Browsing by Subject "LYMPHANGIOGENESIS"

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  • Aspelund, Aleksanteri; Antila, Salli; Proulx, Steven T.; Karlsen, Tine Veronica; Karaman, Sinem; Detmar, Michael; Wiig, Helge; Alitalo, Kari (2015)
    The central nervous system (CNS) is considered an organ devoid of lymphatic vasculature. Yet, part of the cerebrospinal fluid (CSF) drains into the cervical lymph nodes (LNs). The mechanism of CSF entry into the LNs has been unclear. Here we report the surprising finding of a lymphatic vessel network in the dura mater of the mouse brain. We show that dural lymphatic vessels absorb CSF from the adjacent subarachnoid space and brain interstitial fluid (ISF) via the glymphatic system. Dural lymphatic vessels transport fluid into deep cervical LNs (dcLNs) via foramina at the base of the skull. In a transgenic mouse model expressing a VEGF-C/D trap and displaying complete aplasia of the dural lymphatic vessels, macromolecule clearance from the brain was attenuated and transport from the subarachnoid space into dcLNs was abrogated. Surprisingly, brain ISF pressure and water content were unaffected. Overall, these findings indicate that the mechanism of CSF flow into the dcLNs is directly via an adjacent dural lymphatic network, which may be important for the clearance of macromolecules from the brain. Importantly, these results call for a reexamination of the role of the lymphatic system in CNS physiology and disease.
  • Rademakers, Timo; van der Vorst, Emiel P. C.; Daissormont, Isabelle T. M. N.; Otten, Jeroen J. T.; Theodorou, Kosta; Theelen, Thomas L.; Gijbels, Marion; Anisimov, Andrey; Nurmi, Harri; Lindeman, Jan H. N.; Schober, Andreas; Heeneman, Sylvia; Alitalo, Kari; Biessen, Erik A. L. (2017)
    During plaque progression, inflammatory cells progressively accumulate in the adventitia, paralleled by an increased presence of leaky vasa vasorum. We here show that next to vasa vasorum, also the adventitial lymphatic capillary bed is expanding during plaque development in humans and mouse models of atherosclerosis. Furthermore, we investigated the role of lymphatics in atherosclerosis progression. Dissection of plaque draining lymph node and lymphatic vessel in atherosclerotic ApoE(-/-)mice aggravated plaque formation, which was accompanied by increased intimal and adventitial CD3(+) T cell numbers. Likewise, inhibition of VEGF-C/D dependent lymphangiogenesis by AAV aided gene transfer of hVEGFR3-Ig fusion protein resulted in CD3(+) T cell enrichment in plaque intima and adventitia. hVEGFR3-Ig gene transfer did not compromise adventitial lymphatic density, pointing to VEGF-C/D independent lymphangiogenesis. We were able to identify the CXCL12/CXCR4 axis, which has previously been shown to indirectly activate VEGFR3, as a likely pathway, in that its focal silencing attenuated lymphangiogenesis and augmented T cell presence. Taken together, our study not only shows profound, partly CXCL12/CXCR4 mediated, expansion of lymph capillaries in the adventitia of atherosclerotic plaque in humans and mice, but also is the first to attribute an important role of lymphatics in plaque T cell accumulation and development.
  • Gousopoulos, Epameinondas; Proulx, Steven T.; Bachmann, Samia B.; Dieterich, Lothar C.; Scholl, Jeannette; Karaman, Sinem; Bianchi, Roberta; Detmar, Michael (2017)
    Secondary lymphedema is a common complication after cancer treatment, but the pathomechanisms underlying the disease remain unclear. Using a mouse tail lymphedema model, we found an increase in local and systemic levels of the lymphangiogenic factor vascular endothelial growth factor (VEGF)-C and identified CD68(+) macrophages as a cellular source. Surprisingly, overexpression of VEGF-C in a transgenic mouse model led to aggravation of lymphedema with increased immune cell infiltration and vascular leakage compared with wild-type littermates. Conversely, blockage of VEGF-C by overexpression of soluble VEGF receptor-3 reduced edema development, diminishing inflammation and blood vascular leakage. Similar findings were obtained in a hind limb lymph node excision lymphedema model. Flow cytometry analyses and immunofluorescence stainings in lymphedematic tissue showed that VEGF receptor-3 expression was restricted to lymphatic endothelial cells. Our data suggest that endogenous VEGF-C causes blood vascular leakage and fluid influx into the tissue, thus actively contributing to edema formation. These data may provide the basis for future clinical therapeutic approaches.
