A novel lineage restricted, pericyte-like cell line isolated from human embryonic stem cells

Clonal and Scalable Endothelial Progenitor Cell Lines from Human Pluripotent Stem Cells

Human pluripotent stem cells (hPSCs) can be used as a renewable source of endothelial cells for treating cardiovascular disease and other ischemic conditions. Here, we present the derivation and characterization of a panel of distinct clonal embryonic endothelial progenitor cells (eEPCs) lines that were differentiated from human embryonic stem cells (hESCs). The hESC line, ESI-017, was first partially differentiated to produce candidate cultures from which eEPCs were cloned. Endothelial cell identity was assessed by transcriptomic analysis, cell surface marker expression, immunocytochemical marker analysis, and functional analysis of cells and exosomes using vascular network forming assays. The transcriptome of the eEPC lines was compared to various adult endothelial lines as well as various non-endothelial cells including both adult and embryonic origins. This resulted in a variety of distinct cell lines with functional properties of endothelial cells and strong transcriptomic similarity to adult endothelial primary cell lines. The eEPC lines, however, were distinguished from adult endothelium by their novel pattern of embryonic gene expression. We demonstrated eEPC line scalability of up to 80 population doublings (pd) and stable long-term expansion of over 50 pd with stable angiogenic properties at late passage. Taken together, these data support the finding that hESC-derived clonal eEPC lines are a potential source of scalable therapeutic cells and cell products for treating cardiovascular disease. These eEPC lines offer a highly promising resource for the development of further preclinical studies aimed at therapeutic interventions.

Central Nervous System Pericytes Contribute to Health and Disease

Successful neuroprotection is only possible with contemporary microvascular protection. The prevention of disease-induced vascular modifications that accelerate brain damage remains largely elusive. An improved understanding of pericyte (PC) signalling could provide important insight into the function of the neurovascular unit (NVU), and into the injury-provoked responses that modify cell-cell interactions and crosstalk. Due to sharing the same basement membrane with endothelial cells, PCs have a crucial role in the control of endothelial, astrocyte, and oligodendrocyte precursor functions and hence blood-brain barrier stability. Both cerebrovascular and neurodegenerative diseases impair oxygen delivery and functionally impair the NVU. In this review, the role of PCs in central nervous system health and disease is discussed, considering their origin, multipotency, functions and also dysfunction, focusing on new possible avenues to modulate neuroprotection. Dysfunctional PC signalling could also be considered as a potential biomarker of NVU pathology, allowing us to individualize therapeutic interventions, monitor responses, or predict outcomes.

Bioprinted microvasculature: progressing from structure to function

Three-dimensional (3D) bioprinting seeks to unlock the rapid generation of complex tissue constructs, but long-standing challenges with efficientin vitromicrovascularization must be solved before this can become a reality. Microvasculature is particularly challenging to biofabricate due to the presence of a hollow lumen, a hierarchically branched network topology, and a complex signaling milieu. All of these characteristics are required for proper microvascular-and, thus, tissue-function. While several techniques have been developed to address distinct portions of this microvascularization challenge, no single approach is capable of simultaneously recreating all three microvascular characteristics. In this review, we present a three-part framework that proposes integration of existing techniques to generate mature microvascular constructs. First, extrusion-based 3D bioprinting creates a mesoscale foundation of hollow, endothelialized channels. Second, biochemical and biophysical cues induce endothelial sprouting to create a capillary-mimetic network. Third, the construct is conditioned to enhance network maturity. Across all three of these stages, we highlight the potential for extrusion-based bioprinting to become a central technique for engineering hierarchical microvasculature. We envision that the successful biofabrication of functionally engineered microvasculature will address a critical need in tissue engineering, and propel further advances in regenerative medicine andex vivohuman tissue modeling.

