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Friedreich's ataxia (FRDA) is a rare neurodegenerative disease caused by an expansion of a GAA repeat sequence within the Frataxin (FXN) gene. Prominent regions of neurodegeneration include sensory neurons within the dorsal root ganglia. Here we present a set of genetically modified FRDA induced pluripotent stem cell (iPSC) lines that carry an inducible neurogenin-2 (NGN2) expression cassette. Exogenous expression of NGN2 in iPSC derived neural crest progenitors efficiently generates functionally mature sensory neurons. These cell lines will provide a streamlined source of FRDA iPSC sensory neurons for studying both disease mechanism and screening potential therapeutics., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: M Dottori collaborates with Dmitry A. Ovchinnikov, who is an editor for Stem Cell Research. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Friedreich's ataxia (FRDA) is a hereditary neuromuscular disorder. Cardiomyopathy is the leading cause of premature death in FRDA. FRDA cardiomyopathy is a complex and progressive disease with no cure or treatment to slow its progression. At the cellular level, cardiomyocyte hypertrophy, apoptosis and fibrosis contribute to the cardiac pathology. However, the heart is composed of multiple cell types and several clinical studies have reported the involvement of cardiac non-myocytes such as vascular cells, autonomic neurons, and inflammatory cells in the pathogenesis of FRDA cardiomyopathy. In fact, several of the cardiac pathologies associated with FRDA including cardiomyocyte necrosis, fibrosis, and arrhythmia, could be contributed to by a diseased vasculature and autonomic dysfunction. Here, we review available evidence regarding the current understanding of cellular mechanisms for, and the involvement of, cardiac non-myocytes in the pathogenesis of FRDA cardiomyopathy., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Friedreich ataxia (FRDA) is an autosomal recessive disease characterized by degeneration of dorsal root ganglia (DRG) sensory neurons, which is due to low levels of the mitochondrial protein Frataxin. To explore cell replacement therapies as a possible approach to treat FRDA, we examined transplantation of sensory neural progenitors derived from human embryonic stem cells (hESC) and FRDA induced pluripotent stem cells (iPSC) into adult rodent DRG regions. Our data showed survival and differentiation of hESC and FRDA iPSC-derived progenitors in the DRG 2 and 8 weeks post-transplantation, respectively. Donor cells expressed neuronal markers, including sensory and glial markers, demonstrating differentiation to these lineages. These results are novel and a highly significant first step in showing the possibility of using stem cells as a cell replacement therapy to treat DRG neurodegeneration in FRDA as well as other peripheral neuropathies., (© 2021 The Authors. STEM CELLS TRANSLATIONAL MEDICINE published by Wiley Periodicals LLC on behalf of AlphaMed Press.)

Cortical neurospheres (NSPs) derived from human pluripotent stem cells (hPSC), have proven to be a successful platform to investigate human brain development and neuro-related diseases. Currently, many of the standard hPSC neural differentiation media, use concentrations of glucose (approximately 17.5-25 mM) and insulin (approximately 3.2 μM) that are much greater than the physiological concentrations found in the human brain. These culture conditions make it difficult to analyse perturbations of glucose or insulin on neuronal development and differentiation. We established a new hPSC neural differentiation medium that incorporated physiological brain concentrations of glucose (2.5 mM) and significantly reduced insulin levels (0.86 μM). This medium supported hPSC neural induction and formation of cortical NSPs. The revised hPSC neural differentiation medium, may provide an improved platform to model brain development and to investigate neural differentiation signalling pathways impacted by abnormal glucose and insulin levels., (Copyright © 2021. Published by Elsevier Inc.)

Because our beliefs regarding our individuality, autonomy, and personhood are intimately bound up with our brains, there is a public fascination with cerebral organoids, the "mini-brain," the "brain in a dish". At the same time, the ethical issues around organoids are only now being explored. What are the prospects of using human cerebral organoids to better understand, treat, or prevent dementia? Will human organoids represent an improvement on the current, less-than-satisfactory, animal models? When considering these questions, two major issues arise. One is the general challenge associated with using any stem cell-generated preparation for in vitro modelling (challenges amplified when using organoids compared with simpler cell culture systems). The other relates to complexities associated with defining and understanding what we mean by the term "dementia." We discuss 10 puzzles, issues, and stumbling blocks to watch for in the quest to model "dementia in a dish."