  • Viitanen, Tiina P.; Visuri, Mikko T.; Sulo, Eeva; Saarikko, Anne M.; Hartiala, Pauliina (2015)
    Background: Transfer of healthy tissue is commonly used in the treatment of complicated wounds and in reconstruction of tissue defects. Recently, microvascular lymph node transfer (LN) has been used to improve the lymphatic function in lymphedema patients. To elucidate the biological effects of flap transfer (with and without lymph nodes), we have studied the postoperative production of proinflammatory, anti-inflammatory, prolymphangiogenic and antilymphangiogenic cytokines, and growth factors (interleukin 1 alpha [IL-1 alpha], IL-1 beta, tumor necrosis factor alpha [TNF-alpha], IL-10, transforming growth factor beta 1 [TGF-beta 1], IL-4 and IL-13, and vascular endothelial growth factor C [VEGF-C] and VEGF-D) in postoperative wound exudate samples. Methods: Axillary wound exudate samples were analyzed from four patient groups: axillary lymph node dissection (ALND), microvascular breast reconstruction (BR), LN, and combined LN and BR (LN-BR). Results: The concentration of proinflammatory cytokines was low in all the flap transfer groups as opposed to the ALND group, which showed an extensive proinflammatory response. The level of anti-inflammatory and antifibrotic cytokine IL-10 was increased in the LN-BR group samples compared with the ALND and BR groups. In the LN and LN-BR groups, the cytokine profile showed an anti-inflammatory response. Conclusions: Transfer of healthy tissue hinders the proinflammatory response after surgery, which may explain the beneficial effects of flap transfer in various patient groups. In addition, flap transfer with lymph nodes seems to also promote an antifibrotic effect. The clinical effects of LN in lymphedema patients may be mediated by the increased production of prolymphangiogenic growth factor (VEGF-C) and antifibrotic cytokine (IL-10). (C) 2015 Elsevier Inc. All rights reserved.
  • Karaman, Sinem; Hollmen, Maija; Robciuc, Marius R.; Alitalo, Annamari; Nurmi, Harri; Morf, Bettina; Buschle, Dorina; Alkan, H. Furkan; Ochsenbein, Alexandra M.; Alitalo, Kari; Wolfrum, Christian; Detmar, Michael (2015)
    Objective: Elevated serum levels of the lymphangiogenic factors VEGF-C and -D have been observed in obese individuals but their relevance for the metabolic syndrome has remained unknown. Methods: K14-VEGFR-3-Ig (sR3) mice that constitutively express soluble-VEGFR-3eIg in the skin, scavenging VEGF-C and -D, and wildtype (WT) mice were fed either chow or high-fat diet for 20 weeks. To assess the effect of VEGFR-3 blockage on adipose tissue growth and insulin sensitivity, we evaluated weight gain, adipocyte size and hepatic lipid accumulation. These results were complemented with insulin tolerance tests, FACS analysis of adipose tissue macrophages, in vitro 3T3-L1 differentiation assays and in vivo blocking antibody treatment experiments. Results: We show here that sR3 mice are protected from obesity-induced insulin resistance and hepatic lipid accumulation. This protection is associated with enhanced subcutaneous adipose tissue hyperplasia and an increased number of alternatively-activated (M2) macrophages in adipose tissue. We also show that VEGF-C and -D are chemotactic for murine macrophages and that this effect is mediated by VEGFR-3, which is upregulated on M1 polarized macrophages. Systemic antibody blockage of VEGFR-3 in db/db mice reduces adipose tissue macrophage infiltration and hepatic lipid accumulation, and improves insulin sensitivity. Conclusions: These results reveal an unanticipated role of the lymphangiogenic factors VEGF-C and -D in the mediation of metabolic syndrome-associated adipose tissue inflammation. Blockage of these lymphangiogenic factors might constitute a new therapeutic strategy for the prevention of obesity-associated insulin resistance. (C) 2014 The Authors. Published by Elsevier GmbH.
