Insulin production by human embryonic stem cells

Characterization of insulin-producing cells derived from PDX-1-transfected neural stem cells

Islet cell transplantation is a promising treatment strategy for type-1 diabetes. However, functional islet cells are hard to obtain for transplantation and are in short supply. Directing the differentiation of stem cells into insulin‑producing cells, which serve as islet cells, would overcome this shortage. Bone marrow contains hematopoietic stem cells and mesenchymal stem cells. The present study used bone marrow cells isolated from rats and neural stem cells (NSCs) that were derived from bone marrow cells in culture. Strong nestin staining was detected in NSCs, but not in bone marrow stromal cells (BMSCs). In vitro transfection of the pancreatic duodenal homeobox-1 (PDX-1) gene into NSCs generated insulin‑producing cells. Reverse transcription polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA) analysis confirmed that PDX-1-transfected NSCs expressed insulin mRNA and released insulin protein. However, insulin release from PDX-1-transfected NSCs did not respond to the challenge of glucose and glucagon-like peptide-1. These results support the use of bone marrow-derived NSCs as a renewable source of insulin-producing cells for autologous transplantation to treat type-1 diabetes.

Organ engineering--combining stem cells, biomaterials, and bioreactors to produce bioengineered organs for transplantation

Often the only treatment available for patients suffering from diseased and injured organs is whole organ transplant. However, there is a severe shortage of donor organs for transplantation. The goal of organ engineering is to construct biological substitutes that will restore and maintain normal function in diseased and injured tissues. Recent progress in stem cell biology, biomaterials, and processes such as organ decellularization and electrospinning has resulted in the generation of bioengineered blood vessels, heart valves, livers, kidneys, bladders, and airways. Future advances that may have a significant impact for the field include safe methods to reprogram a patient's own cells to directly differentiate into functional replacement cell types. The subsequent combination of these cells with natural, synthetic and/or decellularized organ materials to generate functional tissue substitutes is a real possibility. This essay reviews the current progress, developments, and challenges facing researchers in their goal to create replacement tissues and organs for patients.

Tissue engineering of reproductive tissues and organs

Regenerative medicine and tissue engineering technology may soon offer new hope for patients with serious injuries and end-stage reproductive organ failure. Scientists are now applying the principles of cell transplantation, material science, and bioengineering to construct biological substitutes that can restore and maintain normal function in diseased and injured reproductive tissues. In addition, the stem cell field is advancing, and new discoveries in this field will lead to new therapeutic strategies. For example, newly discovered types of stem cells have been retrieved from uterine tissues such as amniotic fluid and placental stem cells. The process of therapeutic cloning and the creation of induced pluripotent cells provide still other potential sources of stem cells for cell-based tissue engineering applications. Although stem cells are still in the research phase, some therapies arising from tissue engineering endeavors that make use of autologous adult cells have already entered the clinic. This article discusses these tissue engineering strategies for various organs in the male and female reproductive tract.

Stem cells as a tool to improve outcomes of islet transplantation

The publication of the promising results of the Edmonton protocol in 2000 generated optimism for islet transplantation as a potential cure for Type 1 Diabetes Mellitus. Unfortunately, follow-up data revealed that less than 10% of patients achieved long-term insulin independence. More recent data from other large trials like the Collaborative Islet Transplant Registry show incremental improvement with 44% of islet transplant recipients maintaining insulin independence at three years of follow-up. Multiple underlying issues have been identified that contribute to islet graft failure, and newer research has attempted to address these problems. Stem cells have been utilized not only as a functional replacement for β cells, but also as companion or supportive cells to address a variety of different obstacles that prevent ideal graft viability and function. In this paper, we outline the manners in which stem cells have been applied to address barriers to the achievement of long-term insulin independence following islet transplantation.

Isolation of insulin-producing cells from different populations of multipotent stromal cells of the umbilical cord and human adipose tissue

Stromal cells of adipose tissue and human umbilical cord were isolated by the original method from general populations of multipotent subpopulation of multipotent stromal cells exhibiting perivascular phenotype (CD146+, CD31-). Effective directed differentiation of these cells into insulin-producing cells by transient transfection of the gene Pdx1 was demonstrated. Transfection multipotent stromal cells CD146-, CD31- derived from adipose tissue and umbilical cord and isolated by the standard method, did not result in activation of insulin gene transcription. It was shown that the expression of nestin was not necessary for effective pancreatic cell differentiation.

Differentiation of human labia minora dermis-derived fibroblasts into insulin-producing cells

Recent evidence has suggested that human skin fibroblasts may represent a novel source of therapeutic stem cells. In this study, we report a 3-stage method to induce the differentiation of skin fibroblasts into insulin- producing cells (IPCs). In stage 1, we establish the isolation, expansion and characterization of mesenchymal stem cells from human labia minora dermis- derived fibroblasts (hLMDFs) (stage 1: MSC expansion). hLMDFs express the typical mesenchymal stem cell marker proteins and can differentiate into adipocytes, osteoblasts, chondrocytes or muscle cells. In stage 2, DMEM/F12 serum-free medium with ITS mix (insulin, transferrin, and selenite) is used to induce differentiation of hLMDFs into endoderm-like cells, as determined by the expression of the endoderm markers Sox17, Foxa2, and PDX1 (stage 2: mesenchymal-endoderm transition). In stage 3, cells in the mesenchymal- endoderm transition stage are treated with nicotinamide in order to further differentiate into self-assembled, 3-dimensional islet cell-like clusters that express multiple genes related to pancreatic β-cell development and function (stage 3: IPC). We also found that the transplantation of IPCs can normalize blood glucose levels and rescue glucose homeostasis in streptozotocin- induced diabetic mice. These results indicate that hLMDFs have the capacity to differentiate into functionally competent IPCs and represent a potential cell-based treatment for diabetes mellitus.