Adrenomedullary chromaffin cells are catecholamine (CA)-producing cells originating from trunk neural crest (NC) via sympathoadrenal progenitors (SAPs). We generated NC and SAPs from human embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) in vitro via BMP2/FGF2 exposure, ascertained by qPCR and immunoexpression of SOX10, ASCL1, TFAP2α, and PHOX2B, and by fluorescence-activated cell sorting selection for p75NTR and GD2, and confirmed their trunk-like HOX gene expression. We showed that continuing BMP4 and curtailing FGF2 in vitro, augmented with corticosteroid mimetic, induced these cells to upregulate the chromaffin cell-specific marker PNMT and other CA synthesis and storage markers, and we demonstrated noradrenaline and adrenaline by Faglu and high-performance liquid chromatography. We showed these human cells' SAP-like property of migration and differentiation into cells expressing chromaffin cell markers by implanting them into avian embryos in vivo and in chorio-allantoic membrane grafts. These cells have the potential for investigating differentiation of human chromaffin cells and for modeling diseases involving this cell type., (Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.)

The capacity for induced pluripotent stem (iPS) cells to be differentiated into a wide range of neural cell types makes them an attractive donor source for autologous neural transplantation therapies aimed at brain repair. Translation to the in vivo setting has been difficult, however, with mixed results in a wide variety of preclinical models of brain injury and limited information on the basic in vivo properties of neural grafts generated from human iPS cells. Here we have generated a human iPS cell line constitutively expressing green fluorescent protein as a basis to identify and characterize grafts resulting from transplantation of neural progenitors into the adult rat brain. The results show that the grafts contain a mix of neural cell types, at various stages of differentiation, including neurons that establish extensive patterns of axonal growth and progressively develop functional properties over the course of 1 year after implantation. These findings form an important basis for the design and interpretation of preclinical studies using human stem cells for functional circuit re-construction in animal models of brain injury. Stem Cells Translational Medicine 2017;6:1547-1556., (© 2017 The Authors Stem Cells Translational Medicine published by Wiley Periodicals, Inc. on behalf of AlphaMed Press.)

We sought to identify the impacts of Friedreich's ataxia (FRDA) on cardiomyocytes. FRDA is an autosomal recessive degenerative condition with neuronal and non-neuronal manifestations, the latter including progressive cardiomyopathy of the left ventricle, the leading cause of death in FRDA. Little is known about the cellular pathogenesis of FRDA in cardiomyocytes. Induced pluripotent stem cells (iPSCs) were derived from three FRDA individuals with characterized GAA repeats. The cells were differentiated into cardiomyocytes to assess phenotypes. FRDA iPSC- cardiomyocytes retained low levels of FRATAXIN (FXN) mRNA and protein. Electrophysiology revealed an increased variation of FRDA- cardiomyocyte beating rates which was prevented by addition of nifedipine, suggestive of a calcium handling deficiency. Finally, calcium imaging was performed and we identified small amplitude, diastolic and systolic calcium transients confirming a deficiency in calcium handling. We defined a robust FRDA cardiac-specific electrophysiological profile in patient-derived iPSCs which could be used for high throughput compound screening. This cell-specific signature will contribute to the identification and screening of novel treatments for this life-threatening disease.

Friedreich ataxia (FRDA) is an autosomal recessive disease characterised by neurodegeneration and cardiomyopathy that is caused by an insufficiency of the mitochondrial protein, frataxin. Our previous studies described the generation of FRDA induced pluripotent stem cell lines (FA3 and FA4 iPS) that retained genetic characteristics of this disease. Here we extend these studies, showing that neural derivatives of FA iPS cells are able to differentiate into functional neurons, which don't show altered susceptibility to cell death, and have normal mitochondrial function. Furthermore, FA iPS-derived neural progenitors are able to differentiate into functional neurons and integrate in the nervous system when transplanted into the cerebellar regions of host adult rodent brain. These are the first studies to describe both in vitro and in vivo characterization of FA iPS-derived neurons and demonstrate their capacity to survive long term. These findings are highly significant for developing FRDA therapies using patient-derived stem cells.