  • Martinez-Corral, Ines; Zhang, Yan; Petkova, Milena; Ortsater, Henrik; Sjoberg, Sofie; Castillo, Sandra D.; Brouillard, Pascal; Libbrecht, Louis; Saur, Dieter; Graupera, Mariona; Alitalo, Kari; Boon, Laurence; Vikkula, Miikka; Mäkinen, Taija (2020)
    Lymphatic malformations (LMs) are debilitating vascular anomalies presenting with large cysts (macrocystic) or lesions that infiltrate tissues (microcystic). Cellular mechanisms underlying LM pathology are poorly understood. Here we show that the somatic PIK3CA(H1047R) mutation, resulting in constitutive activation of the p110 alpha PI3K, underlies both macrocystic and microcystic LMs in human. Using a mouse model of PIK3CA(H1047R)-driven LM, we demonstrate that both types of malformations arise due to lymphatic endothelial cell (LEC)-autonomous defects, with the developmental timing of p110 alpha activation determining the LM subtype. In the postnatal vasculature, PIK3CA(H1047R) promotes LEC migration and lymphatic hypersprouting, leading to microcystic LMs that grow progressively in a vascular endothelial growth factor C (VEGF-C)-dependent manner. Combined inhibition of VEGF-C and the PI3K downstream target mTOR using Rapamycin, but neither treatment alone, promotes regression of lesions. The best therapeutic outcome for LM is thus achieved by co-inhibition of the upstream VEGF-C/VEGFR3 and the downstream PI3K/mTOR pathways. Lymphatic malformation (LM) is a debilitating often incurable vascular disease. Using a mouse model of LM driven by a disease-causative PIK3CA mutation, the authors show that vascular growth is dependent on the upstream lymphangiogenic VEGF-C signalling, permitting effective therapeutic intervention.
  • Stanczuk, Lukas; Martinez-Corral, Ines; Ulvmar, Maria H.; Zhang, Yang; Lavina, Barbbara; Fruttiger, Marcus; Adams, Ralf H.; Saur, Dieter; Betsholtz, Christer; Ortega, Sagrario; Alitalo, Kari; Graupera, Mariona; Makinen, Taija (2015)
  • Honkanen, Hanne-Kaisa; Izzi, Valerio; Petaisto, Tiina; Holopainen, Tanja; Harjunen, Vanessa; Pihlajaniemi, Taina; Alitalo, Kari; Heljasvaara, Ritva (2016)
    Vascular endothelial growth factor D (VEGF-D) promotes the lymph node metastasis of cancer by inducing the growth of lymphatic vasculature, but its specific roles in tumorigenesis have not been elucidated. We monitored the effects of VEGF-D in cutaneous squamous cell carcinoma (cSCC) by subjecting transgenic mice overexpressing VEGF-D in the skin (K14-mVEGF-D) and VEGF-D knockout mice to a chemical skin carcinogenesis protocol involving 7,12-dimethylbenz[a] anthracene and 12-O-tetradecanoylphorbol-13-acetate treatments. In K14-mVEGF-Dmice, tumor lymphangiogenesis was significantly increased and the frequency of lymph node metastasis was elevated in comparison with controls. Most notably, the papillomas regressed more often in K14-mVEGF-D mice than in littermate controls, resulting in a delay in tumor incidence and a remarkable reduction in the total tumor number. Skin tumor growth and metastasis were not obviously affected in the absence of VEGF-D; however, the knockout mice showed a trend for reduced lymphangiogenesis in skin tumors and in the untreated skin. Interestingly, K14-mVEGF-D mice showed an altered immune response in skin tumors. This consisted of the reduced accumulation of macrophages, mast cells, and CD4(+) T-cells and an increase of cytotoxic CD8(+) T-cells. Cytokine profiling by flow cytometry and quantitative real time PCR revealed that elevated VEGF-D expression results in an attenuated Th2 response and promotes M1/Th1 and Th17 polarization in the early stage of skin carcinogenesis, leading to an anti-tumoral immune environment and the regression of primary tumors. Our data suggest that VEGF-D may be beneficial in early-stage tumors since it suppresses the pro-tumorigenic inflammation, while at later stages VEGF-D-induced tumor lymphatics provide a route for metastasis.
