Neurological effects of COVID-19 and long-COVID-19, as well as neuroinvasion by SARS-CoV-2, still pose several questions and are of both clinical and scientific relevance. We described the cellular and molecular effects of the human brain microvascular endothelial cells (HBMECs) in vitro exposure by SARS-CoV-2 to understand the underlying mechanisms of viral transmigration through the blood–brain barrier. Despite the low to non-productive viral replication, SARS-CoV-2-exposed cultures displayed increased immunoreactivity for cleaved caspase-3, an indicator of apoptotic cell death, tight junction protein expression, and immunolocalization. Transcriptomic profiling of SARS-CoV-2-challenged cultures revealed endothelial activation via NF-κB non-canonical pathway, including RELB overexpression and mitochondrial dysfunction. Additionally, SARS-CoV-2 led to altered secretion of key angiogenic factors and to significant changes in mitochondrial dynamics, with increased mitofusin-2 expression and increased mitochondrial networks. Endothelial activation and remodeling can further contribute to neuroinflammatory processes and lead to further BBB permeability in COVID-19.

Angiogenesis is considered to mediate the beneficial effects of mesenchymal cell therapy in spinal cord injury. After a moderate balloon-compression injury in rats, injections of either human adipose tissue-derived stromal/stem cells (hADSCs) or their conditioned culture media (CM-hADSC) elicited angiogenesis around the lesion site. Both therapies increased vascular density, but the presence of hADSCs in the tissue was required for the full maturation of new blood vessels. Only animals that received hADSC significantly improved their open field locomotion, assessed by the BBB score. Animals that received CM-hADSC only, presented haemorrhagic areas and lack pericytes. Proteomic analyses of human angiogenesis-related factors produced by hADSCs showed that both pro- and anti-angiogenic factors were produced by hADSCs in vitro, but only those related to vessel maturation were detectable in vivo. hADSCs produced PDGF-AA only after insertion into the injured spinal cord. hADSCs attracted resident pericytes expressing NG2, α-SMA, PDGF-Rβ and nestin to the lesion, potentially contributing to blood vessel maturation. We conclude that the presence of hADSCs in the injured spinal cord is essential for tissue repair.

Neurological effects of COVID-19 and long-COVID-19 as well as neuroinvasion by SARS-CoV-2 still pose several questions and are of both clinical and scientific relevance. We described the cellular and molecular effects of the human brain microvascular endothelial cells (HBMECs) in vitro infection by SARS-CoV-2 to understand the underlying mechanisms of viral transmigration through the Blood-Brain Barrier. Despite the low to non-productive viral replication, SARS-CoV-2-infected cultures displayed increased apoptotic cell death and tight junction protein expression and immunolocalization. Transcriptomic profiling of infected cultures revealed endothelial activation via NF-κB non-canonical pathway, including RELB overexpression, and mitochondrial dysfunction. Additionally, SARS-CoV-2 led to altered secretion of key angiogenic factors and to significant changes in mitochondrial dynamics, with increased mitofusin-2 expression and increased mitochondrial networks. Endothelial activation and remodeling can further contribute to neuroinflammatory processes and lead to further BBB permeability in COVID-19.

Angiogenesis is essential not only during embryogenesis but also in adult physiology and disease, relying on vascular endothelial growth factor (VEGF) gradients to guide tip cell sprouting. Cellular prion protein (PrP ^C ), expressed in several neurovascular unit (NVU) cell types, regulates neuronal and astrocytic differentiation through laminin binding, yet its role in angiogenesis remains understudied. Here, we investigated its function in retinal vascular development. In PrP ^C knockout mice, the superficial retinal plexus exhibited increased tip cell density and branching, accompanied by microglial morphofunctional alterations and reduced Vegf-c expression, features consistent with impaired vascular stability. Conditioned media from PrP ^C knockout microglia was sufficient to increase endothelial instability in vitro, indicating that altered microglial signalling can modulate vascular phenotype. Moreover, Laminin 411 / 511 isoforms and Collagen IV showed decreased expression in the retinal vascular basement membrane, supporting altered basement membrane composition. At later developmental stages, absence of PrP ^C led to increased vertical sprouting into deeper retinal layers, resulting in transient hypervascularization of the deep plexus and defective laminin deposition across all vascular layers. These changes were accompanied by altered ZO-1 distribution and disrupted retinal layer organization, as indicated by reduced inter-plexus distance. Collectively, our findings identify PrP ^C as regulator of sprouting angiogenesis and vascular stabilization in the developing retina. The data support a model in which PrP ^C modulates neurovascular interactions, through both microglia-dependent and endothelial-intrinsic mechanisms, although the relative contribution of these components remains to be determined.