Pancreatic islet cell transplantation: an update for interventional radiologists

Pancreatic islet cell transplantation is a promising cellular-based therapy for type 1 diabetes mellitus. This procedure involves portal venous injection of islet cells and affords 1-year insulin independence in as many as 80% of recipients. Although transplant surgeons represent historical drivers of islet therapy, requirement for image guidance and transcatheter techniques has fostered collaboration with interventional radiologists, who are positioned to play a significant role in clinical performance of islet transplantation and in basic science research in this field. This review article aims to familiarize interventional radiologists with islet cell transplantation patient selection, procedure technique, clinical outcomes, and future clinical and research avenues.

Insulin-producing cells from human adipose tissue-derived mesenchymal stem cells detected by atomic force microscope

We successfully differentiated human adipose tissue-derived mesenchymal stem cells (haMSCs) into insulin-producing cells (IPCs) in vitro and did not use any insulin which might be absorbed by cells during in vitro culture. Expression of insulin gene was massively increased by 28,000-fold at day 12 compared with haMSCs (P < 0.05). IPCs could secrete insulin after glucose was stimulated. The higher the concentration of glucose, the more production of insulin was noted. We reported AFM images of IPCs for the first time. AFM images showed that the sizes of cells were similar to each other, and all IPC surface had a porous structure in the cytoplasm area. In sugar-free group, the size of holes was similar (diameter, 1,086.98 ± 156.70 nm; depth, 185.22 ± 52.14 nm). In higher sugar-stimulated group, there were more holes with bigger diameter and smaller depth. (diameter, 3,183.65 ± 2,229.18 nm; depth 109.42 ± 56.26 nm, P < 0.05). We found that the hole diameter and depth could change with the concentration of glucose in media. Concurrently, laser scanning confocal microscopy images indicated that cortical actin network beneath plasma membrane in IPCs was dense and continuous. After glucose stimulation, we found the actin web depolymerized and became discontinuous in IPCs. We speculated that diameter augmentation of holes located in the cytoplasm area in IPCs was one manifestation of excytosis increase.

Reversal of diabetes by the creation of neo-islet tissues into a subcutaneous site using islet cell sheets

BACKGROUND

There remains a paucity of therapeutic approaches to completely treat diabetes mellitus. This study was designed to develop a dispersed islet cell-based tissue engineering approach to engineer functional neo-islet tissues in the absence of traditional bioabsorbable scaffold matrices.

METHODS

Specialized coated plastic dishes were prepared by covalently immobilizing a temperature-responsive polymer, poly(N-isopropylacrylamide), onto the plastic followed by coating with laminin-5. Dispersed rat islet cells were plated on the laminin-5-poly(N-isopropylacrylamide) dishes. After 2 days of culturing, islet cells were harvested as a uniformly connected tissue sheet by lowering the culture temperature from 37°C to 20°C for 30 min. Two harvested islet cell sheets were transplanted into the subcutaneous space of streptozotocin-induced diabetic severe combined immunodeficiency (SCID) mice to engineer neo-islet tissues in vivo. Therapeutic effects were investigated after the tissue engineering procedures.

RESULTS

In all of the diabetic SCID mice transplanted with the islet sheets, serum hyperglycemia was successfully reverted to a steady normoglycemic level. The recipient SCID mice demonstrated positive for serum rat C-peptide and elevated serum insulin levels. Moreover, the islet cell sheet-transplanted SCID mice demonstrated rapid glucose clearance and return of serum glucose levels after intraperitoneal glucose tolerance test. Histological examination revealed that the transplanted islet cell sheets were structured as flat clusters of islet tissues in which an active vascular network manifested within and surrounding the newly formed tissues.

CONCLUSIONS

This study describes a new proof-of-concept therapeutic approach to engineer functional neo-islet tissues for the treatment of type 1 diabetes mellitus.

Embryonic stem cells in safety pharmacology and toxicology

Embryonic stem (ES) cells undergo self-renewal and are pluripotent, i.e., they can give rise to all the types of specialised cells in the body. Scientific knowledge on ES cells is increasing rapidly, leading to opportunities for establishment of ES cell-based in vitro tests for drug discovery, preclinical safety pharmacology and toxicology. The main properties of ES cells making them useful in in vitro assays are that they have a normal diploid karyotype and can provide a large number of cells for high-throughput assays. Human ES cells additionally have the potential to provide solutions to problems related to interspecies differences and methods for screening for human polymorphisms, thus supporting robust human hazard identification and optimised drug discovery strategies. Importantly, ES cell based assays could be potential tools to reduce and perhaps replace, animal experiments. This chapter will describe ongoing research in the use of ES cells in toxicology and safety pharmacology, focusing on the major areas of progress, namely, embryotoxicology, cardiotoxicology and hepatoxicology.