Recent progress and new challenges in modeling of human pluripotent stem cell-derived blood-brain barrier

The blood-brain barrier (BBB) is a semipermeable unit that serves to vascularize the central nervous system (CNS) while tightly regulating the movement of molecules, ions, and cells between the blood and the brain. The BBB precisely controls brain homeostasis and protects the neural tissue from toxins and pathogens. The BBB is coordinated by a tight monolayer of brain microvascular endothelial cells, which is subsequently supported by mural cells, astrocytes, and surrounding neuronal cells that regulate the barrier function with a series of specialized properties. Dysfunction of barrier properties is an important pathological feature in the progression of various neurological diseases. In vitro BBB models recapitulating the physiological and diseased states are important tools to understand the pathological mechanism and to serve as a platform to screen potential drugs. Recent advances in this field have stemmed from the use of pluripotent stem cells (PSCs). Various cell types of the BBB such as brain microvascular endothelial cells (BMECs), pericytes, and astrocytes have been derived from PSCs and synergistically incorporated to model the complex BBB structure in vitro. In this review, we summarize the most recent protocols and techniques for the differentiation of major cell types of the BBB. We also discuss the progress of BBB modeling by using PSC-derived cells and perspectives on how to reproduce more natural BBBs in vitro.

Derivation of Pericytes from Human Pluripotent Stem Cells

Human pluripotent stem cells (hPSCs), either embryonic or induced, offer a plentiful platform for derivation of multiple cell types. Pericytes, generated from hPSCs, are multipotent precursors with vasculogenic features that exhibit high proliferation capability in long-term cultures. Administration of hPSC-pericytes into ischemic murine hind limb is associated with therapeutic angiogenesis and attenuation of muscle wasting. Here, we describe the protocol for derivation of large numbers of pericytes from spontaneously differentiating hPSC-embryoid bodies.

Neurovascular Unit: A critical role in ischemic stroke

Ischemic stroke (IS), a common cerebrovascular disease, results from a sudden blockage of a blood vessel in the brain, thereby restricting blood supply to the area in question, and making a significantly negative impact on human health. Unfortunately, current treatments, that are mainly based on a recanalization of occluded blood vessels, are insufficient or inaccessible to many stroke patients. Recently, the profound influence of the neurovascular unit (NVU) on recanalization and the prognosis of IS have become better understood; in‐depth studies of the NVU have also provided novel approaches for IS treatment. In this article, we review the intimate connections between the changes in the NVU and IS outcomes, and discuss possible new management strategies having practical significance to IS. We discuss the concept of the NVU, as well as its roles in IS blood‐brain barrier regulation, cell preservation, inflammatory immune response, and neurovascular repair. Besides, we also summarize the influence of noncoding RNAs in NVU, and IS therapies targeting the NVU. We conclude that both the pathophysiological and neurovascular repair processes of IS are strongly associated with the homeostatic state of the NVU and that further research into therapies directed at the NVU could expand the range of treatments available for IS.

Engineering Brain-Specific Pericytes from Human Pluripotent Stem Cells

Pericytes (PCs) are a type of perivascular cells that surround endothelial cells of small blood vessels. In the brain, PCs show heterogeneity depending on their position within the vasculature. As a result, PC interactions with surrounding endothelial cells, astrocytes, and neuron cells play a key role in a wide array of neurovascular functions such as regulating blood-brain barrier (BBB) permeability, cerebral blood flow, and helping to facilitate the clearance of toxic cellular molecules. Therefore, a reliable method of engineering brain-specific PCs from human induced pluripotent stem cells (hiPSCs) is critical in neurodegenerative disease modeling. This review summarizes brain-specific PC differentiation of hiPSCs through mesoderm and neural crest induction. Key signaling pathways (platelet-derived growth factor-B [PDGF-B], transforming growth factor [TGF]-β, and Notch signaling) regulating PC function, PC interactions with adjacent cells, and PC differentiation from hiPSCs are also discussed. Specifically, PDGF-BB-platelet-derived growth factor receptor β signaling promotes PC cell survival, TGF-β signal transduction facilitates PC attachment to endothelial cells, and Notch signaling is critical in vascular development and arterial-venous specification. Furthermore, current challenges facing the use of hiPSC-derived PCs are discussed, and their ongoing uses in neurodegenerative disease modeling are identified. Further investigations into PCs and surrounding cell interactions are needed to characterize the roles of brain PCs in various neurodegenerative disorders. Impact statement This article summarizes the work related to brain-specific pericytes (PCs) derived from human pluripotent stem cells (hPSCs). In particular, key signaling pathways regulating PC function, PC interactions with adjacent cells, and PC differentiation from hPSCs were discussed. Furthermore, current challenges facing the use of hPSC-derived PCs were identified, and their ongoing uses in neurodegenerative disease modeling were discussed. The review highlights the important role of cell-cell interactions in blood-brain barrier (BBB) models and neurodegeneration. The summarized findings are significant for establishing pluripotent stem cell-based BBB models toward the applications in drug screening and disease modeling.

