inhibited bone formation through a neonatal calvaria explant culture. These findings are the first to reveal how osteoblasts may be actively suppressed during bone lymphatic invasion in CLAs.

Signaling mechanisms underlying lymphatic vessel dysfunction in skin aging and possible anti-aging strategies

Aging-related skin diseases are gradually increasing due to the imbalance of cutaneous homeostasis in the aging population. Skin aging-induced inflammation promotes systemic inflammation and may lead to whole-body aging. Lymphatic vessels play an important role in maintaining fluid and homeostasis balance. In intrinsically aged skin, the number of lymphatic vessels decrease and their functions decline, which is related to the reduced adhesion junctions between lymphatic endothelial cells, particularly VE-cadherin. VEGFC/VEGFR-3 signal pathway plays an important role in remodeling and expansion of lymphatic vessels; the downregulation of this pathway contributes to the dysfunction of lymphatic vessels. Meanwhile, we proposed some additional mechanisms. Decline of the pumping activity of lymphatic vessels might be related to age-related changes in extracellular matrix, ROS increase, and eNOS/iNOS disturbances. In extrinsically aged skin, the hyperpermeability of lymphatic vessels results from a decrease in endothelial-specific tight junction molecules, upregulation of VEGF-A, and downregulation of the VEGFC/VEGFR-3 signaling pathway. Furthermore, some of the Phyto therapeutics could attenuate skin aging by modulating the lymphatic vessels. This review summarized the lymphatic vessel dysfunction in skin aging and anti-aging strategies based on lymphatic vessel modulation.

Characterization of the soft-tissue wall lining residual periodontal pockets and implications in periodontal wound healing

AIM

To characterize the soft-tissue wall of remaining periodontal pockets for wound healing-related parameters versus healthy gingival crevices in the same individuals.

MATERIALS AND METHODS

Gingival tissues collected from the diseased interface of pockets (GT biopsies) and from healthy gingival crevices (G biopsies) were subjected to RT2-profiler PCR Array for wound healing-related markers and network analysis of differentially expressed genes. Lymphangiogenesis-related gene expression was determined by qRT-PCR. The migration potential of mesenchymal stem cells isolated from GT biopsies (GT-MSCs) and G biopsies (G-MSCs) was evaluated by the scratch- and the transwell migration assays. The total collagen protein content was determined in GT-MSCs and G-MSCs homogenates.

RESULTS

Gene-ontology analysis on significantly upregulated genes expressed in GT biopsies revealed enrichment of several genes involved in processes related to matrix remodeling, collagen deposition, and integrin signaling. No significantly expressed genes were seen in G biopsies. Regarding lymphangiogenesis-related genes, GT biopsies demonstrated greater expression for PROX1 than G biopsies (p = 0.05). Lower migration potential (p < 0.001), yet greater production of collagen protein (p = 0.05), was found for GT-MSCs over G-MSCs.

CONCLUSION

Differential expression patterns of various molecular pathways in biopsies and cell cultures of diseased versus healthy gingival tissues indicate a potential of the former for tissue remodeling and repair.

CLINICAL RELEVANCE

In the course of periodontitis, granulation tissue is formed within a periodontal defect in an attempt to reconstruct the site. Following treatment procedures periodontal granulation tissue remains inflamed but appears to retain healing potential.

Addressing the in vivo delivery of nucleic-acid nanostructure therapeutics

DNA and RNA nanostructures are being investigated as therapeutics, vaccines, and drug delivery systems. These nanostructures can be functionalized with guests ranging from small molecules to proteins with precise spatial and stoichiometric control. This has enabled new strategies to manipulate drug activity and to engineer devices with novel therapeutic functionalities. Although existing studies have offered encouraging in vitro or pre-clinical proof-of-concepts, establishing mechanisms of in vivo delivery is the new frontier for nucleic-acid nanotechnologies. In this review, we first provide a summary of existing literature on the in vivo uses of DNA and RNA nanostructures. Based on their application areas, we discuss current models of nanoparticle delivery, and thereby highlight knowledge gaps on the in vivo interactions of nucleic-acid nanostructures. Finally, we describe techniques and strategies for investigating and engineering these interactions. Together, we propose a framework to establish in vivo design principles and advance the in vivo translation of nucleic-acid nanotechnologies.

Lymphangiogenesis Guidance Mechanisms and Therapeutic Implications in Pathological States of the Cornea

Corneal lymphangiogenesis is one component of the neovascularization observed in several inflammatory pathologies of the cornea including dry eye disease and corneal graft rejection. Following injury, corneal (lymph)angiogenic privilege is impaired, allowing ingrowth of blood and lymphatic vessels into the previously avascular cornea. While the mechanisms underlying pathological corneal hemangiogenesis have been well described, knowledge of the lymphangiogenesis guidance mechanisms in the cornea is relatively scarce. Various signaling pathways are involved in lymphangiogenesis guidance in general, each influencing one or multiple stages of lymphatic vessel development. Most endogenous factors that guide corneal lymphatic vessel growth or regression act via the vascular endothelial growth factor C signaling pathway, a central regulator of lymphangiogenesis. Several exogenous factors have recently been repurposed and shown to regulate corneal lymphangiogenesis, uncovering unique signaling pathways not previously known to influence lymphatic vessel guidance. A strong understanding of the relevant lymphangiogenesis guidance mechanisms can facilitate the development of targeted anti-lymphangiogenic therapeutics for corneal pathologies. In this review, we examine the current knowledge of lymphatic guidance cues, their regulation of inflammatory states in the cornea, and recently discovered anti-lymphangiogenic therapeutic modalities.

Rotator cuff healing is regulated by the lymphatic vasculature

Background

Despite great advances in surgical techniques for rotator cuff tear (RCT) over the past decades, the postoperative failure rate of RCT is still high due to the poor healing competence of bone-tendon interface (BTI). The lymphatic vasculature plays a regulatory role in inflammatory disease and affects tissue healing. However, whether lymphangiogenesis and the role of lymphatic vasculature in the physiopathological process of rotator cuff （RC）injury remains unknown.

Methods

In this study, we constructed a mouse RC injury model and the BTI samples were collected for measurement. Firstly, immunofluorescence was used to investigate the temporal and spatial distribution of lymphangiogenesis in BTI area at different post-injury time points. Subsequently, the mice of experimental group were gavaged with the lymphatic inhibitors (SAR131675) on the first postoperative day to inhibit lymphangiogenesis, while the control group was treated with the vehicle. At postoperative week 2 and 4, the samples were collected for immunofluorescence staining to evaluate lymphatic angiogenesis inhibition. At postoperative week 4 and 8, The supraspinatus (SS) tendon-humeral complexes were collected for bone morphometric, histological and biomechanical tests to assess the healing outcome of the BTI.

