Extracranial transport of brain lymphatics via cranial nerve in human

Extracranial waste transport from the brain interstitial fluid to the deep cervical lymph node (dCLN) is not extensively understood. The present study aims to show the cranial nerves that have a role in the transport of brain lymphatics vessels (LVs), their localization, diameter, and number using podoplanin (PDPN) and CD31 immunohistochemistry (IHC) and Western blotting. Cranial nerve samples from 6 human cases (3 cadavers, and 3 autopsies) were evaluated for IHC and 3 autopsies for Western blotting. The IHC staining showed LVs along the optic, olfactory, oculomotor, trigeminal, facial, glossopharyngeal, accessory, and vagus nerves. However, no LVs present along the trochlear, abducens, vestibulocochlear, and hypoglossal nerves. The LVs were predominantly localized at the endoneurium of the cranial nerve that has motor components, and LVs in the cranial nerves that had sensory components were present in all 3 layers. The number of LVs accompanying the olfactory, optic, and trigeminal nerves was classified as numerous; oculomotor, glossopharyngeal, vagus, and accessory was moderate; and facial nerves was few. The largest diameter of LVs was in the epineurium and the smallest one was in the endoneurium. The majority of Western blotting results correlated with the IHC. The present findings suggest that specific cranial nerves with variable quantities provide a pathway for the transport of wastes from the brain to dCLN. Thus, the knowledge of the transport of brain lymphatics along cranial nerves may help understand the pathophysiology of various neurological diseases.

Magnetic resonance lymphangiography: Establishing normal

BACKGROUND

Despite an increased interest in visualizing the lymphatic vessels with magnetic resonance lymphangiography (MRL), little literature is available describing their appearance in nonlymphedematous individuals. To determine lymphatic abnormalities, an understanding of how healthy lymphatic vessels appear and behave needs to be established. Therefore, in this study, MRL of individuals without a history of lymphatic disease was performed.

METHODS

A total of 25 individuals (15 women) underwent MRL of their lower limbs using a 3.0 T Philips magnetic resonance imaging scanner (Philips Medical Systems). The first nine participants were recruited to establish the concentration of gadolinium-based contrast agent (GBCA) to administer, with the remainder imaged before and after interdigital forefoot GBCA injections at the optimized dose. Outcomes, including lymphatic vessel diameter, tortuosity, and frequency of drainage via particular drainage routes, were recorded.

RESULTS

Healthy lymphatic vessels following the anteromedial pathway were routinely observed in post-contrast T1-weighted images (average tortuosity, 1.09 ± 0.03), with an average of 2.16 ± 0.93 lymphatic vessels with a diameter of 2.47 ± 0.50 mm crossing the anterior ankle. In six limbs, vessels following the anterolateral pathways were observed. No vessels traversing the posterior of the legs were seen. In a subset of 10 vessels, the lymphatic signal, measured at the ankle, peaked 29 minutes, 50 seconds ± 9 minutes, 29 seconds after GBCA administration. No lymphatic vessels were observed in T2-weighted images.

CONCLUSIONS

Contrast-enhanced MRL reliably depicts the lymphatic vessels in the legs of healthy controls. Following interdigital contrast injection, anteromedial drainage appears dominant. Quantitative measures related to lymphatic vessel size, tortuosity, and drainage rate are readily obtainable and could be beneficial for detecting even subtle lymphatic impairment.

Detailed study of collagen, vasculature, and innervation in the human cardiac conduction system

BACKGROUND

The cardiac conduction system (CCS) creates and propagates electrical signals generating the heartbeat. This study aimed to assess the collagen content, vasculature, and innervation in the human sinoatrial and atrioventricular CCS, and surrounding tissue.

MATERIALS AND METHODS

Ten sinoatrial and 17 atrioventricular CCS samples were collected from 17 adult human autopsied hearts. Masson trichrome stain was used to examine collagen, cardiomyocytes, and fat proportions. Immunohistochemically, vessels and lymphatics were studied by CD31 (pan-endothelial marker) and D2-40 (lymphatic endothelium marker) antibodies. General nerve densities were assessed by S100, while sympathetic nerves were studied using tyrosine hydroxylase, parasympathetic nerves with choline acetyltransferase, and GAP43 (neural growth marker) antibodies looked at these components. All components were quantified with QuPath software (Queens University, Belfast, Northern Ireland).

RESULTS

Interstitial collagen was more than two times higher in the sinoatrial vs. atrioventricular CCS (55% vs. 22%). The fat content was 6.3% in the sinoatrial CCS and 6.5% in the atrioventricular CCS. The lymphatic vessel density was increased in the sinoatrial and atrioventricular CCS compared to the surrounding tissue and was lower in the sinoatrial vs. atrioventricular CCS (P=.043). The overall vasculature density did not differ between the SA and AV CCS. The overall innervation and neural growth densities were significantly increased in the CCS compared to the surrounding tissue. The overall innervation was higher in the atrial vs. ventricular CCS (P=.018). The neural growth was higher in the atrial vs. ventricular CCS (P=.018). The sympathetic neural supply was dominant in all the studied regions with the highest density in the sinoatrial CCS.

CONCLUSIONS

Our results provide new insights into the unique morphology of the human CCS collagen, fat, vasculature, and innervation. A deeper understanding of the CCS anatomical components and morphologic substrates' role will help in elucidating the causes of cardiac arrhythmias and provide a basis for further therapeutic interventions.

Computational fluid dynamic modeling of the lymphatic system: a review of existing models and future directions

Historically, research into the lymphatic system has been overlooked due to both a lack of knowledge and limited recognition of its importance. In the last decade however, lymphatic research has gained substantial momentum and has included the development of a variety of computational models to aid understanding of this complex system. This article reviews existing computational fluid dynamic models of the lymphatics covering each structural component including the initial lymphatics, pre-collecting and collecting vessels, and lymph nodes. This is followed by a summary of limitations and gaps in existing computational models and reasons that development in this field has been hindered to date. Over the next decade, efforts to further characterize lymphatic anatomy and physiology are anticipated to provide key data to further inform and validate lymphatic fluid dynamic models. Development of more comprehensive multiscale- and multi-physics computational models has the potential to significantly enhance the understanding of lymphatic function in both health and disease.

Copper nanoparticles and silver nanoparticles impair lymphangiogenesis in zebrafish

Lymphatic system distributes in almost all vertebrate tissues and organs, and plays important roles in the regulation of body fluid balance, lipid absorption and immune monitoring. Although CuNPs or AgNPs accumulation has been reported to be closely associated with delayed hatching and motor dysfunction in zebrafish embryos, their biological effects on lymphangiogenesis remain unknown. In this study, thoracic duct was observed to be partially absent in both CuNPs and AgNPs stressed zebrafish larvae. Specifically, CuNPs stress induced hypermethylation of E2F7/8 binding sites on CCBE1 promoters via their producing ROS, thereby leading to the reduction of binding enrichment of E2F7/8 on CCBE1 promoter and its subsequently reduced expression, then resulting in defective lymphatic vessel formation. Differently, AgNPs stress induced down-regulated CCBE1 expression via down-regulating mRNA and protein levels of E2F7/8 transcription factors, thereby resulting in defective lymphatic vessel formation. This study may be the first to demonstrate that CuNPs and AgNPs damaged lymphangiogenesis during zebrafish embryogenesis, mechanistically, CuNPs epigenetically regulated the expression of lymphangiogenesis regulator CCBE1 via hypermethylating its promoter binding sites of E2F7/8, while AgNPs via regulating E2F7/8 expression. Meanwhile, overexpression of ccbe1 mRNA effectively rescued the lymphangiogenesis defects in both AgNPs and CuNPs stressed larvae, while overexpression of e2f7/8 mRNA effectively rescued the lymphangiogenesis defects in AgNPs rather than CuNPs stressed larvae. The results in this study will shed some light on the safety assessment of nanomaterials applied in medicine and on the ecological security assessments of nanomaterials. Video Abstract.

Lymphatic drainage dysfunction via narrowing of the lumen of cisterna chyli and thoracic duct after luminal dilation

BACKGROUND

The chronological pattern of extrahepatic lymphatic vessel progression in the course of chronic liver disease has not been clarified. This study aimed to clarify the chronological changes in lymphatic vessels with liver disease progression.

METHODS

This was a prospective cross-sectional study that enrolled a total of 199 patients. The maximum diameter of the cisterna chyli (CC) or terminal thoracic duct (tTD) was measured using computed tomography or ultrasonography, respectively. Changes in the maximum diameters of the CC and tTD were evaluated with patients with chronic liver disease as the pilot set (n = 138). Subsequently, we examined whether CC/tTD could be used to re-allocate unclassified patients by the Baveno-VII criteria to appropriately diagnose clinically significant portal hypertension (CSPH) in the pilot and validation sets.

