iPSC-derived Endothelial Cells Research Articles

SARS-CoV-2 causes dysfunction in human iPSC-derived brainmicrovascular endothelial cells potentially by modulating the Wnt signaling pathway.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19), which is associated with various neurological symptoms, including nausea, dizziness, headache, encephalitis, and epileptic seizures. SARS-CoV-2 is considered to affect the central nervous system (CNS) by interacting with the blood-brain barrier (BBB), which is defined by tight junctions that seal paracellular gaps between brain microvascular endothelial cells (BMECs). Although SARS-CoV-2 infection of BMECs has been reported, the detailed mechanism has not been fully elucidated. Using the original strain of SARS-CoV-2, the infection in BMECs was confirmed by a detection of intracellular RNA copy number and localization of viral particles. BMEC functions were evaluated by measuring transendothelial electrical resistance (TEER), which evaluates the integrity of tight junction dynamics, and expression levels of proinflammatory genes. BMEC signaling pathway was examined by comprehensive RNA-seq analysis. We observed that iPSC derived brain microvascular endothelial like cells (iPSC-BMELCs) were infected with SARS-CoV-2. SARS-CoV-2 infection resulted in decreased TEER. In addition, SARS-CoV-2 infection decreased expression levels of tight junction markers CLDN3 and CLDN11. SARS-CoV-2 infection also increased expression levels of proinflammatory genes, which are known to be elevated in patients with COVID-19. Furthermore, RNA-seq analysis revealed that SARS-CoV-2 dysregulated the canonical Wnt signaling pathway in iPSC-BMELCs. Modulation of the Wnt signaling by CHIR99021 partially inhibited the infection and the subsequent inflammatory responses. These findings suggest that SARS-CoV-2 infection causes BBB dysfunction via Wnt signaling. Thus, iPSC-BMELCs are a useful in vitro model for elucidating COVID-19 neuropathology and drug development.

Abstract LB387: Microphysiological modeling of gastric cancer vasculature using iPSC-derived endothelial cells

Abstract Generated induced pluripotent stem cells (iPSCs) from the blood of patients with advanced gastric cancer, differentiating them into endothelial cells and fibroblasts. Utilizing microfluidic 3D cell culture, we intricately reconstructed the observed abnormal blood vessels in gastric cancer patients in a three-dimensional format, capturing real-time neovasculature. Applying deep learning techniques, we virtually labeled the growing blood vessels with fluorescence, unveiling thin and tortuous morphological characteristics specific to patient iPSCs, distinct from those derived from human umbilical cord endothelial cells. The development of a tumor model, vascularized with cancer cells from the same donor, establishes a versatile testbed for evaluating personalized cancer vascular models. Through comprehensive morphological and functional assessments, this platform facilitates screening for patient-specific combination therapies and holds promise as a model for immune response testing. Citation Format: Jihoon Ko, Noo Li Jeon, Young Sun Oh. Microphysiological modeling of gastric cancer vasculature using iPSC-derived endothelial cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB387.

Liver specification of human iPSC-derived endothelial cells transplanted into mouse liver

Background & AimsLiver sinusoidal endothelial cells (LSECs) are important in liver development, regeneration, and pathophysiology, but the differentiation process underlying their tissue-specific phenotype is poorly understood and difficult to study because primary human cells are scarce. The aim of this study was to use human induced pluripotent stem cell (hiPSC)-derived LSEC-like cells to investigate the differentiation process of LSECs. MethodshiPSC-derived endothelial cells (iECs) were transplanted into the livers of Fah−/−/Rag2−/−/Il2rg−/− mice and assessed over a 12-week period. Lineage tracing, immunofluorescence, flow cytometry, plasma human factor VIII measurement, and bulk and single cell transcriptomic analysis were used to assess the molecular and functional changes that occurred following transplantation. ResultsProgressive and long-term repopulation of the liver vasculature occurred as iECs expanded along the sinusoids between hepatocytes and increasingly produced human factor VIII, indicating differentiation into LSEC-like cells. To chart the developmental profile associated with LSEC specification, the bulk transcriptomes of transplanted cells between 1 and 12 weeks after transplantation were compared against primary human adult LSECs. This demonstrated a chronological increase in LSEC markers, LSEC differentiation pathways, and zonation. Bulk transcriptome analysis suggested that the transcription factors NOTCH1, GATA4, and FOS have a central role in LSEC specification, interacting with a network of 27 transcription factors. Novel markers associated with this process included EMCN and CLEC14A. Additionally, single cell transcriptomic analysis demonstrated that transplanted iECs at 4 weeks contained zonal subpopulations with a region-specific phenotype. ConclusionsCollectively, this study confirms that hiPSCs can adopt LSEC-like features and provides insight into LSEC specification. This humanised xenograft system can be applied to further interrogate LSEC developmental biology and pathophysiology, bypassing current logistical obstacles associated with primary human LSECs. Impact and implicationsLiver sinusoidal endothelial cells (LSECs) are important cells for liver biology, but better model systems are required to study them. We present a pluripotent stem cell xenografting model that produces human LSEC-like cells. A detailed and longitudinal transcriptomic analysis of the development of LSEC-like cells is included, which will guide future studies to interrogate LSEC biology and produce LSEC-like cells that could be used for regenerative medicine.

