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.

Multifaceted roles of lymphatic and blood endothelial cells in the tumor microenvironment of hepatocellular carcinoma:A comprehensive review

The tumor microenvironment is a complex network of cells,extracellular matrix,and signaling molecules that plays a critical role in tumor progression and metastasis.Lymphatic and blood vessels are major routes for solid tumor metastasis and essential parts of tumor drainage conduits.However,recent studies have shown that lymphatic endothelial cells(LECs)and blood endothelial cells(BECs)also play multifaceted roles in the tumor microenvironment beyond their structural functions,particularly in hepatocellular carcinoma(HCC).This comprehensive review summarizes the diverse roles played by LECs and BECs in HCC,including their involvement in angiogenesis,immune modulation,lymphangiogenesis,and metastasis.By providing a detailed account of the complex interplay between LECs,BECs,and tumor cells,this review aims to shed light on future research directions regarding the immune regulatory function of LECs and potential therapeutic targets for HCC.

Lymphangiogenesis, Lymphatic Endothelial Cells and Lymphatic Metastasis in Head and Neck Cancer—A Review of Mechanisms

Lymphatic metastasis is a continuous and complicated process. The detailed mechanisms of lymphatic metastasis are still not very clear, despite considerable research efforts in recent years. Previously, it was commonly accepted that there were no lymphatic vessels in the primary tumor. However, recent studies have demonstrated that lymphatic vessels are detectable in certain types of cancer, and more and more evidence has shown that cancer cells invade into local lymph nodes mainly via peritumoral lymphatic vessels, Moreover, activated endothelial cells may also be important, having an influence on lymphatic metastasis of cancer cells. This article, based on recent research findings, provides an in-depth discussion of the relationship between lymphangiogenesis, tumor-derived lymphatic endothelial cells and lymphatic metastasis in head and neck cancer.

Hypoxia Inhibits Proliferation of Human Dermal Lymphatic Endothelial Cells via Downregulation of Carcinoembryonic Antigen-related Cell Adhesion Molecule 1 Expression

Objective:Lymphatic endothelial cell(LEC)proliferation is essential for lymphangiogenesis.Hypoxia induces lymphangiogenesis,but it directly inhibits LEC proliferation and the underlying mechanisms have not been fully understood.The aim of this study was to investigate the role of carcinoembryonic antigen-related cell adhesion molecule 1(CEACAM1)in hypoxia-repressed LEC proliferation.Methods:Human dermal lymphatic endothelial cells(HDLECs)were cultured under normoxic or hypoxic conditions,and cell proliferation was determined using MTT or CCK-8 assays.CEACAM1 expression was silenced by siRNA transfection.Activation of mitogen-activated protein kinases(MAPKs)was examined by Western blotting and blocked by specific inhibitors.Results:Under hypoxia,HDLECs proliferation was suppressed and CEACAM1 expression was downregulated.Silence of CEACAM1 in normoxia inhibited HDLECs proliferation and did not further decrease proliferation in HDLECs in response to hypoxia,suggesting that CEACAM1 may mediate hypoxia-induced inhibition of HDLECs proliferation.In addition,silence of CEACAM1 increased phosphorylation of MAPK molecules:extracellular signal-regulated kinase(ERK),p38 MAPK and Jun N-terminal kinase(JNK)in HDLECs.However,only inhibition of the JNK pathway rescued the reduction of HDLEC proliferation induced by CEACAM1 silence.Conclusion:Our results suggested that hypoxia downregulates CEACAM1 expression by activation of the JNK pathway,leading to inhibition of HDLEC proliferation.These findings may help to understand the mechanisms of LEC-specific response to hypoxia and develop novel therapies for pathological lymphangiogenesis.

