Hyaluronidase-1-mediated glycocalyx impairment underlies endothelial abnormalities in polypoidal choroidal vasculopathy

Origins and functional differences of blood endothelial cells

The interests in blood endothelial cells arise from their therapeutic potential in vascular repair and regeneration. Our understanding of blood endothelial cells that exist in the circulation has been evolving significantly from the original concept of endothelial progenitor cells. Many studies have uncovered heterogeneities of blood endothelial subtypes where some cells express both endothelial and hematopoietic antigens, and others possess either mature or immature endothelial markers. Due to the lack of definitive cell marker identities, there have been momentums in the field to adopt a technical-oriented labeling system based on the cells' involvement in postnatal neovascularization and cell culture derivatives. Our review streamlines nomenclatures for blood endothelial subtypes and standardizes understanding of their functional differences. Broadly, we will discuss about myeloid angiogenic cells (MACs), endothelial colony-forming cells (ECFCs), blood outgrowth endothelial cells (BOECs) and circulating endothelial cells (CECs). The strategic location of blood endothelial cells confers them essential roles in supporting physiological processes. MACs exert angiogenic effects through paracrine mechanisms, while ECFCs are recruited to sites of vascular injury to participate directly in new vessel formation. BOECs are an in vitro derivative of ECFCs. CECs are shed into the bloodstream from damaged vessels, hence reflective of endothelial dysfunction. With clarity on the functional attributes of blood endothelial subtypes, we present recent advances in their applications in disease modelling, along with serving as biomarkers of vascular tissue homeostasis.

Single-Cell Transcriptome of Wet AMD Patient-Derived Endothelial Cells in Angiogenic Sprouting

Age-related macular degeneration (AMD) is a global leading cause of visual impairment in older populations. ‘Wet’ AMD, the most common subtype of this disease, occurs when pathological angiogenesis infiltrates the subretinal space (choroidal neovascularization), causing hemorrhage and retinal damage. Gold standard anti-vascular endothelial growth factor (VEGF) treatment is an effective therapy, but the long-term prevention of visual decline has not been as successful. This warrants the need to elucidate potential VEGF-independent pathways. We generated blood out-growth endothelial cells (BOECs) from wet AMD and normal control subjects, then induced angiogenic sprouting of BOECs using a fibrin gel bead assay. To deconvolute endothelial heterogeneity, we performed single-cell transcriptomic analysis on the sprouting BOECs, revealing a spectrum of cell states. Our wet AMD BOECs share common pathways with choroidal neovascularization such as extracellular matrix remodeling that promoted proangiogenic phenotype, and our ‘activated’ BOEC subpopulation demonstrated proinflammatory hallmarks, resembling the tip-like cells in vivo. We uncovered new molecular insights that pathological angiogenesis in wet AMD BOECs could also be driven by interleukin signaling and amino acid metabolism. A web-based visualization of the sprouting BOEC single-cell transcriptome has been created to facilitate further discovery research.

Analysis of the aqueous humor lipid profile in patients with polypoidal choroidal vasculopathy

This study aimed to investigate the lipid profiles of aqueous humor from polypoidal choroidal vasculopathy (PCV) patients and identify potential biomarkers to increase the understanding of PCV pathomechanism. An ultra-high performance liquid chromatography-tandem mass spectrometry based untargeted lipidomic analysis was performed to acquire lipid profiles of aqueous humor of PCV patients and control subjects. Differentially expressed lipids were identified by univariate and multivariate analyses. A receiver operator characteristic curve (ROC) analysis was conducted to confirm the potential of identified lipids as biomarkers. Sixteen PCV patients and twenty-eight control subjects were enrolled in this study. In total, we identified 33 lipid classes and 639 lipid species in aqueous humor using the LipidSearch software. Of them, 50 differential lipids were obtained by combining univariate and multivariate statistical analyses (VIP>1 and P < 0.05), and 19 potential lipid biomarkers were identified by ROC analysis. In addition, significant alterations were found in several metabolic pathways, including glycerophospholipid, glycerolipid, and glycosylphosphatidylinositol-anchor biosynthesis. This study is the first to systematically characterize the alterations in lipid profiles in aqueous humor of PCV patients and screen for the potential lipid biomarkers for PCV diagnosis and treatment intervention. The results of this study are likely to broaden our understanding of the pathogenesis of PCV and contribute to improvements in the diagnosis and treatment of the disease.