RESULTS

In the pilot set, a scatter-plot showed that both CC and tTD were narrowed as terminal features in chronic liver disease after dilation. Because there was a significant correlation between the CC diameter and hepatic venous pressure gradient (r = 0.724) in unclassified patients, the diagnostic value of CC and tTD for CSPH was good (AUC: 0.961 and 0.913, respectively). After re-allocation, 68 and 27 unclassified patients were reduced to 4 and 5 in the pilot and validation sets, respectively.

CONCLUSION

Both the CC and tTD narrow in the course of liver disease after dilation. Moreover, the maximum diameter of the CC and tTD can be used to re-allocate patients who are unclassified according to the Baveno-VII criteria.

CLINICAL TRIAL NUMBER

UMIN trial no. 000044857.

Unraveling the lymphatic system in the spinal cord meninges: a critical element in protecting the central nervous system

The lymphatic vasculature plays a crucial role in fluid clearance and immune responses in peripheral organs by connecting them to distal lymph nodes. Recently, attention has been drawn to the lymphatic vessel network surrounding the brain's border tissue (Aspelund et al. in J Exp Med 212:991-999, 2015. https://doi.org/10.1084/jem.20142290 ; Louveau et al. in Nat Neurosci 21:1380-1391, 2018. https://doi.org/10.1038/s41593-018-0227-9 ), which guides immune cells in mediating protection against tumors (Song et al. in Nature 577:689-694, 2020. https://doi.org/10.1038/s41586-019-1912-x ) and pathogens Li et al. (Nat Neurosci 25:577-587, 2022. https://doi.org/10.1038/s41593-022-01063-z ) while also contributing to autoimmunity (Louveau et al. 2018) and neurodegeneration (Da Mesquita et al. in Nature 560:185-191, 2018. https://doi.org/10.1038/s41586-018-0368-8 ). New studies have highlighted the integral involvement of meningeal lymphatic vessels in neuropathology. However, our limited understanding of spinal cord meningeal lymphatics and immunity hinders efforts to protect and heal the spinal cord from infections, injury, and other immune-mediated diseases. This review aims to provide a comprehensive overview of the state of spinal cord meningeal immunity, highlighting its unique immunologically relevant anatomy, discussing immune cells and lymphatic vasculature, and exploring the potential impact of injuries and inflammatory disorders on this intricate environment.

YAP1/Piezo1 involve in the dynamic changes of lymphatic vessels in UVR-induced photoaging progress to squamous cell carcinoma

BACKGROUND

UV-induced cutaneous squamous cell carcinoma (cSCC) is one of the most common skin cancers. The constant alterations of the lymphatic-centered immune microenvironment are essential in transforming from photoaging to cSCC. Studying the mechanism will be beneficial for new targets exploration to the early prediction of cSCC.

AIMS

To investigate the dynamic changes and mechanism of the lymphatic-centered immune microenvironment in transforming from photoaging to cSCC induced by ultraviolet irradiation (UVR).

METHODS

TIMER2.0 was used to analyze whether YAP1/VEGFC signaling pathway is involved in lymphangiogenesis in head and neck squamous cell carcinoma (HNSCC). Meanwhile, lymphatic-centered immune microenvironments alterations and the related cumulative survival time were also analyzed. With the accumulated UVR, skin photoaging developed and gradually progressed into actinic keratosis and cSCC on SKH-1 hairless mice. The skin lymphatic-centered immune microenvironment was evaluated at the 0th, 8th, 12th, 16-18th, and 20-24th week of UVR. Skin phenotype was assessed using optical coherence tomography (OCT) and skin image. H&E and Masson's trichrome staining evaluated epidermis and dermis. The structure of lymphatic vessels (LVs), blood vessels, and different types of T cells were evaluated by immunohistochemistry staining. The expression of Piezo1 whose deletion in adult lymphatics led to substantial valve degeneration, VE-cadherin that maintained the permeability of LVs, and YAP1 were evaluated by immunohistochemistry staining as well. Besides, the drainage function of LVs was assessed by Evans Blue assay in vivo.

RESULTS

The lymphatic function and immune cell infiltration underwent adaptive changes under continuous UVR. TIMER2.0 analysis indicated that VEGFC genes high expressed in HNSCC. YAP1 gene expression was positive correlated with VEGFC in HNSCC. LV density increased in human cSCC. More LVs in HNSCC were beneficial to prolong the survival time. VEGFC gene overexpression was positive correlated to CD8+T cell infiltration. More CD8A+T cells and CD8B+T cell infiltration in HNSCC extended survival time. When YAP1 gene overexpression and high infiltration of endothelial cells took place simultaneously might prolong the survival time of HNSCC patients. And high infiltration of CD8+T cells prolonged the survival time as well. In animal studies, UVR-induced eight weeks (photoaging) and 16-18 weeks (precancerous) were two turning points. The density of LVs in UV-8w was the least. When photoaged skin developed into AK lesions (UV-16-18w), LV slightly exceeded healthy skin and proliferated sharply in cSCC (UV-20-24w). YAP1 expression was almost consistent with LV but rose after the photoaging stage. The drainage of cSCC mice induced by UVR was better than that of photoaged skin and worse than that of health skin. The dynamic alterations of LVs number, Piezo1 expression, and collagen might be reasons for it. The expression of Piezo1 was in the highest point after 8 weeks of UVR, then gradually descended to the platform. The total T cells increased slowly, but the infiltration of CD4+T cells increased, and CD8+T cells decreased after eight weeks of UVR. The CD8+T cells and CD4+T cells increased sharply in UV-16-18w and UV-20-24w groups.

CONCLUSION

The lymphatic-centered immune microenvironment underwent adaptive changes under continuous UVR via regulating YAP1/VEGFC and Piezo1. During the formation of cSCC, there are two turning points, eight weeks (photoaging) and 16-18 weeks (precancerous). YAP1, Piezo1, LVs, and immune cells constantly changed with the skin state induced by UVR. According to these changes the process of cSCC can be identified in advance and intervene timely.

Impact of intravenous/intranasal polyinosinic-polycytidylic acid administration on the mediastinal fat-associated lymphoid clusters and lung tissue in healthy mice

BACKGROUND

Polyinosinic-polycytidylic acid (pIC) is a synthetic analog of double-stranded RNA. It is used as a synthetic adjuvant to induce an adaptive immune response. However, the effect of pIC on the development of mediastinal fat-associated lymphoid clusters (MFALCs) that regulate intrathoracic hemostasis has remained unidentified.

METHODS

We investigated the impact of intranasal (i.n.) administration (pIC i.n. group) and intravenous (i.v.) administration (pIC i.v. group) of pIC on both MFALCs and lung tissue.

RESULTS

Compared with the control phosphate-buffered saline (PBS) groups, both pIC-administered groups displayed a significant increase in the MFALC size (particularly in the pIC i.n. group), area of MFALC high endothelial venules (HEVs), area of lymphatic vessels (LVs), number of proliferating cells (particularly in the pIC i.v. group), and number of immune cells (B220+ B-lymphocytes, CD3+ T-lymphocytes, Iba1+ macrophages, and Gr-1+ granulocytes) in both MFALCs and lung tissues. In addition, a positive correlation was detected between MFALC size and proliferating cells, immune cell population, LVs, and HEVs within MFALCs in both groups. Except for the proliferating cell and B-lymphocyte populations in the i.n. administered group and granulocyte populations in both i.n. and i.v. administered routes, such correlations were significant.

CONCLUSION

In all, our data indicate that local or systemic administration of pIC induces the development of MFALCs and can be used as an immunostimulant therapeutic strategy.

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.

Current views on meningeal lymphatics and immunity in aging and Alzheimer's disease

Alzheimer's disease (AD) is an aging-related form of dementia associated with the accumulation of pathological aggregates of amyloid beta and neurofibrillary tangles in the brain. These phenomena are accompanied by exacerbated inflammation and marked neuronal loss, which altogether contribute to accelerated cognitive decline. The multifactorial nature of AD, allied to our still limited knowledge of its etiology and pathophysiology, have lessened our capacity to develop effective treatments for AD patients. Over the last few decades, genome wide association studies and biomarker development, alongside mechanistic experiments involving animal models, have identified different immune components that play key roles in the modulation of brain pathology in AD, affecting its progression and severity. As we will relay in this review, much of the recent efforts have been directed to better understanding the role of brain innate immunity, and particularly of microglia. However, and despite the lack of diversity within brain resident immune cells, the brain border tissues, especially the meninges, harbour a considerable number of different types and subtypes of adaptive and innate immune cells. Alongside microglia, which have taken the centre stage as important players in AD research, there is new and exciting evidence pointing to adaptive immune cells, namely T and B cells found in the brain and its meninges, as important modulators of neuroinflammation and neuronal (dys)function in AD. Importantly, a genuine and functional lymphatic vascular network is present around the brain in the outermost meningeal layer, the dura. The meningeal lymphatics are directly connected to the peripheral lymphatic system in different mammalian species, including humans, and play a crucial role in preserving a "healthy" immune surveillance of the CNS, by shaping immune responses, not only locally at the meninges, but also at the level of the brain tissue. In this review, we will provide a comprehensive view on our current knowledge about the meningeal lymphatic vasculature, emphasizing its described roles in modulating CNS fluid and macromolecule drainage, meningeal and brain immunity, as well as glial and neuronal function in aging and in AD.

