Blood Outgrowth Endothelial Cells Research Articles

The proteomic landscape of in vitro cultured endothelial cells across vascular beds

Blood vessel endothelial cells (EC) display heterogeneity across vascular beds, which is anticipated to drive site-specific vascular pathology. This heterogeneity is assessed using transcriptomics in vivo, and functional assays in vitro, but how proteomes compare across human in vitro cultured ECs remains incompletely characterized. We generated an in-depth human EC proteomic landscape (>8000 proteins) across six organs and two in vitro models in steady-state and upon IFNγ-induced inflammation. EC proteomes displayed a high similarity and organ-specific proteins were limited. Variation between ECs was mainly based on proliferation and differentiation processes in which Blood outgrowth endothelial cells (BOEC) and Human umbilical vein cells (HUVEC) represented the extremes of proteomic phenotypes. The IFNγ response was highly conserved across all samples. Harnessing dynamics in protein abundances we delineated VWF and VE-Cadherin correlation networks. This EC landscape provides an extensive proteomic addition in studying EC biology and heterogeneity from an in vitro perspective.

Exploring the Potential of Saphenous Vein Grafts Ex Vivo: A Model for Intimal Hyperplasia and Re-Endothelialization.

Coronary artery bypass grafting (CABG) utilizing saphenous vein grafts (SVGs) stands as a fundamental approach to surgically treating coronary artery disease. However, the long-term success of CABG is often compromised by the development of intimal hyperplasia (IH) and subsequent graft failure. Understanding the mechanisms underlying this pathophysiology is crucial for improving graft patency and patient outcomes. Objectives: This study aims to explore the potential of an ex vivo model utilizing SVG to investigate IH and re-endothelialization. Methods: A thorough histological examination of 15 surplus SVG procured from CABG procedures at Hospital Canselor Tuanku Muhriz, Malaysia, was conducted to establish their baseline characteristics. Results: SVGs exhibited a mean diameter of 2.65 ± 0.93 mm with pre-existing IH averaging 0.42 ± 0.13 mm in thickness, alongside an observable lack of luminal endothelial cell lining. Analysis of extracellular matrix components, including collagen, elastin, and glycosaminoglycans, at baseline and after 7 days of ex vivo culture revealed no significant changes in collagen but demonstrated increased percentages of elastin and glycosaminoglycans. Despite unsuccessful attempts at re-endothelialization with blood outgrowth endothelial cells, the established ex vivo SVG IH model underscores the multifaceted nature of graft functionality and patency, characterized by IH presence, endothelial impairment, and extracellular matrix alterations post-CABG. Conclusions: The optimized ex vivo IH model provides a valuable platform for delving into the underlying mechanisms of IH formation and re-endothelialization of SVG. Further refinements are warranted, yet this model holds promise for future research aimed at enhancing graft durability and outcomes for CAD patients undergoing CABG.

DNA base editing corrects common hemophilia A mutations and restores factor VIII expression in in vitro and ex vivo models

BackgroundReplacement and nonreplacement therapies effectively control bleeding in hemophilia A (HA) but imply lifelong interventions. Authorized gene addition therapy could provide a cure but still poses questions on durability. FVIIIgene correction would definitively restore factor (F)VIII production, as shown in animal models through nuclease-mediated homologous recombination (HR). However, low efficiency and potential off-target double-strand break still limit HR translatability. ObjectivesTo correct common model single point mutations leading to severe HA through the recently developed double-strand break/HR-independent base editing (BE) and prime editing (PE) approaches. MethodsScreening for efficacy of BE/PE systems in HEK293T cells transiently expressing FVIII variants and validation at DNA (sequencing) and protein (enzyme-linked immunosorbent assay; activated partial thromboplastin time) level in stable clones. Evaluation of rescue in engineered blood outgrowth endothelial cells by lentiviral-mediated delivery of BE. ResultsTransient assays identified the best-performing BE/PE systems for each variant, with the highest rescue of FVIII expression (up to 25% of wild-type recombinant FVIII) for the p.R2166∗ and p.R2228Q mutations. In stable clones, we demonstrated that the mutation reversion on DNA (∼24%) was consistent with the rescue of FVIII secretion and activity of 20% to 30%. The lentiviral-mediated delivery of the selected BE systems was attempted in engineered blood outgrowth endothelial cells harboring the p.R2166∗ and p.R2228Q variants, which led to an appreciable and dose-dependent rescue of secreted functional FVIII. ConclusionOverall data provide the first proof-of-concept for effective BE/PE-mediated correction of HA-causing mutations, which encourage studies in mouse models to develop a personalized cure for large cohorts of patients through a single intervention.

