Multilineage differentiation from human embryonic stem cell lines

Molecular ties between the cell cycle and differentiation in embryonic stem cells

Attainment of the differentiated state during the final stages of somatic cell differentiation is closely tied to cell cycle progression. Much less is known about the role of the cell cycle at very early stages of embryonic development. Here, we show that molecular pathways involving the cell cycle can be engineered to strongly affect embryonic stem cell differentiation at early stages in vitro. Strategies based on perturbing these pathways can shorten the rate and simplify the lineage path of ES differentiation. These results make it likely that pathways involving cell proliferation intersect at various points with pathways that regulate cell lineages in embryos and demonstrate that this knowledge can be used profitably to guide the path and effectiveness of cell differentiation of pluripotent cells.

Mesenchymal stem cell therapy and acute graft-versus-host disease: a review

Mesenchymal stem cells (MSCs) are being widely studied as potential cell therapy agents due to their immunomodulatory properties, which have been established by in vitro studies and in several clinical trials. Within this context, mesenchymal stem cell therapy appears to hold substantial promise, particularly in the treatment of conditions involving autoimmune and inflammatory components. Nevertheless, many research findings are still contradictory, mostly due to difficulties in characterization of the effects of MSCs in vivo. The purpose of this review is to report the mechanisms underlying mesenchymal stem cell therapy for acute graft-versus-host disease, particularly with respect to immunomodulation, migration, and homing, as well as report clinical applications described in the literature.

Disease modeling using human induced pluripotent stem cells: lessons from the liver

Human pluripotent stem cells (hPSCs) have the capacity to differentiate into any of the hundreds of distinct cell types that comprise the human body. This unique characteristic has resulted in considerable interest in the field of regenerative medicine, given the potential for these cells to be used to protect, repair, or replace diseased, injured, and aged cells within the human body. In addition to their potential in therapeutics, hPSCs can be used to study the earliest stages of human development and to provide a platform for both drug screening and disease modeling using human cells. Recently, the description of human induced pluripotent stem cells (hIPSCs) has allowed the field of disease modeling to become far more accessible and physiologically relevant, as pluripotent cells can be generated from patients of any genetic background. Disease models derived from hIPSCs that manifest cellular disease phenotypes have been established to study several monogenic diseases; furthermore, hIPSCs can be used for phenotype-based drug screens to investigate complex diseases for which the underlying genetic mechanism is unknown. As a result, the use of stem cells as research tools has seen an unprecedented growth within the last decade as researchers look for in vitro disease models which closely mimic in vivo responses in humans. Here, we discuss the beginnings of hPSCs, starting with isolation of human embryonic stem cells, moving into the development and optimization of hIPSC technology, and ending with the application of hIPSCs towards disease modeling and drug screening applications, with specific examples highlighting the modeling of inherited metabolic disorders of the liver. This article is part of a Special Issue entitled Linking transcription to physiology in lipodomics.

Self-renewal and cell lineage differentiation strategies in human embryonic stem cells and induced pluripotent stem cells

INTRODUCTION

Since the initial discoveries of human embryonic and induced pluripotent stem cells, many strategies have been developed to utilize the potential of these cells for translational research and disease modeling. The success of these aims and the development of future applications in this area will depend on the ability to generate high-quality and large numbers of differentiated cell types that genetically, epigenetically, and functionally mimic the cells found in the body.

AREAS COVERED

In this review, we highlight the current strategies used to maintain stem cell pluripotency (a measure of stem cell quality), as well as provide an overview of the various differentiation strategies being used to generate cells from all three germ lineages. We also discuss the particular considerations that must be addressed when utilizing these cells for translational therapy, and provide an example of a cell type currently used in clinical trials.

EXPERT OPINION

The major challenge in regenerative medicine and disease modeling will be in generating functional cells of sufficient quality that are physiologically and epigenetically similar to the diverse cells that they are modeled after. By meeting these criteria, these differentiated products can be successfully used in disease modeling, drug/toxicology screens, and cellular replacement therapy.

Neural stem cell therapies for enteric nervous system disorders

The enteric nervous system is vulnerable to a range of congenital and acquired disorders that disrupt the function of its neurons or lead to their loss. The resulting enteric neuropathies are some of the most challenging clinical conditions to manage. Neural stem cells offer the prospect of a cure given their potential ability to replenish missing or dysfunctional neurons. This article discusses diseases that might be targets for stem cell therapies and the barriers that could limit treatment application. We explore various sources of stem cells and the proof of concept for their use. The critical steps that remain to be addressed before these therapies can be used in patients are also discussed. Key milestones include the harvesting of neural stem cells from the human gut and the latest in vivo transplantation studies in animals. The tremendous progress in the field has brought experimental studies exploring the potential of stem cell therapies for the management of enteric neuropathies to the cusp of clinical application.

Detecting clustering and ordering binding patterns among transcription factors via point process models

MOTIVATION

Recent development in ChIP-Seq technology has generated binding data for many transcription factors (TFs) in various cell types and cellular conditions. This opens great opportunities for studying combinatorial binding patterns among a set of TFs active in a particular cellular condition, which is a key component for understanding the interaction between TFs in gene regulation.

RESULTS

As a first step to the identification of combinatorial binding patterns, we develop statistical methods to detect clustering and ordering patterns among binding sites (BSs) of a pair of TFs. Testing procedures based on Ripley's K-function and its generalizations are developed to identify binding patterns from large collections of BSs in ChIP-Seq data. We have applied our methods to the ChIP-Seq data of 91 pairs of TFs in mouse embryonic stem cells. Our methods have detected clustering binding patterns between most TF pairs, which is consistent with the findings in the literature, and have identified significant ordering preferences, relative to the direction of target gene transcription, among the BSs of seven TFs. More interestingly, our results demonstrate that the identified clustering and ordering binding patterns between TFs are associated with the expression of the target genes. These findings provide new insights into co-regulation between TFs.