The emerging roles of long noncoding RNAs in lymphatic vascular development and disease

Recent advances in RNA sequencing technologies helped uncover what was once uncharted territory in the human genome-the complex and versatile world of long noncoding RNAs (lncRNAs). Previously thought of as merely transcriptional "noise", lncRNAs have now emerged as essential regulators of gene expression networks controlling development, homeostasis and disease progression. The regulatory functions of lncRNAs are broad and diverse, and the underlying molecular mechanisms are highly variable, acting at the transcriptional, post-transcriptional, translational, and post-translational levels. In recent years, evidence has accumulated to support the important role of lncRNAs in the development and functioning of the lymphatic vasculature and associated pathological processes such as tumor-induced lymphangiogenesis and cancer metastasis. In this review, we summarize the current knowledge on the role of lncRNAs in regulating the key genes and pathways involved in lymphatic vascular development and disease. Furthermore, we discuss the potential of lncRNAs as novel therapeutic targets and outline possible strategies for the development of lncRNA-based therapeutics to treat diseases of the lymphatic system.

Right lumbar lymph trunk injury after right laparoscopic donor nephrectomy: a case report

Laparoscopic donor nephrectomy (LDN) is increasingly popular because of its advantages over open surgery. Chyle leak after donor nephrectomy is a rare but potentially lethal complication if not treated appropriately. We describe a case of a 43-year-old female patient with no remarkable history who presented a chyle leak on day 2 after right transperitoneal LDN. Since conservative treatment failed, the patient underwent magnetic resonance imaging (MRI) and intranodal lipiodol lymphangiography, which confirmed the chyle leak from the right lumbar lymph trunk into the right renal fossa. The chyle leak was percutaneously embolized twice, on postoperative day (POD) 5 and POD 10, by a mixture of N-butyl-2-cyanoacrylate and lipiodol. The drainage fluid decreased significantly after the second embolization. The subhepatic drainage tube was withdrawn on POD 14, and the patient was discharged on POD 17. MRI lymphangiography and intranodal lipiodol lymphangiography effectively identified the chyle leak point. Percutaneous embolization seems to be a safe, effective method for treating high-output chyle leaks.

Anatomy and function of the lymphatic vessels in the parietal pleura and their plasticity under inflammation in mice

Inflammatory pleuritis often causes pleural effusions, which are drained through lymphatic vessels (lymphatics) in the parietal pleura. The distribution of button- and zipper-like endothelial junctions can identify the subtypes of lymphatics, the initial, pre-collecting, and collecting lymphatics. Vascular endothelial growth factor receptor (VEGFR)-3 and its ligands VEGF-C/D are crucial lymphangiogenic factors. Currently, in the pleura covering the chest walls, the anatomy of the lymphatics and connecting networks of blood vessels are incompletely understood. Moreover, their pathological and functional plasticity under inflammation and the effects of VEGFR inhibition are unclear. This study aimed to learn the above-unanswered questions and immunostained mouse chest walls as whole-mount specimens. Confocal microscopic images and their 3-dimensional reconstruction analyzed the vasculatures. Repeated intra-pleural cavity lipopolysaccharide challenge induced pleuritis, which was also treated with VEGFR inhibition. Levels of vascular-related factors were evaluated by quantitative real-time polymerase chain reaction. We observed the initial lymphatics in the intercostals, collecting lymphatics under the ribs, and pre-collecting lymphatics connecting both. Arteries branched into capillaries and gathered into veins from the cranial to the caudal side. Lymphatics and blood vessels were in different layers with an adjacent distribution of the lymphatic layer to the pleural cavity. Inflammatory pleuritis elevated expression levels of VEGF-C/D and angiopoietin-2, induced lymphangiogenesis and blood vessel remodeling, and disorganized the lymphatic structures and subtypes. The disorganized lymphatics showed large sheet-like structures with many branches and holes inside. Such lymphatics were abundant in zipper-like endothelial junctions with some button-like junctions. The blood vessels were tortuous and had various diameters and complex networks. Stratified layers of lymphatics and blood vessels were disorganized, with impaired drainage function. VEGFR inhibition partially maintained their structures and drainage function. These findings demonstrate anatomy and pathological changes of the vasculatures in the parietal pleura and their potential as a novel therapeutic target.

Open pathways for cerebrospinal fluid outflow at the cribriform plate along the olfactory nerves

BACKGROUND

Routes along the olfactory nerves crossing the cribriform plate that extend to lymphatic vessels within the nasal cavity have been identified as a critical cerebrospinal fluid (CSF) outflow pathway. However, it is still unclear how the efflux pathways along the nerves connect to lymphatic vessels or if any functional barriers are present at this site. The aim of this study was to anatomically define the connections between the subarachnoid space and the lymphatic system at the cribriform plate in mice.

METHODS

PEGylated fluorescent microbeads were infused into the CSF space in Prox1-GFP reporter mice and decalcification histology was utilized to investigate the anatomical connections between the subarachnoid space and the lymphatic vessels in the nasal submucosa. A fluorescently-labelled antibody marking vascular endothelium was injected into the cisterna magna to demonstrate the functionality of the lymphatic vessels in the olfactory region. Finally, we performed immunostaining to study the distribution of the arachnoid barrier at the cribriform plate region.

FINDINGS

We identified that there are open and direct connections from the subarachnoid space to lymphatic vessels enwrapping the olfactory nerves as they cross the cribriform plate towards the nasal submucosa. Furthermore, lymphatic vessels adjacent to the olfactory bulbs form a continuous network that is functionally connected to lymphatics in the nasal submucosa. Immunostainings revealed a discontinuous distribution of the arachnoid barrier at the olfactory region of the mouse.

INTERPRETATION

Our data supports a direct bulk flow mechanism through the cribriform plate allowing CSF drainage into nasal submucosal lymphatics in mice.

FUNDING

This study was supported by the Swiss National Science Foundation (310030_189226), Dementia Research Switzerland-Synapsis Foundation, the Heidi Seiler Stiftung and the Fondation Dr. Corinne Schuler.

Intranodal dynamic contrast-enhanced CT lymphangiography and dynamic contrast-enhanced MR lymphangiography in microminipig

OBJECTIVES

To evaluate the feasibility and image quality of intranodal dynamic contrast-enhanced CT lymphangiography (DCCTL) and dynamic contrast-enhanced MR lymphangiography (DCMRL) in microminipigs.

METHODS

Our institution's committee for animal research and welfare provided approval. Three microminipigs underwent DCCTL and DCMRL after inguinal lymph node injection of 0.1 mL/kg contrast media. Mean CT values on DCCTL and signal intensity (SI) on DCMRL were measured at the venous angle and thoracic duct (TD). The contrast enhancement index (CEI; increase in CT values pre- to post-contrast) and signal intensity ratio (SIR; SI of lymph divided by SI of muscle) were evaluated. The morphologic legibility, visibility, and continuity of lymphatics were qualitatively evaluated using a 4-point scale. Two microminipigs underwent DCCTL and DCMRL after lymphatic disruption and the detectability of lymphatic leakage was evaluated.

RESULTS

The CEI peaked at 5-10 min in all microminipigs. The SIR peaked at 2-4 min in two microminipigs and at 4-10 min in one microminipig. The peak CEI and SIR values were 235.6 HU and 4.8 for venous angle, 239.4 HU and 2.1 for upper TD, and 387.3 HU and 2.1 for middle TD. The visibility and continuity of upper-middle TD scores were 4.0 and 3.3-3.7 for DCCTL, and 4.0 and 4.0 for DCMRL. In the injured lymphatic model, both DCCTL and DCMRL demonstrated lymphatic leakage.

CONCLUSIONS

DCCTL and DCMRL in a microminipig model enabled excellent visualization of central lymphatic ducts and lymphatic leakage, indicating the research and clinical potential of both modalities.

