Adult Human Endothelial Cells Research Articles

Efficacy of echinomycin in hypoxia‐inducible factor‐mediated ocular angiogenesis

AbstractPurposeEchinomycin (EKN), an inhibitor of hypoxia‐inducible factor (HIF)‐1 DNA‐binding activity, has been implied as a possible therapeutic agent in ischemic diseases. We assessed EKN in hypoxia‐driven responses in vitro using human primary adult retinal pigment epithelium cells (aRPE), and in vivo using the laser‐induced mouse choroidal neovascularization (CNV) model.MethodsAdult retinal endothelial were kept at normoxia (20% O2) or exposed to hypoxia (1% O2), in the presence or absence of EKN. Epithelial wound‐healing was used to determine the dose of EKN. Effects of EKN on hypoxia‐mediated pathways were analyzed by western blot for HIF‐1a, qPCR of HIF‐target genes, and proteome array for soluble angiogenic factors. Inhibition of angiogenesis by EKN was determined in human primary adult retinal endothelial cells (aREC), exposed to EKN‐treated hypoxic conditioned aRPE medium by spheroid sprouting assay. 8‐week‐old C57BL/6J mice underwent laser‐induced CNV, as a model of HIF‐associated ocular neovascularization. Animals were treated with EKN and compared to a mouse VEGFR1‐Fc chimera protein (equivalent of aflibercept). CNV lesion area was determined by fluorescein angiography.ResultsAdult retinal endothelial treated with EKN demonstrated hypoxia‐dependent decreased cell proliferation in the wound‐healing assay. Lower HIF‐mediated transcripts were detected in hypoxic aRPE cells treated with EKN compared with non‐treated controls. These results were confirmed by proteome profiler for angiogenic factors, and subsequently reduced hREC sprouting. Laser‐induced mice treated with 1 mg of intravitreally injected EKN demonstrated a significant decrease in vascular lesion area when compared with 1 mg of VEGFR1 chimera or vehicle‐treated controls.ConclusionsOur data suggest EKN as a potent inhibitor of HIF‐mediated angiogenesis in retinal cells and in the mouse model of CNV, which could have future implications in the treatment of patients with neovascular age‐related macular degeneration.

Three-Layered Silk Fibroin Tubular Scaffold for the Repair and Regeneration of Small Caliber Blood Vessels: From Design to in vivo Pilot Tests.

Silk fibroin (SF) is an eligible biomaterial for the development of small caliber vascular grafts for substitution, repair, and regeneration of blood vessels. This study presents the properties of a newly designed multi-layered SF tubular scaffold for vascular grafting (SilkGraf). The wall architecture consists of two electrospun layers (inner and outer) and an intermediate textile layer. The latter was designed to confer high mechanical performance and resistance on the device, while electrospun layers allow enhancing its biomimicry properties and host's tissues integration. In vitro cell interaction studies performed with adult Human Coronary Artery Endothelial Cells (HCAECs), Human Aortic Smooth Muscle Cells (HASMCs), and Human Aortic Adventitial Fibroblasts (HAAFs) demonstrated that the electrospun layers favor cell adhesion, survival, and growth. Once cultured in vitro on the SF scaffold the three cell types showed an active metabolism (consumption of glucose and glutamine, release of lactate), and proliferation for up to 20 days. HAAF cells grown on SF showed a significantly lower synthesis of type I procollagen than on polystyrene, meaning a lower fibrotic effect of the SF substrate. The cytokine and chemokine expression patterns were investigated to evaluate the cells' proliferative and pro-inflammatory attitude. Interestingly, no significant amounts of truly pro-inflammatory cytokines were secreted by any of the three cell types which exhibited a clearly proliferative profile. Good hemocompatibility was observed by complement activation, hemolysis, and hematology assays. Finally, the results of an in vivo preliminary pilot trial on minipig and sheep to assess the functional behavior of implanted SF-based vascular graft identified the sheep as the more apt animal model for next medium-to-long term preclinical trials.

