Christine Cheung

Generation of human vascular smooth muscle subtypes provides insight into embryological origin–dependent disease susceptibility

Heterogeneity of embryological origins is a hallmark of vascular smooth muscle cells (SMCs) and may influence the development of vascular disease. Differentiation of human pluripotent stem cells (hPSCs) into developmental origin–specific SMC subtypes remains elusive. Here we describe a chemically defined protocol in which hPSCs were initially induced to form neuroectoderm, lateral plate mesoderm or paraxial mesoderm. These intermediate populations were further differentiated toward SMCs (>80% MYH11+ and ACTA2+), which displayed contractile ability in response to vasoconstrictors and invested perivascular regions in vivo. Derived SMC subtypes recapitulated the unique proliferative and secretory responses to cytokines previously documented in studies using aortic SMCs of distinct origins. Notably, this system predicted increased extracellular matrix degradation by SMCs derived from lateral plate mesoderm, which was confirmed using rat aortic SMCs from corresponding origins. This differentiation approach will have broad applications in modeling origin-dependent disease susceptibility and in developing bioengineered vascular grafts for regenerative medicine.

Human embryonic stem cell-derived vascular smooth muscle cells in therapeutic neovascularisation

Ischemic diseases remain one of the major causes of morbidity and mortality throughout the world. In recent clinical trials on cell-based therapies, the use of adult stem and progenitor cells only elicited marginal benefits. Therapeutic neovascularisation is the Holy Grail for ischemic tissue recovery. There is compelling evidence from animal transplantation studies that the inclusion of mural cells in addition to endothelial cells (ECs) can enhance the formation of functional blood vessels. Vascular smooth muscle cells (SMCs) and pericytes are essential for the stabilisation of nascent immature endothelial tubes. Despite the intense interest in the utility of human embryonic stem cells (ESCs) for vascular regenerative medicine, ESC-derived vascular SMCs have received much less attention than ECs. This review begins with developmental insights into a range of smooth muscle progenitors from studies on embryos and ESC differentiation systems. We then summarise the methods of derivation of smooth muscle progenitors and cells from human ESCs. The primary emphasis is on the inherent heterogeneity of smooth muscle progenitors and cells and the limitations of current in vitro characterisation. Essential transplantation issues such as the type and source of therapeutic cells, mode of cell delivery, measures to enhance cell viability, putative mechanisms of benefit and long-term tracking of cell fate are also discussed. Finally, we highlight the challenges of clinical compatibility and scaling up for medical use in order to eventually realise the goal of human ESC-based vascular regenerative medicine.

Embryological-Origin–Dependent Differences in Homeobox Expression in Adult Aorta Role in Regional Phenotypic Variability and Regulation of NF-κB Activity

