Perimuscular connective tissue contains more and larger lymphatic vessels than the shallower layers in human gallbladders

AIM： To clarify whether perimuscular connective tissue contains more lymphatic vessels than the shallower layers in human gallbladders. METHODS： Lymphatic vessels were stained immunohistochemically with monoclonal antibody D2-40, which is a specific marker of lymphatic endothelium, in representative sections of 12 normal human gallbladders obtained at the time of resection for colorectal carcinoma liver metastases. In individual gallbladder specimens, nine high-power （×200） fields with the highest lymphatic vessel density （LVD）, termed ＂hot spots＂; were identified for each layer （mucosa, muscle layer, and perimuscular connective tissue）. In individual hot spots, the LVD and relative lymphatic vessel area （LVA） were measured microscopically using a computer-aided image analysis system. The mean LVD and LVA values for the nine hot spots in each layer were used for statistical analyses. RESULTS： In the mucosa, muscle layer, and perimuscular connective tissue, the LVD was 16.1 ± 9.2, 35.4 ± 15.7, and 65.5 ± 12.2, respectively, and the LVA was 0.4 ± 0.4, 2.1 ± 1.1, and 9.4 ± 2.6, respectively. Thus, both the LVD and LVA differed significantly （P 〈 0.001 and P 〈 0.001, respectively; KruskaI-Wallis test） among the individual layers of the wall of the gallbladder, with the highest LVD and LVA values in the perimuscular connective tissue. Most （98 of 108） of the hot spots within the perimuscular connective tissue were located within 500 μm of the lower border of the muscle layer. CONCLUSION： The perimuscular connective tissue contains more and larger lymphatic vessels than the shallower layers in the human gallbladder. This observation partly explains why the incidence of lymph node metastasis is high in T2 （tumor invading the perimuscular connective tissue） or more advanced gallbladder carcinoma.

Meningeal lymphatic vessel crosstalk with central nervous system immune cells in aging and neurodegenerative diseases

Meningeal lymphatic vessels form a relationship between the nervous system and periphery, which is relevant in both health and disease. Meningeal lymphatic vessels not only play a key role in the drainage of brain metabolites but also contribute to antigen delivery and immune cell activation. The advent of novel genomic technologies has enabled rapid progress in the characterization of myeloid and lymphoid cells and their interactions with meningeal lymphatic vessels within the central nervous system. In this review, we provide an overview of the multifaceted roles of meningeal lymphatic vessels within the context of the central nervous system immune network, highlighting recent discoveries on the immunological niche provided by meningeal lymphatic vessels. Furthermore, we delve into the mechanisms of crosstalk between meningeal lymphatic vessels and immune cells in the central nervous system under both homeostatic conditions and neurodegenerative diseases, discussing how these interactions shape the pathological outcomes. Regulation of meningeal lymphatic vessel function and structure can influence lymphatic drainage, cerebrospinal fluid-borne immune modulators, and immune cell populations in aging and neurodegenerative disorders, thereby playing a key role in shaping meningeal and brain parenchyma immunity.

Functional aspects of the brain lymphatic drainage system in aging and neurodegenerative diseases

The phenomenon of an aging population is advancing at a precipitous rate.Alzheimer's disease(AD)and Parkinson's disease(PD)are two of the most common age-associated neurodegenerative diseases,both of which are primarily characterized by the accumulation of toxic proteins and the progressive demise of neuronal structures.Recent discoveries about the brain lymphatic drainage system have precipitated a growing body of investigations substantiating its novel roles,including the clearance of macromolecular waste and the trafficking of immune cells.Notably,aquaporin 4-mediated glymphatic transport,crucial for maintaining neural homeostasis,becomes disrupted during the aging process and is further compromised in the pathogenesis of AD and PD.Functional meningeal lymphatic vessels,which facilitate the drainage of cerebrospinal fluid into the deep cervical lymph nodes,are integral in bridging the central nervous system with peripheral immune responses.Dysfunction in these meningeal lymphatic vessels exacerbates pathological trajectory of the age-related neurodegenerative disease.This review explores modulatory influence of the glymphatic system and meningeal lymphatic vessels on the aging brain and its associated neurodegenerative disorders.It also encapsulates the insights of potential mechanisms and prospects of the targeted non-pharmacological interventions.