KEY POINTS

• Intranodal dynamic contrast-enhanced computed tomography lymphangiography showed a contrast enhancement peak at 5-10 min in all microminipigs. • Intranodal dynamic contrast-enhanced magnetic resonance lymphangiography showed a contrast enhancement peak at 2-4 min in two microminipigs and at 4-10 min in one microminipig. • Both intranodal dynamic contrast-enhanced computed tomography lymphangiography and dynamic contrast-enhanced magnetic resonance lymphangiography demonstrated the central lymphatic ducts and lymphatic leakage.

Primo Vessels Inside Lymphatic Vessels Are Absent in an ALS Mouse Model

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by the selective death of motor neurons in the central nervous system. It is also a representative rare disease among degenerative diseases of the nervous system. Although many drugs for the treatment of degenerative brain diseases are being developed, they are not delivered correctly to the target due to the blood-brain barrier. The present study aimed to analyze changes in the primo vascular system (PVS) in ALS mice with symptoms and the partial oxygen pressure (pO2) in normal mice. In normal mice, we consistently observed primo vessels in lymphatic vessels (L-PVS). However, in ALS mice with symptoms, L-PVS were mostly lost, rendering them difficult to observe. The pO2 of the L-PVS in normal mice was significantly higher than that of normal dermis and lymph nodes.In conclusion, the relatively higher oxygen levels measured in the L-PVS than in normal dermis and lymph nodes suggest a role for the PVS in oxygen transport and enable a hypothesis that the L-PVS can function as a drug delivery pathway.

Anatomy and pathology of lymphatic vessels under physiological and inflammatory conditions in the mouse diaphragm

The lymphatic vessels in the parietal pleura drain fluids. Impaired drainage function and excessive fluid entry in the pleural cavity accumulate effusion. The rat diaphragmatic lymphatics drain fluids from the pleura to the muscle layer. Lymphatic subtypes are characterized by the major distribution of discontinuous button-like endothelial junctions (buttons) in initial lymphatics and continuous zipper-like junctions (zippers) in the collecting lymphatics. Inflammation replaced buttons with zippers in tracheal lymphatics. In the mouse diaphragm, the structural relationship between the lymphatics and blood vessels, the presence of lymphatics in the muscle layer, and the distributions of initial and collecting lymphatics are unclear. Moreover, the endothelial junctional alterations and effects of vascular endothelial growth factor receptor (VEGFR) inhibition under pleural inflammation are unclear. We subjected the whole-mount mouse diaphragms to immunohistochemistry. The lymphatics and blood vessels were distributed in different layers of the pleural membrane. Major lymphatic subtypes were initial lymphatics in the pleura and collecting lymphatics in the muscle layer. Chronic pleural inflammation disorganized the stratified layers of the lymphatics and blood vessels and replaced buttons with zippers in the pleural lymphatics, which impaired drainage function. VEGFR inhibition under inflammation maintained the vascular structures and drainage function. In addition, VEGFR inhibition maintained the lymphatic endothelial junctions and reduced the blood vessel permeability under inflammation. These findings may provide new targets for managing pleural effusions caused by inflammation, such as pleuritis and empyema, which are common pneumonia comorbidities.

Umbilical cord vessels other than the umbilical arteries and vein: a histological study of midterm human fetuses

At birth, the umbilical cord contains various types of thin vessels that are near and outside the umbilicus and separate from the umbilical arteries and vein. These vessels are regarded as the remnant "vitelline vessels" and are often called "umbilical vessels", although this terminology could lead to confusion with the true umbilical arteries and vein. No study has yet comprehensively examined these vessels using histological sections. Our examination of these vessels in 25 midterm fetuses (gestational age: 10-16 weeks) led to five major findings: (i) all specimens had umbilical branches of the inferior epigastric artery; (ii) 5 specimens had vitelline vein remnants; (iii) 4 specimens had a thin artery originating from the left hepatic artery that ran along the umbilical vein; (iv) 2 specimens had a so-called "para-umbilical vein" that was along the umbilical vein and reached the umbilicus; and (v) all specimens had lymphatic vessels originating from the umbilicus that ran caudally along the umbilical artery. The pelvic vein tributaries were well developed along the intra-abdominal umbilical artery, but did not reach the umbilicus. The lymphatic vessel was distinguished from the veins by an intraluminar cluster of lymphocytes attaching to the endothelium. The arterial branch in the umbilical cord did not accompany veins and lymphatic vessels, in contrast to the mother artery in the rectus abdominis. All these thin vessels seemed to be obliterated when the fibrous umbilical ring grew during late-term. The para-umbilical collateral vein in adults might develop outside the fibrous umbilical ring after birth.

Photoacoustic lymphangiography is a possible alternative for lymphedema staging

OBJECTIVE

Photoacoustic imaging is a new technique that uses the photoacoustic effect. In photoacoustic lymphangiography (PAL), images of the lymphatic vessels can be visualized using light-absorbing contrast agents. In the present study, we investigated the efficacy of PAL for lymphedema staging.

METHODS

We performed PAL of the lower extremities and examined the clinical implications of using PAL for staging lymphedema by comparing the PAL images with those obtained using lymphoscintigraphy. Of 47 patients with lymphedema who had been outpatients or hospitalized at our institution between May 2018 and September 2020 and had undergone PAL, 15 with 18 limbs who had also undergone lymphoscintigraphy were included in the present study. The lymphoscintigraphy findings were classified using the Maegawa classification. We also investigated whether PAL could clearly visualize the lymphatic vessels and concisely reflect the disease state by counting the number of lymphatic vessels observed using PAL.

RESULTS

The PAL findings were categorized into three groups: collecting lymphatic vessels, dermal backflow (DBF), and no lymphatic vessels. The collecting lymphatic vessels group corresponded to types 2 and 3 in the Maegawa classification; DBF corresponded to types 3 and 4, and the no lymphatic vessels group corresponded to type 4. The number of lymphatic vessels visualized using PAL was similar to that with lymphoscintigraphy. As the disease progressed, the number of lymphatic vessels observed decreased, increased DBF was detected, and, eventually, the lymphatic vessels were not visible, corresponding to the general changes observed via lymphoscintigraphy with stage progression.

CONCLUSIONS

The findings from PAL and lymphoscintigraphy tended to correspond, suggesting that PAL could be useful for lymphedema staging.

Lymphatic vessels are present in human saccular intracranial aneurysms

Saccular intracranial aneurysm (sIA) rupture leads to subarachnoid haemorrhage and is preceded by chronic inflammation and atherosclerotic changes of the sIA wall. Increased lymphangiogenesis has been detected in atherosclerotic extracranial arteries and in abdominal aortic aneurysms, but the presence of lymphatic vessels in sIAs has remained unexplored. Here we studied the presence of lymphatic vessels in 36 intraoperatively resected sIAs (16 unruptured and 20 ruptured), using immunohistochemical and immunofluorescence stainings for lymphatic endothelial cell (LEC) markers. Of these LEC-markers, both extracellular and intracellular LYVE-1-, podoplanin-, VEGFR-3-, and Prox1-positive stainings were detected in 83%, 94%, 100%, and 72% of the 36 sIA walls, respectively. Lymphatic vessels were identified as ring-shaped structures positive for one or more of the LEC markers. Of the sIAs, 78% contained lymphatic vessels positive for at least one LEC marker. The presence of LECs and lymphatic vessels were associated with the number of CD68+ and CD163+  cells in the sIA walls, and with the expression of inflammation indicators such as serum amyloid A, myeloperoxidase, and cyclo-oxygenase 2, with the presence of a thrombus, and with the sIA wall rupture. Large areas of VEGFR-3 and α-smooth muscle actin (αSMA) double-positive cells were detected in medial parts of the sIA walls. Also, a few podoplanin and αSMA double-positive cells were discovered. In addition, LYVE-1 and CD68 double-positive cells were detected in the sIA walls and in the thrombus revealing that certain CD68+ macrophages are capable of expressing LEC markers. This study demonstrates for the first time the presence of lymphatic vessels in human sIA walls. Further studies are needed to understand the role of lymphatic vessels in the pathogenesis of sIA.

Refractory ascites after laparoscopic cholecystectomy: a case report

BACKGROUND

Laparoscopic cholecystectomy is a common surgical option for gallstone disease with minimal trauma and rapid recovery. Ascites is a relatively uncommon complication after laparoscopic cholecystectomy and is more frequently observed in patients with preoperative abnormal liver function. However, patients without underlying liver disease develop refractory ascites after laparoscopic cholecystectomy are rare. We report a case of massive ascites caused by lymphatic injury after laparoscopic cholecystectomy.