Abstract WMP118: Utilizing Patient-Derived Induced Pluripotent Stem Cells as a Cellular Model for Studying Moyamoya Disease

Introduction: Moyamoya disease (MMD) is a rare cerebrovascular disease that can lead to stroke. A histopathological characteristic in MMD is the thickening of the intimal layer that causes narrowing of the vessel, suggesting dysfunctions in the vascular smooth muscle cells (VSMCs) and endothelial cells (ECs). The mechanism of MMD is largely unknown, due to a lack of established MMD-specific cellular or animal models. In this study, we established patient-derived cellular co-culture models using MMD iPSC-derived ECs and VSMCs. We also generated a 3D vascular organoid model to more closely mimic the MMD vasculature and function. Methods: Peripheral blood mononuclear cells (PBMCs) from MMD patients or healthy controls were used to generate iPSCs (n=4 per group). Differentiated ECs and VSMCs were validated and their functional characteristics were investigated in single and co-cultures. For co-cultures, ECs and VSMCs were labeled with Vibrant cell labeling dyes (DiO and DiD), followed by either transwell migration assay (ECs on bottom of cell culture plate and VSMCs on top Transwell insert) or in vitro angiogenic tube formation assay. Control and MMD iPSCs were used to generate 3D cellular organoids, and their cellular characteristics were examined using immunohistochemistry with antibodies labeling ECs and VSMCs. Results: While single cultures of ECs displayed similar tube formation patterns between control and MMD, co-cultures of ECs with VSMCs showed that MMD ECs failed to stabilize in vitro angiogenic tubes and formed aggregates at 24hr, when compared to control ECs. Transwell migration assays showed MMD VSMCs migrated faster than control VSMCs. Immunostaining of organoids with EC and VSMC markers showed notable differences in cellular composition, with MMD organoid showing compromised integrity of vascular networks, when compared with controls. Conclusions: We have established 3D organoid cellular models and in vitro co-cultures using MMD patient-derived iPSCs. Our co-culture studies revealed functional impairment in MMD EC/VSMC and organoid models revealed distinct characteristics in their vascular networks, possibly contributing to MMD pathology. These results shed useful insight into the cellular and molecular mechanisms driving MMD.

IPSC-Derived Endothelial Cells Reveal LDLR Dysfunction and Dysregulated Gene Expression Profiles in Familial Hypercholesterolemia.

Defects in the low-density lipoprotein receptor (LDLR) are associated with familial hypercholesterolemia (FH), manifested by atherosclerosis and cardiovascular disease. LDLR deficiency in hepatocytes leads to elevated blood cholesterol levels, which damage vascular cells, especially endothelial cells, through oxidative stress and inflammation. However, the distinctions between endothelial cells from individuals with normal and defective LDLR are not yet fully understood. In this study, we obtained and examined endothelial derivatives of induced pluripotent stem cells (iPSCs) generated previously from conditionally healthy donors and compound heterozygous FH patients carrying pathogenic LDLR alleles. In normal iPSC-derived endothelial cells (iPSC-ECs), we detected the LDLR protein predominantly in its mature form, whereas iPSC-ECs from FH patients have reduced levels of mature LDLR and show abolished low-density lipoprotein uptake. RNA-seq of mutant LDLR iPSC-ECs revealed a unique transcriptome profile with downregulated genes related to monocarboxylic acid transport, exocytosis, and cell adhesion, whereas upregulated signaling pathways were involved in cell secretion and leukocyte activation. Overall, these findings suggest that LDLR defects increase the susceptibility of endothelial cells to inflammation and oxidative stress. In combination with elevated extrinsic cholesterol levels, this may result in accelerated endothelial dysfunction, contributing to early progression of atherosclerosis and other cardiovascular pathologies associated with FH.

In Vivo Reprogramming of Adult Liver Sinusoidal Vascular Endothelial Cells into a Hematopoietic Stem and Progenitor Cell Niche