Results

Immunofluorescence results showed that the lymphatic proliferation in the BTI injury area and increased in consistence with the healing time, and the lymphatic hyperplasia area significantly diminished at postoperative week 4. The lymphatic hyperplasia area in the SAR group was significantly lower than that in the control group both at 2 and 4 weeks postoperatively. Moreover, the administration of SAR131675 significantly impeded RC healing, as evidenced by lower histological scores, lower bone morphometric parameters, and worse biomechanical properties in comparison with that in control group at postoperative weeks 4 and 8.

Conclusion

Lymphangiogenesis plays a positive role in RC healing, and targeting the lymphatic drainage at healing site may be a new therapeutic approach to promote RC injury repair.

The translational potential of this article

This is the first study to assess the specific role of lymphatic vessels in RC healing, and improving lymphatic drainage may be a potential new therapeutic approach to facilitate repair of BTI. Further, our study provides a reference for possible future treatment of BTI by intervening the lymphatic system.

The Peripheral Lymphatic System Is Impaired by the Loss of Neuronal Control Associated with Chronic Spinal Cord Injury

Spinal cord injury (SCI) is associated with venous vascular dysfunction below the level of injury, resulting in dysregulation of tissue fluid homeostasis in afflicted skin. The purpose of this study was to determine whether loss of neuronal control in chronic SCI also affects the skin lymphatic system. Morphology of lymphatics was characterized by immunohistochemistry and lymphatic gene expression profiles determined by DNA microarray analysis. In SCI, skin lymphatic function appeared to be impaired, because the ratio of functionally dilated versus collapsed lymphatic vessels was decreased 10-fold compared with control. Consequently, the average lumen area of lymphatic vessels was almost halved, possibly due to the known impaired connective tissue integrity of SCI skin. In fact, collagenases were found to be overexpressed in SCI skin, and dermal collagen structure was impaired. Molecular profiling also suggested an SCI-specific phenotype of increased connective tissue turnover and decreased lymphatic contractility. The total number of lymphatic vessels in SCI skin, however, was doubled, pointing to enhanced lymphangiogenesis. In conclusion, these data show, for the first time, that lymphatic function and development in human skin are under neuronal control. Because peripheral venous and lymphatic vascular defects are associated with disturbed fluid homeostasis, inappropriate wound healing reactions, and impaired skin immunity, they might contribute to the predisposition of afflicted individuals to pressure ulcer formation and wound healing disorders.

Infection in the Developing Brain: The Role of Unique Systemic Immune Vulnerabilities

Central nervous system (CNS) infections remain a major burden of pediatric disease associated with significant long-term morbidity due to injury to the developing brain. Children are susceptible to various etiologies of CNS infection partly because of vulnerabilities in their peripheral immune system. Young children are known to have reduced numbers and functionality of innate and adaptive immune cells, poorer production of immune mediators, impaired responses to inflammatory stimuli and depressed antibody activity in comparison to adults. This has implications not only for their response to pathogen invasion, but also for the development of appropriate vaccines and vaccination strategies. Further, pediatric immune characteristics evolve across the span of childhood into adolescence as their broader physiological and hormonal landscape develop. In addition to intrinsic vulnerabilities, children are subject to external factors that impact their susceptibility to infections, including maternal immunity and exposure, and nutrition. In this review we summarize the current evidence for immune characteristics across childhood that render children at risk for CNS infection and introduce the link with the CNS through the modulatory role that the brain has on the immune response. This manuscript lays the foundation from which we explore the specifics of infection and inflammation within the CNS and the consequences to the maturing brain in part two of this review series.

Copper stress impairs angiogenesis and lymphangiogenesis during zebrafish embryogenesis by down-regulating pERK1/2-foxm1-MMP2/9 axis and epigenetically regulating ccbe1 expression

Molecular transport and cell circulation between tissues and organs through blood and lymphatic vessels are essential for physiological homeostasis in vertebrates. Despite the report of its association with vessel formation in solid tumors, the biological effects of Copper (Cu) accumulation on angiogenesis and lymphangiogenesis during embryogenesis are still unknown. In this study, we unveiled that intersegmental blood circulation was partially blocked in Cu²⁺-stressed zebrafish embryos and cell migration and tube formation were impaired in Cu²⁺-stressed mammalian HUVECs. Specifically, Cu²⁺-stressed embryos showed down-regulation in the expression of amotl2 and its downstream pERK1/2-foxm1-MMP2/9 regulatory axis, and knockdown/knockout of foxm1 in zebrafish embryos phenocopied angiogenesis defects, while FOXM1 knockdown HUVECs phenocopied cell migration and tube formation defects, indicating that excessive Cu²⁺-induced angiogenesis defects and blocked cell migration via down-regulating amotl2-pERK1/2-foxm1-MMP2/9 regulatory axis in both embryos and mammalian cells. Additionally, thoracic duct was revealed to be partially absent in Cu²⁺-stressed zebrafish embryos. Specifically, Cu²⁺-stressed embryos showed down-regulation in the expression of ccbe1 (a gene with pivotal function in lymphangiogenesis) due to the hypermethylation of the E2F7/8 binding sites on ccbe1 promoter to reduce their binding enrichment on the promoter, contributing to the potential mechanisms for down-regulation of ccbe1 and the formation of lymphangiogenesis defects in Cu²⁺-stressed embryos and mammalian cells. These integrated data demonstrate that Cu²⁺ stress impairs angiogenesis and lymphangiogenesis via down-regulation of pERK1/2-foxm1-MMP2/9 axis and epigenetic regulation of E2F7/8 transcriptional activity on ccbe1 expression, respectively.

Targeting Lymphangiogenesis and Lymph Node Metastasis in Liver Cancer

Increased lymphangiogenesis and lymph node metastasis, the important prognostic indicators of aggressive hepatobiliary malignancies such as hepatocellular cancer and cholangiocarcinoma, are associated with poor patient outcome. The liver produces 25% to 50% of total lymphatic fluid in the body and has a dense network of lymphatic vessels. The lymphatic system plays critical roles in fluid homeostasis and inflammation and immune response. Yet, lymphatic vessel alterations and function are grossly understudied in the context of liver pathology. Expansion of the lymphatic network has been documented in clinical samples of liver cancer; and although largely overlooked in the liver, tumor-induced lymphangiogenesis is an important player, increasing tumor metastasis in several cancers. This review aims to provide a detailed perspective on the current knowledge of alterations in the hepatic lymphatic system during liver malignancies, as well as various molecular signaling mechanisms and growth factors that may provide future targets for therapeutic intervention. In addition, the review also addresses current mechanisms and bottlenecks for effective therapeutic targeting of tumor-associated lymphangiogenesis.