AVAILABILITY AND IMPLEMENTATION

See 'www.stat.ucla.edu/∼zhou/TFKFunctions/' for source code.

Human stem cells for craniomaxillofacial reconstruction

Human stem cell research represents an exceptional opportunity for regenerative medicine and the surgical reconstruction of the craniomaxillofacial complex. The correct architecture and function of the vastly diverse tissues of this important anatomical region are critical for life supportive processes, the delivery of senses, social interaction, and aesthetics. Craniomaxillofacial tissue loss is commonly associated with inflammatory responses of the surrounding tissue, significant scarring, disfigurement, and psychological sequelae as an inevitable consequence. The in vitro production of fully functional cells for skin, muscle, cartilage, bone, and neurovascular tissue formation from human stem cells, may one day provide novel materials for the reconstructive surgeon operating on patients with both hard and soft tissue deficit due to cancer, congenital disease, or trauma. However, the clinical translation of human stem cell technology, including the application of human pluripotent stem cells (hPSCs) in novel regenerative therapies, faces several hurdles that must be solved to permit safe and effective use in patients. The basic biology of hPSCs remains to be fully elucidated and concerns of tumorigenicity need to be addressed, prior to the development of cell transplantation treatments. Furthermore, functional comparison of in vitro generated tissue to their in vivo counterparts will be necessary for confirmation of maturity and suitability for application in reconstructive surgery. Here, we provide an overview of human stem cells in disease modeling, drug screening, and therapeutics, while also discussing the application of regenerative medicine for craniomaxillofacial tissue deficit and surgical reconstruction.

Actions of endocrine-disrupting chemicals on stem/progenitor cells during development and disease

Development and fate of the stem cell are regulated by extrinsic signals from the environment. Endocrine-disrupting chemicals which perturb hormonal signaling in utero and during early childhood may cause deregulation of multiple developmental processes, ranging from breakdown of stem cell niche architecture, developmental reprograming and altered stem cell fate to impaired organ and gonad development and sexual differentiation. Therefore, study of the environmental effects on stem cell integrity and normal development is a new and emerging focus for developmental biologists and cell toxicologists. When combined with new human and mouse stem cell-based models, stem cell differentiation dynamics can be studied in more biologically relevant ways. In this study, we review the current status of our understanding of the molecular mechanisms by which endocrine disruptors alter embryonic stem cell and adult stem/progenitor cell fate, organ development, cancer stem cell activity, and tumorigenesis.

Effects of 3D microwell culture on initial fate specification in human embryonic stem cells

Several studies have demonstrated that 3D culture systems influence human embryonic stem cell (hESC) phenotypes and fate choices. However, the effect that these microenvironmental changes have on signaling pathways governing hESC behaviors is not well understood. Here, we have used a 3D microwell array to investigate differences in activation of developmental pathways between 2D and 3D cultures of both undifferentiated hESCs and hESCs undergoing initial differentiation in embryoid bodies (EBs). We observed increased induction into mesoderm and endoderm and differences in expression of genes from multiple signaling pathways that regulate development, including Wnt/β-catenin, TGF-β superfamily, Notch and FGF during EB-mediated differentiation, in 3D microwells as compared with the 2D substrates. In undifferentiated hESCs, we also observed differences in epithelial-mesenchymal transition phenotypes and the TGFβ/BMP pathway between cultures in 3D and 2D. These results illustrate that 3D culture influences multiple pathways that may regulate the differentiation trajectories of hESCs.

How to make spinal motor neurons

All muscle movements, including breathing, walking, and fine motor skills rely on the function of the spinal motor neuron to transmit signals from the brain to individual muscle groups. Loss of spinal motor neuron function underlies several neurological disorders for which treatment has been hampered by the inability to obtain sufficient quantities of primary motor neurons to perform mechanistic studies or drug screens. Progress towards overcoming this challenge has been achieved through the synthesis of developmental biology paradigms and advances in stem cell and reprogramming technology, which allow the production of motor neurons in vitro. In this Primer, we discuss how the logic of spinal motor neuron development has been applied to allow generation of motor neurons either from pluripotent stem cells by directed differentiation and transcriptional programming, or from somatic cells by direct lineage conversion. Finally, we discuss methods to evaluate the molecular and functional properties of motor neurons generated through each of these techniques.

Identification of a distinct small cell population from human bone marrow reveals its multipotency in vivo and in vitro

Small stem cells, such as spore-like cells, blastomere-like stem cells (BLSCs), and very-small embryonic-like stem cells (VSELs) have been described in recent studies, although their multipotency in human tissues has not yet been confirmed. Here, we report the discovery of adult multipotent stem cells derived from human bone marrow, which we call StemBios (SB) cells. These isolated SB cells are smaller than 6 ìm and are DAPI+ and Lgr5+ (Leucine-Rich Repeat Containing G Protein-Coupled Receptor 5). Because Lgr5 has been characterized as a stem cell marker in the intestine, we hypothesized that SB cells may have a similar function. In vivo cell tracking assays confirmed that SB cells give rise to three types of cells, and in vitro studies demonstrated that SB cells cultured in proprietary media are able to grow to 6–25 ìm in size. Once the SB cells have attached to the wells, they differentiate into different cell lineages upon exposure to specific differentiation media. We are the first to demonstrate that stem cells smaller than 6 ìm can differentiate both in vivo and in vitro. In the future, we hope that SB cells will be used therapeutically to cure degenerative diseases.

Small molecules for cell reprogramming and heart repair: progress and perspective

Regenerative medicine for heart failure seeks to replace lost cardiomyocytes. Chemical approaches for producing ample supplies of cells, such as pluripotent stem cells and cardiomyocytes, hold promise as practical means to achieve safe, facile cell-based therapy for cardiac repair and regenerative medicine. In this review, we describe recent advances in the application of small molecules to improve the generation and maintenance of pluripotent stem cells. We also describe new directions in heart repair and regeneration in which chemical approaches may find their application.

