http://diposit.ub.edu/dspace/bitstream/2445/165519/4/L20_2020_Cell_181_905_OA.pdf

Inhibition of SARS-CoV-2 Infections in Engineered Human Tissues Using Clinical-Grade Soluble Human ACE2.

The historical reliance of biological research on the use of animal models has sometimes made it challenging to address questions that are specific to the understanding of human biology and disease. But with the advent of human organoids - which are stem cell-derived 3D culture systems - it is now possible to re-create the architecture and physiology of human organs in remarkable detail. Human organoids provide unique opportunities for the study of human disease and complement animal models. Human organoids have been used to study infectious diseases, genetic disorders and cancers through the genetic engineering of human stem cells, as well as directly when organoids are generated from patient biopsy samples. This Review discusses the applications, advantages and disadvantages of human organoids as models of development and disease and outlines the challenges that have to be overcome for organoids to be able to substantially reduce the need for animal experiments.

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Human organoids: model systems for human biology and medicine.

Blood vessels form a closed circulatory system, whereas lymphatic vessels form a one-way conduit for tissue fluid and leukocytes. In most vertebrates, the main function of lymphatic vessels is to collect excess protein-rich fluid that has extravasated from blood vessels and transport it back into the blood circulation. Lymphatic vessels have an important immune surveillance function, as they import various antigens and activated antigen-presenting cells into the lymph nodes and export immune effector cells and humoral response factors into the blood circulation. Defects in lymphatic function can lead to lymph accumulation in tissues, dampened immune responses, connective tissue and fat accumulation, and tissue swelling known as lymphedema. This review highlights the most recent developments in lymphatic biology and how the lymphatic system contributes to the pathogenesis of various diseases involving immune and inflammatory responses and its role in disseminating tumor cells.

The lymphatic vasculature in disease

4. Biosynthesis of Leukotrienes 5869 4.1. Discovery of the Leukotriene Pathway and a Common Unstable Intermediate 5869 4.2. Conversion of Arachidonic Acid into Leukotriene A4 (LTA4) Is a Two-Step Concerted Reaction Catalyzed by a Single Lipoxygenase 5869 4.3. Structural Elucidation of Slow-Reacting Substance of Anaphylaxis, A Mixture of Leukotrienes 5870 5. Enzymes and Proteins in Leukotriene Biosynthesis 5870 5.1. Cytosolic Phospholipase A2α (cPLA2α) 5870 5.1.1. Molecular Properties and Regulation of cPLA2α 5870 5.1.2. Crystal Structure and Catalytic Mechanism of cPLA2α 5871 5.2. 5-Lipoxygenase (5-LO) 5871 5.2.1. Cellular Expression of 5-LO 5871 5.2.2. Regulation of 5-LO Gene (ALOX5) Transcription 5872 5.2.3. Naturally Occurring Mutations in the Gene Promoter of 5-LO 5872 5.2.4. Allosteric and Post-translational Regulation of 5-LO 5872 5.2.5. Structure function relationships in 5-LO 5872 5.2.6. Crystal Structure of 5-LO 5872 5.3. 5-Lipoxygenase-Activating Protein (FLAP) 5873 5.3.1. FLAP Is Critical for Cellular 5-LO Activity 5873 5.3.2. Effects of FLAP on Leukotriene Production 5873 5.3.3. FLAP Gene (ALOX5AP) and Regulation of Expression 5874 5.3.4. Crystal Structure of FLAP 5874 5.4. LTA4 Hydrolase 5874 5.4.1. LTA4 Hydrolase Is a Substrate-Selective and Suicide-Inactivated Epoxide Hydrolase 5874 5.4.2. LTA4 Hydrolase Is Bifunctional and Belongs to the M1 Family of Zinc Metallopeptidases 5874 5.4.3. LTA4 Hydrolase Cleaves the Chemotactic Pro-Gly-Pro, a Role for the Aminopeptidase Activity during Resolution of Inflammation 5875 5.4.4. Crystal Structure of LTA4 Hydrolase 5875 5.4.5. Mechanism of the Epoxide Hydrolase Reaction 5876 5.4.6. Mechanism of the Aminopeptidase Activity 5876 5.4.7. Two Catalytic Activities Exerted via Specific but Overlapping Active Sites 5877 5.5. LTC4 Synthase 5877 5.5.1. Molecular Properties of LTC4 Synthase 5877 5.5.2. LTC4 Synthase Is a Member of the MAPEG Superfamily of IntegralMembraneProteins 5877 5.5.3. Gene Structure and Regulation of LTC4 Synthase Expression 5877 5.5.4. Crystal Structure of LTC4 Synthase 5877 5.5.5. Catalytic Mechanism of LTC4 Synthase 5878 6. Intracellular Protein Trafficking and Compartmentalization of Leukotriene Biosynthesis 5878 6.1. Translocation of cPLA2α 5878 6.2. Translocation of 5-LO and Association with FLAP on the Nuclear Envelope 5879 6.2.1. 5-LO in the Nucleoplasm 5879 6.2.2. Organization of a Leukotriene Biosynthetic Complex in the Nuclear Membrane 5879 6.3. Leukotriene Biosynthesis in Lipid Bodies and Actions on Extracellular Granules 5879

Lipoxygenase and leukotriene pathways: biochemistry, biology, and roles in disease.