Effects of HLEC on the secreted proteins of epithelial ovarian cancer cells prone to metastasize to lymph nodes

Objective： To study explores the effect of HLEC on the secreted proteins of epithelial ovarian cancer （EOC） cells （SKOV3-PM4） with directional highly lymphatic metastasis. Methods： Supernatants of four groups of cultured cells, namely, SKOV3 （A）, SKOV3＋HLEC （B）, SKOV3-PM4 （C）, SKOV3-PM4＋HLEC （D）, were collected, and their proteins were detected by antibody arrays and iTRAOcZD-LC-MALDI- TOF/TOF/MS. Significantly differential proteins were further analyzed via bioinformatics and validated in human serums and cell media via ELISA. Results： Results of antibody arrays and mass spectrometry demonstrated that GRN and VEGFA were upregulated in group C （compared with group A）, whereas IGFBP7 and SPARC were downregulated in group D （compared with group C）. Comprehensive bioinformatics analysis results showed that IGFBP7 and VEGFA were closely linked to each other. Further validation with serums showed statistical significance in VEGFA and IGFBP7 levels among groups of patients with ovarian cancers, benign tumors, and control groups. Two proteins were upegulated in the first group. VEGFA in the control group was downregulated. For IGFBP, upregulation in the control group and down-regulation in the first group were also observed. Conclusion： The HLEC microenvironment is closely associated with directional metastasis to lymph nodes and with differential proteins including cell stromal proteins and adhesion factors. The upregulation of VEGFA and GRN and the downregulation of SPARC and IGFBP7 are closely associated with directional metastasis to lymph nodes in EOC cells.

Enhancement of anti-PD-L1 antibody plus anlotinib efficacy due to downregulation of PD-L1 in the micro-conduit endothelium within the tumor:a randomized double-blind trial

Objective:The possible enhancing effect of anlotinib on programmed death receptor ligand(PD-L1)antibody and the efficacy-predicting power of PD-L1 in micro-conduit endothelium,including lymphatic endothelial cells(LECs)and blood endothelial cells(BECs),were determined to identify patients who would benefit from this treatment.Methods:PD-L1 positivity in LECs,BECs,and tumor cells(TCs)was assessed using paraffin sections with multicolor immunofluorescence in an investigator’s brochure clinical trial of TQB2450(PD-L1 antibody)alone or in combination with anlotinib in patients with non-small cell lung cancer.Progression-free survival(PFS)with different levels of PD-L1 expression was compared between the two groups.Results:Among 75 patients,the median PFS(mPFS)was longer in patients who received TQB2450 with anlotinib[10 and 12 mg(161 and 194 days,respectively)]than patients receiving TQB2450 alone(61 days)[hazard ratio(HR)_(10 mg)=0.390(95%confidence interval{CI},0.201–0.756),P=0.005;HR_(12 mg)=0.397(0.208–0.756),P=0.005].The results were similar among 58 patients with high PD-L1 expression in LECs and TCs[159 and 209 vs.82 days,HR_(10 mg)=0.445(0.210–0.939),P=0.034;HR_(12 mg)=0.369(0.174–0.784),P=0.009],and 53 patients with high PD-L1 expression in BECs and TCs[161 and 209 vs.41 days,HR_(10 mg)=0.340(0.156–0.742),P=0.007;HR_(12 mg)=0.340(0.159–0.727),P=0.005].No differences were detected in the mPFS between the TQB2450 and combination therapy groups in 13 low/no LEC-expressing and 18 low/no BEC-expressing PD-L1 cases.Conclusions:Mono-immunotherapy is not effective in patients with high PD-L1 expression in LECs and/or BECs.Anlotinib may increase efficacy by downregulating PD-L1 expression in LECs and/or BECs,which is presumed to be a feasible marker for screening the optimal immune patient population undergoing anti-angiogenic therapy.

Low molecular weight heparin suppresses lymphatic endothelial cell proliferation induced by vascular endothelial growth factor C in vitro