Regenerative medicine strategies

Applications of regenerative medicine technology may offer novel therapies for patients with injuries, end-stage organ failure, or other clinical problems. Currently, patients suffering from diseased and injured organs can be treated with transplanted organs. However, there is a severe shortage of donor organs that is worsening yearly as the population ages and new cases of organ failure increase. Scientists in the field of regenerative medicine and tissue engineering are now applying the principles of cell transplantation, material science, and bioengineering to construct biological substitutes that will restore and maintain normal function in diseased and injured tissues. The stem cell field is also advancing rapidly, opening new avenues for this type of therapy. For example, therapeutic cloning and cellular reprogramming may one day provide a potentially limitless source of cells for tissue engineering applications. While stem cells are still in the research phase, some therapies arising from tissue engineering endeavors have already entered the clinical setting successfully, indicating the promise regenerative medicine holds for the future.

Promoting long-term survival of insulin-producing cell grafts that differentiate from adipose tissue-derived stem cells to cure type 1 diabetes

BACKGROUND

Insulin-producing cell clusters (IPCCs) have recently been generated in vitro from adipose tissue-derived stem cells (ASCs) to circumvent islet shortage. However, it is unknown how long they can survive upon transplantation, whether they are eventually rejected by recipients, and how their long-term survival can be induced to permanently cure type 1 diabetes. IPCC graft survival is critical for their clinical application and this issue must be systematically addressed prior to their in-depth clinical trials.

METHODOLOGY/PRINCIPAL FINDINGS

Here we found that IPCC grafts that differentiated from murine ASCs in vitro, unlike their freshly isolated islet counterparts, did not survive long-term in syngeneic mice, suggesting that ASC-derived IPCCs have intrinsic survival disadvantage over freshly isolated islets. Indeed, β cells retrieved from IPCC syngrafts underwent faster apoptosis than their islet counterparts. However, blocking both Fas and TNF receptor death pathways inhibited their apoptosis and restored their long-term survival in syngeneic recipients. Furthermore, blocking CD40-CD154 costimulation and Fas/TNF signaling induced long-term IPCC allograft survival in overwhelming majority of recipients. Importantly, Fas-deficient IPCC allografts exhibited certain immune privilege and enjoyed long-term survival in diabetic NOD mice in the presence of CD28/CD40 joint blockade while their islet counterparts failed to do so.

CONCLUSIONS/SIGNIFICANCE

Long-term survival of ASC-derived IPCC syngeneic grafts requires blocking Fas and TNF death pathways, whereas blocking both death pathways and CD28/CD40 costimulation is needed for long-term IPCC allograft survival in diabetic NOD mice. Our studies have important clinical implications for treating type 1 diabetes via ASC-derived IPCC transplantation.

Endothelial cells in co-culture enhance embryonic stem cell differentiation to pancreatic progenitors and insulin-producing cells through BMP signaling

Endothelial cells (ECs) represent the major component of the embryonic pancreatic niche and play a key role in the differentiation of insulin-producing β cells in vivo. However, it is unknown if ECs promote such differentiation in vitro. We investigated whether interaction of ECs with mouse embryoid bodies (EBs) in culture promotes differentiation of pancreatic progenitors and insulin-producing cells and the mechanisms involved. We developed a co-culture system of mouse EBs and human microvascular ECs (HMECs). An increase in the expression of the pancreatic markers PDX-1, Ngn3, Nkx6.1, proinsulin, GLUT-2, and Ptf1a was observed at the interface between EBs and ECs (EB-EC). No expression of these markers was found at the periphery of EBs cultured without ECs or those co-cultured with mouse embryonic fibroblasts (MEFs). At EB-EC interface, proinsulin and Nkx6.1 positive cells co-expressed phospho-Smad1/5/8 (pSmad1/5/8). Therefore, EBs were treated with HMEC conditioned media (HMEC-CM) suspecting soluble factors involved in bone morphogenetic protein (BMP) pathway activation. Upregulation of PDX-1, Ngn3, Nkx6.1, insulin-1, insulin-2, amylin, SUR1, GKS, and amylase as well as down-regulation of SST were detected in treated EBs. In addition, higher expression of BMP-2/-4 and their receptor (BMPR1A) were also found in these EBs. Recombinant human BMP-2 (rhBMP-2) mimicked the effects of the HMEC-CM on EBs. Noggin (NOG), a BMP antagonist, partially inhibited these effects. These results indicate that the differentiation of EBs to pancreatic progenitors and insulin-producing cells can be enhanced by ECs in vitro and that BMP pathway activation is central to this process.

Small molecules induce efficient differentiation into insulin-producing cells from human induced pluripotent stem cells

Human induced pluripotent stem (hiPS) cells have potential uses for drug discovery and cell therapy, including generation of pancreatic β-cells for diabetes research and treatment. In this study, we developed a simple protocol for generating insulin-producing cells from hiPS cells. Treatment with activin A and a GSK3β inhibitor enhanced efficient endodermal differentiation, and then combined treatment with retinoic acid, a bone morphogenic protein inhibitor, and a transforming growth factor-β (TGF-β) inhibitor induced efficient differentiation of pancreatic progenitor cells from definitive endoderm. Expression of the pancreatic progenitor markers PDX1 and NGN3 was significantly increased at this step and most cells were positive for anti-PDX1 antibody. Moreover, several compounds, including forskolin, dexamethasone, and a TGF-β inhibitor, were found to induce the differentiation of insulin-producing cells from pancreatic progenitor cells. By combined treatment with these compounds, more than 10% of the cells became insulin positive. The differentiated cells secreted human c-peptide in response to various insulin secretagogues. In addition, all five hiPS cell lines that we examined showed efficient differentiation into insulin-producing cells with this protocol.