ATP13A3 variants promote pulmonary arterial hypertension by disrupting polyamine transport.

Potential loss-of-function variants of ATP13A3, the gene encoding a P5B-type transport ATPase of undefined function, were recently identified in patients with pulmonary arterial hypertension (PAH). ATP13A3 is implicated in polyamine transport but its function has not been fully elucidated. In this study, we sought to determine the biological function of ATP13A3 in vascular endothelial cells (ECs) and how PAH-associated variants may contribute to disease pathogenesis. We studied the impact of ATP13A3 deficiency and overexpression in EC models [human pulmonary ECs, blood outgrowth ECs (BOECs), and human microvascular EC 1], including a PAH patient-derived BOEC line harbouring an ATP13A3 variant (LK726X). We also generated mice harbouring an Atp13a3 variant analogous to a human disease-associated variant to establish whether these mice develop PAH. ATP13A3 localized to the recycling endosomes of human ECs. Knockdown of ATP13A3 in ECs generally reduced the basal polyamine content and altered the expression of enzymes involved in polyamine metabolism. Conversely, overexpression of wild-type ATP13A3 increased polyamine uptake. Functionally, loss of ATP13A3 was associated with reduced EC proliferation, increased apoptosis in serum starvation, and increased monolayer permeability to thrombin. The assessment of five PAH-associated missense ATP13A3 variants (L675V, M850I, V855M, R858H, and L956P) confirmed loss-of-function phenotypes represented by impaired polyamine transport and dysregulated EC function. Furthermore, mice carrying a heterozygous germline Atp13a3 frameshift variant representing a human variant spontaneously developed a PAH phenotype, with increased pulmonary pressures, right ventricular remodelling, and muscularization of pulmonary vessels. We identify ATP13A3 as a polyamine transporter controlling polyamine homeostasis in ECs, a deficiency of which leads to EC dysfunction and predisposes to PAH. This suggests a need for targeted therapies to alleviate the imbalances in polyamine homeostasis and EC dysfunction in PAH.

Mutations causing premature termination codons discriminate and generate cellular and clinical variability in HHT

AbstractFor monogenic diseases caused by pathogenic loss-of-function DNA variants, attention focuses on dysregulated gene-specific pathways, usually considering molecular subtypes together within causal genes. To better understand phenotypic variability in hereditary hemorrhagic telangiectasia (HHT), we subcategorized pathogenic DNA variants in ENG/endoglin, ACVRL1/ALK1, and SMAD4 if they generated premature termination codons (PTCs) subject to nonsense-mediated decay. In 3 patient cohorts, a PTC-based classification system explained some previously puzzling hemorrhage variability. In blood outgrowth endothelial cells (BOECs) derived from patients with ACVRL1+/PTC, ENG+/PTC, and SMAD4+/PTC genotypes, PTC-containing RNA transcripts persisted at low levels (8%-23% expected, varying between replicate cultures); genes differentially expressed to Bonferroni P < .05 in HHT+/PTC BOECs clustered significantly only to generic protein terms (isopeptide-bond/ubiquitin-like conjugation) and pulse-chase experiments detected subtle protein maturation differences but no evidence for PTC-truncated protein. BOECs displaying highest PTC persistence were discriminated in unsupervised hierarchical clustering of near-invariant housekeeper genes, with patterns compatible with higher cellular stress in BOECs with >11% PTC persistence. To test directionality, we used a HeLa reporter system to detect induction of activating transcription factor 4 (ATF4), which controls expression of stress-adaptive genes, and showed that ENG Q436X but not ENG R93X directly induced ATF4. AlphaFold accurately modeled relevant ENG domains, with AlphaMissense suggesting that readthrough substitutions would be benign for ENG R93X and other less rare ENG nonsense variants but more damaging for Q436X. We conclude that PTCs should be distinguished from other loss-of-function variants, PTC transcript levels increase in stressed cells, and readthrough proteins and mechanisms provide promising research avenues.