Neutrophil Interactions with the Lymphatic System

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

Predicting the Most Deleterious Missense Nonsynonymous Single-Nucleotide Polymorphisms of Hennekam Syndrome-Causing CCBE1 Gene, In Silico Analysis

Hennekam lymphangiectasia-lymphedema syndrome has been linked to single-nucleotide polymorphisms in the CCBE1 (collagen and calcium-binding EGF domains 1) gene. Several bioinformatics methods were used to find the most dangerous nsSNPs that could affect CCBE1 structure and function. Using state-of-the-art in silico tools, this study examined the most pathogenic nonsynonymous single-nucleotide polymorphisms (nsSNPs) that disrupt the CCBE1 protein and extracellular matrix remodeling and migration. Our results indicate that seven nsSNPs, rs115982879, rs149792489, rs374941368, rs121908254, rs149531418, rs121908251, and rs372499913, are deleterious in the CCBE1 gene, four (G330E, C102S, C174R, and G107D) of which are the highly deleterious, two of them (G330E and G107D) have never been seen reported in the context of Hennekam syndrome. Twelve missense SNPs, rs199902030, rs267605221, rs37517418, rs80008675, rs116596858, rs116675104, rs121908252, rs147974432, rs147681552, rs192224843, rs139059968, and rs148498685, are found to revert into stop codons. Structural homology-based methods and sequence homology-based tools revealed that 8.8% of the nsSNPs are pathogenic. SIFT, PolyPhen2, M-CAP, CADD, FATHMM-MKL, DANN, PANTHER, Mutation Taster, LRT, and SNAP2 had a significant score for identifying deleterious nsSNPs. The importance of rs374941368 and rs200149541 in the prediction of post-translation changes was highlighted because it impacts a possible phosphorylation site. Gene-gene interactions revealed CCBE1's association with other genes, showing its role in a number of pathways and coexpressions. The top 16 deleterious nsSNPs found in this research should be investigated further in the future while researching diseases caused CCBE1 gene specifically HS. The FT web server predicted amino acid residues involved in the ligand-binding site of the CCBE1 protein, and two of the substitutions (R167W and T153N) were found to be involved. These highly deleterious nsSNPs can be used as marker pathogenic variants in the mutational diagnosis of the HS syndrome, and this research also offers potential insights that will aid in the development of precision medicines. CCBE1 proteins from Hennekam syndrome patients should be tested in animal models for this purpose.

In-vitro tumor microenvironment models containing physical and biological barriers for modelling multidrug resistance mechanisms and multidrug delivery strategies

The complexity and heterogeneity of the three-dimensional (3D) tumor microenvironment have brought challenges to tumor studies and cancer treatment. The complex functions and interactions of cells involved in tumor microenvironment have led to various multidrug resistance (MDR) and raised challenges for cancer treatment. Traditional tumor models are limited in their ability to simulate the resistance mechanisms and not conducive to the discovery of multidrug resistance and delivery processes. New technologies for making 3D tissue models have shown the potential to simulate the 3D tumor microenvironment and identify mechanisms underlying the MDR. This review overviews the main barriers against multidrug delivery in the tumor microenvironment and highlights the advances in microfluidic-based tumor models with the success in simulating several drug delivery barriers. It also presents the progress in modeling various genetic and epigenetic factors involved in regulating the tumor microenvironment as a noticeable insight in 3D microfluidic tumor models for recognizing multidrug resistance and delivery mechanisms. Further correlation between the results obtained from microfluidic drug resistance tumor models and the clinical MDR data would open up avenues to gain insight into the performance of different multidrug delivery treatment strategies.

A Decade of Organs-on-a-Chip Emulating Human Physiology at the Microscale: A Critical Status Report on Progress in Toxicology and Pharmacology

Organ-on-a-chip technology has the potential to accelerate pharmaceutical drug development, improve the clinical translation of basic research, and provide personalized intervention strategies. In the last decade, big pharma has engaged in many academic research cooperations to develop organ-on-a-chip systems for future drug discoveries. Although most organ-on-a-chip systems present proof-of-concept studies, miniaturized organ systems still need to demonstrate translational relevance and predictive power in clinical and pharmaceutical settings. This review explores whether microfluidic technology succeeded in paving the way for developing physiologically relevant human in vitro models for pharmacology and toxicology in biomedical research within the last decade. Individual organ-on-a-chip systems are discussed, focusing on relevant applications and highlighting their ability to tackle current challenges in pharmacological research.

Lymphatic Senescence: Current Updates and Perspectives

Simple Summary

The lymphatic system is involved in tissue homeostasis, immune processes as well as transport of lipids, proteins and pathogens. Aging affects all physiological systems. However, it is not well studied how aging affects the lymphatic vasculature. Therefore, this review aims at investigating how senescence could lead to changes in the structure and function of the lymphatic vessels. We report that lymphatic senescence is associated with alterations in lymphatic muscles and nerve fibers, lymphatic endothelial cells membrane dysfunction, as well as changes in lymphatic pump, acute inflammation responses and immune function.

Abstract

Lymphatic flow is necessary for maintenance of vital physiological functions in humans and animals. To carry out optimal lymphatic flow, adequate contractile activity of the lymphatic collectors is necessary. Like in all body systems, aging has also an effect on the lymphatic system. However, limited knowledge is available on how aging directly affects the lymphatic system anatomy, physiology and function. We investigated how senescence leads to alterations in morphology and function of the lymphatic vessels. We used the strategy of a review to summarize the scientific literature of studies that have been published in the area of lymphatic senescence. Searches were carried out on PubMed and Web of Science using predefined search queries. We obtained an initial set of 1060 publications. They were filtered to 114 publications based on strict inclusion and exclusion criteria. Finally, the most appropriate 57 studies that specifically addressed lymphatic senescence have been selected for the preparation of this review. Analysis of the literature showed that lymphatic senescence is associated with alterations in lymphatic muscles and nerve fibers, lymphatic glycocalyx function of lymphatic endothelial cells, effects of chronic ultraviolet light exposure and oxidative stress as well as changes in lymphatic pump, acute inflammation responses and immune function. The current review underscores the relevance of the understudied area of lymphatic senescence. Continued research on the impact of aging on the structure and function of the lymphatic vasculature is needed to provide further insights to develop innovative clinical diagnostic—and treatment—modalities as well as to reduce the morbidity associated with diseases related to the lymphatic system.