Lipofectamine 2000/siRNA complexes cause endoplasmic reticulum unfolded protein response in human endothelial cells.

Lipofectamine 2000 (Lipo2000) delivery system is commonly used for short interfering RNA (siRNA) transfection, whereas the cellular responses have attracted little attention. The purpose of this study is to evaluate the effect of siRNA transfection using Lipo2000 on cellular functions and the possible underlying mechanism. Primary human umbilical vein endothelial cells (HUVECs) and adult human coronary artery endothelial cell line (HCAECs) were treated with different concentrations of a Lipo2000/negative control siRNA (NC siRNA) complex or Lipo2000 for specific durations. The cell proliferation, apoptosis rate, and protein expression of claudin5 (CLDN5) and ETS-related gene (ERG) were analyzed as indicators of cellular function. The effects of the Lipo2000/NC siRNA complex on cellular autophagy and endoplasmic reticulum (ER) unfolded protein response (UPR) were investigated by western blot and real-time polymerase chain reaction analyses; autophagy was also evaluated by transmission electron microscopy. The Lipo2000/NC siRNA complex inhibited proliferation, downregulated various proteins, and increased the apoptosis in both HUVECs and HCAECs. Both autophagy and UPR were observed in HUVECs treated with the Lipo2000/NC siRNA complex, ER stress-induced autophagy acted as a cellular protective factor against apoptosis, as inhibition of autophagy by chemical inhibitors increased the cell apoptosis rate. Chemical chaperones failed to prevent the Lipo2000/siRNA complex-induced UPR. However, knockdown of protein kinase RNA-like ER kinase and inositol-requiring protein1, instead of activating transcription factor-6, partially ameliorated the UPR and reversed the protein level of CLDN5 and ERG downregulated by Lipo2000/NC siRNA complex. This study provides the first evidence that the Lipo2000-mediated transport of siRNA leads to an increase in UPR and ER stress-related apoptosis in endothelial cells.

Evaluation of in vitro cell and blood compatibility and in vivo analgesic activity of plant-derived dietary supplements

ObjectiveIn vitro cell and blood compatibility of three dietary supplements, comprised of multiple plant extracts, Pneumo Go (PG), Green active (GA) and Equistasi (Eq), and their main component, the phytocomplex Matrix U.B.® (Union Bio S.r.l.) (M), were evaluated. Moreover, preliminary in vivo tests were performed on GA in order to assess its ability to reduce pain in an animal model. MethodsCell compatibility was determined using fibroblasts (NIH3T3) and primary adult human microvascular endothelial cells (HMVECad) and the neutral red uptake test. Blood compatibility was evaluated by analyzing blood parameters after incubation of the products with sodium citrate anticoagulated whole blood. Thrombin time was determined by adding thrombin to aliquots of human plasma containing the samples. Clotting time was revealed by an automatic coagulometer. The in vivo analgesic effect of GA was evaluated in Wistar rats using the formalin test. ResultsM and PG reduced the percentage of viable NIH3T3 cells, indicating their interference in the cell cycle. GA and Eq stimulated fibroblast proliferation and neutralized the toxic effect of M. M and PG reduced HMVECad cell viability. GA and Eq did not affect cell viability as well as negative control. The hemocompatibility tests indicated that all the samples did not interfere with fibrinogen. The in vivo test carried out in male rats showed a significant analgesic effect of GA in all formalin-induced pain behaviors. ConclusionNo hemotoxicity and good cell compatibility were found for all the tested samples. GA and Eq were the best candidates for further biocompatibility testing. Moreover, GA reduced pain in the animal model.

Impaired proteostasis in senescent vascular endothelial cells: a perspective on estrogen and oxidative stress in the aging vasculature.