Cardioprotective potential of exosomes derived from blood outgrowth endothelial cells in ischemic cardiomyopathy

Abstract Introduction Blood outgrowth endothelial cell (BOEC)-derived exosomes can effectively induce vascular network formation in vitro and mediate therapeutic neovascularization in a skin wound healing model. We hypothesized that BOEC-derived exosomes can enhance myocardial repair in mice after ischemia-reperfusion (I/R) injury. Methods BOECs were isolated and culture-expanded from peripheral blood of patients with severe ischemic cardiomyopathy (ICMP) in normoxic and hypoxic (1% O2) conditions. Exosomes were isolated from the medium by differential ultracentrifugation, and their size, number, and surface markers were determined by nano tracking analysis (NTA) and immunoblot analysis. Myocardial infarction (MI) was induced via transient LAD ligation for 60 min followed by reperfusion. BOEC-derived exosomes and were resuspended in small fractions (120x10^8 particles per 10 µl) 2.5 µl 4 aliquots were injected under direct vision into the epicardial wall of the peri-infarct region. One month later, left ventricular (LV) structure and function were analyzed using a 7T Bruckner MRI with commercial software Segment in mice that received exosome injections or placebo injections (n=10 and n=8, respectively). Results Quantification of exosomes by NTA showed higher concentrations in the medium of BOECs cultured in hypoxia. Immunoblot analysis confirmed robust expression of exosome markers TSG101 and Flotilin-1. One month after intramyocardial exosome injections, heart rate, LV volumes or LV ejection fraction were similar between mice receiving myocardial exosomes injections (n=10) in the border zone as compared to those receiving placebo (n=8). However, in vivo exosome transfer mediated favorable structural remodeling after MI with lower LV mass indices (p=0.01) and better preserved regional wall thickness in all 4 segments receiving exosomes aliquots (p&amp;lt;0.05) (Figure). Conclusions Our results suggest that BOEC-derived exosomes have favorable post-infarction myocardial structural remodeling. Exosomes may constitute an attractive cell-free therapeutic modality.Figure