Imaging of fetal lymphangiectasias: prenatal and postnatal imaging findings

Lymphangiectasias are lymphatic malformations characterized by the abnormal dilation and morphology of the lymphatic channels. The classification and treatment of these disorders can be challenging given the limited amount of literature available in children. Various imaging modalities are used to confirm suspected diagnosis, plan the most appropriate treatment, and estimate a prognosis. Prenatal evaluation is performed using both prenatal US imaging and fetal MRI. These modalities are paramount for appropriate parental counseling and planning of perinatal care. During the neonatal period, chest US imaging is a useful modality to evaluate pulmonary lymphangiectasia because other modalities such as conventional radiography and CT display nonspecific findings. Finally, the recent breakthroughs in lymphatic imaging with MRI have allowed us to better classify lymphatic disorders. Dynamic contrast-enhanced lymphangiography, conventional lymphangiography and percutaneous lymphatic procedures offer static and dynamic evaluation of the central conducting lymphatics in children, with excellent spatial resolution and the possibility to provide treatment. The purpose of this review is to discuss the normal and abnormal development of the fetal lymphatic system and how to best depict it by imaging during the prenatal and postnatal life.

Epigenetic regulation of the lineage specificity of primary human dermal lymphatic and blood vascular endothelial cells

Lymphatic and blood vascular endothelial cells (ECs) share several molecular and developmental features. However, these two cell types possess distinct phenotypic signatures, reflecting their different biological functions. Despite significant advances in elucidating how the specification of lymphatic and blood vascular ECs is regulated at the transcriptional level during development, the key molecular mechanisms governing their lineage identity under physiological or pathological conditions remain poorly understood. To explore the epigenomic signatures in the maintenance of EC lineage specificity, we compared the transcriptomic landscapes, histone composition (H3K4me3 and H3K27me3) and DNA methylomes of cultured matched human primary dermal lymphatic and blood vascular ECs. Our findings reveal that blood vascular lineage genes manifest a more ‘repressed’ histone composition in lymphatic ECs, whereas DNA methylation at promoters is less linked to the differential transcriptomes of lymphatic versus blood vascular ECs. Meta-analyses identified two transcriptional regulators, BCL6 and MEF2C, which potentially govern endothelial lineage specificity. Notably, the blood vascular endothelial lineage markers CD34, ESAM and FLT1 and the lymphatic endothelial lineage markers PROX1, PDPN and FLT4 exhibited highly differential epigenetic profiles and responded in distinct manners to epigenetic drug treatments. The perturbation of histone and DNA methylation selectively promoted the expression of blood vascular endothelial markers in lymphatic endothelial cells, but not vice versa. Overall, our study reveals that the fine regulation of lymphatic and blood vascular endothelial transcriptomes is maintained via several epigenetic mechanisms, which are crucial to the maintenance of endothelial cell identity.

Properties of rapamycin solid lipid nanoparticles for lymphatic access through the lungs & part I: the effect of size

Background: Lymphangioleiomyomatosis (LAM) is characterized by growth of smooth muscle-like cells in the lungs that spread to other organs via lymphatic vessels. Current oral rapamycin treatment is limited by low bioavailability of approximately 15%. Aim: The effect of inhaled rapamycin solid lipid nanoparticles (Rapa-SLNs) size on its penetration through the lymphatics. Method: Three Rapa-SLN formulations (200-1000 nm) were produced and assessed for particle characteristics and further for toxicity and performance in vitro. Results: Rapa-SLNs of 200 nm inhibited proliferation in TSC2-negative mouse embryonic fibroblast cells and penetrated the respiratory epithelium and lymphatic endothelium significantly faster compared with free rapamycin and larger Rapa-SLNs. Conclusion: Rapa-SLN approximately 200 nm allows efficient entry of rapamycin into the lymphatic system and is therefore a promising treatment for LAM patients.

An Insight into the Angiogenic and Lymphatic Interplay in Pre-eclampsia Comorbid with HIV Infection

PURPOSE OF REVIEW

To provide insight on the imbalance of angiogenic and lymphangiogenic factors in pre-eclampsia, as well as highlight polymorphism in genes related to angiogenesis and lymphangiogenesis.

RECENT FINDINGS

The pregnancy-specific disorder pre-eclampsia is diagnosed by the presence of hypertension with/without proteinuria, after 20 weeks of gestation. The pathogenesis of pre-eclampsia remains ambiguous, but research over the years has identified an imbalance in maternal and foetal factors. Familial predisposition and gene variation are also linked to pre-eclampsia development. The sFlt-1/PIGF ratio has attracted great attention over the years; more recently several researchers have reported that a sFlt-1/PIGF ratio of ≤ 38 can be used to predict short-term absence of pre-eclampsia. This ratio has the potential to prevent adverse pregnancy outcomes and reduce healthcare costs significantly. Genome-wide studies have additionally identified variation in the foetal gene near Flt-1. The development of preeclampsia is not limited to the maternal interface, but foetal involvement as well as genetic interplay is associated with the disorder.

Immunohistochemical expression and prognostic significance of VEGF-C in well-differentiated thyroid cancer

Context

Neoangiogenesis and lymphangio-genesis are essential for the growth of tumor and progression of malignancy.

Objective

The study examined the significance of VEGF-C expression in comparison to classical prognostic factors in differentiated thyroid carcinoma (DTC), as well as an independent prognostic marker in DTC.

Design

The study included 81 patients with DTC allocated in two groups according to the type of cancer (follicular versus papillary) and then compared to expression of VEGF-C and clinicopathological features.

Methods

Expression of VEGF-C was identified with anti-VEGF-C antibody using tris-EDTA buffer Antigen Retrieval Protocol. Each specimen was scored with a semi-quantitative score system (H-score).

Results

The analysis of T staging system showed a linear correlation between the size of a tumor, expression of VEGF-C and recurrence of a disease, with a statistical significance (p < 0.0001). There was a clear and significant correlation between VEGF-C expression and T stage in patients with papillary carcinoma (p = 0.0294). Analysis of invasion of a surgical margin demonstrated significant positivity in patients with papillary thyroid cancers who expressed VEGF-C (p = 0.0207) indicating the worse prognosis of a disease. Also a statistically significant correlation was between VEGF-C and extrathyroid extension, indicating the worse prognosis (p = 0.0133) in papillary cancers. The level of VEGF-C expression was statistically significant in patients with papillary thyroid cancer (p = 0.039).