The heat shock response is an important cytoprotective mechanism for protein homeostasis and is an essential protective response to cellular stress and injury. Studies on changes in the heat shock response with aging have been mixed with regard to whether it is inhibited, and this, at least in part, reflects different tissues and different models. Cellular senescence is a key feature in aging, but work on the heat shock response in cultured senescent (SEN) cells has largely been limited to fibroblasts. Given the prevalence of oxidative injury in the aging cardiovascular system, we investigated whether SEN primary human coronary artery endothelial cells have a diminished heat shock response and impaired proteostasis. In addition, we tested whether this downregulation of heat shock response can be mitigated by 17β-estradiol (E2), which has a critical cardioprotective role in women, as we have previously reported that E2 improves the heat shock response in endothelial cells (Hamilton KL, Mbai FN, Gupta S, Knowlton AA. Arterioscler Thromb Vasc Biol 24: 1628-1633, 2004). We found that SEN endothelial cells, despite their unexpectedly increased proteasome activity, had a diminished heat shock response and had more protein aggregation than early passage cells. SEN cells had increased oxidative stress, which promoted protein aggregation. E2 treatment did not decrease protein aggregation or improve the heat shock response in either early passage or SEN cells. In summary, cellular senescence in adult human endothelial cells is accompanied by increased oxidative stress and a blunting of proteostasis, and E2 did not mitigate these changes. NEW & NOTEWORTHY Senescent human endothelial cells have a diminished heat shock response and increased protein aggregates. Senescent human endothelial cells have increased basal oxidative stress, which increases protein aggregates. Physiological level of 17β-estradiol did not improve proteostasis in endothelial cells.

A systems-approach reveals human nestin is an endothelial-enriched, angiogenesis-independent intermediate filament protein

The intermediate filament protein nestin is expressed during embryonic development, but considered largely restricted to areas of regeneration in the adult. Here, we perform a body-wide transcriptome and protein-profiling analysis to reveal that nestin is constitutively, and highly-selectively, expressed in adult human endothelial cells (EC), independent of proliferative status. Correspondingly, we demonstrate that it is not a marker for tumour EC in multiple malignancy types. Imaging of EC from different vascular beds reveals nestin subcellular distribution is shear-modulated. siRNA inhibition of nestin increases EC proliferation, and nestin expression is reduced in atherosclerotic plaque neovessels. eQTL analysis reveals an association between SNPs linked to cardiovascular disease and reduced aortic EC nestin mRNA expression. Our study challenges the dogma that nestin is a marker of proliferation, and provides insight into its regulation and function in EC. Furthermore, our systems-based approach can be applied to investigate body-wide expression profiles of any candidate protein.

Investigation of quercetin and hyperoside as senolytics in adult human endothelial cells.

Quercetin has been reported to act as a senolytic by selectively removing senescent endothelial cells, and thus it would seem quercetin could revolutionize the field of gerontology. However, given quercetin's narrow therapeutic index reported in work done with human umbilical vein endothelial cells (HUVECs), we hypothesized that quercetin is not innocuous for non-senescent adult human vascular endothelial cells at concentrations that have been reported to be safe for proliferating HUVECs. Furthermore, we investigated quercetin 3-D-galactoside (Q3G; hyperoside), an inactive quercetin derivative that needs to be cleaved by beta-galactosidase overexpressed in senescent cells to release quercetin, as a potential safer senolytic. We compared the effectiveness of quercetin and Q3G in primary human coronary artery endothelial cells (HCAEC), which are adult microvascular cells. We found that quercetin caused cell death in non-senescent endothelial cells at a concentration that has been reported to selectively remove senescent cells, and that Q3G was not cytotoxic to either young or senescent cells. Thus, in primary adult human endothelial cells, quercetin and Q3G are not senolytics. Earlier work reporting positive results was done with HUVECs, and given their origin and the disparate findings from the current study, these may not be the best cells for evaluating potential senolytics in clinically relevant endothelial cells.New and noteworthyPreviously, quercetin has been reported to be a senolytic, a drug that selectively removes senescent cells, in HUVECs. However, we found neither quercetin nor Q3G was effective as a senolytic for adult human endothelial cells.