Hematopoietic stem and progenitor cells (HSPCs) reside in specialized microenvironments known as the HSPC niche. Vascular endothelial cells (ECs) are one of the most abundant and significant components of the niche, providing known supportive factors such as E-selectin, CXCL12, and SCF. During marrow stress, extramedullary hematopoiesis can occur in the liver or spleen, but the process is inefficient. The sinusoidal vessels of the liver share many similarities with marrow sinusoids. Here, we aim to identify the transcription factor (TF) code that specifies the vascular EC fate in HSPC marrow niche by conducting differential gene expression analysis with the non-niche supportive ECs of the liver. We performed scRNAseq analysis on FACS-isolated ECs from adult zebrafish kidney marrow and liver. We found that these ECs express conserved sinusoidal genes, such as sele, flt4 and gpr182. However, marrow ECs have significantly higher expression of HSPC niche supportive genes, including mrc1a, lyve1b and cxcl12a. We further identified putative TFs that are uniquely upregulated in the marrow ECs, namely tfec, mafbb, foxp4, irf8 and hoxb8a. The expression of these candidate TFs was conserved in the mammalian bone marrow ECs, as shown by relevant mouse bone marrow scRNA-seq and human bone marrow RNA-seq analyses. To determine whether these candidate TFs can functionally specify a HSPC niche EC fate, we selectively overexpressed them using a zebrafish liver sinusoidal EC-specific enhancer in vivo. Upon the overexpression of tfec and mafbb together, we found adult zebrafish liver sinusoidal ECs significantly upregulated key genes known for HSPC niche supportive functions in both embryonic and adult zebrafish HSPC niches, including mrc1a (log2FC=4.9, p<0.005) and lyve1b (log2FC=3.6, p<0.005) and dab2 (log2FC=5.0, p<0.005). Overexpression of TFEC and MAFB in human iPSC-derived ECs showed upregulation of HPSC niche supportive genes that we previously identified from zebrafish in vivo studies, including LYVE1 (log2FC=5.6, p<0.005) and DAB2 (log2FC=1.1, p<0.005) . Notably, previously published HSPC niche genes, including CXCL12(log2FC=5.1 p< 0.005) , PTN (log2FC=2.6 p<0.005) and JAG1 (log2FC=1.7 p<0.005), are also upregulated upon TFEC and MAFB overexpression. Furthermore, gene ontology analysis revealed an enrichment of genes related to cell adhesion (p<0.005), migration (p<0.005), and extravasation pathways (p=0.014). A colony-forming unit (CFU) assay of CD34+CD45+ HSPCs co-cultured with TFEC and MAFB overexpressing hiPSC-derived ECs had significantly greater numbers of CFUs compared to those co-cultured with hiPSC-derived ECs without the TF overexpression: CFU-GEMM (23.3±2.4 vs. 10.0±2.1, p=0.004), CFU-G (89.3±13.4 vs. 46.0±4.2, p=0.027), and CFU-E (42.3±3.3 vs. 26.7±0.9, p=0.021). Our findings revealed a TF code that specifies the HSPC niche supportive fate of vascular ECs and distinguishes vascular ECs in the hematopoietic niche vs. non-niche organs. These results may translate into novel therapies targeting the sinusoidal vascular niches to better stimulate and support human HSPCs.

Abstract 14173: Generation and Characterization of Clinically Relevant Disease Models for Port Wine Birthmark Using Induced Pluripotent Stem Cells

Introduction: Port Wine Birthmark (PWB) is a congenital vascular malformation with a progressive development. The current treatments for PWB are Pulse Dye Laser and Photodynamic Laser Treatment. However, the efficacy of blanching the birthmark is inadequate, and the reoccurrence after treatment is a major clinical barrier. Developing clinically relevant disease models that can be used for mechanistic and therapeutic development studies is the critical unmet need. Induced pluripotent stem cell (iPSC) is a powerful tool in different disease models and drug discovery. Besides, iPSC-derived cells can retain and exhibit the disease phenotypes from donors. Therefore, iPSCs and their-derived vascular cells could be potential models for PWB study. Hypothesis: It was hypothesized that PWB iPSC-derived endothelial cell (EC) could retain the disease phenotypes, thus serving as clinically relevant disease models. Methods: PWB lesions and normal skin biopsies were cultured for outgrowths of fibroblasts, followed by reprogramming using CytoTune-iPS Kit. The induction of PWB and normal iPSC into EC was performed using reported protocols with tailored modifications. Bulk RNA and ATAC-seq were performed on both iPSC and iPSC-derived EC. The functional phenotypes of iPSC-derived ECs were characterized using in vitro capillary formation and in vivo Matrigel plug-in assays. Results: PWB EC showed impaired tube formation in vitro with larger perimeters (p=6.22x10 -24 ) and thicker branches (p=1.07x10 -77 ) comparing with normal EC. In plug-in assay, the perfused human vasculatures were characterized by using UEA1 and anti-human CD31 antibodies. Perfused vasculature formed by PWB EC showed larger perimeters (p=8.45x10 -6 ) and greater densities (p=7.34x10 -8 ) than those formed by normal EC. Additionally, 16.6% of perfused vessels formed by PWB EC showed perimeters over 300 μm. KEGG analysis of RNA-seq DEGs showed significantly dysregulated pathways related to cell differentiation, organ development, and lipid metabolism in PWB iPSCs and ECs as compared with normal ones. Conclusions: PWB-derived EC retained critical disease related phenotypes including forming enlarged vessels and thick branches in vitro and in vivo, which can be utilized as valuable PWB models.

Combined Treatment of Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes and Endothelial Cells Regenerate the Infarcted Heart in Mice and Non-Human Primates.