Factor VIII Is an Endothelial Factor That Promotes Vessel Stability

Background: Hemophilia A (HA) is a rare bleeding disorder caused by the absence or dysfunction of factor VIII (FVIII). Clinical manifestations include spontaneous bleedings that primarily consist of hemarthroses and intracranial hemorrhages. Attenuated microvascular endothelial functionality is observed in HA patients suggesting a dysfunction in endothelial cells (ECs). Current therapeutic practice consists of replacement therapy with recombinant FVIII (rFVIII), either as needed to treat acute hemorrhages, or as prophylaxis to prevent bleeds. It is well established that FVIII is largely secreted by ECs and in particular by sinusoidal endothelial cells in the liver. Healthy and HA ECs can be isolated from the peripheral blood as blood outgrowth endothelial cells (BOECs) or can be differentiated from induced pluripotent stem cells (iPSCs). Here we show that, in addition to its role in blood coagulation, FVIII plays a role in endothelial cell functionality. Aims: To elucidate the potential impact of FVIII on EC stability and to investigate the effect of different rFVIII products on the maintenance of EC functionality. Methods: BOECs isolated from HA patients and healthy donors were used. HA BOECs were treated in vitro with B-domain deleted (BDD; simoctocog alfa) or full-length (FL) rFVIII products, and EC functionality was evaluated by tubulogenic, migration, permeability and proliferation assays. The impact of the different rFVIII products on vessel formation and permeability was evaluated in vivo in NOD/SCID γ-Null (NSG) and NOD/SCID γ-Null HA (NSG-HA) mice. Results: In vitro results demonstrated a weakening in tubulogenesis, migration potential and permeability in HA ECs vs healthy ECs and a significant enhancing of tubule network formation in HA BOECs treated with BDD-rFVIII or FL-rFVIII. Quantification of nodes, junctions, branches and the total length of the vessel-like structures confirmed that treatment of HA BOECs with BDD-rFVIII or FL-rFVIII improved HA BOEC function. Moreover, migration assays of HA BOECs treated with BDD-rFVIII or FL-rFVIII showed that the migration ability of HA BOECs was improved after treatment with either of the rFVIII products. We also evaluated whether rFVIII could ameliorate cell permeability. When treated with either rFVIII, the HA BOEC monolayer was less permeable to fluorescein isothiocyanate (FITC)-labeled dextran compared with that from non-treated HA BOECs. Vessel permeability assays in vivo demonstrated a significant reduction of dye extravasation in NSG-HA mice treated with rFVIII, with an improvement in mice treated with BDD-rFVIII compared with FL-rFVIII. Conclusion: In conclusion, information about the possible extra-coagulative role of FVIII may be crucial to understand the key molecular targets missing in HA patients at the cellular level that impair EC functionality. Knowledge of the possible effect of different rFVIII products on ECs functionality can lead to new therapeutic approaches potentially resulting in safer and more efficient treatment of HA.

The endosomal system of primary human vascular endothelial cells and albumin-FcRn trafficking.

Human serum albumin (HSA) has a long circulatory half-life owing, in part, to interaction with the neonatal Fc receptor (FcRn or FCGRT) in acidic endosomes and recycling of internalised albumin. Vascular endothelial and innate immune cells are considered the most relevant cells for FcRn-mediated albumin homeostasis in vivo. However, little is known about endocytic trafficking of FcRn-albumin complexes in primary human endothelial cells. To investigate FcRn-albumin trafficking in physiologically relevant endothelial cells, we generated primary human vascular endothelial cell lines from blood endothelial precursors, known as blood outgrowth endothelial cells (BOECs). We mapped the endosomal system in BOECs and showed that BOECs efficiently internalise fluorescently labelled HSA predominantly by fluid-phase macropinocytosis. Pulse-chase studies revealed that intracellular HSA molecules co-localised with FcRn in acidic endosomal structures and that the wildtype HSA, but not the non-FcRn-binding HSAH464Q mutant, was excluded from late endosomes and/or lysosomes. Live imaging revealed that HSA is partitioned into FcRn-positive tubules derived from maturing macropinosomes, which are then transported towards the plasma membrane. These findings identify the FcRn-albumin trafficking pathway in primary vascular endothelial cells, relevant to albumin homeostasis.

Origin, prospective identification, and function of circulating endothelial colony-forming cells in mice and humans.

Most circulating endothelial cells are apoptotic, but rare circulating endothelial colony-forming cells (C-ECFCs), also known as blood outgrowth endothelial cells, with proliferative and vasculogenic activity can be cultured; however, the origin and naive function of these C-ECFCs remains obscure. Herein, detailed lineage tracing revealed murine C-ECFCs emerged in the early postnatal period, displayed high vasculogenic potential with enriched frequency of clonal proliferative cells compared with tissue-resident ECFCs, and were not committed to or derived from the BM hematopoietic system but from tissue-resident ECFCs. In humans, C-ECFCs were present in the CD34bright cord blood mononuclear subset, possessed proliferative potential and in vivo vasculogenic function in a naive or cultured state, and displayed a single cell transcriptome sharing some umbilical venous endothelial cell features, such as a higher protein C receptor and extracellular matrix gene expression. This study provides an advance for the field by identifying the origin, naive function, and antigens to prospectively isolate C-ECFCs for translational studies.