Neural progenitor cells from human induced pluripotent stem cells generated less autogenous immune response

The breakthrough development of induced pluripotent stem cells (iPSCs) raises the prospect of patient-specific treatment for many diseases through the replacement of affected cells. However, whether iPSC-derived functional cell lineages generate a deleterious immune response upon auto-transplantation remains unclear. In this study, we differentiated five human iPSC lines from skin fibroblasts and urine cells into neural progenitor cells (NPCs) and analyzed their immunogenicity. Through co-culture with autogenous peripheral blood mononuclear cells (PBMCs), we showed that both somatic cells and iPSC-derived NPCs do not stimulate significant autogenous PBMC proliferation. However, a significant immune reaction was detected when these cells were co-cultured with allogenous PBMCs. Furthermore, no significant expression of perforin or granzyme B was detected following stimulation of autogenous immune effector cells (CD3(+)CD8(-) T cells, CD3(+)CD8(+) T cells or CD3(-)CD56(+) NK cells) by NPCs in both PBMC and T cell co-culture systems. These results suggest that human iPSC-derived NPCs may not initiate an immune response in autogenous transplants, and thus set a base for further preclinical evaluation of human iPSCs.

Lung stem and progenitor cells in tissue homeostasis and disease

The mammalian lung is a complex organ containing numerous putative stem/progenitor cell populations that contribute to region-specific tissue homeostasis and repair. In this review, we discuss recent advances in identifying and studying these cell populations in the context of lung homeostasis and disease. Genetically engineered mice now allow for lineage tracing of several lung stem and progenitor cell populations in vivo during different types of lung injury repair. Using specific sets of cell surface markers, these cells can also be isolated from murine and human lung and tested in 3D culture systems and in vivo transplant assays. The pathology of devastating lung diseases, including lung cancers, is likely in part due to dysregulation and dysfunction of lung stem cells. More precise characterization of stem cells with identification of new, unique markers; improvement in isolation and transplant techniques; and further development of functional assays will ultimately lead to new therapies for a host of human lung diseases. In particular, lung cancer biology may be greatly informed by findings in normal lung stem cell biology as evidence suggests that lung cancer is a disease that begins in, and may be driven by, neoplastic lung stem cells.

The reprogramming factor nuclear receptor subfamily 5, group A, member 2 cannot replace octamer-binding transcription factor 4 function in the self-renewal of embryonic stem cells

Although octamer-binding transcription factor 4 (Oct-4) is one of the most intensively studied factors in mammalian development, no cellular genes capable of replacing Oct-4 function in embryonic stem (ES) cells have been found. Recent data show that nuclear receptor subfamily 5, group A, member 2 (Nr5a2) is able to replace Oct-4 function in the reprogramming process; however, it is unclear whether Nr5a2 can replace Oct-4 function in ES cells. In this study, the ability of Nr5a2 to maintain self-renewal and pluripotency in ES cells was investigated. Nr5a2 localized to the nucleus in ES cells, similarly to Oct-4. However, expression of Nr5a2 failed to rescue the stem cell phenotype or to maintain the self-renewal ability of ES cells. Furthermore, as compared with Oct-4-expressing ES cells, Nr5a2-expressing ES cells showed a reduced number of cells in S-phase, did not expand normally, and did not remain in an undifferentiated state. Ectopic expression of Nr5a2 in ES cells was not able to activate transcription of ES cell-specific genes, and gene expression profiling demonstrated differences between Nr5a2-expressing and Oct-4-expressing ES cells. In addition, Nr5a2-expressing ES cells were not able to form teratomas in nude mice. Taken together, these results strongly suggest that the gene regulation properties of Nr5a2 and Oct-4 and their abilities to confer self-renewal and pluripotency of ES cells differ. The present study provides strong evidence that Nr5a2 cannot replace Oct-4 function in ES cells.

Induced pluripotent stem cell (iPSCs) and their application in immunotherapy

The ever-improving technology to generate induced pluripotent stem cells (iPSCs) has increased their potential use as novel candidates for disease modeling, drug screening, regenerative medicine and cell therapy. Indeed, iPSCs offer extensive capacity for self-renewal without the ethical concerns faced by embryonic stem cells (ESCs). With respect to potential applications in the immune system, many studies provide evidence to support that there are exclusive advantages to using iPSCs over other systems. Both hematopoietic stem cells and several types of mature immune cells have successfully been reprogrammed to iPSCs and vice versa, paving a path toward our ability to effectively model patient-specific diseases and provide potentially alternative cell sources for transfusion medicine. Despite these potential advances, some limitations regarding the use of iPSCs in the clinic still remain, including the immunogenicity of iPSCs and their derivatives, which is currently under debate in the field. In this review, we mainly focus on discussing the recent progress being made in the latest differentiation methods and clinical implications of iPSCs with respect to the immune system. Additionally, current issues regarding the clinical application of iPSCs are addressed, especially the controversy surrounding immunogenicity, along with various other perspectives.

Extracellular matrix-mediated differentiation of human embryonic stem cells: differentiation to insulin-secreting beta cells

Stem cells have tremendous potential for treating various human diseases. Protocols have been established to differentiate stem cells into specific lineages through the provision of signals in the form of growth factors, cytokines, or small molecules. Herein we investigate an alternative strategy for directed differentiation of human embryonic stem cells (hESCs)--extracellular-matrix (ECM) mediated differentiation. Decellularized ECM and conditioned media from the appropriate committed cell lines are used to differentiate stem cells to the required phenotype. Applying this strategy to differentiate hESCs to pancreatic beta cells, we have obtained functional cells that secreted insulin in a glucose-responsive manner, and were able to recover normoglycemia in a streptozotocin (STZ)-induced diabetic mouse model. ECM-mediated differentiation was also demonstrated to be effective for the differentiation of hESCs into kidney tubule cells and cardiomyocytes. Gene expression studies suggested the involvement of integrins and catenins in the beta cell differentiation process; in particular, α1, αv, and β1 integrins, and β-catenin showed the highest upregulation. To further elucidate the biochemical and mechanical cues that have led to effective hESC differentiation to beta cells, we have employed an artificial system that allowed for variation of matrix stiffness and combination of individual ECM proteins at various ratios. The differentiation response of hESCs to the native ECM could be approximated by optimizing this system.