  • Suh, Sang Heon; Choe, Kibaek; Hong, Seon Pyo; Jeong, Seung-hwan; Mäkinen, Taija; Kim, Kwang Soon; Alitalo, Kari; Surh, Charles D.; Koh, Gou Young; Song, Joo-Hye (2019)
    A lacteal is a blunt-ended, long, tube-like lymphatic vessel located in the center of each intestinal villus that provides a unique route for drainage of absorbed lipids from the small intestine. However, key regulators for maintaining lacteal integrity are poorly understood. Here, we explore whether and how the gut microbiota regulates lacteal integrity. Germ depletion by antibiotic treatment triggers lacteal regression during adulthood and delays lacteal maturation during the postnatal period. In accordance with compromised lipid absorption, the button-like junction between lymphatic endothelial cells, which is ultrastructurally open to permit free entry of dietary lipids into lacteals, is significantly reduced in lacteals of germ-depleted mice. Lacteal defects are also found in germ-free mice, but conventionalization of germ-free mice leads to normalization of lacteals. Mechanistically, VEGF-C secreted from villus macrophages upon MyD88-dependent recognition of microbes and their products is a main factor in lacteal integrity. Collectively, we conclude that the gut microbiota is a crucial regulator for lacteal integrity by endowing its unique microenvironment and regulating villus macrophages in small intestine.
  • Zhang, Yan; Ulvmar, Maria H.; Stanczuk, Lukas; Martinez-Corral, Ines; Frye, Maike; Alitalo, Kari; Mäkinen, Taija (2018)
    Incomplete delivery to the target cells is an obstacle for successful gene therapy approaches. Here we show unexpected effects of incomplete targeting, by demonstrating how heterogeneous inhibition of a growth promoting signaling pathway promotes tissue hyperplasia. We studied the function of the lymphangiogenic VEGFR3 receptor during embryonic and postnatal development. Inducible genetic deletion of Vegfr3 in lymphatic endothelial cells (LECs) leads to selection of non-targeted VEGFR3(+) cells at vessel tips, indicating an indispensable cell-autonomous function in migrating tip cells. Although Vegfr3 deletion results in lymphatic hypoplasia in mouse embryos, incomplete deletion during post-natal development instead causes excessive lymphangiogenesis. Analysis of mosaically targeted endothelium shows that VEGFR3(-) LECs non-cell-autonomously drive abnormal vessel anastomosis and hyperplasia by inducing proliferation of non-targeted VEGFR3(+) LECs through cell-contactdependent reduction of Notch signaling. Heterogeneity in VEGFR3 levels thus drives vessel hyperplasia, which has implications for the understanding of mechanisms of developmental and pathological tissue growth.
  • Mukenge, Sylvain; Jha, Sawan K.; Catena, Marco; Manara, Elena; Leppänen, Veli-Matti; Lenti, Elisa; Negrini, Daniela; Bertelli, Matteo; Brendolan, Andrea; Jeltsch, Michael; Aldrighetti, Luca (2020)
    Background Milroy-like disease is the diagnostic definition used for patients with phenotypes that resemble classic Milroy disease (MD) but are negative to genetic testing forFLT4. In this study, we aimed at performing a genetic characterization and biochemical analysis of VEGF-C variations found in a female proband born with congenital edema consistent with Milroy-like disease. Methods The proband underwent next-generation sequencing-based genetic testing for a panel of genes associated with known forms of hereditary lymphedema. Segregation analysis was performed on family members by direct sequencing. In vitro studies were performed to evaluate the role of a novel identified variant. Results TwoVEGF-Cvariations were found in the proband, a novel p.(Ser65Arg) and a pathogenic c.148-3_148-2delCA, of paternal and maternal origin, respectively. Functional characterization of the p.(Ser65Arg) variation in vitro showed alterations in VEGF-C processing. Conclusions Our findings reveal an interesting case in which biallelic variants inVEGF-Care found in a patient with Milroy-like lymphedema. These data expand our understanding of the etiology of congenital Milroy-like lymphedema.
