iPS cell technologies: significance and applications to CNS regeneration and disease

Forced cell cycle exit and modulation of GABAA, CREB, and GSK3β signaling promote functional maturation of induced pluripotent stem cell-derived neurons

Although numerous protocols have been developed for differentiation of neurons from a variety of pluripotent stem cells, most have concentrated on being able to specify effectively appropriate neuronal subtypes and few have been designed to enhance or accelerate functional maturity. Of those that have, most employ time courses of functional maturation that are rather protracted, and none have fully characterized all aspects of neuronal function, from spontaneous action potential generation through to postsynaptic receptor maturation. Here, we describe a simple protocol that employs the sequential addition of just two supplemented media that have been formulated to separate the two key phases of neural differentiation, the neurogenesis and synaptogenesis, each characterized by different signaling requirements. Employing these media, this new protocol synchronized neurogenesis and enhanced the rate of maturation of pluripotent stem cell-derived neural precursors. Neurons differentiated using this protocol exhibited large cell capacitance with relatively hyperpolarized resting membrane potentials; moreover, they exhibited augmented: 1) spontaneous electrical activity; 2) regenerative induced action potential train activity; 3) Na(+) current availability, and 4) synaptic currents. This was accomplished by rapid and uniform development of a mature, inhibitory GABAAreceptor phenotype that was demonstrated by Ca(2+) imaging and the ability of GABAAreceptor blockers to evoke seizurogenic network activity in multielectrode array recordings. Furthermore, since this protocol can exploit expanded and frozen prepatterned neural progenitors to deliver mature neurons within 21 days, it is both scalable and transferable to high-throughput platforms for the use in functional screens.

Challenges and Strategies for Regenerating the Lacrimal Gland

The lacrimal gland produces the aqueous component of tears, including electrolytes, peptides, and glycoproteins necessary to maintain homeostasis and optical properties of the ocular surface. Stem cells that contribute to the homeostasis of the lacrimal gland are under extensive study. It is still unclear whether such stem cells are of mesenchymal or epithelial origin. It is also possible that a unique epithelial stem cell undergoes epithelial-mesenchymal transition and contributes to the mesenchyme. Developmental studies in mice have shown that a network of growth factors contributes to epithelial-mesenchymal interaction during morphogenesis of the lacrimal gland. Recently, the developmental process was successfully recapitulated in vitro, providing a valuable tool for study of lacrimal gland development and possibly opening doors to regenerative therapy. While further studies are required to identify and appreciate the potential of lacrimal gland stem cells, advances in stem cell biology in general should become a catalyst towards developing regenerative therapy of the lacrimal gland.

Controlling the Regional Identity of hPSC-Derived Neurons to Uncover Neuronal Subtype Specificity of Neurological Disease Phenotypes

The CNS contains many diverse neuronal subtypes, and most neurological diseases target specific subtypes. However, the mechanism of neuronal subtype specificity of disease phenotypes remains elusive. Although in vitro disease models employing human pluripotent stem cells (PSCs) have great potential to clarify the association of neuronal subtypes with disease, it is currently difficult to compare various PSC-derived subtypes. This is due to the limited number of subtypes whose induction is established, and different cultivation protocols for each subtype. Here, we report a culture system to control the regional identity of PSC-derived neurons along the anteroposterior (A-P) and dorsoventral (D-V) axes. This system was successfully used to obtain various neuronal subtypes based on the same protocol. Furthermore, we reproduced subtype-specific phenotypes of amyotrophic lateral sclerosis (ALS) and Alzheimer’s disease (AD) by comparing the obtained subtypes. Therefore, our culture system provides new opportunities for modeling neurological diseases with PSCs.