Pericytes improve locomotor recovery after spinal cord injury in male and female neonatal rats

OBJECTIVE

It is not known how activation of the hypoxia-inducible factor (HIF) pathway in pericytes, cells of the microvascular wall, influences new capillary growth. We tested the hypothesis that HIF-activated pericytes promote angiogenesis in a neonatal model of spinal cord injury (SCI).

METHODS

Human placental pericytes stimulated with cobalt chloride and naïve pericytes were injected into the site of a thoracic hemi-section of the spinal cord in rat pups on postnatal day three (P3). Hindlimb motor recovery and Doppler blood flow perfusion at the site of transection were measured on P10. Immunohistochemistry was used to visualize vessel and neurofilament density for quantification.

RESULTS

Injection of HIF-activated pericytes resulted in greater vascular density in males but did not result in improved motor function for males or females. Injection of non-HIF-activated pericytes resulted improved motor function recovery in both sexes (males, 2.722 ± 0.31-fold score improvement; females, 3.824 ± 0.58-fold score improvement, P < .05) but produced no significant changes in vessel density.

CONCLUSIONS

HIF-activated pericytes promote vascular density in males post-SCI. Acute delivery of non-HIF-activated pericytes at the site of injury can improve motor recovery post-SCI.

Evaluation of the biofilm formation of Staphylococcus aureus and Pseudomonas aeruginosa on human umbilical cord CD146+ stem cells and stem cell-based decellularized matrix

This study aims to evaluate the CD146+ stem cells obtained from the human umbilical cord and their extracellular matrix proteins on in vitro Pseudomonas aeruginosa and Staphylococcus aureus biofilms to understand their possible antimicrobial activity. CD146+ stem cells were determined according to cell surface markers and differentiation capacity. Characterization of the decellularized matrix was done with DAPI, Masson's Trichrome staining and proteome analysis. Cell viability/proliferation of cells in co-cultures was evaluated by WST-1 and crystal-violet staining. The effects of cells and decellularized matrix proteins on biofilms were investigated on a drip flow biofilm reactor and their effects on gene expression were determined by RT-qPCR. We observed that CD146/105+ stem cells could differentiate adipogenically and decellularized matrix showed negative DAPI and positive collagen staining with Masson' s Trichrome. Proteome analysis of the decellularized matrix revealed some matrix components and growth factors. Although the decellularized matrix significantly reduced the cell counts of P. aeruginosa, no significant difference was observed for S. aureus cells in both groups. Supporting data was obtained from the gene expression results of P. aeruginosa with the significant down-regulation of rhlR and lasR. For S. aureus, icaADBC genes were significantly up-regulated when grown on the decellularized matrix.