The lymphatic system:a therapeutic target for central nervous system disorders

The lymphatic vasculature forms an organized network that covers the whole body and is involved in fluid homeostasis,metabolite clearance,and immune surveillance.The recent identification of functional lymphatic vessels in the meninges of the brain and the spinal cord has provided novel insights into neurophysiology.They emerge as major pathways for fluid exchange.The abundance of immune cells in lymphatic vessels and meninges also suggests that lymphatic vessels are actively involved in neuroimmunity.The lymphatic system,through its role in the clearance of neurotoxic proteins,autoimmune cell infiltration,and the transmission of pro-inflammatory signals,participates in the pathogenesis of a variety of neurological disorders,including neurodegenerative and neuroinflammatory diseases and traumatic injury.Vascular endothelial growth factor C is the master regulator of lymphangiogenesis,a process that is critical for the maintenance of central nervous system homeostasis.In this review,we summarize current knowledge and recent advances relating to the anatomical features and immunological functions of the lymphatic system of the central nervous system and highlight its potential as a therapeutic target for neurological disorders and central nervous system repair.

The lymphatic drainage systems in the brain:a novel target for ischemic stroke?

Recent studies have proposed three lymphatic drainage systems in the brain,that is,the glymphatic system,the intramural periarterial drainage pathway,and meningeal lymphatic vessels,whose roles in various neurological diseases have been widely explored.The glymphatic system is a fluid drainage and waste clearance pathway that utilizes perivascular space and aquaporin-4 protein located in the astrocyte endfeet to provide a space for exchange of cerebrospinal fluid and interstitial fluid.The intramural periarterial drainage pathway drives the flow of interstitial fluid through the capillary basement membrane and the arterial tunica media.Meningeal lymphatic vessels within the dura mater are involved in the removal of cerebral macromolecules and immune responses.After ischemic stroke,impairment of these systems could lead to cerebral edema,accumulation of toxic factors,and activation of neuroinflammation,while restoration of their normal functions can improve neurological outcomes.In this review,we summarize the basic concepts of these drainage systems,including drainage routes,physiological functions,regulatory mechanisms,and detection technologies.We also focus on the roles of lymphatic drainage systems in brain injury after ischemic stroke,as well as recent advances in therapeutic strategies targeting these drainage systems.These findings provide information for potential novel strategies for treatment of stroke.

Latanoprost eye drops induce conjunctival lymphatic vessel development

AIM:To investigate the effect of latanoprost eye drops on the conjunctival lymphatics.METHODS:Twenty-four healthy New Zealand White rabbits weighing 1.5 to 2.0 kg were randomly divided into three groups:latanoprost group(n=8)administered with latanoprost eye drops once a day for 2 mo,carteolol group(n=8)administered with carteolol eye drops once a day for 2 mo,and control group(n=8)without any treatment.The conjunctival tissues in the three groups were extracted to investigate the expression levels of 5’-nucleotidase(5’-Nase)by Western blot,reverse transcription-polymerase chain reaction(RT-PCR),and immunofluorescence staining,respectively.RESULTS:The protein expression level of 5’-Nase was significantly higher in latanoprost group than carteolol group(F=231.175,P<0.001)and control group(P<0.001),while there was no significant difference between the carteolol group and the control group(P>0.05).The m RNA expression level of 5’-Nase in the latanoprost group was also significantly higher than carteolol group(F=71.169 P<0.005)and control group(P<0.005).The conjunctival lymphatics were positive immunofluorescence stained with the 5’-Nase antibodies in the latanoprost group and not stained in the control group.CONCLUSION:Latanoprost eye drops can induce conjunctival lymphangiogenesis which may be concerned in clinical implications.