The Human Blood-Nerve Barrier Transcriptome

The blood-nerve barrier (BNB), formed by tight junction-forming microvessels within peripheral nerve endoneurium, exists to regulate its internal microenvironment essential for effective axonal signal transduction. Relatively little is known about the unique human BNB molecular composition. Such knowledge is crucial to comprehend the relationships between the systemic circulation and peripheral nerves in health, adaptations to intrinsic or extrinsic perturbations and alterations that may result in disease. We performed RNA-sequencing on cultured early- and late-passage adult primary human endoneurial endothelial cells and laser-capture microdissected endoneurial microvessels from four cryopreserved normal adult human sural nerves referenced to the Genome Reference Consortium Human Reference 37 genome browser, using predefined criteria guided by known transcript or protein expression in vitro and in situ. We identified 12881 common transcripts associated by 125 independent biological networks, defined as the normal adult BNB transcriptome, including a comprehensive array of transporters and specialized intercellular junctional complex components. These identified transcripts and their interacting networks provide insights into peripheral nerve microvascular morphogenesis, restrictive barrier formation, influx and efflux transporters with relevance to understanding peripheral nerve homeostasis and pharmacology, including targeted drug delivery and the mediators of leukocyte trafficking in peripheral nerves during normal immunosurveillance.

Comparison of tissue factor expression and activity in foetal and adult endothelial cells

: Tissue factor (TF) is not usually expressed by endothelial cells but can be induced in these cells by inflammatory cytokines. Many studies have used human umbilical vein endothelial cells (HUVEC) as a model to examine the regulation of TF expression. However, there is a question as to whether this reflects TF expression in adult endothelial cells. This study compared TF expression and the release of TF-positive microvesicles in HUVEC and adult human dermal blood endothelial cells (HDBEC) in response to tumour necrosis factor α (TNFα) and interleukin-1 β (IL-1β). Cells were treated with the inflammatory cytokines and TF mRNA and total protein expression was examined by real-time RT-PCR and TF ELISA. Cell surface TF activity was measured in the calibrated automated thrombogram assay, as were microvesicle concentrations and microvesicle-associated TF activity. The TF antigen content of the microvesicles was determined by TF ELISA. Both HUVEC and HDBEC expressed increased levels of TF mRNA in response to TNFα and IL-1β within 2 h. TF antigen expression increased in both cell types, reaching a maximum at 6 h, with HUVEC expressing significantly higher levels compared with HDBEC in response to TNFα. However, increases in TF-specific thrombin generation were similar on both HUVEC and HDBEC and both cell types also released comparable levels of TF-positive microvesicles. HUVEC and HDBEC respond similarly to TNFα and IL-1β in terms of TF expression, and both are suitable models to examine cell surface TF activity and TF-positive microvesicle release in endothelial cells.

Kalirin and CHD7: novel endothelial dysfunction indicators in circulating extracellular vesicles from hypertensive patients with albuminuria.

Despite of the great advances in anti-hypertensive therapies, many patients under Renin-Angiotensin- System (RAS) suppression develop albuminuria, which is a clear indicator of therapeutic inefficiency. Hence, indicators of vascular function are needed to assess patients’ condition and help deciding future therapies.Proteomic analysis of circulating extracellular vesicles (EVs) showed two proteins, kalirin and chromodomain-helicase-DNA-binding protein 7 (CHD7), increased in albuminuric patients. A positive correlation of both with the expression of the endothelial activation marker E-selectin was found in EVs. In vitro analysis using TNFα-treated adult human endothelial cells proved their involvement in endothelial cell activation.Hence, we propose protein levels of kalirin and CHD7 in circulating EVs as novel endothelial dysfunction markers to monitor vascular condition in hypertensive patients with albuminuria.

Characterization and Prospective of Human Corneal Endothelial Progenitors.