Transcriptome and proteome profiles of human umbilical cord vein CD146+ stem cells

In this study we used two different techniques in order to isolate pericytes from the wall of human umbilical cord vein and get two different groups of cells were named as "pellet and primer cells". These groups were compared with each other according to their morphologies and stem cell marker expressions. Also, these two different populations were compared with each other and with human bone marrow mesenchymal stem cells (BM-MSCs) according to their transcriptomic profiles. Then, pellet cells proteomic profiles were determined. Our results showed that morphologies and cell surface marker expressions of pellet cells and primer cells are similar. On the other hand, according to immunofluorescence staining results, in contrast to primer cells, pellet cells showed positive NG2 and PDGFR-β staining. As a result of gene expression profiling, pellet cells have upregulated genes related with muscle, neural and immune cell differentiation, development and pluripotency. On the other hand, primer cells have upregulated adhesion pathway-related genes. In addition to differences between pellet and primer cells, the gene expression profiles of these cell groups are also different from BM-MSCs. The results of transcriptome and proteome analysis of pellet cells were in consistent with each other.

Induction of Mesoderm and Neural Crest-Derived Pericytes from Human Pluripotent Stem Cells to Study Blood-Brain Barrier Interactions

In the CNS, perivascular cells (“pericytes”) associate with endothelial cells to mediate the formation of tight junctions essential to the function of the blood-brain barrier (BBB). The BBB protects the CNS by regulating the flow of nutrients and toxins into and out of the brain. BBB dysfunction has been implicated in the progression of Alzheimer's disease (AD), but the role of pericytes in BBB dysfunction in AD is not well understood. In the developing embryo, CNS pericytes originate from two sources: mesoderm and neural crest. In this study, we report two protocols using mesoderm or neural crest intermediates, to generate brain-specific pericyte-like cells from induced pluripotent stem cell (iPSC) lines created from healthy and AD patients. iPSC-derived pericytes display stable expression of pericyte surface markers and brain-specific genes and are functionally capable of increasing vascular tube formation and endothelial barrier properties.

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Mesoderm and neural crest-derived pericytes (PCs) from hPSCs termed mPCs and ncPCs

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mPCs and ncPCs express general and brain-specific pericyte genes

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mPCs and ncPCs associate with and promote barrier properties of endothelial cells

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WNT is important, but not necessary for neural crest-derived PC specification

Pericytes in Alzheimer's Disease: Novel Clues to Cerebral Amyloid Angiopathy Pathogenesis

Pericytes in the central nervous system attract growing attention of neurobiologists because of obvious opportunities to use them as target cells in numerous brain diseases. Functional activity of pericytes includes control of integrity of the endothelial cell layer, regeneration of vascular cells, and regulation of microcirculation. Pericytes are well integrated in the so-called neurovascular unit (NVU) serving as a platform for effective communications of neurons, astrocytes, endothelial cells, and pericytes. Contribution of pericytes to the establishment and maintaining the structural and functional integrity of blood-brain barrier is confirmed in numerous experimental and clinical studies. The review covers current understandings on the role of pericytes in molecular pathogenesis of NVU/BBB dysfunction in Alzheimer's disease with the special focus on the development of cerebral amyloid angiopathy, deregulation of cerebral angiogenesis, and progression of BBB breakdown seen in Alzheimer's type neurodegeneration.

In Vitro Murine Hematopoiesis Supported by Signaling from a Splenic Stromal Cell Line

There are very few model systems which demonstrate hematopoiesis in vitro. Previously, we described unique splenic stromal cell lines which support the in vitro development of hematopoietic cells and particularly myeloid cells. Here, the 5G3 spleen stromal cell line has been investigated for capacity to support the differentiation of hematopoietic cells from progenitors in vitro. Initially, 5G3 was shown to express markers of mesenchymal but not endothelial or hematopoietic cells and to resemble perivascular reticular cells in the bone marrow through gene expression. In particular, 5G3 resembles CXCL12-abundant reticular cells or perivascular reticular cells, which are important niche elements for hematopoiesis in the bone marrow. To analyse the hematopoietic support function of 5G3, specific signaling pathway inhibitors were tested for the ability to regulate cell production in vitro in cocultures of stroma overlaid with bone marrow-derived hematopoietic stem/progenitor cells. These studies identified an important role for Wnt and Notch pathways as well as tyrosine kinase receptors like c-KIT and PDGFR. Cell production in stromal cocultures constitutes hematopoiesis, since signaling pathways provided by splenic stroma reflect those which support hematopoiesis in the bone marrow.