Relationship between LYVE-1, VEGFR-3 and CD44 gene expressions and lymphatic metastasis in gastric cancer

AIM: To investigate the expression levels of lymphatic vessel endothelial hyaluronan receptor-1 (LYVE-1), vascular endothelial growth factor receptor-3 (VEGFR-3) and CD44 genes and the relationship between their lev- els and clinicopathological parameters in gastric cancer.METHODS: Tissue samples were obtained from 33 patients (8 females) with gastric cancer. mRNA levels of LYVE-1, VEGFR-3 and CD44 in normal and tumor tissues were quantitatively measured using real time polymerase chain reaction. The results were correlated with lymph node metastasis, histological type and differentiation of the tumor, T-stage, and presence of vascular, perineural and lymphatic invasions. The distribution of molecules in the tissue was evaluated using immunohistochemistry. RESULTS: LYVE-1, CD44 and VEGFR-3 gene expression levels were significantly higher in gastric cancer than in normal tissue. While there was no correlation between gene expressions and clinicopathologic fea- tures such as histologic type, differentiation and stage, gene expression levels were found to be increased in conjunction with positive lymph node/total lymph node ratio and the presence of perineural invasion. A significant correlation was also found between LYVE-1 and CD44 over-expressions and perineural invasion and lymph node positivity in gastric cancers. When the dis- tribution of LYVE-1 antibody-stained lymphatic vessels in tissue was evaluated, lymphatic vessels were located intra-tumorally in 13% and peri-tumorally in 27% of the patients. Moreover, lymph node metastases were also positive in all patients with LYVE-1-staining. CONCLUSION: LYVE-1, VEGFR-3 and CD44 all play an important role in lymphangiogenesis, invasion and metastasis. LYVE-1 is a perfectly reliable lymphatic vessel marker and useful for immunohistochemistry.

Detection of D2-40 monoclonal antibody-labeled lymphatic vessel invasion in esophageal squamous cell carcinoma and its clinicopathologic significance

Objective： This study aims to investigate the clinicopathologic significance of lymphatic vessel invasion （LVI） labeled by D2-40 monoclonal antibody in esophageal squamous cell carcinoma （ESCC）. Methods： Immunohistochemical assay was used to detect the expression of D2-40 and LVI in 107 ESCC patients. Then, the correlation between the clinicopathologic feature and the overall survival time of the patients was analyzed. Results： The lymph node metastasis rates were 70% and 21% in the LVI-positive and LVI-negative groups, respectively. The nodal metastasis rate was higher in the LVI-positive group than in the LVI-negative group. Multivariate regression analysis showed that LVI was related to nodal metastasis （P〈0.001）. The median survival time of the patients was 26 and 43 months in the LVI-positive and LVI-negative groups, respectively. Mthough univariate regression analysis showed significant difference between the two groups （P=0.014）, multivariate regression analysis revealed that LVI was not an independent prognostic factor for overall survival in the ESCC patients （P=0.062）. Lymphatic node metastasis （P=0.031）, clinical stage （P=0.019）, and residual tumor （P=0.026） were the independent prognostic factors. Conclusion： LVI labeled by D2-40 monoclonal antibody is a risk factor predictive of lymph node metastasis in ESCC patients.

Lymphangiogenesis:A new player in cancer progression

Lymph node metastasis is the hallmark of colon cancer progression,and is considered one of the most important prognostic factors.Recently,there has been growing evidence that tumor lymphangiogenesis(formation of new lymphatic vessels) plays an important role in this process.Here,we review the latest f indings of the role of lymphangiogenesis in colorectal cancer progression,and discuss its clinical application as a biomarker and target for new therapy.Understanding the molecular pathways that regulate lymphangiogenesis is mandatory to pave the way for the development of new therapies for cancer.In the future,tailored treatments consisting of combinations of chemotherapy,other targeted therapies,and anti-lymphangiogenesis agents will hopefully improve patient outcomes.This progression to the clinic must be guided by new avenues of research,such as the identif ication of biomarkers that predict response to treatment.