Conclusions

This study undoubtedly demonstrates that VEGF-C expression is an evident negative prognostic factor in patients with papillary thyroid carcinoma, along with the classic prognostic factors, such as a larger tumor size, tumor margin involvement, extrathyroid extension, i.e. local aggressiveness.

Non-coding RNAs as Regulators of Lymphangiogenesis in Lymphatic Development, Inflammation, and Cancer Metastasis

Non-coding RNAs (ncRNAs), which do not encode proteins, have pivotal roles in manipulating gene expression in development, physiology, and pathology. Emerging data have shown that ncRNAs can regulate lymphangiogenesis, which refers to lymphatics deriving from preexisting vessels, becomes established during embryogenesis, and has a close relationship with pathological conditions such as lymphatic developmental diseases, inflammation, and cancer. This review summarizes the molecular mechanisms of lymphangiogenesis in lymphatic development, inflammation and cancer metastasis, and discusses ncRNAs' regulatory effects on them. Therapeutic targets with regard to lymphangiogenesis are also discussed.

Avian Reticuloendotheliosis Viral Oncogene Related B Regulates Lymphatic Endothelial Cells during Vessel Maturation and Is Required for Lymphatic Vessel Function in Adult Mice

NF-κB signals through canonical transcription factor p65 (RelA)/p50 and noncanonical avian reticuloendotheliosis viral oncogene related B (RelB)/p52 pathways. The RelA/p50 is involved in basal and inflammatory lymphangiogenesis. However, the role of RelB/p52 in lymphatic vessel biology is unknown. Herein, we investigated changes in lymphatic vessels (LVs) in mice deficient in noncanonical NF-κB signaling and the function of RelB in lymphatic endothelial cells (LECs). LVs were examined in Relb^-/-, p52^-/-, or control mice, and the gene expression profiles in LECs with RelB knockdown. Relb^-/-, but not p52^-/-, mice exhibited multiple LV abnormalities. They include the following: i) increased capillary vessel diameter, ii) reduced smooth muscle cell (SMC) coverage of mature vessels, iii) leakage, and iv) loss of active and passive lymphatic flow. Relb^-/- mature LVs had thinner vessel walls, more apoptotic LECs and SMCs, and fewer LEC junctions. RelB knockdown LECs had decreased growth, survival, and adhesion, and dysregulated signaling pathways involving these cellular events. These results suggest that Relb^-/- mice have abnormal LVs, mainly in mature vessels with reduced SMC coverage, leakage, and loss of contractions. RelB knockdown in LECs leads to reduced growth, survival, and adhesion. RelB plays a vital role in LEC-mediated LV maturation and function.

A Novel Self-Assembly Nanocrystal as Lymph Node-Targeting Delivery System: Higher Activity of Lymph Node Targeting and Longer Efficacy Against Lymphatic Metastasis

Mitoxantrone (MTO) is used to treat certain types of cancer, mostly metastatic cancer. While the drug has poor aqueous solubility and high side effects. Self-assembly nanocrystal is a novel lymphatic targeting delivery system. In our study, MTO self-assembly nanocrystal (MTO NC) was successfully prepared to improve lymphatic targeting ability and reduce its toxicity. MTO NCs had small size, stable potential, and uniform distribution. The average particle size of MTO NCs was less than 100 nm with the 0.218 PDI and - 6.6 mV the Zeta potential value. TEM images showed that MTO NCs had a sphere-like morphology with smooth surface and uniform distribution; Atomic force microscopy (AFM) images gave a 3D surface of MTO NCs. Polarizing microscope micrograph (PLM) of MTO NCs in lymph nodes demonstrated the crystal structure of MTO NCs when it was exposed to physiological condition. Transmission electron microscopy showed the presence of MTO NCs in mice lymph nodes. Pharmacokinetic parameters of MTO strongly demonstrated that MTO NCs could target the lymph nodes after subcutaneous injection. Moreover, tissue distribution results indicated that MTO NCs were mainly absorbed by the lymphatics and reduced system toxicity. Finally, a lymphatic metastasis mice model was established to precede the pharmacodynamics of MTO NCs, and using MTO liposomes as a reference preparation, the inhibitory effect of MTO NCs on lymphatic metastasis was markedly higher. Briefly, MTO NCs, as a novel self-assembled lymphatic targeting system, can accumulate in the metastatic lymph nodes and lead anticancer drug to kill cancer cells and control lymphatic metastasis with extremely low systemic toxicity.

Hyaluronan Derived From the Limbus is a Key Regulator of Corneal Lymphangiogenesis

Purpose

We recently reported that the glycosaminoglycan hyaluronan (HA), which promotes inflammatory angiogenesis in other vascular beds, is an abundant component of the limbal extracellular matrix. Consequently, we have explored the possibility that HA contributes to lymphangiogenesis in the inflamed cornea.

Methods

To study the role of HA on lymphangiogenesis, we used mice lacking the hyaluronan synthases and injury models that induce lymphangiogenesis.

Results

Here we report that HA regulates corneal lymphangiogenesis, both during post-natal development and in response to adult corneal injury. Furthermore, we show that injury to the cornea by alkali burn upregulates both HA production and lymphangiogenesis and that these processes are ablated in HA synthase 2 deficient mice.

Conclusion

These findings raise the possibility that therapeutic blockade of HA-mediated lymphangiogenesis might prevent the corneal scarring and rejection that frequently results from corneal transplantation.

Tumor-Associated Protein Profiles in Kaposi Sarcoma and Mimicking Vascular Tumors, and Their Pathological Implications

We investigated protein profiles specific to vascular lesions mimicking Kaposi sarcoma (KS), based on stepwise morphogenesis progression of KS. We surveyed 26 tumor-associated proteins in 130 cases, comprising 39 benign vascular lesions (BG), 14 hemangioendotheliomas (HE), 37 KS, and 40 angiosarcomas (AS), by immunohistochemistry. The dominant proteins in KS were HHV8, lymphatic markers, Rb, phosphorylated Rb, VEGF, and galectin-3. Aberrant expression of p53, inactivation of cell cycle inhibitors, loss of beta-catenin, and increased VEGFR1 were more frequent in AS. HE had the lowest Ki-67 index, and the inactivation rates of cell cycle inhibitors in HE were between those of AS and BG/KS. Protein expression patterns in BG and KS were similar. Clustering analysis showed that the 130 cases were divided into three clusters: AS-rich, BG-rich, and KS-rich clusters. The AS-rich cluster was characterized by high caveolin-1 positivity, abnormal p53, high Ki-67 index, and inactivated p27. The KS-rich cluster shared the features of KS, and the BG-rich group had high positive expression rates of galectin-3 and low bcl2 expression. In conclusion, although the rate was different, AS and HE tended to have less cell cycle marker expression than KS, and features of BG and activated KS cell signaling were similar.