Establishment and characterization of an embryonic pericyte cell line

OBJECTIVE

Pericytes are specialized perivascular cells embedded within the basement membrane. These cells envelope the abluminal surface of endothelial cells and promote microvessel homeostasis. Recent discoveries of unique pericyte functions, particularly in neural tissues, underscore the need for overcoming existing challenges in establishing a functionally validated pericyte cell line. Here, we present methodologies for addressing these challenges as well as an embryonic pericyte cell line for use with in vitro and ex vivo experimental models.

METHODS

We isolated an enriched population of NG2:DsRed+ pericytes from E12.5 mice. This pericyte cell line was compared to MEFs with respect to gene expression, cell morphology and migration, and engagement with endothelial cells during junction stabilization and angiogenesis.

RESULTS

NG2+ pericytes displayed gene expression patterns, cell morphology, and 2D migration behaviors distinct from MEFs. In three different vessel formation models, pericytes from this line migrated to and incorporated into developing vessels. When co-cultured with HUVECs, these pericytes stimulated more robust VE-Cadherin junctions between HUVECs as compared to MEFs, as well as contributed to HUVEC organization into primitive vascular structures.

CONCLUSIONS

Our data support use of this pericyte cell line in a broad range of models to further understand pericyte functionality during normal and pathological conditions.

Generation of human umbilical cord vein CD146+ perivascular cell origined three-dimensional vascular construct

Small-diameter vascular grafts are needed for the treatment of coronary artery diseases in the case of limited accessibility of the autologous vessels. Synthetic scaffolds have many disadvantages so in recent years vascular constructs (VCs) made from cellularized natural scaffolds was seen to be very promising but number of studies comprising this area is very limited. In our study, our aim is to generate fully natural triple-layered VC that constitutes all the layers of blood vessel with vascular cells. CD146+ perivascular cells (PCs) were isolated from human umbilical cord vein (HUCV) and differentiated into smooth muscle cells (SMCs) and fibroblasts. They were then combined with collagen type I/elastin/dermatan sulfate and collagen type I/fibrin to form tunica media and tunica adventitia respectively. HUCV endothelial cells (ECs) were seeded on the construct by cell sheet engineering method after fibronectin and heparin coating. Characterization of the VC was performed by immunolabeling, histochemical staining and electron microscopy (SEM and TEM). Differentiated cells were identified by means of immunofluorescent (IF) labeling. SEM and TEM analysis of VCs revealed the presence of three histologic tunicae. Collagen and elastic fibers were observed within the ECM by histochemical staining. The vascular endothelial growth factor receptor expressing ECs in tunica intima; α-SMA expressing SMCs in tunica media and; the tenascin expressing fibroblasts in tunica adventitia were detected by IF labeling. In conclusion, by combining natural scaffolds and vascular cells differentiated from CD146+ PCs, VCs can be generated layer by layer. This study will provide a preliminary blood vessel model for generation of fully natural small-diameter vascular grafts.

The Microvascular Pericyte: Approaches to Isolation, Characterization, and Cultivation

The microvascular pericyte was identified in 1873 by the French scientist Charles Benjamin Rouget and originally called the Rouget cell (Rouget.Sciences 88:916-8, 1879). However, it was not until the early 1900s that Rouget's work was confirmed, and the Rouget cell renamed the pericyte by virtue of its peri-endothelial location (Dore. Brit J Dermatol 35:398-404, 1923; Zimmermann. Z Anat Entwicklungsgesch 68:3-109, 1923). Over the years a large number of publications have emerged, but the pericyte has remained a truly enigmatic cell. This is due, in part, by the paucity of easy and reliable methods to isolate and characterize the cell as well as its heterogeneity and pluripotent characteristics. However, more recent advances in molecular genetics and development of novel cell isolation and imaging techniques have enable scientists to more readily define pericyte function. This chapter will discuss general approaches to the isolation, characterization, and propagation of primary pericytes in the establishment of cell lines. We will attempt to dispel misinterpretations about the pericyte that cloud the literature.