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The regional identity of PSC-derived neurons can be controlled precisely

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Phenotypes between different neuronal subtypes were compared successfully

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Neuronal subtype-specific phenotypes of ALS and AD were reproduced in vitro

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A novel tool is offered to study subtype specificity of disease phenotypes

Understanding the molecular basis of autism in a dish using hiPSCs-derived neurons from ASD patients

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder characterized by deficits in social cognition, language development, and repetitive/restricted behaviors. Due to the complexity and heterogeneity of ASD and lack of a proper human cellular model system, the pathophysiological mechanism of ASD during the developmental process is largely unknown. However, recent progress in induced pluripotent stem cell (iPSC) technology as well as in vitro neural differentiation techniques have allowed us to functionally characterize neurons and analyze cortical development during neural differentiation. These technical advances will increase our understanding of the pathogenic mechanisms of heterogeneous ASD and help identify molecular biomarkers for patient stratification as well as personalized medicine. In this review, we summarize our current knowledge of iPSC generation, differentiation of specific neuronal subtypes from iPSCs, and phenotypic characterizations of human ASD patient-derived iPSC models. Finally, we discuss the current limitations of iPSC technology and future directions of ASD pathophysiology studies using iPSCs.

Activity and High-Order Effective Connectivity Alterations in Sanfilippo C Patient-Specific Neuronal Networks

Induced pluripotent stem cell (iPSC) technology has been successfully used to recapitulate phenotypic traits of several human diseases in vitro. Patient-specific iPSC-based disease models are also expected to reveal early functional phenotypes, although this remains to be proved. Here, we generated iPSC lines from two patients with Sanfilippo type C syndrome, a lysosomal storage disorder with inheritable progressive neurodegeneration. Mature neurons obtained from patient-specific iPSC lines recapitulated the main known phenotypes of the disease, not present in genetically corrected patient-specific iPSC-derived cultures. Moreover, neuronal networks organized in vitro from mature patient-derived neurons showed early defects in neuronal activity, network-wide degradation, and altered effective connectivity. Our findings establish the importance of iPSC-based technology to identify early functional phenotypes, which can in turn shed light on the pathological mechanisms occurring in Sanfilippo syndrome. This technology also has the potential to provide valuable readouts to screen compounds, which can prevent the onset of neurodegeneration.

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Fibroblasts from two Sanfilippo C patients were reprogrammed to obtain iPSCs

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iPSCs were successfully differentiated to neural cells that mimic the disease

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Networks of patients’ neurons show altered activity and connectivity

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Early functional phenotypes are prevented in gene-corrected patients’ neurons

Bioengineered Lacrimal Gland Organ Regeneration in Vivo

The lacrimal gland plays an important role in maintaining a homeostatic environment for healthy ocular surfaces via tear secretion. Dry eye disease, which is caused by lacrimal gland dysfunction, is one of the most prevalent eye disorders and causes ocular discomfort, significant visual disturbances, and a reduced quality of life. Current therapies for dry eye disease, including artificial tear eye drops, are transient and palliative. The lacrimal gland, which consists of acini, ducts, and myoepithelial cells, develops from its organ germ via reciprocal epithelial-mesenchymal interactions during embryogenesis. Lacrimal tissue stem cells have been identified for use in regenerative therapeutic approaches aimed at restoring lacrimal gland functions. Fully functional organ replacement, such as for tooth and hair follicles, has also been developed via a novel three-dimensional stem cell manipulation, designated the Organ Germ Method, as a next-generation regenerative medicine. Recently, we successfully developed fully functional bioengineered lacrimal gland replacements after transplanting a bioengineered organ germ using this method. This study represented a significant advance in potential lacrimal gland organ replacement as a novel regenerative therapy for dry eye disease. In this review, we will summarize recent progress in lacrimal regeneration research and the development of bioengineered lacrimal gland organ replacement therapy.