Meningeal lymphatic vasculature,a general target for glioblastoma therapy?

Glioblastoma(GBM)causes nearly universal mortality as a result of the failure of conventional therapies including surgical resection,targeted radiation therapy,and chemotherapy.An increasingly important treatment option is combining immunotherapy with other therapies in both preclinical and clinical studies.The central nervous system(CNS)has been historically considered an immune privileged area,but increasing evidence,including the recent rediscovery of meningeal lymphatic vessels(MLVs),has overturned this notion.MLVs are populated by multiple immune cells and connect the CNS to the periphery by draining cerebrospinal fluid with soluble CNS antigens and immune cells into cervical lymph nodes.In the past few years,more and more studies have indicated that MLVs are involved in the regulation of inflammation and the immune response in the pathogenesis of various CNS diseases including GBM.Here,we explore the critical interlinkages between MLVs and GBM therapies including chemotherapy,radiotherapy and immunotherapy,and propose the meningeal lymphatic vasculature as a general target for GBM therapy.

Molecular events in the jaw vascular unit:A traditional review of the mechanisms involved in inflammatory jaw bone diseases

Inflammatory jaw bone diseases are common in stomatology,including periodontitis,peri-implantitis,medication-related osteonecrosis of the jaw,radiation osteomyelitis of the jaw,age-related osteoporosis,and other specific infections.These diseases may lead to tooth loss and maxillofacial deformities,severely affecting patients'quality of life.Over the years,the reconstruction of jaw bone deficiency caused by inflammatory diseases has emerged as a medical and socioeconomic challenge.Therefore,exploring the pathogenesis of inflammatory diseases associated with jaw bones is crucial for improving prognosis and developing new targeted therapies.Accumulating evidence indicates that the integrated bone formation and dysfunction arise from complex interactions among a network of multiple cell types,including osteoblast-associated cells,immune cells,blood vessels,and lymphatic vessels.However,the role of these different cells in the inflammatory process and the'rules'with which they interact are still not fully understood.Although many investigations have focused on specific pathological processes and molecular events in inflammatory jaw diseases,few articles offer a perspective of integration.Here,we review the changes and mechanisms of various cell types in inflammatory jaw diseases,with the hope of providing insights to drive future research in this field.

Immunohistochemical molecular markers as predictors of curability of endoscopically resected submucosal colorectal cancer

AIM: To clarify the usefulness of immunohistochemical molecular markers in predicting lymph node metastasis of submucosal colorectal cancer. METHODS: We examined microvessel density, lymphatic vessel density, the Ki-67 labeling index, expression of MUC1 and Matrix metalloproteinase-7 (MMP-7) in tumor cells, and expression of cathepsin D in stromal cells at the invasive front by immunostaining of samples resected from 214 patients with submucosal colorectal cancer. Pathologic features were assessed on hematoxylin-eosin- stained samples. We evaluated the relations between clinicopathologic/immunohistochemical features and lymph node metastasis. RESULTS: Lesions of the superficial type, with an unfavorable histologic grade, budding, lymphatic involvement, high microvessel density (≥ 40), high lymphatic vessel density (≥ 9), high Ki-67 labeling index (≥ 42), and positivity of MUC1, cathepsin D, and MMP-7 showed a significantly high incidence of lymph node metastasis. Multivariate analysis revealed that high microvessel density, unfavorable histologic grade, cathepsin D positivity, high lymphatic vessel density, superficial type, budding, and MUC1 positivity were independent risk factors for lymph node metastasis.A combined examination with four independent immunohistochemical markers (microvessel density, cathepsin D, lymphatic vessel density, and MUC1) revealed that all lesions that were negative for all markers or positive for only one marker were negative for lymph node metastasis. CONCLUSION: Analysis of a combination of immuno- histochemical molecular markers in endoscopically resected specimens of submucosal colorectal cancer allows prediction of curability regardless of the pathologic features visible of hematoxylin-eosin-stained sections.