Directed self-assembly of a xenogeneic vascularized endocrine pancreas for type 1 diabetes

Intrahepatic islet transplantation is the standard cell therapy for β cell replacement. However, the shortage of organ donors and an unsatisfactory engraftment limit its application to a selected patients with type 1 diabetes. There is an urgent need to identify alternative strategies based on an unlimited source of insulin producing cells and innovative scaffolds to foster cell interaction and integration to orchestrate physiological endocrine function. We previously proposed the use of decellularized lung as a scaffold for β cell replacement with the final goal of engineering a vascularized endocrine organ. Here, we prototyped this technology with the integration of neonatal porcine islet and healthy subject-derived blood outgrowth endothelial cells to engineer a xenogeneic vascularized endocrine pancreas. We validated ex vivo cell integration and function, its engraftment and performance in a preclinical model of diabetes. Results showed that this technology not only is able to foster neonatal pig islet maturation in vitro, but also to perform in vivo immediately upon transplantation and for over 18 weeks, compared to normal performance within 8 weeks in various state of the art preclinical models. Given the recent progress in donor pig genetic engineering, this technology may enable the assembly of immune-protected functional endocrine organs.

The loss of glycocalyx integrity impairs complement factor H binding and contributes to cyclosporine-induced endothelial cell injury.

Calcineurin inhibitors (CNIs) are associated with nephrotoxicity, endothelial cell dysfunction, and thrombotic microangiopathy (TMA). Evolving evidence suggests an important role for complement dysregulation in the pathogenesis of CNI-induced TMA. However, the exact mechanism(s) of CNI-induced TMA remain(s) unknown. Using blood outgrowth endothelial cells (BOECs) from healthy donors, we evaluated the effects of cyclosporine on endothelial cell integrity. Specifically, we determined complement activation (C3c and C9) and regulation (CD46, CD55, CD59, and complement factor H [CFH] deposition) as these occurred on the endothelial cell surface membrane and glycocalyx. We found that exposing the endothelium to cyclosporine resulted in a dose- and time-dependent enhancement of complement deposition and cytotoxicity. We, therefore, employed flow cytometry, Western blotting/CFH cofactor assays, and immunofluorescence imaging to determine the expression of complement regulators and the functional activity and localization of CFH. Notably, while cyclosporine led to the upregulation of complement regulators CD46, CD55, and CD59 on the endothelial cell surface, it also diminished the endothelial cell glycocalyx through the shedding of heparan sulfate side chains. The weakened endothelial cell glycocalyx resulted in decreased CFH surface binding and surface cofactor activity. Our findings confirm a role for complement in cyclosporine-induced endothelial injury and suggest that decreased glycocalyx density, induced by cyclosporine, is a mechanism that leads to complement alternative pathway dysregulation via decreased CFH surface binding and cofactor activity. This mechanism may apply to other secondary TMAs-in which a role for complement has so far not been recognized-and provide a potential therapeutic target and an important marker for patients on calcineurin inhibitors.

Vascular graft with native-like mechanical properties

Elastomeric SG-80A and SG-93A polyurethanes (PUs) were electrospun separately to develop microfibrous vascular grafts. The mechanical properties, suture retention strength, and burst pressure of the grafts were compared to coronary arteries (CA). Biodegradation of the graft materials and adhesion of porcine blood outgrowth endothelial cells (PBOECs) to the graft surfaces were evaluated in vitro. The SG-80A grafts showed tensile properties, suture retention strength, and burst pressure lower than SG-93A grafts but similar to CA. No graft materials were degraded in the enzymatic or oxidative environment over 30 days. Both grafts supported PBOEC adhesion.

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.

Vascular Transcriptomics: Investigating Endothelial Activation and Vascular Dysfunction Using Blood Outgrowth Endothelial Cells, Organ-Chips, and RNA Sequencing.