Remuscularization of the mammalian heart can be achieved after cell transplantation of human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (CMs). However, several hurdles remain before implementation into clinical practice. Poor survival of the implanted cells is related to insufficient vascularization, and the potential for fatal arrhythmogenesis is associated with the fetal cell-like nature of immature CMs. We generated 3 lines of hiPSC-derived endothelial cells (ECs) and hiPSC-CMs from 3 independent donors and tested hiPSC-CM sarcomeric length, gap junction protein, and calcium-handling ability in coculture with ECs. Next, we examined the therapeutic effect of the cotransplantation of hiPSC-ECs and hiPSC-CMs in nonobese diabetic-severe combined immunodeficiency (NOD-SCID) mice undergoing myocardial infarction (n≥4). Cardiac function was assessed by echocardiography, whereas arrhythmic events were recorded using 3-lead ECGs. We further used healthy non-human primates (n=4) with cell injection to study the cell engraftment, maturation, and integration of transplanted hiPSC-CMs, alone or along with hiPSC-ECs, by histological analysis. Last, we tested the cell therapy in ischemic reperfusion injury in non-human primates (n=4, 3, and 4 for EC+CM, CM, and control, respectively). Cardiac function was evaluated by echocardiography and cardiac MRI, whereas arrhythmic events were monitored by telemetric ECG recorders. Cell engraftment, angiogenesis, and host-graft integration of human grafts were also investigated. We demonstrated that human iPSC-ECs promote the maturity and function of hiPSC-CMs in vitro and in vivo. When cocultured with ECs, CMs showed more mature phenotypes in cellular structure and function. In the mouse model, cotransplantation augmented the EC-accompanied vascularization in the grafts, promoted the maturity of CMs at the infarct area, and improved cardiac function after myocardial infarction. Furthermore, in non-human primates, transplantation of ECs and CMs significantly enhanced graft size and vasculature and improved cardiac function after ischemic reperfusion. These results demonstrate the synergistic effect of combining iPSC-derived ECs and CMs for therapy in the postmyocardial infarction heart, enabling a promising strategy toward clinical translation.

Human iPSC-derived endothelial cells promote CNS remyelination via BDNF and mTORC1 pathway.

Damage of myelin is a component of many diseases in the central nervous system (CNS). The activation and maturation of the quiescent oligodendrocyte progenitor cells (OPCs) are the crucial cellular processes for CNS remyelination, which is influenced by neuroinflammation in the lesion microenvironment. Endothelial cells derived from human induced pluripotent stem cells (hiPSC-ECs) have shown promise in restoring function in various preclinical animal models. Here we ask whether and whether transplantation of hiPSC-ECs could benefit remyelination in a mouse model of CNS demyelination. Our results show that in vitro, hiPSC-ECs increase OPC proliferation, migration and differentiation via secreted soluble factors including brain-derived neurotrophic factor (BDNF). hiPSC-ECs also promote the survival of oligodendrocyte lineage cells in vitro and in vivo. Transplantation of hiPSC-ECs into a toxin-induced demyelination lesion in mouse corpus callosum (CC) leads to increased density of oligodendrocyte lineage cells and level of myelin in demyelinated area, correlated with a decreased neuroinflammation and an increased proportion of pro-regenerative M2 phenotype in microglia/macrophages. The hiPSC-EC-exposed oligodendrocyte lineage cells showed significant increase in the level of phosphorylated S6 ribosomal protein (pS6) both in vitro and in vivo, indicating an involvement of mTORC1 pathway. These results suggest that hiPSC-ECs may benefit myelin protection and regeneration which providing a potential source of cell therapy for a wide range of diseases and injuries associated with myelin damage.

Amyloid-β exposed astrocytes induce iron transport from endothelial cells at the blood-brain barrier by altering the ratio of apo- and holo-transferrin.

Excessive brain iron accumulation is observed early in the onset of Alzheimer's disease, notably prior to widespread proteinopathy. These findings suggest that increases in brain iron levels are due to a dysregulation of the iron transport mechanism at the blood-brain barrier. Astrocytes release signals (apo- and holo-transferrin) that communicate brain iron needs to endothelial cells in order to modulate iron transport. Here we use iPSC-derived astrocytes and endothelial cells to investigate how early-disease levels of amyloid-β disrupt iron transport signals secreted by astrocytes to stimulate iron transport from endothelial cells. We demonstrate that conditioned media from astrocytes treated with amyloid-β stimulates iron transport from endothelial cells and induces changes in iron transport pathway proteins. The mechanism underlying this response begins with increased iron uptake and mitochondrial activity by the astrocytes, which in turn increases levels of apo-transferrin in the amyloid-β conditioned astrocyte media leading to increased iron transport from endothelial cells. These novel findings offer a potential explanation for the initiation of excessive iron accumulation in early stages of Alzheimer's disease. What's more, these data provide the first example of how the mechanism of iron transport regulation by apo- and holo-transferrin becomes misappropriated in disease that can lead to iron accumulation. The clinical benefit from understanding early dysregulation in brain iron transport in AD cannot be understated. If therapeutics can target this early process, they could possibly prevent the detrimental cascade that occurs with excessive iron accumulation.