Cell reprogramming and neuronal differentiation applied to neurodegenerative diseases: Focus on Parkinson's disease

Adult cells from patients can be reprogrammed to induced pluripotent stem cells (iPSCs) which successively can be used to obtain specific cells such as neurons. This remarkable breakthrough represents a new way of studying diseases and brought new therapeutic perspectives in the field of regenerative medicine. This is particular true in the neurology field, where few techniques are amenable to study the affected tissue of the patient during illness progression, in addition to the lack of neuroprotective therapies for many diseases. In this review we discuss the advantages and unresolved issues of cell reprogramming and neuronal differentiation. We reviewed evidence using iPSCs-derived neurons from neurological patients. Focusing on data obtained from Parkinson's disease (PD) patients, we show that iPSC-derived neurons possess morphological and functional characteristics of this disease and build a case for the use of this technology to study PD and other neuropathologies while disease is in progress. These data show the enormous impact that this new technology starts to have on different purposes such as the study and design of future therapies of neurological disease, especially PD.

Utility of Scalp Hair Follicles as a Novel Source of Biomarker Genes for Psychiatric Illnesses

BACKGROUND

Identifying beneficial surrogate genetic markers in psychiatric disorders is crucial but challenging.

METHODS

Given that scalp hair follicles are easily accessible and, like the brain, are derived from the ectoderm, expressions of messenger RNA (mRNA) and microRNA in the organ were examined between schizophrenia (n for first/second = 52/42) and control subjects (n = 62/55) in two sets of cohort. Genes of significance were also analyzed using postmortem brains (n for case/control = 35/35 in Brodmann area 46, 20/20 in cornu ammonis 1) and induced pluripotent stem cells (n = 4/4) and pluripotent stem cell-derived neurospheres (n = 12/12) to see their role in the central nervous system. Expression levels of mRNA for autism (n for case/control = 18/24) were also examined using scalp hair follicles.

RESULTS

Among mRNA examined, FABP4 was downregulated in schizophrenia subjects by two independent sample sets. Receiver operating characteristic curve analysis determined that the sensitivity and specificity were 71.8% and 66.7%, respectively. FABP4 was expressed from the stage of neurosphere. Additionally, microarray-based microRNA analysis showed a trend of increased expression of hsa-miR-4449 (p = .0634) in hair follicles from schizophrenia. hsa-miR-4449 expression was increased in Brodmann area 46 from schizophrenia (p = .0007). Finally, we tested the expression of nine putative autism candidate genes in hair follicles and found decreased CNTNAP2 expression in the autism cohort.

CONCLUSIONS

Scalp hair follicles could be a beneficial genetic biomarker resource for brain diseases, and further studies of FABP4 are merited in schizophrenia pathogenesis.

Applications of Induced Pluripotent Stem Cells in Studying the Neurodegenerative Diseases

Neurodegeneration is the umbrella term for the progressive loss of structure or function of neurons. Incurable neurodegenerative disorders such as Alzheimer's disease (AD) and Parkinson's disease (PD) show dramatic rising trends particularly in the advanced age groups. However, the underlying mechanisms are not yet fully elucidated, and to date there are no biomarkers for early detection or effective treatments for the underlying causes of these diseases. Furthermore, due to species variation and differences between animal models (e.g., mouse transgenic and knockout models) of neurodegenerative diseases, substantial debate focuses on whether animal and cell culture disease models can correctly model the condition in human patients. In 2006, Yamanaka of Kyoto University first demonstrated a novel approach for the preparation of induced pluripotent stem cells (iPSCs), which displayed similar pluripotency potential to embryonic stem cells (ESCs). Currently, iPSCs studies are permeating many sectors of disease research. Patient sample-derived iPSCs can be used to construct patient-specific disease models to elucidate the pathogenic mechanisms of disease development and to test new therapeutic strategies. Accordingly, the present review will focus on recent progress in iPSC research in the modeling of neurodegenerative disorders and in the development of novel therapeutic options.