Vascular organ-chip or vessel-chip technology has significantly impacted our ability to model microphysiological vasculature. These biomimetic platforms have garnered significant interest from scientists and pharmaceutical companies as drug screening models. However, these models still lack the inclusion of patient-specific vasculature in the form of patient-derived endothelial cells. Blood outgrowth endothelial cells are patient blood-derived endothelial progenitors that have gained interest from the vascular biology community as an autologous endothelial cell alternative and have also been incorporated with the vessel-chip model. Next-generation sequencing techniques like RNA sequencing can further unlock the potential of personalized vessel-chips in discerning patient-specific hallmarks of endothelial dysfunction. Here we present a detailed protocol for (1) isolating blood outgrowth endothelial cells from patient blood samples, (2) culturing them in microfluidic vessel-chips, (3) isolating and preparing RNA from individual vessel-chips for sequencing, and (4) performing differential gene expression and bioinformatics analyses of vascular dysfunction and endothelial activation pathways. This method focuses specifically on identification of pathways and genes involved in vascular homeostasis and pathology, but can easily be adapted for the requirements of other systems. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Isolation of blood outgrowth endothelial cells from patient blood Basic Protocol 2: Culture of blood outgrowth endothelial cells in microfluidic vessel-chips Basic Protocol 3: Isolation of RNA from autologous vessel-chips Basic Protocol 4: Differential gene expression and bioinformatics analyses of endothelial activation pathways.

241.3: Generation of Prevascularized Endocrine Constructs to Treat Type 1 Diabetes

Introduction: The goal of our study was to generate a functional, prevascularized endocrine constructs utilizing amniotic membrane derived hydrogel, islets and blood outgrowth endothelial cells (BOECs) to be transplanted in diabetic hosts. Methods: Human amniotic membranes were dissected from placentas decellularized, lyophilized, and solubilized to obtain hydrogels. DNA quantification and scanning electron microscopy showed complete removal of cellular components and preserved extracellular matrix. Characterization studies demonstrated widespread distribution of all essential structural proteins, including collagen, GAGs and laminin. The islets and BOECs were admixed in amnion derived hydrogels and cultured in specially designed media to enhance endothelial cell assembly into tubular, vascular-like structures. Constructs were kept under culture for 3 days. Glucose stimulated insulin secretion (GSIS) tests showed an adequate insulin secretion in response to high glucose stimulation, confirming the functional activity of the prevascularized endocrine constructs. Results: To test in vivo biocompatibility and function, the vascularized constructs generated from 500 IEQ rat islets and 2× 105 human derived BOECs were implanted under the skin of the diabetic NSG mice. Transplantation of the constructs led to rapid and long-term (90 days) normalization of blood glucose levels. Removal of the grafts led to recurrence of hyperglycemia within 24 hours, indicating that the transplanted constructs was responsible for normalized glucose levels. Histological analysis of the explanted grafts revealed healthy islet morphology and perfect revascularization. Grafts stained positive for insulin and human specific CD 31 indicating presence of human endothelial cells in newly formed intra-islet micro vessels. Conclusion: Our findings show that amnion derived hydrogel seeded with endocrine pancreatic tissue and endothelial cells could be used for functional, preveascularized endocrine construct bioengineering. This work is supported by grants from the European Commission (Horizon 2020 Framework Program; VANGUARD grant 874700), the European Foundation for the Study of Diabetes (EFSD), the Juvenile Diabetes Research Foundation (JDRF; grant 3-SRA-2020-926-S-B) and the Shota Rustaveli National Science Foundation (grant FR-19-19760).

Exploring Endothelial Colony-Forming Cells to Better Understand the Pathophysiology of Disease: An Updated Review.