O-222 Functional characterization and clinical implications of patient-specific iPSC-derived endothelial cells to unravel the pathogenesis associated with androgen-mediated endothelial dysfunction in polycystic ovarian syndrome

Abstract Study question Whether and how the endothelial cell (EC) dysfunction is involved in the pathogenesis of PCOS revealed by iPSC-based disease modeling? Summary answer PCOS-specific iPSC-derived ECs were successfully established and the results showed that EC proliferation and function were impaired in PCOS through the androgen receptor(AR)-mediated signaling pathway. What is known already ECs have been shown to play critical biological roles in the regulation of vascular tone and inflammatory process and any injury to ECs or disturbance in their homeostasis is called EC dysfunction, which has been recognized as an early marker of atherosclerosis and cardiovascular diseases. Several studies have also revealed indirect evidence of EC dysfunction among women with PCOS, including elevated circulatory markers of endothelial damage and impaired vascular structure. But whether and how EC dysfunction is involved in the pathogenesis of PCOS is still unclear. Study design, size, duration This is an experimental study at tertiary university hospital. iPSCs were established from skin fibroblasts and peripheral blood mononuclear cells from two patients with PCOS and two control participants. Participants/materials, setting, methods iPSCs were differentiated into ECs through monoculture with chemically defined conditions. Single cell RNA sequencing (scRNA-seq) was performed on the iPSCs-derived ECs to compare the differences between PCOS and control. iPSCs-derived ECs were treated with different dosages (1, 10 and 100 nM) of dihydrotestosterone (DHT). Cell cycle phases were analyzed by flow cytometry with BrdU incorporation assay. The expression of AR, cyclin-dependent kinase 1 (CDK1) and vascular endothelial growth factor (VEGF) were analyzed using rtPCR. Main results and the role of chance Up to 90% of iPSC-derived ECs successfully expressed EC markers, including CD31, CD144 and von Willebrand Factor in both PCOS and control groups, showing a high differentiation efficiency in the present study. The pathway enrichment analysis of transcriptomic data of iPSC-derived ECs showed functional differences involving cell cycle process, VEGF signaling and apoptotic process between PCOS and control. Analysis using sc-RNA seq revealed decreased cellular proliferation in the PCOS iPSC-derived ECs compared to control group, which was due to cell cycle arrest revealed by flow cytometry. The modulating effects of androgen on the proliferation and gene expression of iPSC-derived ECs were further investigated. DHT at doses ranging from 1 to 100 nM stimulated iPSC-derived ECs proliferation in the control group through upregulation of AR, CDK1 and VEGF gene expression. In contrast, DHT did not promote the cellular proliferation of PCOS iPSC-derived ECs at physiological concentrations of 1 and 10 nM and the expression of AR, CDK1, and VEGF remained unchanged. These data suggest that DHT-induced cellular proliferation and the expression of associated genes were more sensitive and dose-dependent in the control iPSC-derived ECs and blunted in the PCOS iPSC-derived ECs. Limitations, reasons for caution One of the major limitations of our study was the limited number of cases during the establishment of iPSCs, which was unable to reflect the heterogeneity and complexity of PCOS. Wider implications of the findings Impaired cellular proliferation and differentially expressed genes involved in cell proliferation, immune responses, cardiovascular functions, and apoptosis were observed among PCOS iPSC-derived ECs. Additionally, androgen-induced ECs proliferation was blunted in PCOS through a diminished AR/VEGF/cyclin D1 signaling pathway, which might hinder VEGF-dependent vascular repair and probably increase cardiovascular risks. Trial registration number not applicable

Proteomics of novel induced pluripotent stem cell-derived vascular endothelial cells reveal extensive similarity with an immortalized human endothelial cell line.

The vascular endothelium constitutes the inner lining of the blood vessel, and malfunction and injuries of the endothelium can cause cardiovascular diseases as well as other diseases including stroke, tumor growth, and chronic kidney failure. Generation of effective sources to replace injured endothelial cells (ECs) could have significant clinical impact, and somatic cell sources like peripheral or cord blood cannot credibly supply enough endothelial cell progenitors for multitude of treatments. Pluripotent stem cells are a promising source for a reliable EC supply, which have the potential to restore tissue function and treat vascular diseases. We have developed methods to differentiate induced pluripotent stem cells (iPSCs) efficiently and robustly across multiple iPSC lines into nontissue-specific pan vascular ECs (iECs) with high purity. These iECs present with canonical endothelial cell markers and exhibit measures of endothelial cell functionality with the uptake of Dil fluorescent dye-labeled acetylated low-density lipoprotein (Dil-Ac-LDL) and tube formation. Using proteomic analysis, we revealed that the iECs are more proteomically similar to established human umbilical vein ECs (HUVECs) than to iPSCs. Posttranslational modifications (PTMs) were most shared between HUVECs and iECs, and potential targets for increasing the proteomic similarity of iECs to HUVECs were identified. Here we demonstrate an efficient robust method to differentiate iPSCs into functional ECs, and for the first time provide a comprehensive protein expression profile of iECs, which indicates their similarities with a widely used immortalized HUVECs, allowing for further mechanistic studies of EC development, signaling, and metabolism for future regenerative applications.NEW & NOTEWORTHY We have developed methods to differentiate induced pluripotent stem cells (iPSCs) across multiple iPSC lines into nontissue-specific pan vascular ECs (iECs) and demonstrated the proteomic similarity of these cells to a widely used endothelial cell line (HUVECs). We also identified posttranslational modifications and targets for increasing the proteomic similarity of iECs to HUVECs. In the future, iECs can be used to study EC development, signaling, and metabolism for future regenerative applications.

