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

We have previously provided the first genetic evidence that angiotensin converting enzyme 2 (ACE2) is the critical receptor for severe acute respiratory syndrome coronavirus (SARS-CoV), and ACE2 protects the lung from injury, providing a molecular explanation for the severe lung failure and death due to SARS-CoV infections. ACE2 has now also been identified as a key receptor for SARS-CoV-2 infections, and it has been proposed that inhibiting this interaction might be used in treating patients with COVID-19. However, it is not known whether human recombinant soluble ACE2 (hrsACE2) blocks growth of SARS-CoV-2. Here, we show that clinical grade hrsACE2 reduced SARS-CoV-2 recovery from Vero cells by a factor of 1,000-5,000. An equivalent mouse rsACE2 had no effect. We also show that SARS-CoV-2 can directly infect engineered human blood vessel organoids and human kidney organoids, which can be inhibited by hrsACE2. These data demonstrate that hrsACE2 can significantly block early stages of SARS-CoV-2 infections.

Generation of blood vessel organoids from human pluripotent stem cells.

Blood vessels are fundamental to animal life and have critical roles in many diseases, such as stroke, myocardial infarction and diabetes. The vasculature is formed by endothelial cells that line the vessel and are covered with mural cells, specifically pericytes in smaller vessels and vascular smooth muscle cells (vSMCs) in larger-diameter vessels. Both endothelial cells and mural cells are essential for proper blood vessel function and can be derived from human pluripotent stem cells (hPSCs). Here, we describe a protocol to generate self-organizing 3D human blood vessel organoids from hPSCs that exhibit morphological, functional and molecular features of human microvasculature. These organoids are differentiated via mesoderm induction of hPSC aggregates and subsequent differentiation into endothelial networks and pericytes in a 3D collagen I-Matrigel matrix. Blood vessels form within 2-3 weeks and can be further grown in scalable suspension culture. Importantly, in vitro-differentiated human blood vessel organoids transplanted into immunocompromised mice gain access to the mouse circulation and specify into functional arteries, arterioles and veins.

Apelin inhibition prevents resistance and metastasis associated with anti-angiogenic therapy.

Angiogenesis is a hallmark of cancer, promoting growth and metastasis. Anti-angiogenic treatment has limited efficacy due to therapy-induced blood vessel alterations, often followed by local hypoxia, tumor adaptation, progression, and metastasis. It is therefore paramount to overcome therapy-induced resistance. We show that Apelin inhibition potently remodels the tumor microenvironment, reducing angiogenesis, and effectively blunting tumor growth. Functionally, targeting Apelin improves vessel function and reduces polymorphonuclear myeloid-derived suppressor cell infiltration. Importantly, in mammary and lung cancer, Apelin prevents resistance to anti-angiogenic receptor tyrosine kinase (RTK) inhibitor therapy, reducing growth and angiogenesis in lung and breast cancer models without increased hypoxia in the tumor microenvironment. Apelin blockage also prevents RTK inhibitor-induced metastases, and high Apelin levels correlate with poor prognosis of anti-angiogenic therapy patients. These data identify a druggable anti-angiogenic drug target that reduces tumor blood vessel densities and normalizes the tumor vasculature to decrease metastases.

Human blood vessel organoids as a model of diabetic vasculopathy.

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.

A reversible haploid mouse embryonic stem cell biobank resource for functional genomics.

The ability to directly uncover the contributions of genes to a given phenotype is fundamental for biology research. However, ostensibly homogeneous cell populations exhibit large clonal variance that can confound analyses and undermine reproducibility. Here we used genome-saturated mutagenesis to create a biobank of over 100,000 individual haploid mouse embryonic stem (mES) cell lines targeting 16,970 genes with genetically barcoded, conditional and reversible mutations. This Haplobank is, to our knowledge, the largest resource of hemi/homozygous mutant mES cells to date and is available to all researchers. Reversible mutagenesis overcomes clonal variance by permitting functional annotation of the genome directly in sister cells. We use the Haplobank in reverse genetic screens to investigate the temporal resolution of essential genes in mES cells, and to identify novel genes that control sprouting angiogenesis and lineage specification of blood vessels. Furthermore, a genome-wide forward screen with Haplobank identified PLA2G16 as a host factor that is required for cytotoxicity by rhinoviruses, which cause the common cold. Therefore, clones from the Haplobank combined with the use of reversible technologies enable high-throughput, reproducible, functional annotation of the genome.

Inhibition of CBLB protects from lethal Candida albicans sepsis.

Fungal infections claim an estimated 1.5 million lives each year. Mechanisms that protect from fungal infections are still elusive. Recognition of fungal pathogens relies on C-type lectin receptors (CLRs) and their downstream signaling kinase SYK. Here we report that the E3 ubiquitin ligase CBLB controls proximal CLR signaling in macrophages and dendritic cells. We show that CBLB associates with SYK and ubiquitinates SYK, dectin-1, and dectin-2 after fungal recognition. Functionally, CBLB deficiency results in increased inflammasome activation, enhanced reactive oxygen species production, and increased fungal killing. Genetic deletion of Cblb protects mice from morbidity caused by cutaneous infection and markedly improves survival after a lethal systemic infection with Candida albicans. On the basis of these findings, we engineered a cell-permeable CBLB inhibitory peptide that protects mice from lethal C. albicans infections. We thus describe a key role for Cblb in the regulation of innate antifungal immunity and establish a novel paradigm for the treatment of fungal sepsis.