Biomarkers of Human Pluripotent Stem Cell-Derived Cardiac Lineages

Human pluripotent stem cells (hPSCs) offer a practical source for the de novo generation of cardiac tissues and a unique opportunity to investigate cardiovascular lineage commitment. Numerous strategies have focused on the in vitro production of cardiomyocytes, smooth muscle, and endothelium from hPSCs. However, these differentiation protocols often yield undesired cell types. Thus, establishing a set of stage-specific markers for pure cardiac subpopulations will assist in defining the hierarchy of cardiac differentiation, aid in the development of cellular therapy, and facilitate drug screening and disease modeling. The recent characterization of many such markers is enabling the isolation of major cardiac lineages and subpopulations from differentiating hPSCs. We provide here a comprehensive review detailing the suite of biomarkers used to differentiate cardiac lineages from mixed hPSC-derived populations.

Paving the Way Toward Complex Blood-Brain Barrier Models Using Pluripotent Stem Cells

A tissue with great need to be modeled in vitro is the blood-brain barrier (BBB). The BBB is a tight barrier that covers all blood vessels in the brain and separates the brain microenvironment from the blood system. It consists of three cell types [neurovascular unit (NVU)] that contribute to the unique tightness and selective permeability of the BBB and has been shown to be disrupted in many diseases and brain disorders, such as vascular dementia, stroke, multiple sclerosis, and Alzheimer's disease. Given the progress that pluripotent stem cells (PSCs) have made in the past two decades, it is now possible to produce many cell types from the BBB and even partially recapitulate this complex tissue in vitro. In this review, we summarize the most recent developments in PSC differentiation and modeling of the BBB. We also suggest how patient-specific human-induced PSCs could be used to model BBB dysfunction in the future. Lastly, we provide perspectives on how to improve production of the BBB in vitro, for example by improving pericyte differentiation protocols and by better modeling the NVU in the dish.

A systematic review: differentiation of stem cells into functional pericytes

Pericytes are an integral cellular component of vascular structures. Numerous studies have investigated various stem cell types as potential sources of pericytes for application in cell-based therapy. The diverse stem cell types and variable experimental protocols of these studies make it imperative to evaluate the relevant scientific literature on the basis of a unified standard. The purpose of this systematic review is to rigorously evaluate the relevant scientific literature for conclusive evidence that stem cells can differentiate into functional pericytes. An online literature search was conducted up to July 2016. Eligible papers were evaluated on 4 pertinent criteria: 1) appropriate controls, 2) markers to confirm pericyte phenotype, 3) techniques for assessing pericyte functionality, and 4) differentiation efficiency of the protocol. Our search yielded 20 eligible studies (from 2006 to 2016), 12 of which were published in the past 5 yr. Of these 20 articles, only 1 had positive control, and 5 papers evaluated differentiation efficiency. The most commonly used pericyte markers were neuron-glial antigen 2, platelet-derived growth factor receptor-β, and α-smooth muscle actin. Three articles were associated with adipose stem cells, 4 with mesenchymal stem cells, and 7 with pluripotent stem cells, whereas the remaining 6 articles were based on other miscellaneous stem cell types. Stem cells can serve as a potential source of pericytes, but there should be standardized guidelines in future studies for assessing pericyte differentiation.-Xu, J., Gong, T., Heng, B. C., Zhang, C. F. A systematic review: differentiation of stem cells into functional pericytes.