An in vitro mechanism study on the proliferation and pluripotency of human embryonic stems cells in response to magnesium degradation

Magnesium (Mg) is a promising biodegradable metallic material for applications in cellular/tissue engineering and biomedical implants/devices. To advance clinical translation of Mg-based biomaterials, we investigated the effects and mechanisms of Mg degradation on the proliferation and pluripotency of human embryonic stem cells (hESCs). We used hESCs as the in vitro model system to study cellular responses to Mg degradation because they are sensitive to toxicants and capable of differentiating into any cell types of interest for regenerative medicine. In a previous study when hESCs were cultured in vitro with either polished metallic Mg (99.9% purity) or pre-degraded Mg, cell death was observed within the first 30 hours of culture. Excess Mg ions and hydroxide ions induced by Mg degradation may have been the causes for the observed cell death; hence, their respective effects on hESCs were investigated for the first time to reveal the potential mechanisms. For this purpose, the mTeSR®1 hESC culture media was either modified to an alkaline pH of 8.1 or supplemented with 0.4–40 mM of Mg ions. We showed that the initial increase of media pH to 8.1 had no adverse effect on hESC proliferation. At all tested Mg ion dosages, the hESCs grew to confluency and retained pluripotency as indicated by the expression of OCT4, SSEA3, and SOX2. When the supplemental Mg ion dosages increased to greater than 10 mM, however, hESC colony morphology changed and cell counts decreased. These results suggest that Mg-based implants or scaffolds are promising in combination with hESCs for regenerative medicine applications, providing their degradation rate is moderate. Additionally, the hESC culture system could serve as a standard model for cytocompatibility studies of Mg in vitro, and an identified 10 mM critical dosage of Mg ions could serve as a design guideline for safe degradation of Mg-based implants/scaffolds.

Regulation of PTEN/Akt pathway enhances cardiomyogenesis and attenuates adverse left ventricular remodeling following thymosin β4 Overexpressing embryonic stem cell transplantation in the infarcted heart

Thymosin β4 (Tβ4), a small G-actin sequestering peptide, mediates cell proliferation, migration, and angiogenesis. Whether embryonic stem (ES) cells, overexpressing Tβ4, readily differentiate into cardiac myocytes in vitro and in vivo and enhance cardioprotection following transplantation post myocardial infarction (MI) remains unknown. Accordingly, we established stable mouse ES cell lines, RFP-ESCs and Tβ4-ESCs, expressing RFP and an RFP-Tβ4 fusion protein, respectively. In vitro, the number of spontaneously beating embryoid bodies (EBs) was significantly increased in Tβ4-ESCs at day 9, 12 and 15, compared with RFP-ESCs. Enhanced expression of cardiac transcriptional factors GATA-4, Mef2c and Txb6 in Tβ4-EBs, as confirmed with real time-PCR analysis, was accompanied by the increased number of EB areas stained positive for sarcomeric α-actin in Tβ4-EBs, compared with the RFP control, suggesting a significant increase in functional cardiac myocytes. Furthermore, we transplanted Tβ4-ESCs into the infarcted mouse heart and performed morphological and functional analysis 2 weeks after MI. There was a significant increase in newly formed cardiac myocytes associated with the Notch pathway, a decrease in apoptotic nuclei mediated by an increase in Akt and a decrease in levels of PTEN. Cardiac fibrosis was significantly reduced, and left ventricular function was significantly augmented in the Tβ4-ESC transplanted group, compared with controls. It is concluded that genetically modified Tβ4-ESCs, potentiates their ability to turn into cardiac myocytes in vitro as well as in vivo. Moreover, we also demonstrate that there was a significant decrease in both cardiac apoptosis and fibrosis, thus improving cardiac function in the infarcted heart.

Forever young: SIRT3 a shield against mitochondrial meltdown, aging, and neurodegeneration

Caloric restriction (CR), fasting, and exercise have long been recognized for their neuroprotective and lifespan-extending properties; however, the underlying mechanisms of these phenomena remain elusive. Such extraordinary benefits might be linked to the activation of sirtuins. In mammals, the sirtuin family has seven members (SIRT1–7), which diverge in tissue distribution, subcellular localization, enzymatic activity, and targets. SIRT1, SIRT2, and SIRT3 have deacetylase activity. Their dependence on NAD⁺ directly links their activity to the metabolic status of the cell. High NAD⁺ levels convey neuroprotective effects, possibly via activation of sirtuin family members. Mitochondrial sirtuin 3 (SIRT3) has received much attention for its role in metabolism and aging. Specific small nucleotide polymorphisms in Sirt3 are linked to increased human lifespan. SIRT3 mediates the adaptation of increased energy demand during CR, fasting, and exercise to increased production of energy equivalents. SIRT3 deacetylates and activates mitochondrial enzymes involved in fatty acid β-oxidation, amino acid metabolism, the electron transport chain, and antioxidant defenses. As a result, the mitochondrial energy metabolism increases. In addition, SIRT3 prevents apoptosis by lowering reactive oxygen species and inhibiting components of the mitochondrial permeability transition pore. Mitochondrial deficits associated with aging and neurodegeneration might therefore be slowed or even prevented by SIRT3 activation. In addition, upregulating SIRT3 activity by dietary supplementation of sirtuin activating compounds might promote the beneficial effects of this enzyme. The goal of this review is to summarize emerging data supporting a neuroprotective action of SIRT3 against Alzheimer’s disease, Huntington’s disease, Parkinson’s disease, and amyotrophic lateral sclerosis.