Background Pancreatic cancer is one of the most aggressive human malignancies. Lymphangiogenesis plays an important role in lymph node metastasis of many solid tumors. It is well known that low molecular weight heparins （LMWHs） can inhibit cell growth, cell invasion and angiogenesis, which are key processes in tumor progression. Methods We measured the expression of vascular endothelial growth factor C （VEGF-C） in pancreatic cancer cells （PANC-1） using reverse transcription-polymerase chain reaction （RT-PCR） and Western blotting. We used an in vitro assay to evaluate the anti-lymphangiogenic effect of an LMWH, Fragmin, on human lymphatic endothelial cell （HLEC） proliferation. Results Fragmin at a low concentration can effectively inhibits HLEC proliferation induced by VEGF-C. VEGF-C secreted by PANC-1 cells stimulated HLEC proliferation. Low concentration LMWH suppressed HLEC proliferation induced by VEGF-C but did not affect proliferation or VEGF-C expression of PANC-1 cells, whereas high concentrations of LMWH inhibited PANC-1 cell proliferation. Conclusions These results suggest that VEGF-C released by cancer cells plays an important role in promoting HLEC proliferation. The LMWH Fragmin has anti-lymphangiogenic effects and may inhibit lymphatic metastasis in pancreatic cancer.

Induced dural lymphangiogenesis facilities soluble amyloid-beta clearance from brain in a transgenic mouse model of Alzheimer's disease

Impaired amyloid-β clearance from the brain is a core pathological event in Alzheimer＇s disease.The therapeutic effect of current pharmacotherapies is unsatisfactory,and some treatments cause severe side effects.The meningeal lymphatic vessels might be a new route for amyloid-β clearance.This study investigated whether promoting dural lymphangiogenesis facilitated the clearance of amyloid-β from the brain.First,human lymphatic endothelial cells were treated with 100 ng/m L recombinant human vascular endothelial growth factor-C（rh VEGF-C） protein.Light microscopy verified that rh VEGF-C,a specific ligand for vascular endothelial growth factor receptor-3（VEGFR-3）,significantly promoted tube formation of human lymphatic endothelial cells in vitro.In an in vivo study,200 μg/m L rh VEGF-C was injected into the cisterna magna of APP/PS1 transgenic mice,once every 2 days,four times in total.Immunofluorescence staining demonstrated high levels of dural lymphangiogenesis in Alzheimer＇s disease mice.One week after rh VEGF-C administration,enzyme-linked immunosorbent assay results showed that levels of soluble amyloid-β were decreased in cerebrospinal fluid and brain.The Morris water maze test demonstrated that spatial cognition was restored.These results indicate that the upregulation of dural lymphangiogenesis facilities amyloid-β clearance from the brain of APP/PS1 mice,suggesting the potential of the VEGF-C/VEGFR-3 signaling pathway as a therapeutic target for Alzheimer＇s disease.

Tumor reactive stroma in cholangiocarcinoma:The fuel behind cancer aggressiveness

Cholangiocarcinoma(CCA) is a highly aggressive epithelial malignancy still carrying a dismal prognosis, owing to early lymph node metastatic dissemination and striking resistance to conventional chemotherapy. Although mechanisms underpinning CCA progression are still a conundrum, it is now increasingly recognized that the desmoplastic microenvironment developing in conjunction with biliary carcinogenesis, recently renamed tumor reactive stroma(TRS), behaves as a paramount tumor-promoting driver. Indeed, once being recruited, activated and dangerously co-opted by neoplastic cells, the cellular components of the TRS(myofibroblasts, macrophages, endothelial cells and mesenchymal stem cells) continuously rekindle malignancy by secreting a huge variety of soluble factors(cyto/chemokines, growth factors, morphogens and proteinases). Furthermore, these factors are long-term stored within an abnormally remodeled extracellular matrix(ECM), which in turn can deleteriously mold cancer cell behavior. In this review, we will highlight evidence for the active role played by reactive stromal cells(as well as by the TRS-associated ECM) in CCA progression, including an overview of the most relevant TRS-derived signals possibly fueling CCA cell aggressiveness. Hopefully, a deeper knowledge of the paracrine communications reciprocally exchanged between cancer and stromal cells will steer the development of innovative, combinatorial therapies, which can finally hinder the progression of CCA, as well as of other cancer types with abundant TRS, such as pancreatic and breast carcinomas.