Lymphatic Migration of Immune Cells

Lymphatic vessels collect interstitial fluid that has extravasated from blood vessels and return it to the circulatory system. Another important function of the lymphatic network is to facilitate immune cell migration and antigen transport from the periphery to draining lymph nodes. This migration plays a crucial role in immune surveillance, initiation of immune responses and tolerance. Here we discuss the significance and mechanisms of lymphatic migration of innate and adaptive immune cells in homeostasis, inflammation and cancer.

Lymphatic vessel density as a prognostic indicator in Asian NSCLC patients: a meta-analysis

BACKGROUND

To determine the association of lymphatic vessel density (LVD) with the prognosis of Asian non-small cell lung cancer (NSCLC) patients via a meta-analysis.

METHODS

Eligible studies were selected by searching PubMed and EMBASE from inception to July 25, 2017. The reference lists of the retrieved articles were also consulted. The information was independently screened by two authors. When heterogeneity was significant, a random-effects model was used to determine overall pooled risk estimates.

RESULTS

A total of 15 studies with 1075 patients were finally included in the meta-analysis. LVD was positively associated with the prognosis of NSCLC in the overall analysis (hazard ratio (HR) 1.14, 95% confidence interval (95% CI): 1.02-1.27, p = 0.000, I² = 73.2%). Subgroup analyses were performed on 5 VEGFR-3 groups (p = 0.709, I² = 0.0%), 3 LYVE-1 groups (p = 0.01, I² = 86.4%), 5 D2-40 groups (p = 0.019, I² = 66.2%), and 2 podoplanin groups (p = 0.094, I² = 64.5%). Sensitivity analysis indicated robust results. There was no publication bias.

CONCLUSIONS

LVD is an indicator of poor prognosis in Asian NSCLC patients.

Long-acting parenteral combination antiretroviral loaded nano-drug delivery system to treat chronic HIV-1 infection: A humanized mouse model study

Human immunodeficiency virus (HIV) patients are often diagnosed in the chronic stage of HIV/AIDS. Combination antiretroviral therapy (cART) has improved quality of life for HIV-infected patients. Present study describes a novel long-acting parenteral formulation of combination antiretroviral (cARV) loaded nano-drugs for treating chronic HIV-1 (cHIV) in a humanized-BLT (hu-BLT) mice model. The cARV (elvitegravir+tenofovir alafenamide+emtricitabine; EVG+TAF+FTC) drugs (mimicking marketed Genvoya^® one-pill for HIV-treatment) were encapsulated in poly (lactic-co-glycolic acid) nanoparticles (NPs). To establish cHIV, hu-BLT mice were intravaginally challenged with HIV-1 and maintained for 15 weeks. Plasma viral load (pVL) was monitored by RT-PCR to confirm cHIV. Baseline pVL (week 15) was comparable between treated (n = 10) and control (n = 5) mice groups. Subsequently, treatment hu-BLT mice received 3 subcutaneous doses of cARV NPs (417 mg/kg per dose; n = 10), biweekly, and a fourth/terminal dose a week later. Prior to each treatment and on sacrifice (week 24), pVL was determined. Within three subcutaneous doses of cARV NPs, a non-detectable pVL was established (week 19) and continued until week 22. After the establishment of a non-detectable pVL (week 19-22), 4 treated-mice were sacrificed for tissue drug concentration determination by LC-MS/MS analysis. A considerable amount of cARV was detected at the HIV-infection target and reservoir organs. Subsequently, pVL rebounded comparable to control group by week 24, (7 weeks post-terminal dosage). The present study demonstrated cARV NPs augments sustained ARV efficacy in the cHIV humanized-mouse model. Therefore, cARV NPs could be a novel delivery system to treat cHIV patients, by overcoming drawbacks of conventional cART.

Dual Effects of Alpha-Hydroxy Acids on the Skin

AHAs are organic acids with one hydroxyl group attached to the alpha position of the acid. AHAs including glycolic acid, lactic acid, malic acid, tartaric acid, and citric acid are often used extensively in cosmetic formulations. AHAs have been used as superficial peeling agents as well as to ameliorate the appearance of keratoses and acne in dermatology. However, caution should be exercised in relation to certain adverse reactions among patients using products with AHAs, including swelling, burning, and pruritus. Whether AHAs enhance or decrease photo damage of the skin remains unclear, compelling us to ask the question, is AHA a friend or a foe of the skin? The aim of this manuscript is to review the various biological effects and mechanisms of AHAs on human keratinocytes and in an animal model. We conclude that whether AHA is a friend or foe of human skin depends on its concentration. These mechanisms of AHAs are currently well understood, aiding the development of novel approaches for the prevention of UV-induced skin damage.

COMP-angiopoietin-1 ameliorates inflammation-induced lymphangiogenesis in dextran sulfate sodium (DSS)-induced colitis model

Alterations in the intestinal lymphatic network are pathological processes as related to inflammatory bowel disease (IBD). In this study, we demonstrated that reduction in inflammation-induced lymphangiogenesis ameliorates experimental acute colitis. A soluble and stable angiopoietin-1 (Ang1) variant, COMP-Ang1, possesses anti-inflammatory and angiogenic effects. We investigated the effects of COMP-Ang1 on an experimental colonic inflammation model. Experimental colitis was induced in mice by administering 3% dextran sulfate sodium (DSS) via drinking water. We determined body weight, disease activity indices, histopathological scores, lymphatic density, anti-ER-HR3 staining, and the expression of members of the vascular endothelial growth factor (VEGF) family and various inflammatory cytokines in the mice. The density of lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1) and VEGFR-3-positive lymphatic vessels increased in mice with DSS-induced colitis. We observed that COMP-Ang1-treated mice showed less weight loss, fewer clinical signs of colitis, and longer colons than Ade-DSS-treated mice. COMP-Ang1 also significantly reduced the density of LYVE-1-positive lymphatic vessels and the disruption of colonic architecture that is normally associated with colitis and repressed the immunoregulatory response. Further, COMP-Ang1 treatment reduced both M1 and M2 macrophage infiltration into the inflamed colon, which involved inhibition of VEGF-C and D expression. Thus, COMP-Ang1, which acts by reducing inflammation-induced lymphangiogenesis, may be used as a novel therapeutic for the treatment of IBD and other inflammatory diseases.