The prospect of induced pluripotent stem cells for diabetes mellitus treatment

A continuous search for a permanent cure for diabetes mellitus is underway with several remarkable discoveries over the past few decades. One of these is the potential of pancreatic stem/progenitor cells to rejuvenate functional β cells. However, the existence of these cell populations is still obscure and a lack of phenotype characterization hampers their use in clinical settings. Cellular reprogramming through induced pluripotent stem (iPS) cell technology can become an alternative strategy to generate insulin-producing cells in a relatively safe (autologous-derived cells, thus devoid of rejection risk) and efficient way (high cellular proliferation) but retain a precise morphological and genetic composition, similar to that of the native β cells. iPS cell technology is a technique of transducing any cell types with key transcription factors to yield embryonic-like stem cells with high clonogenicity and is able to give rise into all cell lineages from three germ layers (endoderm, ectoderm, and mesoderm). This approach can generate β-like pancreatic cells that are fully functional as proven by either in vitro or in vivo studies. This novel proof-of-concept stem cell technology brings new expectations on applying stem cell therapy for diabetes mellitus in clinical settings.

Stem cell-based therapeutic applications in retinal degenerative diseases

Retinal degenerative diseases that target photoreceptors or the adjacent retinal pigment epithelium (RPE) affect millions of people worldwide. Retinal degeneration (RD) is found in many different forms of retinal diseases including retinitis pigmentosa (RP), age-related macular degeneration (AMD), diabetic retinopathy, cataracts, and glaucoma. Effective treatment for retinal degeneration has been widely investigated. Gene-replacement therapy has been shown to improve visual function in inherited retinal disease. However, this treatment was less effective with advanced disease. Stem cell-based therapy is being pursued as a potential alternative approach in the treatment of retinal degenerative diseases. In this review, we will focus on stem cell-based therapies in the pipeline and summarize progress in treatment of retinal degenerative disease.

Insulin-producing surrogate β-cells from embryonic stem cells: are we there yet?

Embryonic stem cells (ESCs) harbor the potential to generate every cell type of the body by differentiation. The use of hESCs holds great promise for potential cell replacement therapies for degenerative diseases including diabetes mellitus. The recently discovered induced pluripotent stem cells (iPSCs) exhibit immense potential for regenerative medicine as they allow the generation of autologous cells tailored to the patients' immune system. Research for insulin-producing surrogate cells from ESCs has yielded highly controversial results, because many steps and factors in the differentiation process are currently still unknown. Thus, there is no consensus on common standard protocols. The protocols presently used established the differentiation from pluripotent cells toward pancreatic progenitor cells. However, none of the differentiation protocols reported to date have generated by exclusive in vitro differentiation sufficient numbers of insulin-producing cells meeting all essential criteria of a β-cell. The cells often lack the crucial function of regulated insulin secretion upon glucose stimulation. This review focuses on past and current approaches to the generation of insulin-producing cells from pluripotent sources, such as ESCs and iPSCs, and critically discusses the hurdles to be taken before insulin-secreting surrogate cells derived from these stem cells will be of clinical use in humans.

Mechanotransduction: tuning stem cells fate

It is a general concern that the success of regenerative medicine-based applications is based on the ability to recapitulate the molecular events that allow stem cells to repair the damaged tissue/organ. To this end biomaterials are designed to display properties that, in a precise and physiological-like fashion, could drive stem cell fate both in vitro and in vivo. The rationale is that stem cells are highly sensitive to forces and that they may convert mechanical stimuli into a chemical response. In this review, we describe novelties on stem cells and biomaterials interactions with more focus on the implication of the mechanical stimulation named mechanotransduction.

Musculoskeletal tissue engineering with human umbilical cord mesenchymal stromal cells

Multipotent mesenchymal stromal cells (MSCs) hold tremendous promise for tissue engineering and regenerative medicine, yet with so many sources of MSCs, what are the primary criteria for selecting leading candidates? Ideally, the cells will be multipotent, inexpensive, lack donor site morbidity, donor materials should be readily available in large numbers, immunocompatible, politically benign and expandable in vitro for several passages. Bone marrow MSCs do not meet all of these criteria and neither do embryonic stem cells. However, a promising new cell source is emerging in tissue engineering that appears to meet these criteria: MSCs derived from Wharton's jelly of umbilical cord MSCs. Exposed to appropriate conditions, umbilical cord MSCs can differentiate in vitro along several cell lineages such as the chondrocyte, osteoblast, adipocyte, myocyte, neuronal, pancreatic or hepatocyte lineages. In animal models, umbilical cord MSCs have demonstrated in vivo differentiation ability and promising immunocompatibility with host organs/tissues, even in xenotransplantation. In this article, we address their cellular characteristics, multipotent differentiation ability and potential for tissue engineering with an emphasis on musculoskeletal tissue engineering.