Relations between lymphangiogenesis and the size of pterygium

AIM: To examine the relations between lymphangiogenesis and the size of pterygium. METHODS: Tissues from 88 primary and 34 recurrent pterygia were evaluated, and those from 7 nasal epibulbar conjunctiva segments were used as controls. Pterygium slices from each patient were stained with LYVE-1 monodonal antibodies to identify lymphatic microvessel for calculating lymph-vascular area (LVA), lymph-microvascular density (LMD) and lymph-vascular luminal diameter (LVL). Also, the relations between lymphangiogenesis (measuring by LVA, LMD and LVL) and the size of pterygium (extension, width and area) were explored. RESULTS: There were a few LYVE-1 ((+)) lymphatic vessels in normal epibulbar conjunctiva segments. However, the number of lymphatic vessels slightly increased in primary pterygia and dramatically increased in recurrent pterygia. LVA, LMD and LVL significantly increased in recurrent pterygia in comparison with primary pterygia (all P<0.05). Both LMD and LVA were correlated with the width and area of pterygia (both P<0.05), and LVA was also correlated with the extension of pterygia(P<0.05). CONCLUSION: Lymphangiogenesis is correlated with the size of pterygium. The outgrowth of lymphatic vessels might contribute to the development of pterygia.

Photostimulation of lymphatic clearance ofβ‑amyloid from mouse brain:a new strategy for the therapy of Alzheimer’s disease

Alzheimer’s disease(AD)is an age-related neurodegenerative disorder that poses a signifcant burden on socio-economic and healthcare systems worldwide.However,the currently available therapy of AD is limited,and new strategies are needed to enhance the clearance ofβ-amyloid(Aβ)protein and improve cognitive function.Photobiomodulation(PBM)is a noninvasive and efective therapeutic method that has shown promise in treating various brain diseases.Here,we demonstrate that 1267-nm PBM signifcantly alleviates cognitive decline in the 5xFAD mouse model of AD and is safe as it does not induce a signifcant increase in cortical temperature.Moreover,with the combination of 3D tissue optical clearing imaging and automatic brain region segmentation,we show that PBM-mediated reductions of Aβplaques in diferent subregions of prefrontal cortex and the hippocampus are diferent.The PBM-induced lymphatic clearance of Aβfrom the brain is associated with improvement of memory and cognitive functions in 5xFAD mice.Our results suggest that the modulation of meningeal lymphatic vessels(MLVs)should play an important role in promoting Aβclearance.Collectively,this pilot study demonstrates that PBM can safely accelerate lymphatic clearance of Aβfrom the brain of 5xFAD mice,promoting improvement of neurocognitive status of AD animals suggesting that PBM can be an efective and bedside therapy for AD.

Biomechanical control of lymphatic vessel physiology and functions

The ever-growing research on lymphatic biology has clearly identified lymphatic vessels as key players that maintain human health through their functional roles in tissue fluid homeostasis,immunosurveillance,lipid metabolism and inflammation.It is therefore not surprising that the list of human diseases associated with lymphatic malfunctions has grown larger,including issues beyond lymphedema,a pathology traditionally associated with lymphatic drainage insufficiency.Thus,the discovery of factors and pathways that can promote optimal lymphatic functions may offer new therapeutic options.Accumulating evidence indicates that aside from biochemical factors,biomechanical signals also regulate lymphatic vessel expansion and functions postnatally.Here,we review how mechanical forces induced by fluid shear stress affect the behavior and functions of lymphatic vessels and the mechanisms lymphatic vessels employ to sense and transduce these mechanical cues into biological signals.