Regenerative therapy for hippocampal degenerative diseases: lessons from preclinical studies

Increase in life expectancy has put neurodegenerative diseases on the rise. Amongst these, degenerative diseases involving hippocampus like Alzheimer's disease (AD) and temporal lobe epilepsy (TLE) are ranked higher as it is vulnerable to excitotoxicity induced neuronal dysfunction and death resulting in cognitive impairment. Modern medicines have not succeeded in halting the progression of these diseases rendering them incurable and often fatal. Under such scenario, regenerative studies employing stem cells or their by-products in animal models of AD and TLE have yielded encourageing results. This review focuses on the distinct cell types, such as hippocampal cell lines, neural precursor cells, embryonic stem cells derived neural precursor cells, induced pluripotent stem cells, induced neurons and mesenchymal stem cells, which can be employed to rescue hippocampal functions in neurodegenerative diseases like AD and TLE. Besides, the divergent mechanisms through which cell based therapy confer neuroprotection, current impediments and possible improvements in stem cell transplantation strategies are discussed. Authors are aware of the voluminous literature available on this issue and have made a sincere attempt to put forth the current status of research in the field of cell based therapy concurrently discussing the promise it holds for combating neurodegenerative diseases like AD and TLE in the near future. Copyright © 2015 John Wiley & Sons, Ltd.

Connectivity and circuitry in a dish versus in a brain

In order to understand and find therapeutic strategies for neurological disorders, disease models that recapitulate the connectivity and circuitry of patients’ brain are needed. Owing to many limitations of animal disease models, in vitro neuronal models using patient-derived stem cells are currently being developed. However, prior to employing neurons as a model in a dish, they need to be evaluated for their electrophysiological properties, including both passive and active membrane properties, dynamics of neurotransmitter release, and capacity to undergo synaptic plasticity. In this review, we survey recent attempts to study these issues in human induced pluripotent stem cell-derived neurons. Although progress has been made, there are still many hurdles to overcome before human induced pluripotent stem cell-derived neurons can fully recapitulate all of the above physiological properties of adult mature neurons. Moreover, proper integration of neurons into pre-existing circuitry still needs to be achieved. Nevertheless, in vitro neuronal stem cell-derived models hold great promise for clinical application in neurological diseases in the future.

Cloning and variation of ground state intestinal stem cells

Stem cells of the gastrointestinal tract, pancreas, liver, and other columnar epithelia collectively resist cloning in their elemental states. Here we demonstrate the cloning and propagation of highly clonogenic, “ground state” stem cells of the human intestine and colon. We show that derived stem cell pedigrees sustain limited copy number and sequence variation despite extensive serial passaging and display exquisitely precise, cell-autonomous commitment to epithelial differentiation consistent with their origins along the intestinal tract. This developmentally patterned and epigenetically maintained commitment of stem cells likely enforces the functional specificity of the adult intestinal tract. Using clonally-derived colonic epithelia, we show that toxins A or B of the enteric pathogen C. difficile recapitulate the salient features of pseudomembranous colitis. The stability of the epigenetic commitment programs of these stem cells, coupled with their unlimited replicative expansion and maintained clonogenicity, suggests certain advantages for their use in disease modeling and regenerative medicine.

Stem cell research and regenerative medicine in 2014: first year of regenerative medicine in Japan

It is my great pleasure to announce that we were able to publish the Japan Issue in Stem Cells and Development, especially in this year 2014. This year, 2014, is said to be the First Year of Regenerative Medicine in Japan. This movement is likely to be based on the establishment of a new law system regarding regenerative medicine (an Act for Ensuring the Safety of Regenerative Medicine or the so-called Regenerative Medicine Law) and the partial revision of the Pharmaceutical Affairs Law (PAL). Both laws will come into effect in 2014 in this country. These new law systems are expected to have a great impact on the facilitation of R&D related to regenerative medicine and stem cell biology. In the present Japan Issue, some excellent stem cell research in this country will be introduced to celebrate the First Year of Regenerative Medicine in Japan.