Regenerative medicine for insulin deficiency: creation of pancreatic islets and bioartificial pancreas

Recent advances in pancreas organogenesis have greatly improved the understanding of cell lineage from inner cell mass to fully differentiated β-cells. Based upon such knowledge, insulin-producing cells similar to β-cells to a certain extent have been generated from various cell sources including embryonic stem cells (ESCs) and induced pluripotent stem (iPS) cells, although fully differentiated cells comparable to β-cells are not yet available. The bioartificial pancreas is a therapeutic approach to enable allo- and xenotransplantation of islets without immune suppression. Among several types of bioartificial pancreases (BAPs), micro-encapsulated porcine islets are already in use in clinical trials and may, perhaps, replace islet transplantation in the near future. Some types of bioartificial pancreas such as macro-encapsulation are also useful for keeping transplanted cells enclosed in case retrieval is necessary. Therefore, early clinical applications of artificially generated β-like cells, especially those from ESCs or iPS cells, will be considered in combination with retrievable BAPs.

Tissue engineering: current strategies and future directions

Novel therapies resulting from regenerative medicine and tissue engineering technology may offer new hope for patients with injuries, end-stage organ failure, or other clinical issues. Currently, patients with diseased and injured organs are often treated with transplanted organs. However, there is a shortage of donor organs that is worsening yearly as the population ages and as the number of new cases of organ failure increases. Scientists in the field of regenerative medicine and tissue engineering are now applying the principles of cell transplantation, material science, and bioengineering to construct biological substitutes that can restore and maintain normal function in diseased and injured tissues. In addition, the stem cell field is a rapidly advancing part of regenerative medicine, and new discoveries in this field create new options for this type of therapy. For example, new types of stem cells, such as amniotic fluid and placental stem cells that can circumvent the ethical issues associated with embryonic stem cells, have been discovered. The process of therapeutic cloning and the creation of induced pluripotent cells provide still other potential sources of stem cells for cell-based tissue engineering applications. Although stem cells are still in the research phase, some therapies arising from tissue engineering endeavors that make use of autologous, adult cells have already entered the clinical setting, indicating that regenerative medicine holds much promise for the future.

Immune and cell therapy in type 1 diabetes: too little too late?

INTRODUCTION

Type 1 diabetes is caused by autoimmune destruction of insulin-producing β-cells. Intensive insulin therapy protects most patients against chronic complications of diabetes, but exposes patients to acute complications like hypoglycaemia and impacts on quality of life. Therapies that aim at protecting or restoring endogenous insulin secretion might help in decreasing the risk of severe hypoglycemia and long-term complications.

AREAS COVERED

This article reviews the literature of clinical immunotherapy and β-cell transplantation in treatment of type 1 diabetes with specific focus on the effect on preserving and restoring β-cell mass.

EXPERT OPINION

Several studies in recent-onset type 1 diabetic patients have provided proof of principle that immunotherapy can preserve residual functional β-cell mass. The observation that this strategy is most effective early in the disease process opens possibilities of arresting and even preventing type 1 diabetes. In patients with too few or no surviving β-cells, current protocols of β-cell transplantation can restore functional β-cell mass up to 25% of levels in healthy controls. Unfortunately, both strategies to date are followed by progressive decline of endogenous insulin secretion later on. Strategies to restore functional β-cell mass to a higher level and to restore immune tolerance are thus needed.

Stem cell therapy for diabetes: progress and prospects

Stem cells can supply sufficient islet cells for cell replacement therapy in patients with diabetes. Many types of stem cells, including embryonic stem (ES) cells, induced pluripotent stem (iPS) cells, and somatic stem cells, have been shown to be able to differentiate into insulin-producing cells either in vitro or in vivo, which could ameliorate hyperglycemia in diabetic animal models. Furthermore, several small-scale pilot clinical studies have demonstrated the potential efficacy of autologous hematopoietic stem cell transplantation in treating diabetes. Great progress has been made in basic research on the differentiation of insulin-producing cells from human ES cells, in which the ethical debate and immunological rejection are unavoidable. Use of human iPS cells and autologous somatic stem cells can avoid such problems. However, the safety of iPS cells in future clinical application and the amplification, identification and differentiation of somatic stem cells deserve further investigation. This paper aims to present an overview of different types of stem cells, strategies for differentiation into islet cells, and the problems and prospects of stem cell therapy for diabetes.

Stem cells and the endocrine pancreas

BACKGROUND

Diabetes can be treated by β-cell replacement therapy but the supply of graft material from human donors is too limited to make a significant clinical impact. Substitute β-cells generated from stem cell populations offer a potential source for the large numbers of cells required.

SOURCES OF DATA

Primary peer-reviewed reports of experimental studies.

AREAS OF AGREEMENT

Embryonic stem cells and/or induced pluripotent stem (iPS) cells are currently the most promising starting populations from which to generate large numbers of β-cells. Differentiation protocols that recapitulate in vivo development generate insulin-expressing cells in vitro.

AREAS OF CONTROVERSY

Differentiation outcomes may depend on the source of the initial pluripotent cells. The insulin-expressing cells are not fully functional. In vivo maturation is inconsistent and not well understood.

AREAS TIMELY FOR DEVELOPING RESEARCH

Improvement of current protocols for complete in vitro differentiation to a functional β-cell phenotype. Systematic analysis to identify the most appropriate starting material. Improved purification methods to ensure safety of material for clinical transplantation.