KEY MESSAGES

COMP-Ang1 decreases inflammatory-induced lymphangiogenesis in experimental acute colitis. COMP-Ang1 improves the symptom of DSS-induced inflammatory response. COMP-Ang1 reduces the expression of pro-inflammatory cytokines in inflamed colon. COMP-Ang1 reduces the expression of VEGFs in inflamed colon. COMP-Ang1 prevents infiltration of macrophages in a DSS-induced colitis model.

Multiple roles of lymphatic vessels in tumor progression

Sentinel lymph node metastasis is a prognostic indicator for systemic tumor spread in many types of cancers, and tumor lymphangiogenesis correlates with reduced survival. Consequently, lymphatic vessels have been suggested to promote tumor progression in multiple ways. Tumor lymphangiogenesis occurs both in primary tumors and at distant (pre-) metastatic sites, and facilitates lymphatic invasion and tumor cell dissemination. Lymphatic vessels have also emerged as regulators of tumor immunity, transporting tumor antigens to lymph nodes and directly interacting with immune cells. Furthermore, lymphatic vessels might provide a 'lymphovascular' niche contributing to the maintenance of stem-like tumor cells that are tightly related to tumor recurrence. Thus, targeting tumor lymphangiogenesis or specific lymphatic-associated functions might represent a promising approach to inhibit tumor progression.

Lymph node metastases: importance of detection and treatment strategies

INTRODUCTION

Lymphatic vessels are the preferential route of most solid tumors to spread their metastases in the body. The onset of metastatic nests in draining lymph nodes (LNs) are a significant indicator of cancer progression and a dismaying sign of worsen staging. Therefore, the individuation and elimination of cancer cells within the lymphatic system (LS) are an important goal. Nevertheless, the targeting of the LS with traditional contrast agents and/or chemotherapeutics is difficult, due to its anatomical structure. For this reason, many studies on new lymphatic delivery systems have been carried out, both to improve lymphatic imaging and to selectively carry chemotherapeutics to LNs, reducing the exposure of healthy tissues to the cytotoxic substances. This is an overview of the present situation in the field of detection and treatment strategies of lymphatic metastases, taking into account the use of nano-drug delivery systems. Nanocarriers, thanks to their small size and other physicochemical characteristics, are suitable vectors for imaging and chemotherapy of the LS.

AREAS COVERED

The role of the LS in tumor progression and importance of treatment and imaging strategies of lymphatic metastases.

EXPERT OPINION

The nanoparticles are a promising approach for treatment and detection of lymphatic metastases. However further studies are necessary in order to evaluate their efficacy in human clinical application.

Lymphatic invasion and the Shields index in predicting melanoma metastases

INTRODUCTION

Findings of the prognostic significance of lymphatic invasion are contradictory. To determine an as efficient cutaneous melanoma metastasis predictor as possible, Shields et al. created a new prognostic index. This study aimed to examine whether the lymphatic invasion analysis and the Shields index calculation can be used in predicting lymph node status in patients with cutaneous melanoma.

METHODS

Lymphatic invasion of 100 melanoma specimens was detected by dual immunohistochemistry staining for the lymphatic endothelial marker D2-40 and melanoma cell S-100 protein. The Shields index was calculated as a logarithm by multiplying the melanoma thickness, square of peritumoural lymphatic vessel density and the number "2" for the present lymphatic invasion.

RESULTS

No statistically significant difference was observed between lymph node metastatic and nonmetastatic melanomas regarding the lymphatic invasion. Metastatic melanomas showed a significantly higher Shields index value than nonmetastatic melanomas (p = 0.00). Area under the receiver operator characteristic (ROC) curve (AUC) proved that the Shields index (AUC = 0.86, 95% confidence interval (CI) 0.79-0.93, p = 0.00) was the most accurate predictor of lymph node status, followed by the melanoma thickness (AUC = 0.76, 95% CI 0.67-0.86, p = 0.00) and American Joint Committee on Cancer (AJCC) staging (AUC = 0.75, 95% CI 0.66-0.85, p = 0.00), while lymphatic invasion was not successful in predicting (AUC = 0.56, 95% CI 0.45-0.67, p = 0.31). The Shields index achieved 81.3% sensitivity and 75% specificity (cut-off mean value).

CONCLUSIONS

Our findings show that D2-40/S-100 immunohistochemical analysis of lymphatic invasion cannot be used for predicting the lymph node status, while the Shields index calculation predicts disease outcome more accurately than the melanoma thickness and AJCC staging.

Evolution of ramucirumab in the treatment of cancer - A review of literature

Ramucirumab is a recombinant human monoclonal antibody and is used in the treatment of advanced malignancies. Its mechanism of action is by inhibiting angiogenesis in tumor cells by targeting the vascular endothelial growth factor receptor 2. United States Food and Drug Administration (FDA) approved it initially in 2014 for the treatment of advanced gastric or gastro-esophageal junction adenocarcinoma and metastatic non-small cell lung carcinoma. It was approved by FDA in 2015 for the treatment of advanced colorectal cancer. This manuscript consolidates pre-clinical trials to phase I, II, and III trial data indicating the effects of ramucirumab on different cancer types, which led to its approval. By comparing these clinical trials alongside each other, we can more easily examine the studies that have already been completed, along with currently ongoing studies and potential further areas of interest for this newly approved treatment. This approach makes it convenient to compare dosages, overall survival, adverse events, as well as possible routes for combination therapy with ramucirumab. By compiling results for various oncological malignancies, we can differentiate between treatments that are effective and have the highest incidence of stable disease, and those that do not seem promising. Ramucirumab has been effective in the treatment of various carcinomas and this article outlines other tumors in which this treatment option may be successful.

Myeloid Wnt ligands are required for normal development of dermal lymphatic vasculature

Resident tissue myeloid cells play a role in many aspects of physiology including development of the vascular systems. In the blood vasculature, myeloid cells use VEGFC to promote angiogenesis and can use Wnt ligands to control vascular branching and to promote vascular regression. Here we show that myeloid cells also regulate development of the dermal lymphatic vasculature using Wnt ligands. Using myeloid-specific deletion of the WNT transporter Wntless we show that myeloid Wnt ligands are active at two distinct stages of development of the dermal lymphatics. As lymphatic progenitors are emigrating from the cardinal vein and intersomitic vessels, myeloid Wnt ligands regulate both their numbers and migration distance. Later in lymphatic development, myeloid Wnt ligands regulate proliferation of lymphatic endothelial cells (LEC) and thus control lymphatic vessel caliber. Myeloid-specific deletion of WNT co-receptor Lrp5 or Wnt5a gain-of-function also produce elevated caliber in dermal lymphatic capillaries. These data thus suggest that myeloid cells produce Wnt ligands to regulate lymphatic development and use Wnt pathway co-receptors to regulate the balance of Wnt ligand activity during the macrophage-LEC interaction.