Endothelial cell (EC) dysfunction has been implicated in a variety of pathological conditions. The collection of ECs from patients is typically conducted postmortem or through invasive procedures, such as surgery and interventional procedures, hampering efforts to clarify the role of ECs in disease onset and progression. In contrast, endothelial colony-forming cells (ECFCs), also termed late endothelial progenitor cells, late outgrowth endothelial cells, blood outgrowth endothelial cells, or endothelial outgrowth cells, are obtained in a minimally invasive manner, namely, by the culture of human peripheral blood mononuclear cells in endothelial growth medium. ECFCs resemble mature ECs phenotypically, genetically, and functionally, making them excellent surrogates for ECs. Numerous studies have been performed that examined ECFC function in conditions such as coronary artery disease, diabetes mellitus, hereditary hemorrhagic telangiectasia, congenital bicuspid aortic valve disease, pulmonary arterial hypertension, venous thromboembolic disease, and von Willebrand disease. Here, we provide an updated review of studies using ECFCs that were performed to better understand the pathophysiology of disease. We also discuss the potential of ECFCs as disease biomarkers and the standardized methods to culture, quantify, and evaluate ECFCs and suggest the future direction of research in this field.

Next generation personalized blood vessel‐on‐chip: Mimicking patient‐specific pathophysiology in sickle cell disease through blood‐derived endothelial progenitors

Advances in tissue engineering and organ‐chip technology have accelerated in vitro research of the vascular system. Incorporating patient‐derived endothelial cells either through direct tissue biopsies or stem cell differentiation techniques further enhance the impact of organ‐chips on precision medicine. However, these methods pose certain challenges and might be difficult to adopt in lab, thereby limiting the predictive power of organ‐chips. Here we report the use of Blood Outgrowth Endothelial Cells (BOECs) directly isolated from patient blood as an alternative to primary and iPSC‐derived endothelial cells for organ‐chip applications. BOECs exhibit the gold‐standard endothelial hallmarks of the “cobblestone” morphology in vitro. When compared to primary HUVECs and iPSC‐derived endothelial cells, healthy BOECs reveal similar levels of growth rates, migration capabilities, de novo vessel formation, response to fluid shear stress and exogenous cytokine inflammation in vitro. To study patient‐specificity, we derive BOECs from two sickle cell disease (SCD) patients with known differences in clinical severity of the disease. Through next generation RNA sequencing, differential gene expression (DGE) analysis and qRT‐PCR, we reveal that SCD patient‐derived BOECs are indeed activated and that the more severe SCD patient exhibited a greater magnitude of activation. This is further confirmed by real‐time recalcified whole blood perfusion through endothelialized vessel‐chips. Blood‐derived endothelial cells may be employed in preclinical research for developing more robust and personalized next‐generation disease models that can ultimately enable clinicians in identifying individuals at high risk of stroke or cardiovascular complications.

Endothelial-immune crosstalk contributes to vasculopathy in nonalcoholic fatty liver disease.

The top cause of mortality in patients with nonalcoholic fatty liver disease (NAFLD) is cardiovascular complications. However, mechanisms of NAFLD‐associated vasculopathy remain understudied. Here, we show that blood outgrowth endothelial cells (BOECs) from NAFLD subjects exhibit global transcriptional upregulation of chemokines and human leukocyte antigens. In mouse models of diet‐induced NAFLD, we confirm heightened endothelial expressions of CXCL12 in the aortas and the liver vasculatures, and increased retention of infiltrated leukocytes within the vessel walls. To elucidate endothelial‐immune crosstalk, we performed immunoprofiling by single‐cell analysis, uncovering T cell intensification in NAFLD patients. Functionally, treatment with a CXCL12‐neutralizing antibody is effective at moderating the enhanced chemotactic effect of NAFLD BOECs in recruiting CD8+ T lymphocytes. Interference with the CXCL12‐CXCR4 axis using a CXCR4 antagonist also averts the impact of immune cell transendothelial migration and restores endothelial barrier integrity. Clinically, we detect threefold more circulating damaged endothelial cells in NAFLD patients than in healthy controls. Our work provides insight into the modulation of interactions with effector immune cells to mitigate endothelial injury in NAFLD.