Reduced expression of semaphorin 3A in osteoclasts causes lymphatic expansion in a Gorham-Stout disease(GSD)mouse model

Gorham-Stout disease(GSD)is a sporadic chronic disease characterized by progressive bone dissolution,absorption,and disappearance along with lymphatic vessel infiltration in bone-marrow cavities.Although the osteolytic mechanism of GSD has been widely studied,the cause of lymphatic hyperplasia in GSD is rarely investigated.In this study,by comparing the RNA expression profile of osteoclasts(OCs)with that of OC precursors(OCPs)by RNA sequencing,we identified a new factor,semaphorin 3A(Sema3A),which is an osteoprotective factor involved in the lymphatic expansion of GSD.Compared to OCPs,OCs enhanced the growth,migration,and tube formation of lymphatic endothelial cells(LECs),in which the expression of Sema3A is low compared to that in OCPs.In the presence of recombinant Sema3A,the growth,migration,and tube formation of LECs were inhibited,further confirming the inhibitory effect of Sema3A on LECs in vitro.Using an LEC-induced GSD mouse model,the effect of Sema3A was examined by injecting lentivirus-expressing Sema3A into the tibiae in vivo.We found that the overexpression of Sema3A in tibiae suppressed the expansion of LECs and alleviated bone loss,whereas the injection of lentivirus expressing Sema3A short hairpin RNA(shRNA)into the tibiae caused GSD-like phenotypes.Histological staining further demonstrated that OCs decreased and osteocalcin increased after Sema3A lentiviral treatment,compared with the control.Based on the above results,we propose that reduced Sema3A in OCs is one of the mechanisms contributing to the pathogeneses of GSD and that expressing Sema3A represents a new approach for the treatment of GSD.

Lymphatic vasculature in tumor metastasis and immunobiology

Lymphatic vessels are essential for tissue fluid homeostasis,immune cell trafficking,and intestinal lipid absorption.The lymphatics have long been recognized to serve as conduits for distant tumor dissemination.However,recent findings suggest that the regional lymphatic vasculature also shapes the immune microenvironment of the tumor mass and potentiates immunotherapy.This review discusses the role of lymphatic vessels in tumor metastasis and tumor immunity.

Peripheral Lymphocyte Subsets as a Marker of Parkinson's Disease in a Chinese Population

In this study, we conducted a clinical analysis of lymphocyte subtypes in 268 patients with Parkinson＇s disease （PD） to assess their clinical impact as a potential marker of advanced PD in Chinese patients. The participants comprised 268 sporadic PD patients and 268 healthy controls. The numbers of natural killer （NK） cells and CD3＋, CD3＋CD4＋, CD3＋CD8＋, and CD19＋ lympho- cytes from peripheral blood were determined by immunos- taining and flow cytometric analysis and the percentages of these CD＋ T cells were calculated. The ratio of regulatory T （Treg）/helper T 17 （Thl7） lymphocytes from 64 PD patients and 46 controls was determined by flow cytometric analysis. The results showed that the percentage of NK cells was higher in advanced PD patients than in controls （22.92% ± 10.08% versus 19.76% ±10.09%, P= 0.006）, while CD3＋ T cells are decreased （62.93% ±9.27% versus 65.75% ± 9.13%, P = 0.005）. The percentage of CD19＋ B cells in male patients was lower （P = 0.021） than in female patients, whereas NK cells were increased （P 〈 0.0001）. The scores on the Unified Parkinson＇s Disease Rating Scale （UPDRS） and the Non-Motor Symptoms Scale in late-onset PD patients were significantly higher than those in earlyonset patients （P = 0.024 and P = 0.007, respectively）. The percentage of CD19＋ B cells in patients with UPDRS scores 〉24 was lower than in those with scores 〈24 （10.17% ± 4.19% versus 12.22% ± 5.39%, P = 0.009）. In addition, the Treg/Th17 ratio in female patients was higher than that in female controls （13.88 ± 6.32 versus 9.94 ±4.06, P = 0.042）. These results suggest that the percentages of NK cells, CD3＋ T cells, and CD19＋ B cells along with the Treg/Th17 ratio in peripheral blood may be used to predict the risk of PD in Chinese individuals and provide fresh avenues for novel diagnostic biomarkers and therapeutic designs.