  • Houssari, Mahmoud; Dumesnil, Anais; Tardif, Virginie; Kivela, Riikka; Pizzinat, Nathalie; Boukhalfa, Ines; Godefroy, David; Schapman, Damien; Hemanthakumar, Karthik A.; Bizou, Mathilde; Henry, Jean-Paul; Renet, Sylvanie; Riou, Gaetan; Rondeaux, Julie; Anouar, Youssef; Adriouch, Sahil; Fraineau, Sylvain; Alitalo, Kari; Richard, Vincent; Mulder, Paul; Brakenhielm, Ebba (2020)
    Objective: Lymphatics play an essential pathophysiological role in promoting fluid and immune cell tissue clearance. Conversely, immune cells may influence lymphatic function and remodeling. Recently, cardiac lymphangiogenesis has been proposed as a therapeutic target to prevent heart failure after myocardial infarction (MI). We investigated the effects of gene therapy to modulate cardiac lymphangiogenesis post-MI in rodents. Second, we determined the impact of cardiac-infiltrating T cells on lymphatic remodeling in the heart. Approach and Results: Comparing adenoviral versus adeno-associated viral gene delivery in mice, we found that only sustained VEGF (vascular endothelial growth factor)-C(C156S)therapy, achieved by adeno-associated viral vectors, increased cardiac lymphangiogenesis, and led to reduced cardiac inflammation and dysfunction by 3 weeks post-MI. Conversely, inhibition of VEGF-C/-D signaling, through adeno-associated viral delivery of soluble VEGFR3 (vascular endothelial growth factor receptor 3), limited infarct lymphangiogenesis. Unexpectedly, this treatment improved cardiac function post-MI in both mice and rats, linked to reduced infarct thinning due to acute suppression of T-cell infiltration. Finally, using pharmacological, genetic, and antibody-mediated prevention of cardiac T-cell recruitment in mice, we discovered that both CD4(+)and CD8(+)T cells potently suppress, in part through interferon-gamma, cardiac lymphangiogenesis post-MI. Conclusions: We show that resolution of cardiac inflammation after MI may be accelerated by therapeutic lymphangiogenesis based on adeno-associated viral gene delivery of VEGF-C-C156S. Conversely, our work uncovers a major negative role of cardiac-recruited T cells on lymphatic remodeling. Our results give new insight into the interconnection between immune cells and lymphatics in orchestration of cardiac repair after injury.
  • Gucciardo, Erika; Loukovaara, Sirpa; Salven, Petri; Lehti, Kaisa (2018)
    Diabetic retinopathy (DR) is the most common diabetic microvascular complication and major cause of blindness in working-age adults. According to the level of microvascular degeneration and ischemic damage, DR is classified into non-proliferative DR (NPDR), and end-stage, proliferative DR (PDR). Despite advances in the disease etiology and pathogenesis, molecular understanding of end-stage PDR, characterized by ischemia- and inflammation-associated neovascularization and fibrosis, remains incomplete due to the limited availability of ideal clinical samples and experimental research models. Since a great portion of patients do not benefit from current treatments, improved therapies are essential. DR is known to be a complex and multifactorial disease featuring the interplay of microvascular, neurodegenerative, metabolic, genetic/epigenetic, immunological, and inflammation-related factors. Particularly, deeper knowledge on the mechanisms and pathophysiology of most advanced PDR is critical. Lymphatic-like vessel formation coupled with abnormal endothelial differentiation and progenitor cell involvement in the neovascularization associated with PDR are novel recent findings which hold potential for improved DR treatment. Understanding the underlying mechanisms of PDR pathogenesis is therefore crucial. To this goal, multidisciplinary approaches and new ex vivo models have been developed for a more comprehensive molecular, cellular and tissue-level understanding of the disease. This is the first step to gain the needed information on how PDR can be better evaluated, stratified, and treated.