Skin-derived mesenchymal stem cells: isolation, culture, and characterization

The increasing interest about stem cell research is linked to the promise of developing such treatments for many life-threatening, debilitating diseases and for cell replacement therapies. Among the various human tissues, skin represents a source characterized by great accessibility and availability with noninvasive procedures and without risks of oncogenesis after their transplantation. In this aim, the identification of suitable protocols for the isolation, characterization, and long-term storage has a pivotal role.

Effect of antibiotics against Mycoplasma sp. on human embryonic stem cells undifferentiated status, pluripotency, cell viability and growth

Human embryonic stem cells (hESCs) are self-renewing pluripotent cells that can differentiate into specialized cells and hold great promise as models for human development and disease studies, cell-replacement therapies, drug discovery and in vitro cytotoxicity tests. The culture and differentiation of these cells are both complex and expensive, so it is essential to extreme aseptic conditions. hESCs are susceptible to Mycoplasma sp. infection, which is hard to detect and alters stem cell-associated properties. The purpose of this work was to evaluate the efficacy and cytotoxic effect of Plasmocin^TM and ciprofloxacin (specific antibiotics used for Mycoplasma sp. eradication) on hESCs. Mycoplasma sp. infected HUES-5 884 (H5 884, stable hESCs H5-brachyury promoter-GFP line) cells were effectively cured with a 14 days Plasmocin^TM 25 µg/ml treatment (curative treatment) while maintaining stemness characteristic features. Furthermore, cured H5 884 cells exhibit the same karyotype as the parental H5 line and expressed GFP, through up-regulation of brachyury promoter, at day 4 of differentiation onset. Moreover, H5 cells treated with ciprofloxacin 10 µg/ml for 14 days (mimic of curative treatment) and H5 and WA09 (H9) hESCs treated with Plasmocin^TM 5 µg/ml (prophylactic treatment) for 5 passages retained hESCs features, as judged by the expression of stemness-related genes (TRA1-60, TRA1-81, SSEA-4, Oct-4, Nanog) at mRNA and protein levels. In addition, the presence of specific markers of the three germ layers (brachyury, Nkx2.5 and cTnT: mesoderm; AFP: endoderm; nestin and Pax-6: ectoderm) was verified in in vitro differentiated antibiotic-treated hESCs. In conclusion, we found that Plasmocin^TM and ciprofloxacin do not affect hESCs stemness and pluripotency nor cell viability. However, curative treatments slightly diminished cell growth rate. This cytotoxic effect was reversible as cells regained normal growth rate upon antibiotic withdrawal.

Low immunogenicity of neural progenitor cells differentiated from induced pluripotent stem cells derived from less immunogenic somatic cells

The groundbreaking discovery of induced pluripotent stem cells (iPS cells) provides a new source for cell therapy. However, whether the iPS derived functional lineages from different cell origins have different immunogenicity remains unknown. It had been known that the cells isolated from extra-embryonic tissues, such as umbilical cord mesenchymal cells (UMCs), are less immunogenic than other adult lineages such as skin fibroblasts (SFs). In this report, we differentiated iPS cells from human UMCs and SFs into neural progenitor cells (NPCs) and analyzed their immunogenicity. Through co-culture with allologous peripheral blood mononuclear cells (PBMCs), we showed that UMCs were indeed less immunogenic than skin cells to simulate proliferation of PBMCs. Surprisingly, we found that the NPCs differentiated from UMC-iPS cells retained low immunogenicity as the parental UMCs based on the PBMC proliferation assay. In cytotoxic expression assay, reactions in most kinds of immune effector cells showed more perforin and granzyme B expression with SF-NPCs stimulation than that with UMC-NPCs stimulation in PBMC co-culture system, in T cell co-culture system as well. Furthermore, through whole genome expression microarray analysis, we showed that over 70 immune genes, including all members of HLA-I, were expressed at lower levels in NPCs derived from UMC-iPS cells than that from SF-iPS cells. Our results demonstrated a phenomenon that the low immunogenicity of the less immunogenic cells could be retained after cell reprogramming and further differentiation, thus provide a new concept to generate functional lineages with lower immunogenicity for regenerative medicine.

Wharton's jelly stem cells: a novel cell source for oral mucosa and skin epithelia regeneration

Perinatal stem cells such as human umbilical cord Wharton's jelly stem cells (HWJSCs) are excellent candidates for tissue engineering because of their proliferation and differentiation capabilities. However, their differentiation potential into epithelial cells at in vitro and in vivo levels has not yet been reported. In this work we have studied the capability of HWJSCs to differentiate in vitro and in vivo to oral mucosa and skin epithelial cells using a bioactive three-dimensional model that mimics the native epithelial-mesenchymal interaction. To achieve this, primary cell cultures of HWJSCs, oral mucosa, and skin fibroblasts were obtained in order to generate a three-dimensional heterotypical model of artificial oral mucosa and skin based on fibrin-agarose biomaterials. Our results showed that the cells were unable to fully differentiate to epithelial cells in vitro. Nevertheless, in vivo grafting of the bioactive three-dimensional models demonstrated that HWJSCs were able to stratify and to express typical markers of epithelial differentiation, such as cytokeratins 1, 4, 8, and 13, plakoglobin, filaggrin, and involucrin, showing specific surface patterns. Electron microscopy analysis confirmed the presence of epithelial cell-like layers and well-formed cell-cell junctions. These results suggest that HWJSCs have the potential to differentiate to oral mucosa and skin epithelial cells in vivo and could be an appropriate novel cell source for the development of human oral mucosa and skin in tissue engineering protocols.