Regenerative medicine for Parkinson's disease

Regenerative medicine for Parkinson’s disease (PD) is expected to develop dramatically with the advancement of biotechnology as represented by induced pluripotent stem cells. Existing therapeutic strategy for PD consists of medication using L-DOPA, surgery such as deep brain stimulation and rehabilitation. Current treatment cannot stop the progression of the disease, although there is definite therapeutic effect. True neurorestoration is strongly desired by regenerative medicine. This review article describes the historical development of regenerative medicine for PD, with a focus on fetal nigral cell transplantation and glial cell line-derived neurotrophic factor infusion. Subsequently, the current status of regenerative medicine for PD in terms of cell therapy and gene therapy are reviewed. In the end, the future direction to realize regenerative medicine for PD is discussed.

Induced pluripotent stem cells restore function in a human cell loss model of open-angle glaucoma

Normally, trabecular meshwork (TM) and Schlemm's canal inner wall endothelial cells within the aqueous humor outflow pathway maintain intraocular pressure within a narrow safe range. Elevation in intraocular pressure, because of the loss of homeostatic regulation by these outflow pathway cells, is the primary risk factor for vision loss due to glaucomatous optic neuropathy. A notable feature associated with glaucoma is outflow pathway cell loss. Using controlled cell loss in ex vivo perfused human outflow pathway organ culture, we developed compelling experimental evidence that this level of cell loss compromises intraocular pressure homeostatic function. This function was restored by repopulation of the model with fresh TM cells. We then differentiated induced pluripotent stem cells (iPSCs) and used them to repopulate this cell depletion model. These differentiated cells (TM-like iPSCs) became similar to TM cells in both morphology and expression patterns. When transplanted, they were able to fully restore intraocular pressure homeostatic function. This successful transplantation of TM-like iPSCs establishes the conceptual feasibility of using autologous stem cells to restore intraocular pressure regulatory function in open-angle glaucoma patients, providing a novel alternative treatment option.

Reprogramming patient-derived cells to study the epilepsies

The epilepsies and related disorders of brain circuitry present significant challenges associated with the use of human cells to study disease mechanisms and develop new therapies. Some of these obstacles are being overcome through the use of induced pluripotent stem cells to obtain patient-derived neural cells for in vitro studies and as a source of cell-based treatments. The field is evolving rapidly with the addition of genome-editing approaches and expanding protocols for generating different neural cell types and three-dimensional tissues, but the application of these techniques to neurological disorders, and particularly to the epilepsies, is in its infancy. We discuss the progress made and the distinct advantages and limitations of using patient-derived cells to study or treat epilepsy, as well as critical future directions for the field.

Controlling immune rejection is a fail-safe system against potential tumorigenicity after human iPSC-derived neural stem cell transplantation

Our previous work reported functional recovery after transplantation of mouse and human induced pluripotent stem cell-derived neural stem/progenitor cells (hiPSC-NS/PCs) into rodent models of spinal cord injury (SCI). Although hiPSC-NS/PCs proved useful for the treatment of SCI, the tumorigenicity of the transplanted cells must be resolved before they can be used in clinical applications. The current study sought to determine the feasibility of ablation of the tumors formed after hiPSC-NS/PC transplantation through immunoregulation. Tumorigenic hiPSC-NS/PCs were transplanted into the intact spinal cords of immunocompetent BALB/cA mice with or without immunosuppressant treatment. In vivo bioluminescence imaging was used to evaluate the chronological survival and growth of the transplanted cells. The graft survival rate was 0% in the group without immunosuppressants versus 100% in the group with immunosuppressants. Most of the mice that received immunosuppressants exhibited hind-limb paralysis owing to tumor growth at 3 months after iPSC-NS/PC transplantation. Histological analysis showed that the tumors shared certain characteristics with low-grade gliomas rather than with teratomas. After confirming the progression of the tumors in immunosuppressed mice, the immunosuppressant agents were discontinued, resulting in the complete rejection of iPSC-NS/PC-derived masses within 42 days after drug cessation. In accordance with the tumor rejection, hind-limb motor function was recovered in all of the mice. Moreover, infiltration of microglia and lymphocytes was observed during the course of tumor rejection, along with apoptosis of iPSC-NS/PC-generated cells. Thus, immune rejection can be used as a fail-safe system against potential tumorigenicity after transplantation of iPSC-NS/PCs to treat SCI.