Embryonic stem cells for osteo-degenerative diseases

Current orthopedic practice to treat osteo-degenerative diseases, such as osteoporosis, calls for antiresorptive therapies and anabolic bone medications. In some cases, surgery, in which metal rods are inserted into the bones, brings symptomatic relief. As these treatments may ameliorate the symptoms, but cannot cure the underlying dysregulation of the bone, the orthopedic field seems ripe for regenerative therapies using transplantation of stem cells. Stem cells bring with them the promise of completely curing a disease state, as these are the cells that normally regenerate tissues in a healthy organism. This chapter assembles reports that have successfully used stem cells to generate osteoblasts, osteoclasts, and chondrocytes - the cells that can be found in healthy bone tissue - in culture, and review and collate studies about animal models that were employed to test the function of these in vitro "made" cells. A particular emphasis is placed on embryonic stem cells, the most versatile of all stem cells. Due to their pluripotency, embryonic stem cells represent the probably most challenging stem cells to bring into the clinic, and therefore, the associated problems are discussed to put into perspective where the field currently is and what we can expect for the future.

Human embryonic stem cells: derivation, culture, and differentiation: a review

The greatest therapeutic promise of human embryonic stem cells (hESC) is to generate specialized cells to replace damaged tissue in patients suffering from various degenerative diseases. However, the signaling mechanisms involved in lineage restriction of ESC to adopt various cellular phenotypes are still under investigation. Furthermore, for progression of hESC-based therapies towards clinical applications, appropriate culture conditions must be developed to generate genetically stable homogenous populations of cells, to hinder possible adverse effects following transplantation. Other critical challenges that must be addressed for successful cell implantation include problems related to survival and functional efficacy of the grafted cells. This review initially describes the derivation of hESC and focuses on recent advances in generation, characterization, and maintenance of these cells. We also give an overview of original and emerging differentiation strategies used to convert hESC to different cell types. Finally, we will discuss transplantation studies of hESC-derived cells with respect to safety and functional recovery.

Harnessing the pancreatic stem cell

Building on the elaborate research studies that have helped map out key decision points in the process of pancreas development, reprogramming of pluripotent embryonic stem cells or induced pluripotent stem cells offers the possibility of overcoming restrictions on tissue supply associated with transplantation of donor islets. In a healthy pancreas, the beta-cell mass can exhibit significant plasticity, as reflected in the normal adaptive response in beta-cell mass to offset the metabolic challenge associated with pregnancy and obesity. In this article, alternative strategies and potential sources of pancreatic stem cells are considered.

Indolactam V/GLP-1-mediated differentiation of human iPS cells into glucose-responsive insulin-secreting progeny

Nuclear reprogramming of somatic tissue enables derivation of induced pluripotent stem (iPS) cells from an autologous, non-embryonic origin. The purpose of the current study was to establish efficient protocols for lineage-specification of human iPS cells into functional glucose-responsive, insulin-producing progeny. We generated human iPS cells, which were then guided with recombinant growth factors that mimic the essential signaling for pancreatic development. Reprogrammed with four stemness factors, human fibroblasts were here converted into authentic iPS cells. Under feeder-free conditions, fate-specification was initiated with activin A and Wnt3a that triggered engagement into definitive endoderm, followed by priming with FGF10 and KAAD-cyclopamine. Addition of retinoic acid, boosted by the pancreatic endoderm inducer indolactam V (ILV), yielded pancreatic progenitors expressing PDX1, NGN3 and NEUROD1 markers. Further guidance, under IGF-1, HGF and DAPT, was enhanced by glucagon like peptide-1 (GLP-1) to generate islet-like cells that expressed pancreas-specific markers including insulin and glucagon. Derived progeny demonstrated sustained expression of PDX1, and functional responsiveness to glucose challenge secreting up to 230 pM of C-peptide. A pancreatogenic cocktail enriched with ILV/GLP-1 offers a proficient means to specify human iPS cells into glucose-responsive hormone-producing progeny, refining the development of a personalized platform for islet-like cell generation.

Derivation and long-term culture of human parthenogenetic embryonic stem cells using human foreskin feeders

PURPOSE

Feeder cells from animals raise considerable concern for contamination because they are directly in contact with embryonic stem cells.

METHODS

To address this issue we collected discarded foreskin tissue and prepared a fibroblast cell line. We transferred one parthenogenetic blastocyst on to these feeder cells, and later observed outgrowth. By this approach, we were able to derive a human parthenogenetic embryonic stem cell line successfully.

RESULTS

The embryonic stem cells had normal morphology, expressed all expected cell surface markers, could differentiate to embryonic bodies upon culture in vitro, and differentiated further to derivatives of all three germ layers.

CONCLUSION

This study indicates that homologous human fibroblasts can be used as feeder cells to support not only the propagation, but also the derivation of ES cells, and this should facilitate studies of therapeutic cloning for research and clinical applications.

Impact of co-culture on pancreatic differentiation of embryonic stem cells

Promise of cellular therapy for type 1 diabetes has inspired the search for transplantable cell sources, and embryonic stem cells (ESCs) have emerged as strong candidates. We have developed a directed differentiation protocol to obtain insulin-producing cells from ESCs. The ESCs are first induced towards a homogeneous monolayer of definitive endoderm-like cells by co-culture with primary hepatocytes. Pancreatic commitment is induced by plating the ESC-derived endoderms on Matrigel, along with Sonic hedgehog inhibition and retinoid induction. More than 70% of differentiated cells positively upregulated Pdx-1, along with pro-endocrine transcription factors Ngn3, β2/neroD1, Nkx2.2 and Nkx6.1. Final maturation to islet-specific cells is achieved by co-culturing the ESC-derived pancreatic endocrine cells with endothelial cells, which resulted in Insulin 1 upregulation in 60% of the cell population, along with high levels of IAPP and Glut2. The differentiated cell population also secreted high levels of insulin. Our findings illustrate the significant effect of co-culture in different stages of differentiation and maturation of ESCs in vitro. Such a high yield of pancreatic islet cells has not yet been reported. Our findings establish a robust protocol for islet differentiation.