CASE PRESENTATION

A 63-year-old woman complained of abdominal discomfort and distension at the twelfth day after a laparoscopic cholecystectomy for gallbladder stones. Subsequently, the patient developed spontaneous bacterial peritonitis and a decreased output of urine. Abdominal computed tomography (CT) identified abdominal effusion. The patient received abdominocentesis and the volume of slightly turbid yellow ascites averaged 1500-2000 ml per day. The results of laboratory analysis of ascitic fluid showed the following: serum-ascites albumin-gradient (SAAG), 11-12 g/L; albumin, 11-14 g/L; triglycerides, 0.91 mmol/L. After the diuretic therapy, repeated large-volume paracentesis with albumin supplementation, administration of antibiotics and renal vasodilating medications, the patient's symptoms did not relieve. Lymphoscintigraphy found a small amount of radioactive filling in the abdominal cavity. The patient finally received surgery with detection and ligation of the lymphatic leak. The ascites disappeared and the patient recovered well.

CONCLUSIONS

For patients with atypical characteristics of chylous ascites, lymphoscintigraphy could help to localize and qualify the diagnosis. Surgical treatment could be considered when conservative treatment fails.

Imaging of fluorescent polymer dots in relation to channels and immune cells in the lymphatic system

Polymer dots (Pdots) have been applied to imaging lymph nodes (LNs) and lymphatic vessels (LVs) in living mice and rats. However, the mechanism of absorption, distribution, metabolism, and excretion of Pdots in LNs and LVs is still unclear. Therefore, the relationship between Pdots and immune cells, LVs and collagen fibers in lymphatics was studied by multiple in vivo and ex vivo microscopic imaging methods and detection techniques. Flow cytometry showed that Pdots could be phagocytosed by macrophages and monocytes, and had no relationship with B cells, T cells and dendric cells in LNs. Silver staining, immunofluorescence and two-photon microscope showed that Pdots gathered in collagen fibers and LVs of LNs. Furthermore, immunofluorescence imaging results verified that Pdots were distributed in the extracellular space of collecting LVs endothelial cells. In addition, Pdots in the collecting LVs were basically cleared by leaking into the surrounding tissue or draining LNs after 21 days of injection. During the long-time observation, Pdots also helped monitor the contraction frequency and variation range of LV. Our study lays a foundation on the research of Pdots as the carrier to study lymphatic structure and function in the future.

Characterization of Lymphatic Vasculature Using Whole-Mount Immunostaining of Mouse Embryonic Dorsal Skin

Understanding the development of the lymphatic vasculature is essential to the understanding of how these vessels function in health and disease. High-resolution imaging of histological techniques such as immunostaining of sectioned tissue provides a snapshot into lymphatic vessel morphogenesis, patterning, and organization. Whole-mount staining of embryonic dermal vasculature allows for a deeper analysis and characterization of the developing lymphatic vascular network.

Analyzing Lymphatic Vessel Patterning in Adult Tissue

Whole-mount immunostaining allows intact tissue to be surveyed in three dimensions, avoiding the more restricted fields of view provided by visualizing thin sections. This technique is particularly useful for imaging lymphatic and blood networks by high-resolution confocal microscopy, revealing how such vessels are spatially positioned, the subcellular arrangements of individual antigens, and interactions with individual cells within the interstitium or vessel lumen. The purpose of this chapter is to provide a practical guide for obtaining images of lymphatic vessels following immunofluorescence staining, primarily in mouse skin.

Imaging Blood Vessels and Lymphatics in Mouse Trachea Wholemounts

Changes in blood vessels and lymphatics in health and disease are easier to understand and interpret when studied microscopically in three dimensions. The mouse trachea is a simple, yet powerful, and versatile model system in which to achieve this. We describe practical immunohistochemical methods for fluorescence and confocal microscopy of wholemounts of the mouse trachea to achieve this purpose in which the entire vasculature can be visualized from the organ level to the cellular and subcellular level. Blood vessels and lymphatics have highly stereotyped vascular architectures that repeat in arcades between the tracheal cartilages. Arterioles, capillaries, and venules can be easily identified for the blood vessels, while the lymphatics consist of initial lymphatics and collecting lymphatics. Even small abnormalities in either blood vessels or lymphatics can be noticed and evaluated in three dimensions. We and others have used the mouse trachea for examining in situ angiogenesis and lymphangiogenesis, vascular development and regression, vessel patency, differences in transgenic mice, and pathological changes, such as increased vascular permeability induced by inflammatory mediators.

Opposing Roles of Vascular Endothelial Growth Factor C in Metastatic Dissemination and Resistance to Radio/Chemotherapy: Discussion of Mechanisms and Therapeutic Strategies

Many cancers can be cured by combining surgery with healthy margins, radiation therapy and chemotherapies. However, when the pathology becomes metastatic, cancers can be incurable. The best situation involves "chronicization" of the pathology even for several years. However, most of the time, patients die within a few months. To disseminate throughout the body, cancer cells must enter the vascular network and seed in another organ. However, during the initiation of cancer processes, the tumor is avascular. Later, the production of angiogenic factors causes tumor neovascularization and subsequent growth and spread, and the presence of blood and/or lymphatic vessels is associated with high grade tumors. Moreover, during tumor development, cancer cells enter lymphatic vessels and disseminate via the lymphatic network. Hence, blood and lymphatic vessels are considered as main routes of metastatic dissemination and cancer aggressiveness. Therefore, anti-angiogenic drugs entered in the therapeutic arsenal from 2004. Despite undeniable effects however, they are far from curative and only prolong survival by a few months.Recently, the concepts of angio/lymphangiogenesis were revisited by analyzing the role of blood and lymphatic vessels at the initiation steps of tumor development. During this period, cancer cells enter lymphatic vessels and activate immune cells within lymph nodes to initiate an antitumor immune response. Moreover, the presence of blood vessels at the proximity of the initial nodule allows immune cells to reach the tumor and eliminate cancer cells. Therefore, blood and lymphatic networks have a beneficial role during a defined time window. Considering only their detrimental effects is a concern. Hence, administration of anti-angio/lymphangiogenic therapies should be revisited to avoid the destruction of networks involved in antitumor immune response. This review mainly focuses on one of the main drivers of lymphangiogenesis, the VEGFC and its beneficial and pejorative roles according to the grade of aggressive tumors.

Whole-mount Immunohistochemistry to Visualize Mouse Embryonic Dermal Lymphatic Vasculature

Lymphatic vessels are abundant in the skin where they regulate interstitial fluid uptake and immune surveillance. Defects in dermal lymphatic vessels, such as fewer vessels and abnormal lymphatic vessel coverage with mural cells, are frequently associated with lymphedema and other lymphatic disorders. Whole-mount immunohistochemistry allows the visualization of dermal lymphatic vessels and identifies morphogenetic defects. Most dermal lymphatic vessels start growing during embryogenesis from lymph sacs that are located close to the axilla towards the dorsal and ventral midlines. Here, we present an approach that we have developed to permeabilize, immunolabel, clear, and visualize the lymphatic vessels. These simple and inexpensive techniques reproducibly generate images of dermal lymphatic vessels with great clarity.

Harnessing biomaterials for lymphatic system modulation

The lymphatic system plays an integral part in regulating immune cell trafficking and the transport of macromolecules. However, its influence on disease progression and drug uptake is understood less than that of the vascular system. To bridge this knowledge gap, biomaterials can be used to investigate the lymphatic system and to provide novel understanding into complex disease processes, including cancer metastasis and inflammation. Insight gained from these mechanistic studies can be further used to design innovative biomaterials to modulate the immune system, improve drug delivery, and promote tissue regeneration. This review article focuses on recent advances in (i) biomaterials used for lymphatic vessel formation, (ii) models for studying lymphatic-immune cells interactions, (iii) pharmaceuticals and their interactions with the lymphatic system, (iv) and strategies for drug delivery via the lymphatic system. Finally, several challenges regarding adopting biomaterials for immunomodulation and future perspectives are discussed. STATEMENT OF SIGNIFICANCE: The lymphatic system plays an integral part in regulating immune cell trafficking and the transport of macromolecules. However, its influence on disease progression and drug uptake is understood less than that of the vascular system. This review article focuses on recent progresses in biomaterials to investigate the lymphatic system and to provide novel understanding into complex disease states. Insight gained from these mechanistic studies can be further used to design innovative biomaterials to modulate the immune system, improve drug delivery, and promote tissue regeneration. Finally, a number of challenges in adopting biomaterials for immunomodulation and future perspectives are discussed.