The pharmacology of regenerative medicine

Regenerative medicine is a rapidly evolving multidisciplinary, translational research enterprise whose explicit purpose is to advance technologies for the repair and replacement of damaged cells, tissues, and organs. Scientific progress in the field has been steady and expectations for its robust clinical application continue to rise. The major thesis of this review is that the pharmacological sciences will contribute critically to the accelerated translational progress and clinical utility of regenerative medicine technologies. In 2007, we coined the phrase "regenerative pharmacology" to describe the enormous possibilities that could occur at the interface between pharmacology, regenerative medicine, and tissue engineering. The operational definition of regenerative pharmacology is "the application of pharmacological sciences to accelerate, optimize, and characterize (either in vitro or in vivo) the development, maturation, and function of bioengineered and regenerating tissues." As such, regenerative pharmacology seeks to cure disease through restoration of tissue/organ function. This strategy is distinct from standard pharmacotherapy, which is often limited to the amelioration of symptoms. Our goal here is to get pharmacologists more involved in this field of research by exposing them to the tools, opportunities, challenges, and interdisciplinary expertise that will be required to ensure awareness and galvanize involvement. To this end, we illustrate ways in which the pharmacological sciences can drive future innovations in regenerative medicine and tissue engineering and thus help to revolutionize the discovery of curative therapeutics. Hopefully, the broad foundational knowledge provided herein will spark sustained conversations among experts in diverse fields of scientific research to the benefit of all.

Excess of O-linked N-acetylglucosamine modifies human pluripotent stem cell differentiation

O-linked-N-acetylglucosamine (O-GlcNAc), a post translational modification, has emerged as an important cue in controlling key cell mechanisms. Here, we investigate O-GlcNAc's role in the maintenance and differentiation of human pluripotent stem cells (hPSC). We reveal that protein expression of O-GlcNAc transferase and hydrolase both decreases during hPSC differentiation. Upregulating O-GlcNAc with O-GlcNAc hydrolase inhibitors has no significant effect on either the maintenance of pluripotency in hPSC culture, or the loss of pluripotency in differentiating hPSC. However, in spontaneously differentiating hPSC, excess O-GlcNAc alters the expression of specific lineage markers: decrease of ectoderm markers (PAX6 by 53-88%, MSX1 by 26-49%) and increase of adipose-related mesoderm markers (PPARγ by 28-100%, C/EBPα by 46-135%). All other lineage markers tested (cardiac, visceral-endoderm, trophectoderm) remain minimally affected by upregulated O-GlcNAc. Interestingly, we also show that excess O-GlcNAc triggers a feedback mechanism that increases O-GlcNAc hydrolase expression by 29-91%. To the best of our knowledge, this is the first report demonstrating that excess O-GlcNAc does not affect hPSC pluripotency in undifferentiated maintenance cultures; instead, it restricts the hPSC differentiation towards specific cell lineages. These data will be useful for developing targeted differentiation protocols and aid in understanding the effects of O-GlcNAc on hPSC differentiation.

Enhanced cardiomyogenic lineage differentiation of adult bone-marrow-derived stem cells grown on cardiogel

The extracellular matrix (ECM) and its components are known to promote growth and cellular differentiation in vitro. Cardiogel, a three-dimensional extracellular matrix derived from cardiac fibroblasts, is evaluated for its cardiomyogenic-differentiation-inducing potential on bone-marrow-derived stem cells (BMSC). BMSC from adult mice were grown on cardiogel and induced to differentiate into specific lineages that were validated by morphological, phenotypic and molecular assays. The data revealed that the cardiogel enhanced cardiomyogenic and adipogenic differentiation and relegated osteogenic differentiation following specific induction. More importantly, increased cardiomyogenic differentiation was also observed following BMSC growth on cardiogel without specific chemical (5-azacytidine) induction. This is the first report of an attempt to use cardiogel as a biomaterial on which to achieve cardiomyogenic differentiation of BMSC without chemical induction. Our study suggests that cardiogel is an efficient extracellular matrix that enhances the cardiomyogenic differentiation of BMSC and that it can therefore be used as a scaffold for cardiac tissue regeneration.

Comparison of odontogenic differentiation of human dental follicle cells and human dental papilla cells

Classical tooth development theory suggests that dental papilla cells (DPCs) are the precursor cells of odontoblasts, which are responsible for dentin development. However, our previous studies have indicated that dental follicle cells (DFCs) can differentiate into odontoblasts. To further our understanding of tooth development, and the differences in dentinogenesis between DFCs and DPCs, the odontogenic differentiation of DFCs and DPCs was characterized in vitro and in vivo. DFCs and DPCs were individually combined with treated dentin matrix (TDM) before they were subcutaneously implanted into the dorsum of mice for 8 weeks. Results showed that 12 proteins were significantly differential, and phosphoserine aminotransferase 1 (PSAT1), Isoform 2 of hypoxia-inducible factor 1-alpha (HIF1A) and Isoform 1 of annexin A2 (ANXA2), were the most significantly differential proteins. These proteins are related to regulation of bone balance, angiogenesis and cell survival in an anoxic environment. Both DFCs and DPCs express odontogenic, neurogenic and peridontogenic markers. Histological examination of the harvested grafts showed that both DFCs and DPCs form pulp-dentin/cementum-periodentium-like tissues in vivo. Hence, DFCs and DPCs have similar odontogenic differentiation potential in the presence of TDM. However, differences in glucose and amino acid metabolism signal transduction and protein synthesis were observed for the two cell types. This study expands our understanding on tooth development, and provides direct evidence for the use of alternative cell sources in tooth regeneration.