Objective—Different vascular beds show differing susceptibility to the development of atherosclerosis, but the molecular mechanisms underlying these differences are incompletely understood. This study aims to identify factors that contribute to the phenotypic heterogeneity of distinct regions of the adult vasculature. Approach and Results—High-throughput mRNA profiling in adult mice reveals higher expression of the homeobox paralogous genes 6 to 10 (Hox6-10) in the athero-resistant thoracic aorta (TA) than in the athero-susceptible aortic arch (AA). Higher homeobox gene expression also occurs in rat and porcine TA, and is maintained in primary smooth muscle cells isolated from TA (TA–SMCs) compared with cells from AA (AA–SMCs). This region-specific homeobox gene expression pattern is also observed in human embryonic stem cells differentiated into neuroectoderm–SMCs and paraxial mesoderm–SMCs, which give rise to AA–SMCs and TA–SMCs, respectively. We also find that, compared with AA and AA–SMCs, TA and TA–SMCs have lower activity of the proinflammatory and proatherogenic nuclear factor-&kgr;B (NF-&kgr;B) and lower expression of NF-&kgr;B target genes, at least in part attributable to HOXA9-dependent inhibition. Conversely, NF-&kgr;B inhibits HOXA9 promoter activity and mRNA expression in SMCs. Conclusion—Our findings support a model of Hox6-10–specified positional identity in the adult vasculature that is established by embryonic cues independently of environmental factors and is conserved in different mammalian species. Differential homeobox gene expression contributes to maintaining phenotypic differences between SMCs from athero-resistant and athero-susceptible regions, at least in part through feedback regulatory mechanisms involving inflammatory mediators, for example, reciprocal inhibition between HOXA9 and NF-&kgr;B.Objective— Different vascular beds show differing susceptibility to the development of atherosclerosis, but the molecular mechanisms underlying these differences are incompletely understood. This study aims to identify factors that contribute to the phenotypic heterogeneity of distinct regions of the adult vasculature. Approach and Results— High-throughput mRNA profiling in adult mice reveals higher expression of the homeobox paralogous genes 6 to 10 ( Hox6-10 ) in the athero-resistant thoracic aorta (TA) than in the athero-susceptible aortic arch (AA). Higher homeobox gene expression also occurs in rat and porcine TA, and is maintained in primary smooth muscle cells isolated from TA (TA–SMCs) compared with cells from AA (AA–SMCs). This region-specific homeobox gene expression pattern is also observed in human embryonic stem cells differentiated into neuroectoderm–SMCs and paraxial mesoderm–SMCs, which give rise to AA–SMCs and TA–SMCs, respectively. We also find that, compared with AA and AA–SMCs, TA and TA–SMCs have lower activity of the proinflammatory and proatherogenic nuclear factor-κB (NF-κB) and lower expression of NF-κB target genes, at least in part attributable to HOXA9-dependent inhibition. Conversely, NF-κB inhibits HOXA9 promoter activity and mRNA expression in SMCs. Conclusion— Our findings support a model of Hox6-10–specified positional identity in the adult vasculature that is established by embryonic cues independently of environmental factors and is conserved in different mammalian species. Differential homeobox gene expression contributes to maintaining phenotypic differences between SMCs from athero-resistant and athero-susceptible regions, at least in part through feedback regulatory mechanisms involving inflammatory mediators, for example, reciprocal inhibition between HOXA9 and NF-κB. # Significance {#article-title-44}

Directed differentiation of embryonic origin–specific vascular smooth muscle subtypes from human pluripotent stem cells

Vascular smooth muscle cells (SMCs) arise from diverse developmental origins. Regional distribution of vascular diseases may, in part, be attributed to this inherent heterogeneity in SMC lineage. Therefore, systems for generating human SMC subtypes of distinct embryonic origins would represent useful platforms for studying the influence of SMC lineage on the spatial specificity of vascular disease. Here we describe how human pluripotent stem cells can be differentiated into distinct populations of SMC subtypes under chemically defined conditions. The initial stage (days 0–5 or 0–7) begins with the induction of three intermediate lineages: neuroectoderm, lateral plate mesoderm and paraxial mesoderm. Subsequently, these precursor lineages are differentiated into contractile SMCs (days 5–19+). At key stages, the emergence of lineage-specific markers confirms recapitulation of embryonic developmental pathways and generation of functionally distinct SMC subtypes. The ability to derive an unlimited supply of human SMCs will accelerate applications in regenerative medicine and disease modeling.

Myocardin Overexpression Is Sufficient for Promoting the Development of a Mature Smooth Muscle Cell-Like Phenotype from Human Embryonic Stem Cells

Background Myocardin is thought to have a key role in smooth muscle cell (SMC) development by acting on CArG-dependent genes. However, it is unclear whether myocardin-induced SMC maturation and increases in agonist-induced calcium signalling are also associated with increases in the expression of non-CArG-dependent SMC-specific genes. Moreover, it is unknown whether myocardin promotes SMC development from human embryonic stem cells. Methodology/Principal Findings The effects of adenoviral-mediated myocardin overexpression on SMC development in human ESC-derived embryoid bodies were investigated using immunofluorescence, flow cytometry and real time RT-PCR. Myocardin overexpression from day 10 to day 28 of embryoid body differentiation increased the number of smooth muscle α-actin+ and smooth muscle myosin heavy chain+ SMC-like cells and increased carbachol-induced contractile function. However, myocardin was found to selectively regulate only CArG-dependent SMC-specific genes. Nevertheless, myocardin expression appeared to be sufficient to specify the SMC lineage. Conclusions/Significance Myocardin increases the development and maturation of SMC-like cells from human embryonic stem cells despite not activating the full repertoire of SMC genes. These findings have implications for vascular tissue engineering and other applications requiring large numbers of functional SMCs.