Use of adipose-derived stem cells in lymphatic tissue engineering and regeneration

The potential to differentiate into different cell lines, added to the easy and cost-effective method of extraction, makes adipose-derived stem cells (ADSCs) an object of interest in lymphedema treatment. Our study’s goal was to conduct a comprehensive systematic review of the use of ADSCs in lymphatic tissue engineering and regeneration. On July 23, 2019, using PubMed/MEDLINE, Cochrane Clinical Answers, Cochrane Central Register of Controlled Trials, and Embase databases, we conducted a systematic review of published literature on the use of ADSCs in lymphatic tissue engineering and regeneration. There were no language or time frame limitations, and the following search strategy was applied: ((Adipose stem cell) OR Adipose-derived stem cell)) AND ((Lymphedema) OR Breast Cancer Lymphedema). Only original research manuscripts were included. Fourteen studies fulfilled the inclusion criteria. Eleven studies were experimental (in vitro or in vivo in animals), and only three were clinical. Publications on the topic demonstrated that ADSCs promote lymphangiogenesis, and its effect could be enhanced by modulation of vascular endothelial growth factor-C, interleukin-7, prospero homeobox protein 1, and transforming growth factor-β1. Pilot clinical studies included 11 patients with breast cancer-related lymphedema, and no significant side effects were present at 12-month follow-up. Literature on the use of ADSCs in lymphatic tissue engineering and regeneration demonstrated promising data. Clinical evidence is still in its infancy, but the scientific community agrees that ADSCs can be useful in regenerative lymphangiogenesis. Data collected in this review indicate that unprecedented advances in lymphedema treatment can be anticipated in the upcoming years.

A systematic review of pharmacologic and cell-based therapies for treatment of lymphedema (2010-2021)

BACKGROUND

Lymphedema describes the accumulation of interstitial fluid that results from lymphatic failure. Lymphedema can be of primary or secondary origin and has been estimated to affect 200 million people worldwide. Secondary lymphedema is commonly due to damage to the lymphatic vessels after surgical procedures. Treatments include compression bandaging and exercise regimens. However, at present, no pharmacologic therapy has been approved. We performed a systematic review of randomized controlled trials (RCTs) that had investigated pharmacologic and cell-based therapies for secondary lymphedema.

METHODS

We searched the databases MEDLINE, Embase, and ClinicalTrials.gov from January 2010 to May 2021. Only RCTs that had investigated pharmacologic and/or cell-based therapies for secondary lymphedema were eligible for inclusion. Those studies that had examined only active filarial infection were excluded. Two of us (J.W., S.T.) independently screened the studies for eligibility.

RESULTS

We identified eight RCTs that met the inclusion criteria. Overall, the studies were of poor quality with a high risk of bias. Ketoprofen demonstrated promising improvements in skin thickness and tissue histopathologic scores. Some evidence was found to suggest that doxycycline might be beneficial for nonfilarial secondary lymphedema, and a single, small RCT demonstrated that selenium might also confer some benefit. Neither synbiotics nor platelet-rich plasma resulted in reduced lymphedema volumes or symptom severity. Also, although bone marrow-derived stem cells resulted in improved symptom scores, no significant volume reduction was detected. Although positive results were demonstrated in trials investigating benzopyrones, previous meta-analyses have cast doubt on their efficacy. No two studies assessed the same intervention; thus, we could not perform a meta-analysis.

CONCLUSIONS

Although the results from some studies appeared promising, the available evidence at present is insufficient for any pharmacologic or cell-based therapy for patients with secondary lymphedema. Furthermore, large, high-quality RCTs are required before treatment recommendations will be possible.

Chylous content might determine the optimal surgical approach for mesenteric lymphatic malformations in childhood

BACKGROUND

Mesenteric lymphatic malformations (LMs) represent rare congenital anomalies that can include chylous or nonchylous content. The pathologic mechanisms explaining this phenomenon are poorly understood and not yet described. Furthermore, the current management approach does not consider the contents of the mesenteric LMs. In the present study, we have defined the relationship between the lymphatic mesenteric cyst content and the histologic evidence of LMs within the bowel wall.

METHODS

We retrospectively investigated all patients with mesenteric LMs treated surgically at our department from 1999 to 2018.

RESULTS

A total of 11 patients (6 girls and 5 boys) were included in our analysis. Seven patients had presented with LMs located in the jejunal mesentery, three in the ileocecal region, and only one in the mesocolon transversum and omentum. Of the 11 children, 7 had had LMs with nonchylous content and 4 had presented with chylous content LMs. Intestinal resection was performed in all 4 patients with chylous content LMs and 4 patients with nonchylous content LMs. Histopathologic evaluation of the surgical specimens determined that only the LMs with chylous content displayed malformed lymphatic channels throughout the bowel wall. The resected small bowel of four patients with nonchylous content showed no LM extension throughout the intestinal wall.

CONCLUSIONS

LMs with chylous content seem to develop from malformed lymphatic channels within the bowel wall. In such cases, segmental intestinal resection is mandatory. In contrast, mesenteric LMs with nonchylous content can potentially be treated without bowel resection if the blood supply can be preserved. This finding is, to the best of our knowledge, reported in the present study for the first time.

Volumetric ADC histogram analysis for preoperative evaluation of LVSI status in stage I endometrioid adenocarcinoma

OBJECTIVES

To investigate the value of volumetric ADC histogram metrics for evaluating lymphovascular space invasion (LVSI) status in stage I endometrioid adenocarcinoma (EAC).

METHODS

Preoperative MRI of 227 patients with stage I EAC were retrospectively analyzed. ADC histogram data were derived from the whole tumor with ROIs drawn on all slices of DWI scans (b = 0, 1000 s/mm²). The Student t-test was performed to compare ADC histogram metrics (minADC, maxADC, and meanADC; 10th, 25th, 50th, 75th, and 90th percentiles of ADC; skewness; and kurtosis) between the LVSI-positive and LVSI-negative groups, as well as between stage Ia and Ib EACs. ROC curve analysis was carried out to evaluate the diagnostic performance of ADC histogram metrics in predicting LVSI status in EAC.

RESULTS

The minADC and meanADC and 10th, 25th, 50th, 75th, and 90th percentiles of ADC were significantly lower in LVSI-positive EACs compared with those in the LVSI-negative groups for stage I, Ia, and Ib EACs (all p < 0.05). MeanADC ≤ 0.857 × 10^-3 mm²/s, meanADC ≤ 0.854 × 10^-3 mm²/s, and the 90th percentile of ADC ≤ 1.06 × 10^-3 mm²/s yielded the largest AUC of 0.844, 0.844, and 0.849 for evaluating LVSI positivity in stage I, Ia, and Ib tumors, respectively, with sensitivity of 75.4%, 75.0%, and 76.2%; specificity of 80.0%, 83.1%, and 82.1%; and accuracy of 79.3%, 81.5%, and 79.6%, respectively.

CONCLUSION

Volumetric ADC histogram metrics might be helpful for the preoperative evaluation of LVSI status and personalized clinical management in patients with stage I EAC.

KEY POINTS

• Volumetric ADC histogram analysis helps evaluate LVSI status preoperatively. • LVSI-positive EAC is associated with a reduction in multiple volumetric ADC histogram metrics. • MeanADC and the 90th percentile of ADC were shown to be best in evaluating LVSI- positivity in stage Ia and Ib EACs, respectively.

A preliminary observational study on the vascular, nerve, and lymphatic anatomy and histology of the labia minora from cadaveric and surgical samples

INTRODUCTION AND HYPOTHESIS

To better understand details of the fine anatomy of the labia minora, present images of the vascular anatomy and characterize the nerve and lymphatic distribution of the labia minora.

METHODS

Two fixed and five fresh cadaveric specimens were perfused and dissected, and the vascular network was photographed. Labia minora samples, prepared from cadavers, and tissue resulting from labia reduction surgery underwent hematoxylin and eosin staining and S100 and D2-40 immunohistochemical staining.

RESULTS

Arteries emanated from the base to the edge of the labia minora, where there was a larger feeding artery, and the arteries were anastomosed. The veins formed anastomotic branches in the same direction as the edge of the labia minora. Arteries and veins that accessed the labia minora were successfully perfused at the same time with no obvious association. Sensory nerve endings were abundant, mostly larger with myelinated nerve trunks and Schwann cells in the central area with suggested neurovascular associations and smaller with no obvious aggregation at the edge. The medial area had 23.63 ± 11.82 nerves/view, the lateral area 21.30 ± 11.49 nerves/view (P > 0.05). The thickest nerve bundle was 3.16 ± 1.41 mm from the medial epidermis and 3.13 ± 1.47 mm from the lateral epidermis. Lymphatic vessels showed no obvious regional distribution. Labia minora were 21.77 ± 5.69 mm wide with 252.87 ± 63.01 lymphatic vessels at 3.67 ± 1.61/mm2 density. The shortest inner diameter of dilated lymphatic vessels was 161.09 ± 49.99 μm.

CONCLUSION

A larger feeding artery exists in the labia minora, which should be noticed in the pre-surgery design of labiaplasty. No difference was observed in the nerve distribution between the medial and lateral sides. Lymphedema might not be the cause of labial hypertrophy.