Corneal endothelial cells play a critical role in maintaining corneal transparency and dysfunction of these cells caused by aging, diseases (such as Fuch's dystrophy), injury or surgical trauma, which can lead to corneal edema and blindness. Due to their limited proliferative capacity in vivo, the only treatment method is via transplantation of a cadaver donor cornea. However, there is a severe global shortage of donor corneas. To circumvent such issues, tissue engineering of corneal tissue is a viable option thanks to the recent discoveries in this field. In this review, we summarize the recent advances in reprogramming adult human corneal endothelial cells into their progenitor status, the expansion methods and characteristics of human corneal endothelial progenitors, and their potential clinical applications as corneal endothelial cell grafts.

Impact of CCR5, integrase and protease inhibitors on human endothelial cell function, stress, inflammation and senescence.

Ageing HIV-infected patients present an increased incidence of cardiovascular diseases, endothelial dysfunction being an early alteration. Some protease inhibitors (PIs) have been shown to increase the risk of cardiovascular disease. We evaluated here the effects of CCR5 or integrase inhibitors as compared to PIs on endothelial functions in vitro. Human coronary artery endothelial cells (HCAEC) from adult and old non-HIV-infected donors were treated for 15 days with the CCR5 inhibitor maraviroc, the integrase inhibitors dolutegravir or raltegravir or the ritonavir-boosted PIs, darunavir (DRV/r) or atazanavir (ATV/r), all at Cmax concentrations. We evaluated endothelial function, secretion of adhesion molecules and cytokines, inflammation, oxidative stress and senescence. In endothelial cells from adult donors, we confirmed that ATV/r and DRV/r adversely affected all assessed endothelial functions and enhanced senescence, these effects being mild for DRV/r. Raltegravir had no effect and maraviroc a mild anti-inflammatory effect. Dolutegravir decreased inflammation, by inhibiting the NFκB pathway, and senescence, by repressing the p21 pathway. Moreover, HCAEC from an old donor presented, constitutively, a high level of senescence. Raltegravir mildly affected inflammation and senescence while maraviroc and dolutegravir decreased oxidative stress, inflammation and senescence and improved endothelial dysfunction. We report here that the integrase inhibitor dolutegravir and the CCR5 inhibitor maraviroc reduced inflammation of human adult endothelial cells to different extents while raltegravir was neutral. Dolutegravir also reduced senescence, while PI/r increased inflammation and senescence. It is important to address the clinical relevance of these results.

Human airway organoid engineering as a step toward lung regeneration and disease modeling.

Organoids represent both a potentially powerful tool for the study cell-cell interactions within tissue-like environments, and a platform for tissue regenerative approaches. The development of lung tissue-like organoids from human adult-derived cells has not previously been reported. Here we combined human adult primary bronchial epithelial cells, lung fibroblasts, and lung microvascular endothelial cells in supportive 3D culture conditions to generate airway organoids. We demonstrate that randomly-seeded mixed cell populations undergo rapid condensation and self-organization into discrete epithelial and endothelial structures that are mechanically robust and stable during long term culture. After condensation airway organoids generate invasive multicellular tubular structures that recapitulate limited aspects of branching morphogenesis, and require actomyosin-mediated force generation and YAP/TAZ activation. Despite the proximal source of primary epithelium used in the airway organoids, discrete areas of both proximal and distal epithelial markers were observed over time in culture, demonstrating remarkable epithelial plasticity within the context of organoid cultures. Airway organoids also exhibited complex multicellular responses to a prototypical fibrogenic stimulus (TGF-β1) in culture, and limited capacity to undergo continued maturation and engraftment after ectopic implantation under the murine kidney capsule. These results demonstrate that the airway organoid system developed here represents a novel tool for the study of disease-relevant cell-cell interactions, and establishes this platform as a first step toward cell-based therapy for chronic lung diseases based on de novo engineering of implantable airway tissues.

Reduction in cardiolipin decreases mitochondrial spare respiratory capacity and increases glucose transport into and across human brain cerebral microvascular endothelial cells.