  • Frye, Maike; Taddei, Andrea; Dierkes, Cathrin; Martinez-Corral, Ines; Fielden, Matthew; Ortsäter, Henrik; Kazenwadel, Jan; Calado, Dinis P.; Ostergaard, Pia; Salminen, Marjo; He, Liqun; Harvey, Natasha L.; Kiefer, Friedemann; Mäkinen, Taija (2018)
    Tissue and vessel wall stiffening alters endothelial cell properties and contributes to vascular dysfunction. However, whether extracellular matrix (ECM) stiffness impacts vascular development is not known. Here we show that matrix stiffness controls lymphatic vascular morphogenesis. Atomic force microscopy measurements in mouse embryos reveal that venous lymphatic endothelial cell (LEC) progenitors experience a decrease in substrate stiffness upon migration out of the cardinal vein, which induces a GATA2-dependent transcriptional program required to form the first lymphatic vessels. Transcriptome analysis shows that LECs grown on a soft matrix exhibit increased GATA2 expression and a GATA2-dependent upregulation of genes involved in cell migration and lymphangiogenesis, including VEGFR3. Analyses of mouse models demonstrate a cell-autonomous function of GATA2 in regulating LEC responsiveness to VEGF-C and in controlling LEC migration and sprouting in vivo. Our study thus uncovers a mechanism by which ECM stiffness dictates the migratory behavior of LECs during early lymphatic development.
  • Karaman, Sinem; Alitalo, Kari (2017)
    Using an in vivo reporter for lymphangiogenesis, a recent study in Nature from Olmeda et al. ( 2017) describes a new subset of melanomas that induce systemic pre-conditioning of distant organs for formation of tumor metastatic niches, and identifies the responsible factor as the pleiotropic cytokine midkine.
  • Almahmoudi, Rabeia; Kasanen, Merimaija; Sieviläinen, Meri; Salem, Abdelhakim; Pirinen, Matti; Salo, Tuula; Al-Samadi, Ahmed (2019)
    Tongue squamous cell carcinoma (TSCC) has a poor prognosis due to its early metastasis via blood and lymphatic vessels. We performed a systematic review to investigate the prognostic significance of blood microvessel density (MVD) and lymphatic vessel density (LVD) in TSCC patients. We conducted a systematic search in Ovid Medline, Scopus, and Cochrane libraries. All studies that evaluated the prognostic significance of MVD/LVD markers in TSCC were systematically retrieved. Our results showed that MVD/LVD markers, CD31, CD34, CD105, factor VIII, LYVE‐1, and D2‐40 were evaluated in TSCC patients until 28 June 2018. Six out of 13 studies reported markers that were associated with poor prognosis in TSCC. Two out of three studies suggested that a high number of D2‐40+ vessels predicated low overall survival (OS); the third study reported that the ratio of D2‐40+ over factor VIII+ vessels is associated with low OS. Most of the other markers had controversial results for prognostication. We found higher expression of MVD/LVD markers were commonly, but not always, associated with shorter survival in TSCC patients. It is therefore not currently possible to recommend implementation of these markers as reliable prognosticators in clinical practice. More studies (especially for D2‐40) with larger patient cohorts are needed.