Cerebrospinal fluid outflow: a review of the historical and contemporary evidence for arachnoid villi, perineural routes, and dural lymphatics

Cerebrospinal fluid (CSF) is produced by the choroid plexuses within the ventricles of the brain and circulates through the subarachnoid space of the skull and spinal column to provide buoyancy to and maintain fluid homeostasis of the brain and spinal cord. The question of how CSF drains from the subarachnoid space has long puzzled scientists and clinicians. For many decades, it was believed that arachnoid villi or granulations, outcroppings of arachnoid tissue that project into the dural venous sinuses, served as the major outflow route. However, this concept has been increasingly challenged in recent years, as physiological and imaging evidence from several species has accumulated showing that tracers injected into the CSF can instead be found within lymphatic vessels draining from the cranium and spine. With the recent high-profile rediscovery of meningeal lymphatic vessels located in the dura mater, another debate has emerged regarding the exact anatomical pathway(s) for CSF to reach the lymphatic system, with one side favoring direct efflux to the dural lymphatic vessels within the skull and spinal column and another side advocating for pathways along exiting cranial and spinal nerves. In this review, a summary of the historical and contemporary evidence for the different outflow pathways will be presented, allowing the reader to gain further perspective on the recent advances in the field. An improved understanding of this fundamental physiological process may lead to novel therapeutic approaches for a wide range of neurological conditions, including hydrocephalus, neurodegeneration and multiple sclerosis.

Percutaneous afferent lymphatic vessel sclerotherapy for postoperative lymphatic leakage after previous ineffective therapeutic transpedal lymphangiography

BACKGROUND

To demonstrate the efficacy of percutaneous computed tomography (CT)-guided afferent lymphatic vessel sclerotherapy (ALVS) in the treatment of postoperative lymphatic leakage (LL) after ineffective therapeutic transpedal lymphangiography (TL).

METHODS

A retrospective review in this institute involving 201 patients was conducted from May 2011 to September 2018. Patients diagnosed with postoperative LL undergoing ineffective therapeutical TL before the performance of percutaneous CT-guided ALVS were involved. Technical success and clinical success of TL and ALVS were established. The technical success and efficacy of ALVS in the treatment of postoperative LL after ineffective therapeutic TL were assessed. The clinical success rate of ALVS is also assessed, and the complications are reviewed.

RESULTS

In total, nine patients were involved including three patients (33.3%) presented with chylothorax, three patients (33.3%) presented with inguinal lymphatic fistula/lymphocele, and three patients (33.3%) presented with lymphatic fistula in the thigh; 27 ± 18 days (mean ± standard deviation) after surgery, therapeutic TL was successfully performed and showed definite afferent lymphatic vessel and leakage site in all the patients. Due to clinical failure after TLs, the following ALVS was performed with a mean interval of 12 ± 8 days after TL. The technical success rate was 9/9 (100.0%, 95% confidence interval [CI] 63.1-100.0%). An average of 2.7 ± 1.3 mL 95% ethanol as sclerosant agent was injected during the procedure. The clinical success was observed in 8 of the 9 patients (88.9%, 95% CI 51.8-99.7%) with a time between ALVS and the LL cure of 8 ± 6 days. No complications were reported.

CONCLUSIONS

Our results showed the role of percutaneous CT-guided ALVS as a safe, feasible, and effective salvage treatment for postoperative LL after ineffective TL.

Glue Embolization of Lymphopseudoaneurysm for Chylous Ascites after Retroperitoneal Surgery

OBJECTIVE

To assess the safety and efficacy of lymphopseudoaneurysm (LPA) glue (n-butyl cyanoacrylate [NBCA]) embolization in the management of chylous ascites after retroperitoneal surgery.

MATERIALS AND METHODS

A retrospective analysis from January 2014 to October 2018 was performed in six patients (4 females and 2 males; mean age, 45.3 ± 14.2 years; range, 26-61 years) who underwent LPA embolization for chylous ascites developing after retroperitoneal surgery involving the perirenal space (four donor nephrectomies, one partial nephrectomy, and one retroperitoneal lymphadenectomy). After placing a percutaneous drainage catheter into the LPA or adjacent lymphocele, embolization was performed by filling the LPA itself with a mixture of glue and Lipiodol (Guerbet).

RESULTS

Daily drainage from percutaneously placed drains exceeded 300 mL/day despite medical and surgical treatment (volume: mean, 1173 ± 1098 mL; range, 305-2800 mL). Intranodal lymphangiography was performed in four of the six patients and revealed leakage in 2 patients. Percutaneous embolization of the LPA was successful in all patients using an NBCA and Lipiodol mixture in a ratio of 1:1-1:2 (volume: mean, 4.3 ± 1.1 mL; range, 3-6 mL). Chylous ascites was resolved and the drainage catheter was removed in all patients within 4 days after the procedure (mean, 2.0 ± 1.8 days; range, 0-4 days). No procedure-related complications or recurrence of chylous ascites occurred during a mean follow-up period of 37.3 months (range, 21.1-48.4 months).

CONCLUSION

Glue embolization of LPA has the potential to be a feasible and effective treatment method for the management of chylous ascites after retroperitoneal surgery.

Current advances in lymphoedema management

Lymphoedema is the accumulation of protein-rich interstitial fluid within subcutaneous tissue and skin as a result of dysfunction of the lymphatic system. It is an underestimated, widely neglected and debilitating chronic condition. This article presents an overview of lymphoedema and recent advances in its management.

Lymphatic Capillaries in Aging

The lymphatic system is responsible for fluid drainage from almost every organ in the body. It sustains tissue homeostasis and is also a central part of the immune system. With the discovery of cell-specific markers and transgenic mouse models, it has become possible to gain some insight into the developmental and functional roles of lymphatic endothelial cells (LECs). Only recently, a more direct regulatory role has been assigned to LECs in their functions in immunity responses and chronic diseases. Here, we discuss the changes occurring in aged lymphatic system and the role of lymphatic capillaries in some age-related diseases and experimental animal models.

Investigating lymphangiogenesis in a sacrificially bioprinted volumetric model of breast tumor tissue

Lymphatic vessels, as a means to metastasize, are frequently recruited by tumor tissues during their progression. However, reliable in vitro models to dissect the intricate crosstalk between lymphatic vessels and tumors are still in urgent demand. Here, we describe a tissue-engineering method based on sacrificial bioprinting, to develop an enabling model of the human breast tumor with embedded multiscale lymphatic vessels, which is compatible with existing microscopy to examine the processes of lymphatic vessel sprouting and breast tumor cell migration in a physiologically relevant volumetric microenvironment. This platform will potentially help shed light on the complex biology of the tumor microenvironment, tumor lymphangiogenesis, lymphatic metastasis, as well as tumor anti-lymphangiogenic therapy in the future. We further anticipate wide adoption of the method to the production of various tissues and their models with incorporation of lymphatics vessels towards relevant applications.

A proposal for a semiquantitative scoring system for lymphedema using Non-contrast Magnetic Resonance Lymphography (NMRL): Reproducibility among readers and correlation with clinical grading

PURPOSE

To assess the ability and reproducibility of Non-contrast Magnetic Resonance Lymphography (NMRL) in detecting and quantify lymphedema, using a semiquantitative scoring system.

METHODS AND MATERIAL

This is a monocentric retrospective study of 134 consecutive patients with a clinical diagnosis of limb lymphedema who performed a Non-contrast Magnetic Resonance Lymphography (NMRL) at our Institution between November 2014 and February 2017. Lymphedema was classified based both on clinical and radiologic evaluation. An NMRL total score was obtained for each limb's segment and compared to the clinical grade, used as reference standard. NMRL intra-observer, inter-observer variability and intraclass correlation were calculated. NMRL sensitivity, specificity, and accuracy in identifying lymphedema were provided. Based on score distribution an NMRL four-stage system was developed.

RESULTS

NMRL showed 92% sensitivity, 77% specificity and 82% accuracy in identifying lymphedema. An almost perfect agreement was obtained by expert operators, while substantial agreement was obtained by non-expert operators. Substantial agreement resulted also for the inter-observer variability (Cohen's Kappa K = 0.73, CI 95% [0.69-0.78]). The intra-class correlation showed an almost perfect relationship both by expert and non-expert operators. Excellent correlation between clinical grade and NMRL score and between clinical grade and NMRL stage were found for each segment.

CONCLUSIONS

NMRL is a confident and reproducible exam with high sensitivity, good specificity and high accuracy in lymphedema detection; the semiquantitative NMRL score resulted a reliable and reproducible tool able to quantify lymphedema severity.