Stem cell therapy in heart diseases: a review of selected new perspectives, practical considerations and clinical applications

Degeneration of cardiac tissues is considered a major cause of mortality in the western world and is expected to be a greater problem in the forthcoming decades. Cardiac damage is associated with dysfunction and irreversible loss of cardiomyocytes. Stem cell therapy for ischemic heart failure is very promising approach in cardiovascular medicine. Initial trials have indicated the ability of cardiomyocytes to regenerate after myocardial injury. These preliminary trials aim to translate cardiac regeneration strategies into clinical practice. In spite of advances, current therapeutic strategies to ischemic heart failure remain very limited. Moreover, major obstacles still need to be solved before stem cell therapy can be fully applied. This review addresses the current state of research and experimental data regarding embryonic stem cells (ESCs), myoblast transplantation, histological and functional analysis of transplantation of co-cultured myoblasts and mesenchymal stem cells, as well as comparison between mononuclear and mesenchymal stem cells in a model of myocardium infarction. We also discuss how research with stem cell transplantation could translate to improvement of cardiac function.

Lung stem and progenitor cells

Over the past few years, new insights have been added to the study of stem cells in the adult lung. The exploration of endogenous lung progenitors as well as the study of exogenously delivered stem cell populations holds promise for advancing our understanding of the biology of lung repair mechanisms. Moreover, it opens new possibilities for the use of stem cell therapy for the development of regenerative medicine approaches for the treatment of lung disease. Here, we discuss the main types of lung epithelial progenitor populations; the potential of endothelial progenitors, mesenchymal stem cells and embryonic stem cells for lung therapy, as well as summarize the cellular mechanisms involved.

Regenerative medicine for congenital malformations

This is a review of the progress in regenerative medicine and concepts behind the field of tissue engineering and cell transplantation as it applies to congenital malformations. It is based on the Journal of Pediatric Surgery invited lecture to the BAPS/EUPSA Congress in Rome, Italy, June 2012.

Concise review: a high-content screening approach to stem cell research and drug discovery

High-throughput screening (HTS) is a technology widely used for early stages of drug discovery in pharmaceutical and biotechnology industries. Recent hardware and software improvements have enabled HTS to be used in combination with subcellular resolution microscopy, resulting in cell image-based HTS, called high-content screening (HCS). HCS allows the acquisition of deeper knowledge at a single-cell level such that more complex biological systems can be studied in a high-throughput manner. The technique is particularly well-suited for stem cell research and drug discovery, which almost inevitably require single-cell resolutions for the detection of rare phenotypes in heterogeneous cultures. With growing availability of facilities, instruments, and reagent libraries, small-to-moderate scale HCS can now be carried out in regular academic labs. We envision that the HCS technique will play an increasing role in both basic mechanism study and early-stage drug discovery on stem cells. Here, we review the development of HCS technique and its past application on stem cells and discuss possible future developments.

Biomaterials and stem cells for tissue engineering

INTRODUCTION

Organ failure and tissue loss are challenging health issues due to widespread injury, the lack of organs for transplantation and limitations of conventional artificial implants. The field of tissue engineering aims to provide alternative living substitutes that restore, maintain or improve tissue function.

AREAS COVERED

In this paper, a wide range of porous scaffolds are reviewed, with an emphasis on phase-separation techniques that generate advantageous nanofibrous 3D scaffolds for stem cell-based tissue engineering applications. In addition, methods for presentation and delivery of bioactive molecules to mimic the properties of stem cell niches are summarized. Recent progress in using these bioinstructive scaffolds to support stem cell differentiation and tissue regeneration is also presented.

EXPERT OPINION

Stem cells have great clinical potential because of their capability to differentiate into multiple cell types. Biomaterials have served as artificial extracellular environments to regulate stem cell behavior. Biomaterials with various physical, mechanical and chemical properties can be designed to control stem cell development for regeneration.

CONCLUSION

The research at the interface of stem cell biology and biomaterials has made and will continue to make exciting advances in tissue engineering.

Substrate topography and size determine the fate of human embryonic stem cells to neuronal or glial lineage

Efficient derivation of neural cells from human embryonic stem cells (hESCs) remains an unmet need for the treatment of neurological disorders. The limiting factors for current methods include being labor-intensive, time-consuming and expensive. In this study, we hypothesize that the substrate topography, with optimal geometry and dimension, can modulate the neural fate of hESCs and enhance the efficiency of differentiation. A multi-architectural chip (MARC) containing fields of topographies varying in geometry and dimension was developed to facilitate high-throughput analysis of topography-induced neural differentiation in vitro. The hESCs were subjected to "direct differentiation", in which small clumps of undifferentiated hESCs were cultured directly without going through the stage of embryoid body formation, on the MARC with N2 and B27 supplements for 7 days. The gene and protein expression analysis indicated that the anisotropic patterns like gratings promoted neuronal differentiation of hESCs while the isotropic patterns like pillars and wells promoted the glial differentiation of hESCs. This study showed that optimal combination of topography and biochemical cues could shorten the differentiation period and allowed derivation of neurons bearing longer neurites that were aligned along the grating axis. The MARC platform would enable high-throughput screening of topographical substrates that could maximize the efficiency of neuronal differentiation from pluripotent stem cells.

Experimental and clinical factors influencing long-term stable in vitro expansion of multipotent neural cells from human adult temporal lobes

Autologous adult human neural stem cells may be used for regenerative cell therapies bypass potential ethical problems. However, stable in vitro expansion protocols and experimental/clinical factors influencing primary cultures need to be further elucidated for clinically applicable techniques. To address these issues, we obtained biopsy specimens from 23 temporal lobe epilepsy patients and adult human multipotent neural cells (ahMNCs) were primarily cultured in a defined attachment culture condition. When the success of primary cultures was defined as stable expansion of cells (>ten in vitro passages) and expression of NSC markers, success rate of the primary culture was 39% (nine of 23 temporal lobes). During the long-term expansion, expressions of NSC markers and differentiation potentials into astrocytes and neurons were maintained. After the 18th sub-culture, spontaneous senescence and differentiation were observed, and the cultivated ahMNCs ceased their proliferation. The culture results were not affected by seizure characteristics; however, an older age (>40 years) and a smaller sample volume (<2 ml) were found to exert negative influences on the primary culture results. Furthermore therapeutic effects of ahMNCs against stroke were analyzed in an animal model. Transplantation of ahMNCs cells reduced infarction volumes and enhanced motor activity, significantly. The results here would provide promising experimental and clinical strategy of using patient-specific autologous ahMNCs in regenerative medicine in the future.