Superior osteogenic capacity of human embryonic stem cells adapted to matrix-free growth compared to human mesenchymal stem cells

Human mesenchymal stem cells (hMSCs) represent a promising source of cells for bone tissue engineering. However, their low frequencies and limited proliferation restrict their clinical utility. An alternative is the use of human embryonic stem cells (hESCs), but labor-intensive expansion with the need for coating support limits their clinical use. We have previously derived a cell line from hESCs denoted matrix-free growth (MFG)-hESC that are independent of coating support for expansion, and we here compare its osteogenic capacity to that of hMSCs. Microarray analysis of hMSCs and MFG-hESCs revealed differential expression of genes involved in ossification. MFG-hESCs have significantly higher expression of secreted phosphoprotein 1 (SPP1) during osteogenic differentiation, whereas the opposite was true for alkaline phosphatase (ALPL), transforming growth factor, beta 1 (TGFB2), runt-related transcription factor 2 (RUNX2), and forkhead box C1 (FOXC1), as well as the activity of the ALPL enzyme, demonstrating that these two cell types differentiate into the osteogenic lineage using different signaling pathways. von Kossa staining, time-of-flight secondary ion mass spectrometry, and measurement of calcium and phosphate in the extracellular matrix demonstrated a superior ability of the MFG-hESCs to produce a mineralized matrix compared to hMSCs. The superior ability of the MFG-hESCs to form mineralized matrix compared to hMSCs demonstrates that MFG-hESCs are a promising alternative to the use of adult stem cells in future bone regenerative applications.

Generation of functional insulin-producing cells from human embryonic stem cells in vitro

Human pancreatic islet transplantation at present is the preferred therapeutic option for type I diabetes treatment. However, this therapy is not widely utilized because of the severe shortage of donor islets. The capacity for self-renewal and differentiation of human embryonic stem (hES) cells makes them a potential new source for generation of functional pancreatic islet cells for treating type I diabetes mellitus. Here, we report a simple and effective protocol, carried out in a serum-free system, which could induce human ES cells to differentiate into functional insulin-producing cells. Activin A was first used in the initial stage to induce definitive endoderm lineage differentiation from human ES cells. And all-trans Retinoic Acid (RA) was then utilized to promote pancreatic differentiation. After maturation in the final induction stage with bFGF and Nicotinamide, the differentiated cells expressed islet specific markers. The secretion of insulin and C-peptide by these cells corresponded to the variations in glucose levels. Our method provides a promising in vitro differentiation model for studying the mechanisms of human pancreas development and illustrates the potential of using human ES cells for the treatment of type I diabetes mellitus.

Enhanced insulin production from murine islet beta cells incubated on poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)

Islet transplantation represents an important alternative for the treatment of diabetes. However, the selection of suitable materials is critical for the success of such an implantation application. In this study, cellular migration, aggregation, and insulin production of a murine islet beta-cell line, NIT-1 cells on microbially produced polyesters poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB) or polylactic acid (PLA) films were investigated. Spherical islet-like structures were only detected on PHBHHx films after 48 h cultivation. To understand the mechanism underlying the formation of cell aggregates, NIT-1-GFP, a stable transfectant of the green fluorescent protein was used in a time-lapse imaging study. Cell aggregation began on PHBHHx at 2 h, and became obvious at 4 h. Furthermore, cells on PHBHHx displayed higher metabolic activities measured by MTT assay than that on tissue culture plate. More importantly, insulin gene expression as well as extracellular secretion was upregulated after growth on PHBHHx for 72 h. Thus, PHBHHx can be a strong candidate for islet transplantation.

Nestin action during insulin-secreting cell differentiation

Nestin, which was initially identified as a marker of neural stem cells, has been reported in regenerating pancreas as well as in early embryonic stem (ES) cell derivatives. However, little is known about its specific roles in stem cells as a functional regulator. We investigated the source of the action of nestin in ES and adult pancreatic ductal stem (PDS) cells in regard to the neogenesis of insulin-secreting beta-cells. In ES cells, suppression of nestin by gene silencing led to an increased expression of the pluripotency-associated genes, including Oct 4, Nanog, and SSEA-1, before embryoid body (EB) formation, whereas it reduced endodermal and pancreatic transcription factors in EBs. Inhibition of nestin expression in adult PDS cells caused a low expression of pancreatic transcription factors and islet hormones, leading to poor beta-cell development and insulin secretion. These data may indicate not only that nestin is a simple stem cell marker, but also that it constitutes a functional factor at the time of stem cell differentiation. We suggest that nestin plays pivotal roles as an intermediate regulator governing both stemness and differentiation of stem cells in the process of their differentiation into insulin-secreting cells.