Microvessel endothelial cells form part of the blood-brain barrier, a restrictively permeable interface that allows transport of only specific compounds into the brain. Cardiolipin is a mitochondrial phospholipid required for function of the electron transport chain and ATP generation. We examined the role of cardiolipin in maintaining mitochondrial function necessary to support barrier properties of brain microvessel endothelial cells. Knockdown of the terminal enzyme of cardiolipin synthesis, cardiolipin synthase, in hCMEC/D3 cells resulted in decreased cellular cardiolipin levels compared to controls. The reduction in cardiolipin resulted in decreased mitochondrial spare respiratory capacity, increased pyruvate kinase activity, and increased 2-deoxy-[(3) H]glucose uptake and glucose transporter-1 expression and localization to membranes in hCMEC/D3 cells compared to controls. The mechanism for the increase in glucose uptake was an increase in adenosine-5'-monophosphate kinase and protein kinase B activity and decreased glycogen synthase kinase 3 beta activity. Knockdown of cardiolipin synthase did not affect permeability of fluorescent dextran across confluent hCMEC/D3 monolayers grown on Transwell(®) inserts. In contrast, knockdown of cardiolipin synthase resulted in an increase in 2-deoxy-[(3) H]glucose transport across these monolayers compared to controls. The data indicate that in hCMEC/D3 cells, spare respiratory capacity is dependent on cardiolipin. In addition, reduction in cardiolipin in these cells alters their cellular energy status and this results in increased glucose transport into and across hCMEC/D3 monolayers. Microvessel endothelial cells form part of the blood-brain barrier, a restrictively permeable interface that allows transport of only specific compounds into the brain. In human adult brain endothelial cell hCMEC/D3 monolayers cultured on Transwell(®) plates, knockdown of cardiolipin synthase results in decrease in mitochondrial cardiolipin and decreased mitochondrial spare respiratory capacity. The reduced cardiolipin results in an increased activity of adenosine monophosphate kinase (pAMPK) and protein kinase B (pAKT) and decreased activity of glycogen synthase kinase 3 beta (pGSK3β) which results in elevated glucose transporter-1 (GLUT-1) expression and association with membranes. This in turn increases 2-dexoyglucose uptake from the apical medium into the cells with a resultant 2-deoxyglucose movement into the basolateral medium.

Mechanical Injury Induces Brain Endothelial-Derived Microvesicle Release: Implications for Cerebral Vascular Injury during Traumatic Brain Injury.

It is well established that the endothelium responds to mechanical forces induced by changes in shear stress and strain. However, our understanding of vascular remodeling following traumatic brain injury (TBI) remains incomplete. Recently published studies have revealed that lung and umbilical endothelial cells produce extracellular microvesicles (eMVs), such as microparticles, in response to changes in mechanical forces (blood flow and mechanical injury). Yet, to date, no studies have shown whether brain endothelial cells produce eMVs following TBI. The brain endothelium is highly specialized and forms the blood-brain barrier (BBB), which regulates diffusion and transport of solutes into the brain. This specialization is largely due to the presence of tight junction proteins (TJPs) between neighboring endothelial cells. Following TBI, a breakdown in tight junction complexes at the BBB leads to increased permeability, which greatly contributes to the secondary phase of injury. We have therefore tested the hypothesis that brain endothelium responds to mechanical injury, by producing eMVs that contain brain endothelial proteins, specifically TJPs. In our study, primary human adult brain microvascular endothelial cells (BMVEC) were subjected to rapid mechanical injury to simulate the abrupt endothelial disruption that can occur in the primary injury phase of TBI. eMVs were isolated from the media following injury at 2, 6, 24, and 48 h. Western blot analysis of eMVs demonstrated a time-dependent increase in TJP occludin, PECAM-1 and ICAM-1 following mechanical injury. In addition, activation of ARF6, a small GTPase linked to extracellular vesicle production, was increased after injury. To confirm these results in vivo, mice were subjected to sham surgery or TBI and blood plasma was collected 24 h post-injury. Isolation and analysis of eMVs from blood plasma using cryo-EM and flow cytometry revealed elevated levels of vesicles containing occludin following brain trauma. These results indicate that following TBI, the cerebral endothelium undergoes vascular remodeling through shedding of eMVs containing TJPs and endothelial markers. The detection of this shedding potentially allows for a novel methodology for real-time monitoring of cerebral vascular health (remodeling), BBB status and neuroinflammation following a TBI event.