[Perspectives of cell therapy in sequelae from cerebrovascular accidents]

INTRODUCTION

Spontaneous intracerebral hemorrhage (ICH) is associated with mortality between 40 and 50% of cases. Among the survivors, only 10% are independent after one month, there is no effective treatment of sequelae, except for the limited possibilities providing for rehabilitation.

OBJECTIVES

We review the current experience with intracerebral transplantation of mesenchymal stem cells (MSCs) obtained from bone marrow as a potential treatment of neurological sequelae occurring after experimental ICH.

MATERIAL AND METHODS

We describe the model of ICH by intracerebral administration of collagenaseIV at basal ganglia level in Wistar rats. Neurological deficits caused by ICH can be quantified through a variety of functional assessment test (NMSS, Rota-rod, VTB-test). 5×10allogeneic MSCs in 10μl of saline were administered intracerebrally in 10 animals, 2 months after ICH. In another 10 animals (controls) the same volume of saline was administered. Changes in the functional deficits were assessed during the next 6 months in both experimental groups.

RESULTS

The results suggested therapeutic efficacy of MSCs transplantation and showed that transplanted stem cells can survive in the injured brain, transforming into neurons and glial cells. This form of cell therapy induces reactivation of endogenous neurogenesis at the subventricular zone (SVZ) and achieves antiapoptotic protective effect in the injured brain.

CONCLUSIONS

Cell therapy represents an important field of research with potential clinical application to treatment of neurological sequels, currently considered irreversible. Neurosurgeons should become involved in the development of these new techniques that are likely to shape the future of this specialty.

Stem cell and biomaterials research in dental tissue engineering and regeneration

This review summarizes approaches used in tissue engineering and regenerative medicine, with a focus on dental applications. Dental caries and periodontal disease are the most common diseases resulting in tissue loss. To replace or regenerate new tissues, various sources of stem cells have been identified such as somatic stem cells from teeth and peridontium. Advances in biomaterial sciences including microfabrication, self-assembled biomimetic peptides, and 3-dimensional printing hold great promise for whole-organ or partial tissue regeneration to replace teeth and periodontium.

Confined 3D microenvironment regulates early differentiation in human pluripotent stem cells

The therapeutic potential of human pluripotent stem (hPS) cells is threatened, among various problems, by the difficulty to homogenously direct cell differentiation into specific lineages. The transition from hPSC into committed differentiated cells is accompanied by secretome activity, remodeling of extracellular matrix and self-organization into germ layers. In this work, we aimed to investigate how different three-dimensional microenvironments regulate the early differentiation of the three germ layers in human embryonic stem (hES) cells derived embryoid bodies. In particular, a permeable, biocompatible, hydrogel microwell array was specifically designed for recreating a confined niche in which EB secreted molecules accumulate in accordance with hydrogel diffusional cut-off. Fluorescence recovery after photobleaching technique was performed to accurately evaluate hydrogel permeability, mesh size and diffusional cutoff for soluble molecules. Three different culture conditions of EB culture were analyzed: suspension, confinement in microwells of width/depth ratio 1:1 and 1:2. Results show that EBs cultured in microwells are viable and have comparable average size after 8 days culture. Whole genome microarrays show that significative differential gene expression was observed between suspension and confined EBs culture. In particular, EBs culture in microwells promotes the expression of genes involved in pattern specification processes, brain development, ectoderm and endoderm differentiation. On the contrary, suspension EBs express instead genes involved in mesoderm specification and heart development. These results suggest that local accumulation of EBs secreted molecules drives differentiation patterns, as confirmed by immunofluorescence of germ layer markers, in hydrogel confined EB culture from both hES cells and human induced pluripotent stem (hiPS) cells. Our findings highlight an additional potential role of biomaterial in controlling hPSC differentiation through secreted factor niche specification.

Identification of specific pluripotent stem cell death--inducing small molecules by chemical screening

A potential application of embryonic and inducible pluripotent stem cells for the therapy of degenerative diseases involves pure somatic cells, free of tumorigenic undifferentiated embryonic and inducible pluripotent stem cells. In complex collections of chemicals with pharmacological potential we expect to find molecules able to induce specific pluripotent stem cell death, which could be used in some cell therapy settings to eliminate undifferentiated cells. Therefore, we have screened a chemical library of 1120 small chemicals to identify compounds that induce specifically apoptotic cell death in undifferentiated mouse embryonic stem cells (ESCs). Interestingly, three compounds currently used as clinically approved drugs, nortriptyline, benzethonium chloride and methylbenzethonium chloride, induced differential effects in cell viability in ESCs versus mouse embryonic fibroblasts (MEFs). Nortriptyline induced apoptotic cell death in MEFs but not in ESCs, whereas benzethonium and methylbenzethonium chloride showed the opposite effect. Nortriptyline, a tricyclic antidepressant, has also been described as a potent inhibitor of mitochondrial permeability transition, one of two major mechanisms involved in mitochondrial membrane permeabilization during apoptosis. Benzethonium chloride and methylbenzethonium chloride are quaternary ammonium salts used as antimicrobial agents with broad spectrum and have also been described as anticancer agents. A similar effect of benzethonium chloride was observed in human induced pluripotent stem cells (hiPSCs) when compared to both primary human skin fibroblasts and an established human fibroblast cell line. Human fibroblasts and hiPSCs were similarly resistant to nortriptyline, although with a different behavior. Our results indicate differential sensitivity of ESCs, hiPSCs and fibroblasts to certain chemical compounds, which might have important applications in the stem cell-based therapy by eliminating undifferentiated pluripotent stem cells from stem cell-derived somatic cells to prevent tumor formation after transplantation for therapy of degenerative diseases.