  • Gramolelli, Silvia; Cheng, Jianpin; Martinez-Corral, Ines; Vähä-Koskela, Markus; Elbasani, Endrit; Kaivanto, Elisa; Rantanen, Ville; Tuohinto, Krista; Hautaniemi, Sampsa; Bower, Mark; Haglund, Caj; Alitalo, Kari; Mäkinen, Taija; Petrova, Tatiana V.; Lehti, Kaisa; Ojala, Päivi M. (2018)
    The transcription factor PROX1 is essential for development and cell fate specification. Its function in cancer is context-dependent since PROX1 has been shown to play both oncogenic and tumour suppressive roles. Here, we show that PROX1 suppresses the transcription of MMP14, a metalloprotease involved in angiogenesis and cancer invasion, by binding and suppressing the activity of MMP14 promoter. Prox1 deletion in murine dermal lymphatic vessels in vivo and in human LECs increased MMP14 expression. In a hepatocellular carcinoma cell line expressing high endogenous levels of PROX1, its silencing increased both MMP14 expression and MMP14-dependent invasion in 3D. Moreover, PROX1 ectopic expression reduced the MMP14-dependent 3D invasiveness of breast cancer cells and angiogenic sprouting of blood endothelial cells in conjunction with MMP14 suppression. Our study uncovers a new transcriptional regulatory mechanism of cancer cell invasion and endothelial cell specification.
  • Nitschke, Maximilian; Bell, Alexander; Karaman, Sinem; Amouzgar, Meelad; Rutkowski, Joseph M.; Scherer, Philipp E.; Alitalo, Kari; McDonald, Donald M. (2017)
    Chylous pleural effusion (chylothorax) frequently accompanies lymphatic vessel malformations and other conditions with lymphatic defects. Although retrograde flow of chyle from the thoracic duct is considered a potential mechanism underlying chylothorax in patients and mouse models, the path chyle takes to reach the thoracic cavity is unclear. Herein, we use a novel transgenic mouse model, where doxycycline-induced overexpression of vascular endothelial growth factor (VEGF)-C was driven by the adipocyte-specific promoter adiponectin (ADN), to determine how chylothorax forms. Surprisingly, 100% of adult ADN-VEGF-C mice developed chylothorax within 7 days. Rapid, consistent appearance of chylothorax enabled us to examine the step-by-step development in otherwise normal adult mice. Dynamic imaging with a fluorescent tracer revealed that lymph in the thoracic duct of these mice could enter the thoracic cavity by retrograde flow into enlarged paravertebral Lymphatics and subpleural lymphatic plexuses that had incompetent Lymphatic valves. Pleural mesothelium overlying the lymphatic plexuses underwent exfoliation that increased during doxycycline exposure. Together, the findings indicate that chylothorax in ADN-VEGF-C mice results from retrograde flow of chyle from the thoracic duct into lymphatic tributaries with defective valves. Chyle extravasates from these plexuses and enters the thoracic cavity through exfoliated regions of the pleural mesothelium.
  • Karaman, Sinem; Hollmen, Maija; Yoon, Sun-Young; Alkan, H. Furkan; Alitalo, Kari; Wolfrum, Christian; Detmar, Michael (2016)
    Obesity comprises great risks for human health, contributing to the development of other diseases such as metabolic syndrome, type 2 diabetes and cardiovascular disease. Previously, obese patients were found to have elevated serum levels of VEGF-C, which correlated with worsening of lipid parameters. We recently identified that neutralization of VEGF-C and -D in the subcutaneous adipose tissue during the development of obesity improves metabolic parameters and insulin sensitivity in mice. To test the hypothesis that VEGF-C plays a role in the promotion of the metabolic disease, we used K14-VEGF-C mice that overexpress human VEGF-C under control of the keratin-14 promoter in the skin and monitored metabolic parameters over time. K14-VEGF-C mice had high levels of VEGF-C in the subcutaneous adipose tissue and gained more weight than wildtype littermates, became insulin resistant and had increased ectopic lipid accumulation at 20 weeks of age on regular mouse chow. The metabolic differences persisted under high-fat diet induced obesity. These results indicate that elevated VEGF-C levels contribute to metabolic deterioration and the development of insulin resistance, and that blockade of VEGF-C in obesity represents a suitable approach to alleviate the development of insulin resistance.
  • Nilsson, Ingrid; Bahram, Fuad; Li, Xiujuan; Gualandi, Laura; Koch, Sina; Jarvius, Malin; Soderberg, Ola; Anisimov, Andrei; Kholova, Ivana; Pytowski, Bronislaw; Baldwin, Megan; Yla-Herttuala, Seppo; Alitalo, Kari; Kreuger, Johan (2010)