Two Histone Variants TH2A and TH2B Enhance Human Induced Pluripotent Stem Cell Generation.

There are two major methods of reprogramming: generation of induced pluripotent stem cells (iPSCs) by overexpressing embryonic stem cell-specific transcription factors (OCT4, SOX2, KLF4, and c-MYC) and somatic cell nuclear transfer by oocyte-specific factors. Previously, we reported oocyte-enriched histone variants TH2A, TH2B, and the histone chaperone nucleoplasmin (NPM2) enhance the reprogramming by OSKM in mice by inducing open chromatin structure. In this study, we showed that human TH2A, TH2B, and NPM2 enhance the OSKM-induced reprogramming of adult and neonatal human dermal fibroblasts and umbilical vein endothelial cells. Pluripotency of iPSCs generated by coexpressing OSKM, TH2A, TH2B, and NPM2 was shown by in vitro and in vivo differentiation assays. These iPSCs gave rise to highly differentiated teratomas compared to iPSCs induced by OSKM alone. Genome-wide analysis suggests a possibility that TH2A, TH2B, and NPM2 might regulate genes that are involved in naïve stem cell stage. Thus, TH2A, TH2B, and NPM2 enhance reprogramming of human somatic cells and improve the quality of human iPSCs.

Featured Article: Differential regulation of endothelial nitric oxide synthase phosphorylation by protease-activated receptors in adult human endothelial cells.

Protease-activated receptors have been shown to regulate endothelial nitric oxide synthase through the phosphorylation of specific sites on the enzyme. It has been established that PAR-2 activation phosphorylates eNOS-Ser-1177 and leads to the production of the potent vasodilator nitric oxide, while PAR-1 activation phosphorylates eNOS-Thr-495 and decreases nitric oxide production in human umbilical vein endothelial cells. In this study, we hypothesize a differential coupling of protease-activated receptors to the signaling pathways that regulates endothelial nitric oxide synthase and nitric oxide production in primary adult human coronary artery endothelial cells. Using Western Blot analysis, we showed that thrombin and the PAR-1 activating peptide, TFLLR, lead to the phosphorylation of eNOS-Ser-1177 in human coronary artery endothelial cells, which was blocked by SCH-79797 (SCH), a PAR-1 inhibitor. Using the nitrate/nitrite assay, we also demonstrated that the thrombin- and TFLLR-induced production of nitric oxide was inhibited by SCH and L-NAME, a NOS inhibitor. In addition, we observed that TFLLR, unlike thrombin, significantly phosphorylated eNOS-Thr-495, which may explain the observed delay in nitric oxide production in comparison to that of thrombin. Activation of PAR-2 by SLIGRL, a PAR-2 specific ligand, leads to dual phosphorylation of both catalytic sites but primarily regulated eNOS-Thr-495 phosphorylation with no change in nitric oxide production in human coronary artery endothelial cells. PAR-3, known as the non-signaling receptor, was activated by TFRGAP, a PAR-3 mimicking peptide, and significantly induced the phosphorylation of eNOS-Thr-495 with minimal phosphorylation of eNOS-Ser-1177 with no change in nitric oxide production. In addition, we confirmed that PAR-mediated eNOS-Ser-1177 phosphorylation was Ca(2+)-dependent using the Ca(2+) chelator, BAPTA, while eNOS-Thr-495 phosphorylation was mediated via Rho kinase using the ROCK inhibitor, Y-27632, suggesting protease-activated receptor coupling to Gq and G12/13, respectively. These data suggest a vascular bed specific differential coupling of protease-activated receptors to the signaling pathways that regulate endothelial nitric oxide synthase and nitric oxide production that may be responsible for endothelial dysfunction associated with cardiovascular disease.