Balloon-occluded retrograde glue embolization for intractable lymphorrhea from bilateral iliac lymphatics following surgery for rectal cancer

Lymphorrhea is a rare complication of rectal surgery. Although percutaneous embolization of thoracic or lymphatic ducts is now increasingly being reported for various types of lymphatic leakage, there are only sparse data on lymphatic interventions for lymphorrhea following rectal surgery. A novel balloon-occluded retrograde lymphatic embolization (BRLE) technique can be a simple and effective option for intractable lymphorrhea. We report a case of a man with infected lymphorrhea after rectal resection. Transperineal drainage was performed; however, lymphatic leakage persisted after 1 month of conservative treatment. Lymphangiography revealed multifocal leaks from bilateral iliac lymphatics. The proposed BRLE technique was performed via a balloon catheter inserted through the transperineal drainage. The balloon allowed occlusion of lymphatic outflow and forceful retrograde injection to achieve denser accumulation of n-butyl cyanoacrylate. Tight embolization of bilateral iliac lymphatics and drastic improvement of the leakage was achieved. To the best of our knowledge, this is the first report of percutaneous embolization for lymphorrhea after rectal surgery. This case supports the efficacy of the BRLE as a simple and effective therapeutic option for such persistent multifocal lymphatic leaks.

The cell-cell junctions of mammalian testes. III. Absence of an endothelial cell layer covering the peritubular wall of the seminiferous tubules-an immunocytochemical correction of a 50-year-old error in the literature

In the molecular biological and ultrastructural studies of the peritubular wall cells encasing the seminiferous tubules of mammalian testes, we found it necessary to characterize the outermost cell layer bordering on the interstitial space in detail. For half a century, the extremely thin cells of this monolayer have in the literature been regarded as part of a lymphatic endothelium, in particular in rodents. However, our double-label immunofluorescence microscopical results have shown that in all six mammalian species examined, including three rodent ones (rat, mouse, guinea pig), this classification is not correct: the very attenuated cells of this monolayer are not of lymphatic endothelial nature as they do not contain established endothelial marker molecules. In particular, they do not contain claudin-5-positive tight junctions, VE-cadherin-positive adherens junctions, "lymph vessel endothelium hyaluronan receptor 1" (LYVE-1), podoplanin, protein myozap and "von Willebrand Factor" (vWF). By contrast and as controls, all these established marker molecules for the lymphatic endothelial cell type are found in the endothelia of the lymph and-partly also-blood vessels located nearby in the interstitial space. Thus, our results provide evidence that the monolayer cells covering the peritubular wall do not contain endothelial marker molecules and hence are not endothelial cells. We discuss possible methodological reasons for the maintenance of this incorrect cell type classification in the literature and emphasize the value of molecular analyses using multiple cell type-specific markers, also with respect to physiology and medical sciences.

Proximal ligation after the side-to-end anastomosis recovery technique for lymphaticovenous anastomosis

Background

Lymphaticovenous anastomosis is an important surgical treatment for lymphedema, with lymphaticovenous side-to-end anastomosis (LVSEA) and lymphaticovenous end-to-end anastomosis being the most frequently performed procedures. However, LVSEA can cause lymphatic flow obstruction because of regurgitation and tension in the anastomosis. In this study, we introduce a novel and simple procedure to overcome this problem.

Methods

Thirty-five female patients with lower extremity lymphedema who underwent lymphaticovenous anastomosis at our hospital were included in this study. Eighty-five LVSEA procedures were performed, of which 12 resulted in insufficient venous blood flow. For these 12 anastomoses, the proximal lymphatic vessel underwent clipping after the anastomotic procedure and the venous inflow was monitored. Subsequently, the proximal ligation after side-to-end anastomosis recovery (PLASTER) technique, which involves ligating the proximal side of the lymphatic vessel, was applied. A postoperative evaluation was performed using indocyanine green 6 months after surgery.

Results

Despite the clipping procedure, three of the 12 anastomoses still showed poor venous inflow. Therefore, it was not possible to apply the PLASTER technique in those cases. Among the nine remaining anastomoses in which the PLASTER technique was applied, three (33%) were patent.

Conclusions

Our findings show that achieving patent anastomosis is challenging when postoperative venous inflow is poor. We achieved good results by performing proximal ligation after LVSEA. Thus, the PLASTER technique is a particularly useful recovery technique when LVSEA does not result in good run-off.

Lymphatic system identification, pathophysiology and therapy in the cardiovascular diseases

The mammalian circulatory system comprises both the cardiovascular system and the lymphatic system. In contrast to the closed, high-pressure and circular blood vascular circulation, the lymphatic system forms an open, low-pressure and unidirectional transit network from the extracellular space to the venous system. It plays a key role in regulating tissue fluid homeostasis, absorption of gastrointestinal lipids, and immune surveillance throughout the body. Despite the critical physiological functions of the lymphatic system, a complete understanding of the lymphatic vessels lags far behind that of the blood vasculatures due to the challenge of their visualization. During the last 20 years, discoveries of underlying genes responsible for lymphatic vessel biology, combined with state-of-the-art lymphatic function imaging and quantification techniques, have established the importance of the lymphatic vasculature in the pathogenesis of cardiovascular diseases including lymphedema, obesity and metabolic diseases, dyslipidemia, hypertension, inflammation, atherosclerosis and myocardial infraction. In this review, we highlight the most recent advances in the field of lymphatic vessel biology, with an emphasis on the new identification techniques of lymphatic system, pathophysiological mechanisms of atherosclerosis and myocardial infarction, and new therapeutic perspectives of lymphangiogenesis.

Lymphatic spread of T2 gallbladder carcinoma: Regional lymphadenectomy is required independent of tumor location

BACKGROUND

This study aimed to investigate the incidence and distribution of regional lymph node metastasis according to tumor location, and to clarify whether tumor location could determine the extent of regional lymphadenectomy in patients with pathological T2 (pT2) gallbladder carcinoma.

METHODS

In total, 81 patients with pT2 gallbladder carcinoma (25 with pT2a tumors and 56 with pT2b tumors) who underwent radical resection were enrolled. Tumor location was determined histologically in each gallbladder specimen.

RESULTS

Survival after resection was significantly worse in patients with pT2b tumors than those with pT2a tumors (5-year survival, 72% vs. 96%; p = 0.027). Tumor location was an independent prognostic factor on multivariate analysis (hazard ratio, 14.162; p = 0.018). The incidence of regional lymph node metastasis was significantly higher in patients with pT2b tumors than in those with pT2a tumors (46% vs. 20%; p = 0.028). However, the number of positive nodes was similar between the two groups (median, 2 vs. 2; p = 0.910). For node-positive patients with pT2b tumors, metastasis was found in every regional node group (12%-63%), whereas even for node-positive patients with pT2a tumors, metastasis was observed in regional node groups outside the hepatoduodenal ligament.

CONCLUSIONS

Tumor location in patients with pT2 gallbladder carcinoma can predict the presence or absence of regional lymph node metastasis but not the number and anatomical distribution of positive regional lymph nodes. The extent of regional lymphadenectomy should not be changed even in patients with pT2a tumors, provided that they are fit enough for surgery.

The history of anatomical research of lymphatics - From the ancient times to the end of the European Renaissance

Very often, descriptions of the scientific discovery of the lymphatic system start with Gaspare Aselli, probably because of his so captivating account. Nevertheless, there was prior and even very old evidence of the lymphatic vessels, which was of course known to Aselli himself, as he cited most of these antique references. In fact, the first insights were contributed by the Hippocratic School. The Alexandrian School added quite a lot but unfortunately most of that knowledge is not extant and can only be appreciated by translations or citations by other authors such as Galen. The 'dark' middle ages did not add to the anatomical knowledge of the lymphatics, and only the rise of the Renaissance brought new insights. Even at that time, Aselli was not the first to identify at least some components of the lymphatic system, but he was actually the first to present a proper account in a book dedicated to the "lacteal veins". Afterwards the interest rose enormously and cumulated in one of the first priority - or plagiarism - disputes, the Rudbeck-Bartholin feud. Surprisingly, William Harvey, the discoverer of the systemic blood circulation, ignored, at least in part, the progress of the discoveries in lymphatic circulation. This narrative review tries to summarize the major contributions to the anatomical knowledge of the lymphatic system from the ancient times up to the end of the European Renaissance.

Observation of the cytoarchitecture of the human esophageal mucosa with special attention to the lamina muscularis mucosae and the distribution of lymphatic vessels

The cytoarchitecture of the esophageal mucosa was examined by using light microscopy, transmission electron microscopy, and scanning electron microscopy. The cytoarchitecture of the muscularis mucosae varied greatly among the cervical, thoracic, and abdominal esophagus, especially in the cervical esophagus, the muscularis mucosae suffered a loss and the distribution of lymphatic vessels also varied according to the site. It was suggested that these morphological differences would have a strong influence on the infiltration of esophageal cancer and the mode of lymph node metastasis.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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