Matrix stiffness regulates the tight junction phenotypes and local barrier properties in tricellular regions in an iPSC-derived BBB model

The blood-brain barrier (BBB) can respond to various mechanical cues such as shear stress and substrate stiffness. In the human brain, the compromised barrier function of the BBB is closely associated with a series of neurological disorders that are often also accompanied by the alteration of brain stiffness. In many types of peripheral vasculature, higher matrix stiffness decreases barrier function of endothelial cells through mechanotransduction pathways that alter cell-cell junction integrity. However, human brain endothelial cells are specialized endothelial cells that largely resist changes in cell morphology and key BBB markers. Therefore, it has remained an open question how matrix stiffness affects barrier integrity in the human BBB. To gain insight into the effects of matrix stiffness on BBB permeability, we differentiated brain microvascular endothelial-like cells from human induced pluripotent stem cells (iBMEC-like cells) and cultured the cells on extracellular matrix-coated hydrogels of varying stiffness. We first detected and quantified the junction presentation of key tight junction (TJ) proteins. Our results show matrix-dependent junction phenotypes in iBMEC-like cells, where cells on softer gels (1 kPa) have significantly lower continuous and total TJ coverages. We also determined that these softer gels also lead to decreased barrier function in a local permeability assay. Furthermore, we found that matrix stiffness regulates the local permeability of iBMEC-like cells through the balance of continuous ZO-1 TJs and no junction regions ZO-1 in tricellular regions. Together, these findings provide valuable insights into the effects of matrix stiffness on TJ phenotypes and local permeability of iBMEC-like cells. Statement of SignificanceBrain mechanical properties, including stiffness, are particularly sensitive indicators for pathophysiological changes in neural tissue. The compromised function of the blood-brain barrier is closely associated with a series of neurological disorders often accompanied by altered brain stiffness. In this study, we use polymeric biomaterials and provide new evidence that biomaterial stiffness regulates the local permeability in iPSC-derived brain endothelial cells in tricellular regions through the tight junction protein ZO-1. Our findings provide valuable insights into the changes in junction architecture and barrier permeability in response to different substrate stiffnesses. Since BBB dysfunction has been linked to many diseases, understanding the influence of substrate stiffness on junction presentations and barrier permeability could lead to the development of new treatments for diseases associated with BBB dysfunction or drug delivery across BBB systems.

Apo- and holo-transferrin differentially interact with hephaestin and ferroportin in a novel mechanism of cellular iron release regulation

BackgroundApo- (iron free) and holo- (iron bound) transferrin (Tf) participate in precise regulation of brain iron uptake at endothelial cells of the blood–brain barrier. Apo-Tf indicates an iron-deficient environment and stimulates iron release, while holo-Tf indicates an iron sufficient environment and suppresses additional iron release. Free iron is exported through ferroportin, with hephaestin as an aid to the process. Until now, the molecular mechanisms of apo- and holo-Tf influence on iron release was largely unknown.MethodsHere we use a variety of cell culture techniques, including co-immunoprecipitation and proximity ligation assay, in iPSC-derived endothelial cells and HEK 293 cells to investigate the mechanism by which apo- and holo-Tf influence cellular iron release. Given the established role of hepcidin in regulating cellular iron release, we further explored the relationship of hepcidin to transferrin in this model.ResultsWe demonstrate that holo-Tf induces the internalization of ferroportin through the established ferroportin degradation pathway. Furthermore, holo-Tf directly interacts with ferroportin, whereas apo-Tf directly interacts with hephaestin. Only pathophysiological levels of hepcidin disrupt the interaction between holo-Tf and ferroportin, but similar hepcidin levels are unable to interfere with the interaction between apo-Tf and hephaestin. The disruption of the holo-Tf and ferroportin interaction by hepcidin is due to hepcidin’s ability to more rapidly internalize ferroportin compared to holo-Tf.ConclusionsThese novel findings provide a molecular mechanism for apo- and holo-Tf regulation of iron release from endothelial cells. They further demonstrate how hepcidin impacts these protein–protein interactions, and offer a model for how holo-Tf and hepcidin cooperate to suppress iron release. These results expand on our previous reports on mechanisms mediating regulation of brain iron uptake to provide a more thorough understanding of the regulatory mechanisms mediating cellular iron release in general.