Efficient Generation of Human Embryonic Stem Cell-Derived Corneal Endothelial Cells by Directed Differentiation.

AimTo generate human embryonic stem cell derived corneal endothelial cells (hESC-CECs) for transplantation in patients with corneal endothelial dystrophies.Materials and MethodsFeeder-free hESC-CECs were generated by a directed differentiation protocol. hESC-CECs were characterized by morphology, expression of corneal endothelial markers, and microarray analysis of gene expression.ResultshESC-CECs were nearly identical morphologically to primary human corneal endothelial cells, expressed Zona Occludens 1 (ZO-1) and Na+/K+ATPaseα1 (ATPA1) on the apical surface in monolayer culture, and produced the key proteins of Descemet’s membrane, Collagen VIIIα1 and VIIIα2 (COL8A1 and 8A2). Quantitative PCR analysis revealed expression of all corneal endothelial pump transcripts. hESC-CECs were 96% similar to primary human adult CECs by microarray analysis.ConclusionhESC-CECs are morphologically similar, express corneal endothelial cell markers and express a nearly identical complement of genes compared to human adult corneal endothelial cells. hESC-CECs may be a suitable alternative to donor-derived corneal endothelium.

A microfluidic device for 2D to 3D and 3D to 3D cell navigation

Microfluidic devices have received wide attention and shown great potential in the field of tissue engineering and regenerative medicine. Investigating cell response to various stimulations is much more accurate and comprehensive with the aid of microfluidic devices. In this study, we introduced a microfluidic device by which the matrix density as a mechanical property and the concentration profile of a biochemical factor as a chemical property could be altered. Our microfluidic device has a cell tank and a cell culture chamber to mimic both 2D to 3D and 3D to 3D migration of three types of cells. Fluid shear stress is negligible on the cells and a stable concentration gradient can be obtained by diffusion. The device was designed by a numerical simulation so that the uniformity of the concentration gradients throughout the cell culture chamber was obtained. Adult neural cells were cultured within this device and they showed different branching and axonal navigation phenotypes within varying nerve growth factor (NGF) concentration profiles. Neural stem cells were also cultured within varying collagen matrix densities while exposed to NGF concentrations and they experienced 3D to 3D collective migration. By generating vascular endothelial growth factor concentration gradients, adult human dermal microvascular endothelial cells also migrated in a 2D to 3D manner and formed a stable lumen within a specific collagen matrix density. It was observed that a minimum absolute concentration and concentration gradient were required to stimulate migration of all types of the cells. This device has the advantage of changing multiple parameters simultaneously and is expected to have wide applicability in cell studies.

WNT10B Enhances Proliferation through β-Catenin and RAC1 GTPase in Human Corneal Endothelial Cells

The cornea is the anterior, transparent tissue of the human eye that serves as its main refractive element. Corneal endothelial cells are arranged as a monolayer on the posterior surface of the cornea and function as a pump to counteract the leakiness of its basement membrane. Maintaining the cornea in a slightly dehydrated state is critical for the maintenance of corneal transparency. Adult human corneal endothelial cells are G1-arrested, even in response to injury, leading to an age-dependent decline in endothelial cell density. Corneal edema and subsequent vision loss ensues when endothelial cell density decreases below a critical threshold. Vision loss secondary to corneal endothelial dysfunction is a common indication for transplantation in developed nations. An impending increase in demand for and a current global shortage of donor corneas will necessitate the development of treatments for vision loss because of endothelial dysfunction that do not rely on donor corneas. Wnt ligands regulate many critical cellular functions, such as proliferation, making them attractive candidates for modulation in corneal endothelial dysfunction. We show that WNT10B causes nuclear transport and binding of RAC1 and β-catenin in human corneal endothelial cells, leading to the activation of Cyclin D1 expression and proliferation. Our findings indicate that WNT10B promotes proliferation in human corneal endothelial cells by simultaneously utilizing both β-catenin-dependent and -independent pathways and suggest that its modulation could be used to treat vision loss secondary to corneal endothelial dysfunction.