Mechanosensing by ß1 integrin induces angiocrine signals for liver growth and survival.

Angiocrine signals derived from endothelial cells are an important component of intercellular communication and have a key role in organ growth, regeneration and disease1-4. These signals have been identified and studied in multiple organs, including the liver, pancreas, lung, heart, bone, bone marrow, central nervous system, retina and some cancers1-4. Here we use the developing liver as a model organ to study angiocrine signals5,6, and show that the growth rate of the liver correlates both spatially and temporally with blood perfusion to this organ. By manipulating blood flow through the liver vasculature, we demonstrate that vessel perfusion activates ß1 integrin and vascular endothelial growth factor receptor 3 (VEGFR3). Notably, both ß1 integrin and VEGFR3 are strictly required for normal production of hepatocyte growth factor, survival of hepatocytes and liver growth. Ex vivo perfusion of adult mouse liver and in vitro mechanical stretching of human hepatic endothelial cells illustrate that mechanotransduction alone is sufficient to turn on angiocrine signals. When the endothelial cells are mechanically stretched, angiocrine signals trigger in vitro proliferation and survival of primary human hepatocytes. Our findings uncover a signalling pathway in vascular endothelial cells that translates blood perfusion and mechanotransduction into organ growth and maintenance.

Vascular lumen formation.

PURPOSE OF REVIEW: The lumen of a blood vessel is essential for providing blood to any given tissue. Here, we discuss the molecular and cellular mechanisms underlying vascular lumen formation in invertebrates and vertebrates and highlight a new hypothesis describing oxygen transport in human malignant tumors. RECENT FINDINGS: Several cellular mechanisms exist for blood vessel formation, that is vasculogenesis, intercellular and intracellular sprouting angiogenesis, and intussusceptive angiogenesis, all of which might follow common molecular principles to form a vascular lumen. The latter includes junctional remodeling and generation of apical endothelial cell surfaces, electrostatic deadhesion of these cell surfaces to create a small lumen between two or more apposing endothelial cells or a cavity within an endothelial cell, and force-dependent expansion or extension of the vascular lumen. Whereas these events require endothelial cells, vascular lumen formation in invertebrates mostly occurs in their absence. As therapeutically targeting endothelial cells alone does not prevent vascular supply and growth of human malignant tumors, the possibility exists that some tumors employ invertebrate-like mechanisms of vascular lumen formation. SUMMARY: Whereas the molecular mechanisms of endothelial cell-based vascular lumen formation are beginning to be understood, it is still largely unknown how invertebrates and some malignant tumors establish a circulatory system in the absence of endothelium.

Optimization of sepsis therapy based on patient-specific digital precision diagnostics using next generation sequencing (DigiSep-Trial)-study protocol for a randomized, controlled, interventional, open-label, multicenter trial.

BACKGROUND: Sepsis is triggered by an infection and represents one of the greatest challenges of modern intensive care medicine. With regard to a targeted antimicrobial treatment strategy, the earliest possible pathogen detection is of crucial importance. Until now, culture-based detection methods represent the diagnostic gold standard, although they are characterized by numerous limitations. Culture-independent molecular diagnostic procedures represent a promising alternative. In particular, the plasmatic detection of circulating, cell-free DNA by next-generation sequencing (NGS) has shown to be suitable for identifying disease-causing pathogens in patients with bloodstream infections. METHODS: The DigiSep-Trial is a randomized, controlled, interventional, open-label, multicenter trial characterizing the effect of the combination of NGS-based digital precision diagnostics with standard-of-care microbiological analyses compared to solely standard-of-care microbiological analyses in the clinical picture of sepsis/septic shock. Additional anti-infective expert consultations are provided for both study groups. In 410 patients (n = 205 per arm) with sepsis/septic shock, the study examines whether the so-called DOOR-RADAR (Desirability of Outcome Ranking/Response Adjusted for Duration of Antibiotic Risk) score (representing a combined endpoint including the criteria (1) intensive/intermediate care unit length of stay, (2) consumption of antibiotics, (3) mortality, and (4) acute kidney injury (AKI)) can be improved by an additional NGS-based diagnostic concept. We also aim to investigate the cost-effectiveness of this new diagnostic procedure. It is postulated that intensive/intermediate care unit length of stay, mortality rate, incidence of AKI, the duration of antimicrobial therapy as well as the costs caused by complications and outpatient aftercare can be reduced. Moreover, a significant improvement in patient's quality of life is expected. DISCUSSION: The authors´ previous work suggests that NGS-based diagnostics have a higher specificity and sensitivity compared to standard-of-care microbiological analyses for detecting bloodstream infections. In combination with the here presented DigiSep-Trial, this work provides the optimal basis to establish a new NGS-driven concept as part of the national standard based on the best possible evidence. TRIAL REGISTRATIONS: DRKS-ID DRKS00022782 . Registered on August 25, 2020 ClinicalTrials.gov NCT04571801 . Registered October 1, 2020.

Vascular lumen formation.

The vascular system developed early in evolution. It is required in large multicellular organisms for the transport of nutrients, oxygen, and waste products to and from tissues. The vascular system is composed of hollow tubes, which have a high level of complexity in vertebrates. Vasculogenesis describes the de novo formation of blood vessels, e.g., aorta formation in vertebrate embryogenesis. In contrast, angiogenesis is the formation of blood vessels from preexisting ones, e.g., sprouting of intersomitic blood vessels from the aorta. Importantly, the lumen of all blood vessels in vertebrates is lined and formed by endothelial cells. In both vasculogenesis and angiogenesis, lumen formation takes place in a cord of endothelial cells. It involves a complex molecular mechanism composed of endothelial cell repulsion at the cell-cell contacts within the endothelial cell cords, junctional rearrangement, and endothelial cell shape change. As the vascular system also participates in the course of many diseases, such as cancer, stroke, and myocardial infarction, it is important to understand and make use of the molecular mechanisms of blood vessel formation to better understand and manipulate the pathomechanisms involved.

Pharmacological manipulation of blood and lymphatic vascularization in ex vivo-cultured mouse embryos.

Formation of new blood and lymphatic vessels is involved in many physiological and pathological processes, including organ and tumor growth, cancer cell metastasis, fluid drainage and lymphedema. Therefore, the ability to manipulate vascularization in a mammalian system is of particular interest to researchers. Here we describe a method for pharmacological manipulation of de novo and sprouting blood and lymphatic vascular development in ex vivo-cultured mouse embryos. The described protocol can also be used to evaluate the properties of pharmacological agents in growing mammalian tissues and to manipulate other developmental processes. The whole procedure, from embryo isolation to image quantification, takes 3-5 d, depending on the analysis and age of the embryos.

Electrostatic cell-surface repulsion initiates lumen formation in developing blood vessels.

Blood vessels function in the uptake, transport, and delivery of gases and nutrients within the body. A key question is how the central lumen of blood vessels develops within a cord of vascular endothelial cells. Here, we demonstrate that sialic acids of apical glycoproteins localize to apposing endothelial cell surfaces and generate repelling electrostatic fields within an endothelial cell cord. Both in vitro and in vivo experiments show that the negative charge of sialic acids is required for the separation of endothelial cell surfaces and subsequent lumen formation. We also demonstrate that sulfate residues can substitute for sialic acids during lumen initiation. These results therefore reveal a key step in the creation of blood vessels, the most abundant conduits in the vertebrate body. Because negatively charged mucins and proteoglycans are often found on luminal cell surfaces, it is possible that electrostatic repulsion is a general principle also used to initiate lumen formation in other organs.