Mila Borri

Attention to exploring endothelial cell (EC) metabolism is increasing, but a holistic perspective on the metabolic adaptations of ECs during angiogenic proliferation is still missing. Here, we use a previously in-house developed computational EC-adapted genome-scale metabolic model that recapitulates known metabolic features in proliferating ECs to predict novel pathways central to biomass synthesis. We unveil the metabolic function of the glutamate–aspartate antiporter SLC25A13, previously overlooked in ECs, as a key regulator of glutamine utilization and provide evidence regarding its contribution to the generation of cholesterol and other biomass precursors. To our knowledge, predominant SLC25A13-linked utilization of glutamine for cholesterol synthesis has not been reported in other cell types in prior literature. Silencing of SLC25A13 in ECs reduced proliferation and vessel sprouting in vitro as well as in a choroidal neovascularization mouse model. These insights underscore the particular characteristics of EC metabolism and may warrant further evaluation of SLC25A13 as a putative new anti-angiogenic target.

Blood–brain barrier (BBB) integrity is critical for brain homeostasis, with malfunctions contributing to neurovascular and neurodegenerative disorders. Mechanistic studies on BBB function have been mostly conducted in rodent and in vitro models, which recapitulate some disease features, but have limited translatability to humans and pose challenges for drug discovery. Here we report on a fully human induced pluripotent stem (iPS)-cell-derived, microfluidic three-dimensional (3D) BBB model consisting of endothelial cells (ECs), mural cells and astrocytes. Our model expresses typical fate markers, forms a barrier in vessel-like tubes and enables perfusion, including with human blood. Deletion of FOXF2 in ECs, a major risk gene for cerebral small vessel disease, induced key features of BBB dysfunction, including compromised cell junction integrity and enhanced caveolae formation. Proteomic analysis revealed dysregulated endocytosis and cell junction pathways. Disease features phenocopied those seen in mice with EC-specific Foxf2 deficiency. Moreover, lipid-nanoparticle-based treatment with Foxf2 mRNA rescued BBB deficits, demonstrating the potential for drug development.

Global population aging is an escalating challenge in modern society, especially as it impairs the function of multiple organs and increases the burden of age-related diseases. The kidneys, in particular, experience function decline, reduced regenerative capacity, and increased susceptibility to injury as they age. As a result, the prevalence of chronic kidney disease (CKD) rises with aging, further contributing to the growing health burden in older populations. One of the key factors in this process is the dysfunction of specialized renal endothelial cells (RECs), which are essential for maintaining kidney health by regulating blood flow and supporting filtration, solute and water reabsorption, and vascular integrity. As the kidneys age, REC dysfunction drives vascular and microenvironmental changes, contributing to the overall decline in kidney function. In this review, we outline the structural and functional effects of aging on the kidney’s macrovascular and microvascular compartments and provide a phenotypic description of the aged endothelium. We particularly focus on the molecular and metabolic rewiring driving and sustaining growth-arrested EC senescence phenotype. We finally give an overview of senotherapies acting on ECs, especially of those modulating metabolism. Given that the pathophysiological processes underlying kidney aging largely overlap with those observed in CKD, REC rejuvenation could also benefit patients with CKD. Moreover, such interventions may hold promise in improving the outcomes of aged kidney transplants. Hence, advancing our understanding of REC and kidney aging will create opportunities for innovations that could improve outcomes for both elderly individuals and patients with CKD.

Human induced pluripotent stem cell-derived kidney organoids have potential for disease modeling and to be developed into clinically transplantable auxiliary tissue. However, they lack a functional vasculature, and the sparse endogenous endothelial cells (ECs) are lost upon prolonged culture in vitro, limiting maturation and applicability. Here, we use intracoelomic transplantation in chicken embryos followed by single-cell RNA sequencing and advanced imaging platforms to induce and study vasculogenesis in kidney organoids. We show expansion of human organoid-derived ECs that reorganize into perfused capillaries and form a chimeric vascular network with host-derived blood vessels. Ligand-receptor analysis infers extensive potential interactions of human ECs with perivascular cells upon transplantation, enabling vessel wall stabilization. Perfused glomeruli display maturation and morphogenesis to capillary loop stage. Our findings demonstrate the beneficial effect of vascularization on not only epithelial cell types, but also the mesenchymal compartment, inducing the expansion of ´on target´ perivascular stromal cells, which in turn are required for further maturation and stabilization of the neo-vasculature. The here described vasculogenic capacity of kidney organoids will have to be deployed to achieve meaningful glomerular maturation and kidney morphogenesis in vitro.

Complex multicellular life in mammals relies on functional cooperation of different organs for the survival of the whole organism. The kidneys play a critical part in this process through the maintenance of fluid volume and composition homeostasis, which enables other organs to fulfil their tasks. The renal endothelium exhibits phenotypic and molecular traits that distinguish it from endothelia of other organs. Moreover, the adult kidney vasculature comprises diverse populations of mostly quiescent, but not metabolically inactive, endothelial cells (ECs) that reside within the kidney glomeruli, cortex and medulla. Each of these populations supports specific functions, for example, in the filtration of blood plasma, the reabsorption and secretion of water and solutes, and the concentration of urine. Transcriptional profiling of these diverse EC populations suggests they have adapted to local microenvironmental conditions (hypoxia, shear stress, hyperosmolarity), enabling them to support kidney functions. Exposure of ECs to microenvironment-derived angiogenic factors affects their metabolism, and sustains kidney development and homeostasis, whereas EC-derived angiocrine factors preserve distinct microenvironment niches. In the context of kidney disease, renal ECs show alteration in their metabolism and phenotype in response to pathological changes in the local microenvironment, further promoting kidney dysfunction. Understanding the diversity and specialization of kidney ECs could provide new avenues for the treatment of kidney diseases and kidney regeneration.