Browsing by Subject "VASCULATURE"

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  • Jacob, Laurent; Boisserand, Ligia Simoes Braga; Geraldo, Luiz Henrique Medeiros; Neto, Jose de Brito; Mathivet, Thomas; Antila, Salli; Barka, Besma; Xu, Yunling; Thomas, Jean-Mickael; Pestel, Juliette; Aigrot, Marie-Stephane; Song, Eric; Nurmi, Harri; Lee, Seyoung; Alitalo, Kari; Renier, Nicolas; Eichmann, Anne; Thomas, Jean-Leon (2019)
    Cranial lymphatic vessels (LVs) are involved in the transport of fluids, macromolecules and central nervous system (CNS) immune responses. Little information about spinal LVs is available, because these delicate structures are embedded within vertebral tissues and difficult to visualize using traditional histology. Here we show an extended vertebral column LV network using three-dimensional imaging of decalcified iDISCO(+)-clarified spine segments. Vertebral LVs connect to peripheral sensory and sympathetic ganglia and form metameric vertebral circuits connecting to lymph nodes and the thoracic duct. They drain the epidural space and the dura mater around the spinal cord and associate with leukocytes. Vertebral LVs remodel extensively after spinal cord injury and VEGF-C-induced vertebral lymphangiogenesis exacerbates the inflammatory responses, T cell infiltration and demyelination following focal spinal cord lesion. Therefore, vertebral LVs add to skull meningeal LVs as gatekeepers of CNS immunity and may be potential targets to improve the maintenance and repair of spinal tissues.
  • 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)
  • Korhonen, Emilia A.; Murtomäki, Aino; Jha, Sawan Kumar; Anisimov, Andrey; Pink, Anne; Zhang, Yan; Stritt, Simon; Liaqat, Inam; Stanczuk, Lukas; Alderfer, Laura; Sun, Zhiliang; Kapiainen, Emmi; Singh, Abhishek; Sultan, Ibrahim; Lantta, Anni; Leppänen, Veli Matti; Eklund, Lauri; He, Yulong; Augustin, Hellmut G.; Vaahtomeri, Kari; Saharinen, Pipsa; Makinen, Taija; Alitalo, Kari (2022)
    Vascular endothelial growth factor C (VEGF-C) induces lymphangiogenesis via VEGF receptor 3 (VEGFR3), which is encoded by the most frequently mutated gene in human primary lymphedema. Angiopoietins (Angs) and their Tie receptors regulate lymphatic vessel development, and mutations of the ANGPT2 gene were recently found in human primary lymphedema. However, the mechanistic basis of Ang2 activity in lymphangiogenesis is not fully understood. Here, we used gene deletion, blocking Abs, transgene induction, and gene transfer to study how Ang2, its Tie2 receptor, and Tie1 regulate lymphatic vessels. We discovered that VEGF-C-induced Ang2 secretion from lymphatic endothelial cells (LECs) was involved in full Akt activation downstream of phosphoinositide 3 kinase (PI3K). Neonatal deletion of genes encoding the Tie receptors or Ang2 in LECs, or administration of an Ang2-blocking Ab decreased VEGFR3 presentation on LECs and inhibited lymphangiogenesis. A similar effect was observed in LECs upon deletion of the PI3K catalytic p110α subunit or with smallmolecule inhibition of a constitutively active PI3K located downstream of Ang2. Deletion of Tie receptors or blockade of Ang2 decreased VEGF-C-induced lymphangiogenesis also in adult mice. Our results reveal an important crosstalk between the VEGF-C and Ang signaling pathways and suggest new avenues for therapeutic manipulation of lymphangiogenesis by targeting Ang2/Tie/PI3K signaling.
  • 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.
  • 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.
  • Nurmi, Harri; Saharinen, Pipsa; Zarkada, Georgia; Zheng, Wei; Robciuc, Marius R.; Alitalo, Kari (2015)
    Vascular endothelial growth factor C (VEGF-C) binding to its tyrosine kinase receptor VEGFR-3 drives lymphatic vessel growth during development and in pathological processes. Although the VEGF-C/VEGFR-3 pathway provides a target for treatment of cancer and lymphedema, the physiological functions of VEGF-C in adult vasculature are unknown. We show here that VEGF-C is necessary for perinatal lymphangiogenesis, but required for adult lymphatic vessel maintenance only in the intestine. Following Vegfc gene deletion in adult mice, the intestinal lymphatic vessels, including the lacteal vessels, underwent gradual atrophy, which was aggravated when also Vegfd was deleted. VEGF-C was expressed by a subset of smooth muscle cells adjacent to the lacteals in the villus and in the intestinal wall. TheVegfc-deleted mice showed defective lipid absorption and increased fecal excretion of dietary cholesterol and fatty acids. When fed a high-fat diet, the Vegfc-deficient mice were resistant to obesity and had improved glucose metabolism. Our findings indicate that the lymphangiogenic growth factors provide trophic and dynamic regulation of the intestinal lymphatic vasculature, which could be especially important in the dietary regulation of adiposity and cholesterol metabolism.