Stent-based delivery of AAV2 vectors encoding oxidation-resistant apoA1

In-stent restenosis (ISR) complicates revascularization in the coronary and peripheral arteries. Apolipoprotein A1 (apoA1), the principal protein component of HDL possesses inherent anti-atherosclerotic and anti-restenotic properties. These beneficial traits are lost when wild type apoA1(WT) is subjected to oxidative modifications. We investigated whether local delivery of adeno-associated viral (AAV) vectors expressing oxidation-resistant apoA1(4WF) preserves apoA1 functionality. The efflux of 3H-cholesterol from macrophages to the media conditioned by endogenously produced apoA1(4WF) was 2.1-fold higher than for apoA1(WT) conditioned media in the presence of hypochlorous acid emulating conditions of oxidative stress. The proliferation of apoA1(WT)- and apoA1(4FW)-transduced rat aortic smooth muscle cells (SMC) was inhibited by 66% ± 10% and 65% ± 11%, respectively, in comparison with non-transduced SMC (p < 0.001). Conversely, the proliferation of apoA1(4FW)-transduced, but not apoA1(WT)-transduced rat blood outgrowth endothelial cells (BOEC) was increased 41% ± 5% (p < 0.001). Both apoA1 transduction conditions similarly inhibited basal and TNFα-induced reactive oxygen species in rat aortic endothelial cells (RAEC) and resulted in the reduced rat monocyte attachment to the TNFα-activated endothelium. AAV2-eGFP vectors immobilized reversibly on stainless steel mesh surfaces through the protein G/anti-AAV2 antibody coupling, efficiently transduced cells in culture modeling stent-based delivery. In vivo studies in normal pigs, deploying AAV2 gene delivery stents (GDS) preloaded with AAV2-eGFP in the coronary arteries demonstrated transduction of the stented arteries. However, implantation of GDS formulated with AAV2-apoA1(4WF) failed to prevent in-stent restenosis in the atherosclerotic vasculature of hypercholesterolemic diabetic pigs. It is concluded that stent delivery of AAV2-4WF while feasible, is not effective for mitigation of restenosis in the presence of severe atherosclerotic disease.

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

BackgroundPolypoidal choroidal vasculopathy (PCV), a subtype of age-related macular degeneration (AMD), is a global leading cause of vision loss in older populations. Distinct from typical AMD, PCV is characterized by polyp-like dilatation of blood vessels and turbulent blood flow in the choroid of the eye. Gold standard anti-vascular endothelial growth factor (anti-VEGF) therapy often fails to regress polypoidal lesions in patients. Current animal models have also been hampered by their inability to recapitulate such vascular lesions. These underscore the need to identify VEGF-independent pathways in PCV pathogenesis.ResultsWe cultivated blood outgrowth endothelial cells (BOECs) from PCV patients and normal controls to serve as our experimental disease models. When BOECs were exposed to heterogeneous flow, single-cell transcriptomic analysis revealed that PCV BOECs preferentially adopted migratory-angiogenic cell state, while normal BOECs undertook proinflammatory cell state. PCV BOECs also had a repressed protective response to flow stress by demonstrating lower mitochondrial functions. We uncovered that elevated hyaluronidase-1 in PCV BOECs led to increased degradation of hyaluronan, a major component of glycocalyx that interfaces between flow stress and vascular endothelium. Notably, knockdown of hyaluronidase-1 in PCV BOEC improved mechanosensitivity, as demonstrated by a significant 1.5-fold upregulation of Krüppel-like factor 2 (KLF2) expression, a flow-responsive transcription factor. Activation of KLF2 might in turn modulate PCV BOEC migration. Barrier permeability due to glycocalyx impairment in PCV BOECs was also reversed by hyaluronidase-1 knockdown. Correspondingly, hyaluronidase-1 was detected in PCV patient vitreous humor and plasma samples.ConclusionsHyaluronidase-1 inhibition could be a potential therapeutic modality in preserving glycocalyx integrity and endothelial stability in ocular diseases with vascular origin.