Electrochemical study of the intracellular transduction of vascular endothelial growth factor induced nitric oxide synthase activity using a multi-channel biocompatible microelectrode array

BACKGROUND Nitric oxide (NO) plays a major role in physiology as a biological mediator. NO has been identified in nervous, immune and vascular systems and is a critical parameter in numerous pathologies, such as cancer. This article describes the electrochemical biomeasurements of NO synthase (NOS) activity from cultured endothelial cells using a multiple microelectrode array. METHODS Firstly, the effect of biocompatible fibronectin coating on electrochemical measurements was investigated. Secondly, endothelial cells were deposited on the fibronectin coated sensor and NO release was triggered with vascular endothelial growth factor (VEGF). N(G)-nitro-L-arginine methyl ester (L-NAME) was used as an inhibitor of NO production, and different kinase blockers were investigated. Change in NOS activity was quantified using differential pulse voltammetry before and after addition of VEGF. RESULTS Our results show that carefully applied layers of fibronectin have a very limited effect on electrochemistry and that VEGF induces an increase in NOS activity that is mainly mediated through the phosphatidylinositol 3 kinase (PI-3), and not by the extracellular signal-regulated kinases 1/2. Results obtained using electrochemical sensors were supported by wound healing assay demonstrating the critical role of phosphatidylinositol 3 kinase and extracellular signal-regulated kinases 1/2 for angiogenesis. CONCLUSION Electrochemical study of the intracellular transduction of the VEGF signal leading to NO synthesis was achieved, showing the critical role of PI-3 kinase. GENERAL SIGNIFICANCE This study presents an electrochemical sensor allowing measurements of NOS activity in cell cultures and tissue samples.

Embryological Origin of Human Smooth Muscle Cells Influences Their Ability to Support Endothelial Network Formation

Vascular smooth muscle cells (SMCs) from distinct anatomic locations derive from different embryonic origins. Here we investigated the respective potential of different embryonic origin‐specific SMCs derived from human embryonic stem cells (hESCs) to support endothelial network formation in vitro. SMCs of three distinct embryological origins were derived from an mStrawberry‐expressing hESC line and were cocultured with green fluorescent protein‐expressing human umbilical vein endothelial cells (HUVECs) to investigate the effects of distinct SMC subtypes on endothelial network formation. Quantitative analysis demonstrated that lateral mesoderm (LM)‐derived SMCs best supported HUVEC network complexity and survival in three‐dimensional coculture in Matrigel. The effects of the LM‐derived SMCs on HUVECs were at least in part paracrine in nature. A TaqMan array was performed to identify the possible mediators responsible for the differential effects of the SMC lineages, and a microarray was used to determine lineage‐specific angiogenesis gene signatures. Midkine (MDK) was identified as one important mediator for the enhanced vasculogenic potency of LM‐derived SMCs. The functional effects of MDK on endothelial network formation were then determined by small interfering RNA‐mediated knockdown in SMCs, which resulted in impaired network complexity and survival of LM‐derived SMC cocultures. The present study is the first to show that SMCs from distinct embryonic origins differ in their ability to support HUVEC network formation. LM‐derived SMCs best supported endothelial cell network complexity and survival in vitro, in part through increased expression of MDK. A lineage‐specific approach might be beneficial for vascular tissue engineering and therapeutic revascularization.