The role of type I interferon on trisomy 21 endothelial angiogenesis

Rationale: Down syndrome (DS), resulting from Trisomy 21 (T21), is the most common chromosomal disorder worldwide. Cardiopulmonary complications are a leading cause of morbidity and mortality in DS. Pulmonary disorders include pulmonary hypertension and pulmonary capillaritis, which can result from a dysregulated lung endothelium. One of the major pathways consistently activated in DS is the type I interferon (IFN-I) pathway. High IFN-I inhibits VEGF induced development of capillary like structures, thus playing an anti-angiogenic role. Therefore, we aim to characterize the effects of IFN-I on T21 and euploid iPSC-derived endothelial cells (iPSC-ECs). Methods: Endothelial cell populations from single cell sequencing data of age matched T21 and Non-T21 prenatal lungs were carefully analyzed. Four iPSC lines were derived from age and sex matched T21 and non-T21 human fetal lung fibroblasts and used for endothelial cell differentiation using standardized kits and protocols from Stem Cell Technologies. FACs analysis confirmed endothelial cell purity and differentiation success: CD31+CD34+CD144+CD45-. For angiogenesis assays, endothelial cells were plated onto Cultrex in Ibidi angiogenesis 96-well plates with varying concentrations (0 to 10 4 pM) of IFNβ for 24 hours. Phase contrast images were taken with a 2.5X lens and analyzed in FIJI with the polygon shape tool to measure continuous mesh areas (CMA), defined here as a continuous endothelial cell layer undisrupted by branching structures. Results: Pathway analysis from our scRNAseq data demonstrated an upregulation of the IFN-I pathway across T21 endothelial clusters. T21 and non-T21 iPSC lines exhibited markers of pluripotency (OCT4, NANOG, SOX2, LIN28) and successfully generated pure populations of endothelial cells (~98% CD31+CD34+CD144+CD45-) by passage 2. Quantification demonstrated that at baseline T21 iPSC-ECs consistently had a significantly larger mean CMA than that of non-T21 iPSC-ECs (p< 0.01, n=4). High concentrations of IFN treatment (10 4 pM) resulted in an increased CMA in non-T21 cultures (p=0.14; n=4), trending towards baseline T21 cultures (p=0.28, n=4). Additionally, we observed a significant increase in the CMA of T21 cultures treated with 10 4 pM IFNβ (p=0.04, n=4). Conclusion: Our data suggest decreased angiogenesis in T21 iPSC-ECs may be caused by hyperactive IFN-I signaling. Further studies are needed to determine the mechanisms by which IFN-I regulates angiogenesis in T21 lungs. NIH/NHLBI/OD HL155104-01A1, NIH/NHLBI HL141856, NIH/NHLBI R21HL165411-01, NIH/NICHD 2R24HD000836-52 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Review on the Method of Generating Vascular Cells from iPSCs and Its Application

Induced Pluripotent Stem Cells (iPSCs) embryonic-like stem cells are reprogrammed from skin or adult somatic cells. iPSC-derived cardiovascular cells have been widely used in many cardiovascular disease models and drug discovery. This paper reviews and summarizes the method of generating three different types of iPSC-derived cardiovascular cells, including iPSC-derived Endothelial Cells (ECs), Cardiomyocytes (CMs), and Vascular Smooth Muscle Cells (vSMCs), and the application of these iPSC-derived cardiovascular cells. The diseases discussed in this paper are pulmonary arterial hypertension (PAH) and critical limb ischemia (CLI). Additionally, construction of tissue-engineered blood vessels (TEBVs) for vascular grafting has also been discussed. To conclude, iPSCs, as a promising technique, is used in disease modeling, drug screening, tissue engineering, and the discovery of specific cardiovascular therapies for various patients.

Lonafarnib and everolimus reduce pathology in iPSC-derived tissue engineered blood vessel model of Hutchinson-Gilford Progeria Syndrome

Hutchinson-Gilford Progeria Syndrome (HGPS) is a rare, fatal genetic disease that accelerates atherosclerosis. With a limited pool of HGPS patients, clinical trials face unique challenges and require reliable preclinical testing. We previously reported a 3D tissue engineered blood vessel (TEBV) microphysiological system fabricated with iPSC-derived vascular cells from HGPS patients. HGPS TEBVs exhibit features of HGPS atherosclerosis including loss of smooth muscle cells, reduced vasoactivity, excess extracellular matrix (ECM) deposition, inflammatory marker expression, and calcification. We tested the effects of HGPS therapeutics Lonafarnib and Everolimus separately and together, currently in Phase I/II clinical trial, on HGPS TEBVs. Everolimus decreased reactive oxygen species levels, increased proliferation, reduced DNA damage in HGPS vascular cells, and improved vasoconstriction in HGPS TEBVs. Lonafarnib improved shear stress response of HGPS iPSC-derived endothelial cells (viECs) and reduced ECM deposition, inflammation, and calcification in HGPS TEBVs. Combination treatment with Lonafarnib and Everolimus produced additional benefits such as improved endothelial and smooth muscle marker expression and reduced apoptosis, as well as increased TEBV vasoconstriction and vasodilation. These results suggest that a combined trial of both drugs may provide cardiovascular benefits beyond Lonafarnib, if the Everolimus dose can be tolerated.