Metastasis is the leading cause of cancer mortality. The metastatic cascade represents a multi-step process which includes local tumor cell invasion, entry into the vasculature followed by the exit of carcinoma cells from the circulation and colonization at the distal sites. At the earliest stage of successful cancer cell dissemination, the primary cancer adapts the secondary site of tumor colonization involving the tumor–stroma crosstalk. The migration and plasticity of cancer cells as well as the surrounding environment such as stromal and endothelial cells are mandatory. Consequently, the mechanisms of cell movement are of utmost relevance for targeted intervention of which three different types have been reported. Tumor cells can migrate either collectively, in a mesenchymal or in an amoeboid type of movement and intravasate the blood or lymph vasculature. Intravasation by the interaction of tumor cells with the vascular endothelium is mechanistically poorly understood. Changes in the epithelial plasticity enable carcinoma cells to switch between these types of motility. The types of migration may change depending on the intervention thereby increasing the velocity and aggressiveness of invading cancer cells. Interference with collective or mesenchymal cell invasion by targeting integrin expression or metalloproteinase activity, respectively, resulted in an amoeboid cell phenotype as the ultimate exit strategy of cancer cells. There are little mechanistic details reported in vivo showing that the amoeboid behavior can be either reversed or efficiently inhibited. Future concepts of metastasis intervention must simultaneously address the collective, mesenchymal and amoeboid mechanisms of cell invasion in order to advance in anti-metastatic strategies as these different types of movement can coexist and cooperate. Beyond the targeting of cell movements, the adhesion of cancer cells to the stroma in heterotypic circulating tumor cell emboli is of paramount relevance for anti-metastatic therapy.

Initial steps of metastasis: Cell invasion and endothelial transmigration

The increasing prevalence of diabetes has resulted in a global epidemic1. Diabetes is a major cause of blindness, kidney failure, heart attacks, stroke and amputation of lower limbs. These are often caused by changes in blood vessels, such as the expansion of the basement membrane and a loss of vascular cells2-4. Diabetes also impairs the functions of endothelial cells5 and disturbs the communication between endothelial cells and pericytes6. How dysfunction of endothelial cells and/or pericytes leads to diabetic vasculopathy remains largely unknown. Here we report the development of self-organizing three-dimensional human blood vessel organoids from pluripotent stem cells. These human blood vessel organoids contain endothelial cells and pericytes that self-assemble into capillary networks that are enveloped by a basement membrane. Human blood vessel organoids transplanted into mice form a stable, perfused vascular tree, including arteries, arterioles and venules. Exposure of blood vessel organoids to hyperglycaemia and inflammatory cytokines in vitro induces thickening of the vascular basement membrane. Human blood vessels, exposed in vivo to a diabetic milieu in mice, also mimic the microvascular changes found in patients with diabetes. DLL4 and NOTCH3 were identified as key drivers of diabetic vasculopathy in human blood vessels. Therefore, organoids derived from human stem cells faithfully recapitulate the structure and function of human blood vessels and are amenable systems for modelling and identifying the regulators of diabetic vasculopathy, a disease that affects hundreds of millions of patients worldwide.

Human blood vessel organoids as a model of diabetic vasculopathy

In individuals with mammary carcinoma, the most relevant prognostic predictor of distant organ metastasis and clinical outcome is the status of axillary lymph node metastasis. Metastases form initially in axillary sentinel lymph nodes and progress via connecting lymphatic vessels into postsentinel lymph nodes. However, the mechanisms of consecutive lymph node colonization are unknown. Through the analysis of human mammary carcinomas and their matching axillary lymph nodes, we show here that intrametastatic lymphatic vessels and bulk tumor cell invasion into these vessels highly correlate with formation of postsentinel metastasis. In an in vitro model of tumor bulk invasion, human mammary carcinoma cells caused circular defects in lymphatic endothelial monolayers. These circular defects were highly reminiscent of defects of the lymphovascular walls at sites of tumor invasion in vivo and were primarily generated by the tumor-derived arachidonic acid metabolite 12S-HETE following 15-lipoxygenase-1 (ALOX15) catalysis. Accordingly, pharmacological inhibition and shRNA knockdown of ALOX15 each repressed formation of circular defects in vitro. Importantly, ALOX15 knockdown antagonized formation of lymph node metastasis in xenografted tumors. Furthermore, expression of lipoxygenase in human sentinel lymph node metastases correlated inversely with metastasis-free survival. These results provide evidence that lipoxygenase serves as a mediator of tumor cell invasion into lymphatic vessels and formation of lymph node metastasis in ductal mammary carcinomas.

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Lipoxygenase mediates invasion of intrametastatic lymphatic vessels and propagates lymph node metastasis of human mammary carcinoma xenografts in mouse

Monika Hämmerle

Papers

Human blood vessel organoids as a model of diabetic vasculopathy

Lipoxygenase mediates invasion of intrametastatic lymphatic vessels and propagates lymph node metastasis of human mammary carcinoma xenografts in mouse