Endothelial Progenitor Cells for the Vascularization of Engineered Tissues

Self-assembled microvasculature from cocultures of endothelial cells (ECs) and stromal cells has significantly advanced efforts to vascularize engineered tissues by enhancing perfusion rates in vivo and producing investigative platforms for microvascular morphogenesis in vitro. However, to clinically translate prevascularized constructs, the issue of EC source must be resolved. Endothelial progenitor cells (EPCs) can be noninvasively supplied from the recipient through adult peripheral and umbilical cord blood, as well as derived from induced pluripotent stem cells, alleviating antigenicity issues. EPCs can also differentiate into all tissue endothelium, and have demonstrated potential for therapeutic vascularization. Yet, EPCs are not the standard EC choice to vascularize tissue constructs in vitro. Possible reasons include unresolved issues with EPC identity and characterization, as well as uncertainty in the selection of coculture, scaffold, and culture media combinations that promote EPC microvessel formation. This review addresses these issues through a summary of EPC vascular biology and the effects of tissue engineering design parameters upon EPC microvessel formation. Also included are perspectives to integrate EPCs with emerging technologies to produce functional, organotypic vascularized tissues.

Engineering Blood and Lymphatic Microvascular Networks in Fibrin Matrices

Vascular network engineering is essential for nutrient delivery to tissue-engineered constructs and, consequently, their survival. In addition, the functionality of tissues also depends on tissue drainage and immune cell accessibility, which are the main functions of the lymphatic system. Engineering both the blood and lymphatic microvasculature would advance the survival and functionality of tissue-engineered constructs. The aim of this study was to isolate pure populations of lymphatic endothelial cells (LEC) and blood vascular endothelial cells (BEC) from human dermal microvascular endothelial cells and to study their network formation in our previously described coculture model with adipose-derived stromal cells (ASC) in fibrin scaffolds. We could follow the network development over a period of 4 weeks by fluorescently labeling the cells. We show that LEC and BEC form separate networks, which are morphologically distinguishable and sustainable over several weeks. In addition, lymphatic network development was dependent on vascular endothelial growth factor (VEGF)-C, resulting in denser networks with increasing VEGF-C concentration. Finally, we confirm the necessity of cell–cell contact between endothelial cells and ASC for the formation of both blood and lymphatic microvascular networks. This model represents a valuable platform for in vitro drug testing and for the future in vivo studies on lymphatic and blood microvascularization.

Coordinated lymphangiogenesis is critical in lymph node development and maturation

BACKGROUND

Lymph node (LN) formation requires multiple but coordinated signaling from intrinsic and extrinsic cellular components during embryogenesis. However, the contribution and role of lymphatic vessels (LVs) in LN formation and maturation are poorly defined. Here, using lymphatic-specific reporters, Prox1-GFP mice and Vegfc^+/LacZ mice, we analyzed migration, assembly, and ingrowth of lymphatic endothelial cells (LECs) in LNs during pre- and postnatal development.

RESULTS

Prox1⁺ LECs form string-like connections rather than lymph sac-like structures until E14.5, but the LEC coverage around LN anlagen completes before birth. Compared to wild-type littermates, Vegfc^+/LacZ mice had markedly smaller LNs in neonates and adults, presumably due to the decrease in LTi cell clusters and migrating Prox1⁺ LECs during embryogenesis. In addition, Vegfc-haploinsufficiency or inhibition of VEGFR3 signaling led to an impairment of LN LV ingrowth, resulting in a significant decrease in LN volume. These data indicate that VEGF-C/VEGFR3 signaling plays a substantial role in normal LN formation through proper migration and organization of LECs.

CONCLUSIONS

Taken together, our results provide compelling evidence that the contribution of LVs through VEGF-C/VEGFR3 signaling is critical in LN development and maturation. Developmental Dynamics 245:1189-1197, 2016. © 2016 Wiley Periodicals, Inc.

Targeting Immunomodulatory Agents to the Gut-Associated Lymphoid Tissue

In addition to fluid haemostasis and lipid absorption, the lymphatic system and lymphoid tissues serve as the major host of immune cells where immune responses are evoked. Impaired function of the immune system might lead to serious diseases which are often treated by immunomodulators. This chapter briefly explores the physiology of an important part of the lymphatic system, the gut-associated lymphoid tissues (GALT). Currently used strategies for targeting GALT by immunomodulators for enhanced activity and/or decreased side effects are discussed. Strategies range from simple oral co-administration of immunomodulators with lipids to more advanced lipid-based formulations, polymer-based nanoparticle formulations and prodrugs. These targeting approaches successfully increase the concentration of immunomodulators achieved in the GALT and, more importantly, enhance immunomodulatory effects. Therefore, targeting immunomodulators to GALT represent a promising approach in the treatment of diseases where the immune system is actively involved.

Understanding lymphangiogenesis in knockout models, the cornea, and ocular diseases for the development of therapeutic interventions

A major focus of cancer research for several decades has been understand the ability of tumors to induce new blood vessel formation, a process known as angiogenesis. Unfortunately, only limited success has been achieved in the clinical application of angiogenesis inhibitors. We now know that lymphangiogenesis, the growth of lymphatic vessels, likely also plays a major role in tumor progression. Thus, therapeutic strategies targeting lymphangiogenesis or both lymphangiogenesis and angiogenesis may represent promising approaches for treating cancer and other diseases. Importantly, research progress toward understanding lymphangiogenesis is significantly behind that related to angiogenesis. A PubMed search of "angiogenesis" returns nearly 80,000 articles, whereas a search of "lymphangiogenesis" returns 2,635 articles. This stark contrast can be explained by the lack of molecular markers for identifying the invisible lymphatic vasculature that persisted until less than 2 decades ago, combined with the intensity of research interest in angiogenesis during the past half century. Still, significant strides have been made in developing strategies to modulate lymphangiogenesis, largely using ocular disease models. Here we review the current knowledge of lymphangiogenesis in the context of knockout models, ocular diseases, the biology of activators and inhibitors, and the potential for therapeutic interventions targeting this process.