Transplanted human iPSC-derived vascular endothelial cells promote functional recovery by recruitment of regulatory T cells to ischemic white matter in the brain

BackgroundIschemic stroke in white matter of the brain induces not only demyelination, but also neuroinflammation. Peripheral T lymphocytes, especially regulatory T cells (Tregs), are known to infiltrate into ischemic brain and play a crucial role in modulation of inflammatory response there. We previously reported that transplantation of vascular endothelial cells generated from human induced pluripotent stem cells (iVECs) ameliorated white matter infarct. The aim of this study is to investigate contribution of the immune system, especially Tregs, to the mechanism whereby iVEC transplantation ameliorates white matter infarct.MethodsiVECs and human Tregs were transplanted into the site of white matter lesion seven days after induction of ischemia. The egress of T lymphocytes from lymph nodes was sequestered by treating the animals with fingolimod (FTY720). The infarct size was evaluated by magnetic resonance imaging. Immunohistochemistry was performed to detect the activated microglia and macrophages, T cells, Tregs, and oligodendrocyte lineage cells. Remyelination was examined by Luxol fast blue staining.ResultsiVEC transplantation reduced ED-1+ inflammatory cells and CD4+ T cells, while increased Tregs in the white matter infarct. Treatment of the animals with FTY720 suppressed neuroinflammation and reduced the number of both CD4+ T cells and Tregs in the lesion, suggesting the importance of infiltration of these peripheral immune cells into the lesion in aggravation of neuroinflammation. Suppression of neuroinflammation by FTY720 per se, however, did not promote remyelination in the infarct. FTY720 treatment negated the increase in the number of Tregs by iVEC transplantation in the infarct, and attenuated remyelination promoted by transplanted iVECs, while it did not affect the number of oligodendrocyte lineage cells increased by iVEC transplantation. Transplantation of Tregs together with iVECs into FTY720-treated ischemic white matter did not affect the number of oligodendrocyte lineage cells, while it remarkably promoted myelin regeneration.ConclusionsiVEC transplantation suppresses neuroinflammation, but suppression of neuroinflammation per se does not promote remyelination. Recruitment of Tregs by transplanted iVECs contributes significantly to promotion of remyelination in the injured white matter.

Protection of cell therapeutics from antibody-mediated killing by CD64 overexpression

Allogeneic cell therapeutics for cancer therapy or regenerative medicine are susceptible to antibody-mediated killing, which diminishes their efficacy. Here we report a strategy to protect cells from antibody-mediated killing that relies on engineered overexpression of the IgG receptor CD64. We show that human and mouse iPSC-derived endothelial cells (iECs) overexpressing CD64 escape antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity from IgG antibodies in vitro and in ADCC-enabled mice. When CD64 expression was combined with hypoimmune genetic modifications known to protect against cellular immunity, B2M−/−CIITA−/− CD47/CD64-transgenic iECs were resistant to both IgG antibody-mediated and cellular immune killing in vitro and in humanized mice. Mechanistic studies demonstrated that CD64 or its intracellularly truncated analog CD64t effectively capture monomeric IgG and occupy their Fc, and the IgG bind and occupy their target antigens. In three applications of the approach, human CD64t-engineered thyroid epithelial cells, pancreatic beta cells and CAR T cells withstood clinically relevant levels of graft-directed antibodies and fully evaded antibody-mediated killing.

IPSC-Derived Corneal Endothelial Cells.

The corneal endothelium is the innermost monolayer of the cornea that maintains corneal transparency and thickness. However, adult human corneal endothelial cells (CECs) possess limited proliferative capacity, and injuries can only be repaired by migration and enlargement of resident cells. When corneal endothelial cell density is lower than the critical level (400-500 cells/mm2) due to disease or trauma, corneal endothelial dysfunction will occur and lead to corneal edema. Corneal transplantation remains the most effective clinical treatment therapy but is limited by the global shortage of healthy corneal donors. Recently, researchers have developed several alternative strategies for the treatment of corneal endothelial disease, including the transplantation of cultured human CECs and artificial corneal endothelial replacement. Early-stage results show that these strategies can effectively resolve corneal edema and restore corneal clarity and thickness, but the long-term efficacy and safety remain to be further validated. Induced pluripotent stem cells (iPSCs) represent an ideal cell source for the treatment and drug discovery of corneal endothelial diseases, which can avoid the ethical-related and immune-related problems of human embryonic stem cells (hESCs). At present, many approaches have been developed to induce the differentiation of corneal endothelial-like cells from human induced pluripotent stem cells (hiPSCs). Their safety and efficacy for the treatment of corneal endothelial dysfunction have been confirmed in rabbit and nonhuman primate animal models. Therefore, the iPSC-derived corneal endothelial cell model may provide a novel effective platform for basic and clinical research of disease modeling, drug screening, mechanistic investigation, and toxicology testing.