Lymphatic endothelial cells regulate B-cell homing to lymph nodes via a NIK-dependent mechanism

B cells home to the lymph nodes(LNs)via high endothelial venules(HEVs)under the guidance of chemokines,particularly CXCL13.However,as CXCL13 is not directly made in HEVs,the molecular mechanism mediating B-cell homing to LNs has remained unclear.We show here that nuclear factor(NF)-κB-inducing kinase(NIK),a kinase mediating activation of the noncanonical NF-κB pathway,functions in lymphatic endothelial cells(LECs)to regulate B-cell homing to LNs.LEC-conditional deletion of NIK in mice did not affect the integrity or global function of lymphatic vessels but caused a severe reduction in the frequency of B cells in LNs.The LEC-specific NIK deficiency did not affect the survival of B cells or the frequency of B cells in the spleen.B-cell adoptive transfer studies revealed that the LEC-specific NIK deletion impairs the ability of LNs to recruit B cells.We further show that NIK mediates expression of the chemokines CXCL13 and CCL19 in LECs.Although CCL19 is also expressed in blood endothelial cells(BECs),CXCL13 is not produced in BECs.These results suggest that NIK regulates naive B-cell homing to LNs via mediating production of the B-cell homing chemokine CXCL13 in LECs.

Peripheral clearance of brain-derived Aβ in Alzheimer's disease: pathophysiology and therapeutic perspectives

Alzheimer’s disease(AD)is the most common type of dementia,and no disease-modifying treatments are available to halt or slow its progression.Amyloid-beta(Aβ)is suggested to play a pivotal role in the pathogenesis of AD,and clearance of Aβfrom the brain becomes a main therapeutic strategy for AD.Recent studies found that Aβclearance in the periphery contributes substantially to reducing Aβaccumulation in the brain.Therefore,understanding the mechanism of how Aβis cleared in the periphery is important for the development of effective therapies for AD.In this review,we summarized recent findings on the mechanisms of Aβefflux from the brain to the periphery and discuss where and how the brain-derived Aβis cleared in the periphery.Based on these findings,we propose future strategies to enhance peripheral Aβclearance for the prevention and treatment of AD.This review provides a novel perspective to understand the pathogenesis of AD and develop interventions for this disease from a systemic approach.

The relationship between platelet-derived growth factor expression and angiogenesis/lymphangiogenesis in cervical cancer

This paper is aimed to examine if changes in platelet-derived growth factor(PDGF)expression at different stages of cervical cancer are related to the variation in blood vessel density(BVD)and lymphatic vessel density(LVD)to evaluate the relationship between PDGF expression and stages and metastasis of cervical cancer.Polymerase chain reaction(PCR)and RT-PCR were used to detect the expression levels of PDGF in 45 cervical cancer tissue samples(the experimental group).The samples were immunohistochemically stained with mono-clonal antibodies D2-40 and CD34,and BVD and LVD were measured.The expressions of PDGF-A,-B,and-D were all higher in the experimental group than in the control group(P<0.05);no significant difference was found in the expression of PDGF-C between the experi-mental group and the control group(P>0.05).PDGF-A and-B expression was positively related with BVD and LVD(P<0.01,R=0.49,0.527,0.327,0.68).The expression levels of PDGF-C and-D were not significantly related with BVD and LVD.At the early stage of cervical cancer,BVD and LVD were significantly higher than in the controls(P<0.01).The BVD and LVD in tissues in the surrounding areas of cervical cancer were significantly higher than in tissues at cancer center,and LVD was related to lymph node metastasis(P<0.001).BVD and LVD were not associated with the differentiation and pathological stages of cervical cancer.The expressions of PDGF-A,-B,and-D in cervical cancer were closely related with the clinical stages of cervical cancer.PDGF-A and-B were intimately associated with the lymph node metastasis and prognosis of cervical cancer.