Stroke biomarkers in clinical practice: A critical appraisal

ABSTRACT Biomarkers provide critical mechanistic insights to key biologic processes that occur during cerebral ischemia which, when carefully applied, can improve clinical decision‐making in acute stroke management. The translation of a blood‐based biomarker in ischemic stroke to clinical practice is challenging, in part, due to the complexity of ischemic stroke pathogenesis and the presence of a blood‐brain barrier that restricts the release of brain‐specific markers into the circulation. The pathologic and clinical aspects of ischemic stroke are described in this review, where a non‐exhaustive list of biomarkers that interrogate different aspects of ischemic stroke such as oxidative damage, inflammation, thrombus formation, cardiac function and brain injury are described. The potential roles of these biomarkers are further examined under different clinical scenarios aimed at (1) averting the risk of hemorrhagic transformation, (2) identifying individuals at risk of early neurologic deterioration and malignant infarction, (3) aiding in the diagnosis of ischemic stroke and its differentiation from other stroke mimics, (4) guiding the search for stroke etiology, and (5) assessing stroke risk within the community. Researchers should explore the roles of stroke biomarkers to enhance clinical decision‐making that is presently largely based on intuition and subjective reasoning. HIGHLIGHTSBiomarkers provide mechanistic insights to key biologic processes during stroke.Biomarkers can aid in clinical decision‐making during stroke management.Prognostic significance of stroke biomarkers could be further examined.

Contributions of BMPR2 Mutations and Extrinsic Factors to Cellular Phenotypes of Pulmonary Arterial Hypertension Revealed by iPSC Modeling.

Supported by funding from the British Heart Foundation (BHF) (project grant PG/14/31/30786 and programme grant RG/13/4/30107), the Cambridge National Institute for Health Research Biomedical Research Centre, the Dinosaur Trust, Fondation Leducq, the Medical Research Council (MRC Experimental Challenge Award – MR/KO20919/1), Pulmonary Hypertension Association UK, Fight for Sight and the Robert McAlpine Foundation. NWM was supported by a BHF Chair Award (CH/09/001/25945) and FNK was supported by a BHF PhD studentship (FS/13/51/30636) and a travel grant from St Catharine’s College Cambridge. AAR and NWM would also like to acknowledge support from the BHF Centre of Regenerative Medicine, Oxford and Cambridge (RM/13/3/30159), the BHF Centre for Research Excellence (RE/13/6/30180), the BHF IPAH cohort grant (SP/12/12/29836), Selwyn and St Catharine’s Colleges, Cambridge, and a Pfizer European Young Researcher of the Year award to AAR.

Human Stem Cell-Derived Endothelial-Hepatic Platform for Efficacy Testing of Vascular-Protective Metabolites From Nutraceuticals

Atherosclerosis underlies many cardiovascular and cerebrovascular diseases. Nutraceuticals are emerging as a therapeutic moiety for restoring vascular health. Unlike small‐molecule drugs, the complexity of ingredients in nutraceuticals often confounds evaluation of their efficacy in preclinical evaluation. It is recognized that the liver is a vital organ in processing complex compounds into bioactive metabolites. In this work, we developed a coculture system of human pluripotent stem cell‐derived endothelial cells (hPSC‐ECs) and human pluripotent stem cell‐derived hepatocytes (hPSC‐HEPs) for predicting vascular‐protective effects of nutraceuticals. To validate our model, two compounds (quercetin and genistein), known to have anti‐inflammatory effects on vasculatures, were selected. We found that both quercetin and genistein were ineffective at suppressing inflammatory activation by interleukin‐1β owing to limited metabolic activity of hPSC‐ECs. Conversely, hPSC‐HEPs demonstrated metabolic capacity to break down both nutraceuticals into primary and secondary metabolites. When hPSC‐HEPs were cocultured with hPSC‐ECs to permit paracrine interactions, the continuous turnover of metabolites mitigated interleukin‐1β stimulation on hPSC‐ECs. We observed significant reductions in inflammatory gene expressions, nuclear translocation of nuclear factor κB, and interleukin‐8 production. Thus, integration of hPSC‐HEPs could accurately reproduce systemic effects involved in drug metabolism in vivo to unravel beneficial constituents in nutraceuticals. This physiologically relevant endothelial‐hepatic platform would be a great resource in predicting the efficacy of complex nutraceuticals and mechanistic interrogation of vascular‐targeting candidate compounds. Stem Cells Translational Medicine 2017;6:851–863