According to 2010 estimates from The National Institute on Deafness and other Communication Disorders, approximately 17% (36 million) American adults have reported some degree of hearing loss. Currently, the only clinical treatment available for those with severe-to-profound hearing loss is a cochlear implant, which is designed to electrically stimulate the auditory nerve in the absence of hair cells. Whilst the cochlear implant has been revolutionary in terms of providing hearing to the severe-to-profoundly deaf, there are variations in cochlear implant performance which may be related to the degree of degeneration of auditory neurons following hearing loss. Hence, numerous experimental studies have focused on enhancing the efficacy of cochlear implants by using neurotrophins to preserve the auditory neurons, and more recently, attempting to replace these dying cells with new neurons derived from stem cells. As a result, several groups are now investigating the potential for both embryonic and adult stem cells to replace the degenerating sensory elements in the deaf cochlea. Recent advances in our knowledge of stem cells and the development of induced pluripotency by Takahashi and Yamanaka in 2006, have opened a new realm of science focused on the use of induced pluripotent stem (iPS) cells for therapeutic purposes. This review will provide a broad overview of the potential benefits and challenges of using iPS cells in combination with a cochlear implant for the treatment of hearing loss, including differentiation of iPS cells into an auditory neural lineage and clinically relevant transplantation approaches.

Pluripotent stem cells are a potential source of autologous cells for cell and tissue regenerative therapies. They have the ability to renew indefinitely while retaining the capacity to differentiate into all cell types in the body. With developments in cell therapy and tissue engineering these cells may provide an option for treating tissue loss in organs which do not repair themselves. Limitations to clinical translation of pluripotent stem cells include poor cell survival and low cell engraftment in vivo and the risk of teratoma formation when the cells do survive through implantation. In this study, implantation of human induced-pluripotent stem (hiPS) cells, suspended in Matrigel, into an in vivo vascularized tissue engineering chamber in nude rats resulted in substantial engraftment of the cells into the highly vascularized rat tissues formed within the chamber. Differentiation of cells in the chamber environment was shown by teratoma formation, with all three germ lineages evident within 4 weeks. The rate of teratoma formation was higher with partially differentiated hiPS cells (as embryoid bodies) compared to undifferentiated hiPS cells (100% versus 60%). In conclusion, the in vivo vascularized tissue engineering chamber supports the survival through implantation of human iPS cells and their differentiated progeny, as well as a novel platform for rapid teratoma assay screening for pluripotency., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Friedreich ataxia (FRDA) is an autosomal recessive disorder characterised by neurodegeneration and cardiomyopathy. It is caused by a trinucleotide (GAA) repeat expansion in the first intron of the FXN gene that results in reduced synthesis of FXN mRNA and its protein product, frataxin. We report the generation of induced pluripotent stem (iPS) cell lines derived from skin fibroblasts from two FRDA patients. Each of the patient-derived iPS (FA-iPS) cell lines maintain the GAA repeat expansion and the reduced FXN mRNA expression that are characteristic of the patient. The FA-iPS cells are pluripotent and form teratomas when injected into nude mice. We demonstrate that following in vitro differentiation the FA-iPS cells give rise to the two cell types primarily affected in FRDA, peripheral neurons and cardiomyocytes. The FA-iPS cell lines have the potential to provide valuable models to study the cellular pathology of FRDA and to develop high-throughput drug screening assays. We have previously demonstrated that stable insertion of a functional human BAC containing the intact FXN gene into stem cells results in the expression of frataxin protein in differentiated neurons. As such, iPS cell lines derived from FRDA patients, following correction of the mutated gene, could provide a useful source of immunocompatible cells for transplantation therapy.

It is possible to generate induced pluripotent stem (iPS) cells from mouse and human somatic cells by ectopic expression of defined sets of transcription factors. However, the recommendation that somatic cells should be utilized at early passages for induced reprogramming limits their therapeutic application. Here we report successful reprogramming of human fibroblasts after more than 20 passages in vitro, to a pluripotent state with four transcription factors: Oct4, Sox2, Klf4, and c-Myc. The late passage-derived human iPS cells resemble human embryonic stem cells in morphology, cell surface antigens, pluripotent gene expression profiles, and epigenetic states. Moreover, these iPS cells differentiate into cell types representative of the three germ layers in teratomas in vivo, and directed neuronal differentiation in vitro., (© 2011 Cognizant Comm. Corp.)

The great potential of induced pluripotent cells (iPS) cells is that it allows the possibility of deriving pluripotent stem cells from any human patient. Generation of patient-derived stem cells serves as a great source for developing cell replacement therapies and also for creating human cellular model systems of specific diseases or disorders. This is only of benefit if there are well-established differentiation assay systems to generate the cell types of interest. This chapter describes robust and well-characterized protocols for differentiating iPS cells to neural progenitors, neurons, glia and neural crest cells. These established assays can be applied to iPS cell lines derived from patients with neurodegenerative disorders to study cellular mechanisms associated with neurodegeneration as well as investigating the regenerative potential of patient derived stem cells.