Intranasal delivery of stem cells as therapy for central nervous system disease

Stem cells, upon entering the CNS, can preferentially migrate into disease foci, where they exert therapeutic effects that compensate for lost tissue, reconstructing damaged neuronal circuitry and establishing in the brain a new microenvironment suitable for cell survival. However, the route of stem cell delivery into the CNS remains a challenge: with systemic administration (e.g., intravenous injection), a fraction of cells may be trapped in other organs than the CNS, while direct CNS injections, e.g., intracerebroventricular or transcranial, are invasive. Intranasal (i.n.) delivery of stem cells, in contrast, can effectively bypass the blood-brain barrier, rapidly enter the CNS, and minimize systemic distribution. I.n. delivery of stem cells may therefore be a safe and non-invasive way of targeting the CNS and would thus be a promising therapeutic option for CNS disease. In this review we discuss the i.n. route for stem cell delivery into the CNS, and the perspectives of i.n. stem cell-based therapy in CNS disease.

Utility of Human Stem Cells for Drug Discovery

The pharmaceutical industry continues to struggle to deliver novel and innovative medicines to the market. One of the major challenges in deriving new therapeutics is to more accurately predict the safety and efficacy of the candidate molecule. The current paradigm of drug discovery has several limitations but perhaps the most conspicuous deficiency is the lack of human-based experimental models. The advent of human embryonic stem cells followed by the discovery of induced pluripotent stem (iPS) cells offers unprecedented opportunities for integrating human cellular assays in drug discovery and development. Human iPS cell lines of many diseases have been obtained and iPSC-derived disease affected cells have been utilised for proof-of-concept drug screens to assess efficacy or potential toxicology. The incorporation of iPSC technology thus provides an invaluable opportunity to reduce drug attrition during the process of drug development.

SOX9 as a Predictor for Neurogenesis Potentiality of Amniotic Fluid Stem Cells

Preclinical studies of amniotic fluid-derived cell therapy have been successful in the research of neurodegenerative diseases, peripheral nerve injury, spinal cord injury, and brain ischemia. Transplantation of human amniotic fluid stem cells (AFSCs) into rat brain ventricles has shown improvement in symptoms of Parkinson's disease and also highlighted the minimal immune rejection risk of AFSCs, even between species. Although AFSCs appeared to be a promising resource for cell-based regenerative therapy, AFSCs contain a heterogeneous pool of distinct cell types, rendering each preparation of AFSCs unique. Identification of predictive markers for neuron-prone AFSCs is necessary before such stem cell-based therapeutics can become a reality. In an attempt to identify markers of AFSCs to predict their ability for neurogenesis, we performed a two-phase study. In the discovery phase of 23 AFSCs, we tested ZNF521/Zfp521, OCT6, SOX1, SOX2, SOX3, and SOX9 as predictive markers of AFSCs for neural differentiation. In the validation phase, the efficacy of these predictive markers was tested in independent sets of 18 AFSCs and 14 dental pulp stem cells (DPSCs). We found that high expression of SOX9 in AFSCs is associated with good neurogenetic ability, and these positive correlations were confirmed in independent sets of AFSCs and DPSCs. Furthermore, knockdown of SOX9 in AFSCs inhibited their neuronal differentiation. In conclusion, the discovery of SOX9 as a predictive marker for neuron-prone AFSCs could expedite the selection of useful clones for regenerative medicine, in particular, in neurological diseases and injuries.