Converting human pluripotent stem cells into beta-cells: recent advances and future challenges

PURPOSE OF REVIEW

The transplantation of insulin-producing beta-cells derived from human embryonic stem cells and induced pluripotent stem cells (collectively termed pluripotent stem cells or PSCs) holds great promise for therapy of diabetes mellitus. The purpose of this review is to summarize recent advances in this area, emphasizing the importance of studies of endocrine pancreas development in efforts to direct PSC differentiation into endocrine cells, as well as to outline the major challenges remaining before transplantation of PSC-derived beta-cells can become a reality.

RECENT FINDINGS

Although several protocols to generate glucose-responsive pancreatic beta-cells in vitro have been described, the most successful approaches are those that most closely mimic embryonic development of the endocrine pancreas. Until recently, cells generated by these methods have exhibited immature pancreatic endocrine phenotypes. However, protocols that generate more functional beta-like cells have now been described. In addition, small molecules are being used to improve protocols to direct differentiation of PSCs into endoderm and pancreatic lineages.

SUMMARY

Advances over the last decade suggest that generating functional beta-cells from human PSCs is achievable. However, there are aspects of beta-cell development that are not well understood and are hampering generation of PSC-derived beta-cells. In particular, the signaling pathways that instruct endocrine progenitor cells to differentiate into mature and functional beta-cells are poorly understood. Other significant obstacles remain, including the need for safe and cost-effective differentiation methods for large-scale generation of transplantation quality beta-cells, methods to prevent immune rejection of grafted tissues, and amelioration of the risks of tumorigenesis.

mAb 84, a cytotoxic antibody that kills undifferentiated human embryonic stem cells via oncosis

The monoclonal antibody mAb 84, which binds to podocalyxin-like protein-1 (PODXL) on human embryonic stem cells (hESCs), was previously reported to bind and kill undifferentiated cells in in vitro and in vivo assays. In this study, we investigate the mechanism responsible for mAb 84-induced hESCs cytotoxicity. Apoptosis was likely not the cause of mAb 84-mediated cell death because no elevation of caspase activities or increased DNA fragmentation was observed in hESCs following incubation with mAb 84. Instead, it was preceded by cell aggregation and damage to cell membranes, resulting in the uptake of propidium iodide, and the leakage of intracellular sodium ions. Furthermore, examination of the cell surface by scanning electron microscopy revealed the presence of pores on the cell surface of mAb 84-treated cells, which was absent from the isotype control. This mechanism of cell death resembles that described for oncosis, a form of cell death resulting from membrane damage. Additional data suggest that the binding of mAb 84 to hESCs initiates a sequence of events prior to membrane damage, consistent with oncosis. Degradation of actin-associated proteins, namely, alpha-actinin, paxillin, and talin, was observed. The perturbation of these actin-associated proteins consequently permits the aggregation of PODXL, thus leading to the formation of pores. To our knowledge, this is the first report of oncotic cell death with hESCs as a model.

Generation of pancreatic hormone-expressing islet-like cell aggregates from murine adipose tissue-derived stem cells

The success of cell replacement therapy for diabetes depends on the availability and generation of an adequate number of islets, preferably from an autologous origin. Stem cells are now being probed for the generation of physiologically competent, insulin-producing cells. In this investigation, we explored the potential of adipose tissue-derived stem cells (ASCs) to differentiate into pancreatic hormone-expressing islet-like cell aggregates (ICAs). We initiated ASC culture from epididymal fat pads of Swiss albino mice to obtain mesenchymal cells, murine epididymal (mE)-ASCs. Subsequent single-cell cloning resulted in a homogeneous cell population with a CD29(+)CD44(+)Sca-1(+) surface antigen expression profile. We formulated a 10-day differentiation protocol to generate insulin-expressing ICAs from mE-ASCs by progressively changing the differentiation cocktail on day 1, day 3, and day 5. Our stage-specific approach successfully differentiated mesodermic mE-ASCs into definitive endoderm (cells expressing Sox17, Foxa2, GATA-4, and cytokeratin [CK]-19), then into pancreatic endoderm (cells expressing pancreatic and duodenal homeobox [PDX]-1, Ngn3, NeuroD, Pax4, and glucose transporter 2), and finally into cells expressing pancreatic hormones (insulin, glucagon, somatostatin). Fluorescence-activated cell sorting analysis showed that day 5 ICAs contained 64.84% +/- 7.03% PDX-1(+) cells, and in day 10 mature ICAs, 48.17% +/- 3% of cells expressed C-peptide. Day 10 ICAs released C-peptide in a glucose-dependent manner, exhibiting in vitro functionality. Electron microscopy of day 10 ICAs revealed the presence of numerous secretory granules within the cell cytoplasm. Calcium alginate-encapsulated day 10 ICAs (1,000-1,200), when transplanted i.p. into streptozotocin-induced diabetic mice, restored normoglycemia within 2 weeks. The data presented here demonstrate the feasibility of using ASCs as a source of autologous stem cells to differentiate into the pancreatic lineage.

Pancreatic beta-cell signaling: toward better understanding of diabetes and its treatment

Pancreatic beta-cells play a central role in the maintenance glucose homeostasis by secreting insulin, a key hormone that regulates blood glucose levels. Dysfunction of the beta-cells and/or a decrease in the beta-cell mass are associated closely with the pathogenesis and pathophysiology of diabetes mellitus, a major metabolic disease that is rapidly increasing worldwide. Clarification of the mechanisms of insulin secretion and beta-cell fate provides a basis for the understanding of diabetes and its better treatment. In this review, we discuss cell signaling critical for the insulin secretory function based on our recent studies.