Generation of Naivetropic Induced Pluripotent Stem Cells from Parkinson's Disease Patients for High-Efficiency Genetic Manipulation and Disease Modeling

Suspension culture improves iPSC expansion and pluripotency phenotype

BACKGROUND

Induced pluripotent stem cells (iPSCs) offer potential to revolutionize regenerative medicine as a renewable source for islets, dopaminergic neurons, retinal cells, and cardiomyocytes. However, translation of these regenerative cell therapies requires cost-efficient mass manufacturing of high-quality human iPSCs. This study presents an improved three-dimensional Vertical-Wheel® bioreactor (3D suspension) cell expansion protocol with comparison to a two-dimensional (2D planar) protocol.

METHODS

Sendai virus transfection of human peripheral blood mononuclear cells was used to establish mycoplasma and virus free iPSC lines without common genetic duplications or deletions. iPSCs were then expanded under 2D planar and 3D suspension culture conditions. We comparatively evaluated cell expansion capacity, genetic integrity, pluripotency phenotype, and in vitro and in vivo pluripotency potential of iPSCs.

RESULTS

Expansion of iPSCs using Vertical-Wheel® bioreactors achieved 93.8-fold (IQR 30.2) growth compared to 19.1 (IQR 4.0) in 2D (p < 0.0022), the largest expansion potential reported to date over 5 days. 0.5 L Vertical-Wheel® bioreactors achieved similar expansion and further reduced iPSC production cost. 3D suspension expanded cells had increased proliferation, measured as Ki67⁺ expression using flow cytometry (3D: 69.4% [IQR 5.5%] vs. 2D: 57.4% [IQR 10.9%], p = 0.0022), and had a higher frequency of pluripotency marker (Oct4⁺Nanog⁺Sox2⁺) expression (3D: 94.3 [IQR 1.4] vs. 2D: 52.5% [IQR 5.6], p = 0.0079). q-PCR genetic analysis demonstrated a lack of duplications or deletions at the 8 most commonly mutated regions within iPSC lines after long-term passaging (> 25). 2D-cultured cells displayed a primed pluripotency phenotype, which transitioned to naïve after 3D-culture. Both 2D and 3D cells were capable of trilineage differentiation and following teratoma, 2D-expanded cells generated predominantly solid teratomas, while 3D-expanded cells produced more mature and predominantly cystic teratomas with lower Ki67⁺ expression within teratomas (3D: 16.7% [IQR 3.2%] vs.. 2D: 45.3% [IQR 3.0%], p = 0.002) in keeping with a naïve phenotype.

CONCLUSION

This study demonstrates nearly 100-fold iPSC expansion over 5-days using our 3D suspension culture protocol in Vertical-Wheel® bioreactors, the largest cell growth reported to date. 3D expanded cells showed enhanced in vitro and in vivo pluripotency phenotype that may support more efficient scale-up strategies and safer clinical implementation.

Molecular Features of Parkinson's Disease in Patient-Derived Midbrain Dopaminergic Neurons

BACKGROUND

Despite intense efforts to develop an objective diagnostic test for Parkinson's disease, there is still no consensus on biomarkers that can accurately diagnose the disease.

OBJECTIVE

Identification of biomarkers for idiopathic Parkinson's disease (PD) may enable accurate diagnosis of the disease. We tried to find molecular and cellular differences in dopaminergic (DA) neurons derived from healthy subjects and idiopathic PD patients with or without rest tremor at onset.

METHODS

We measured the expression of genes controlling dopamine synthesis, sequestration, and catabolism as well as the levels of corresponding metabolites and reactive oxygen species in midbrain DA neurons differentiated from induced pluripotent stem cells (iPSCs) of healthy subjects and PD patients with or without rest tremor.

RESULTS

Significant differences in DA-related gene expression, metabolites, and oxidative stress were found between midbrain DA neurons derived from healthy subjects and patients with PD. DA neurons derived from PD patients with or without rest tremor at onset exhibited significant differences in the levels of some of these transcripts, metabolites, and oxidative stress.

CONCLUSION

The unique combination of these quantifiable molecular and cellular traits in iPSC-derived midbrain DA neurons can distinguish healthy subjects from idiopathic PD patients and segregate PD patients with or without rest tremor at onset. The strategy may be used to develop an objective diagnostic test for PD.

Generation of mouse-human chimeric embryos

Naive human pluripotent stem cells (hPSCs) can be used to generate mature human cells of all three germ layers in mouse-human chimeric embryos. Here, we describe a protocol for generating mouse-human chimeric embryos by injecting naive hPSCs converted from the primed state. Primed hPSCs are treated with a mammalian target of rapamycin inhibitor (Torin1) for 3 h and dissociated to single cells, which are plated on mouse embryonic fibroblasts in 2iLI medium, a condition essentially the same for culturing mouse embryonic stem cells. After 3-4 d, bright, dome-shaped colonies with mouse embryonic stem cell morphology are passaged in 2iLI medium. Established naive hPSCs are injected into mouse blastocysts, which produce E17.5 mouse embryos containing 0.1-4.0% human cells as quantified by next-generation sequencing of 18S ribosomal DNA amplicons. The protocol is suitable for studying the development of hPSCs in mouse embryos and may facilitate the generation of human cells, tissues and organs in animals.

High density bioprocessing of human pluripotent stem cells by metabolic control and in silico modeling

To harness the full potential of human pluripotent stem cells (hPSCs) we combined instrumented stirred tank bioreactor (STBR) technology with the power of in silico process modeling to overcome substantial, hPSC‐specific hurdles toward their mass production. Perfused suspension culture (3D) of matrix‐free hPSC aggregates in STBRs was applied to identify and control process‐limiting parameters including pH, dissolved oxygen, glucose and lactate levels, and the obviation of osmolality peaks provoked by high density culture. Media supplements promoted single cell‐based process inoculation and hydrodynamic aggregate size control. Wet lab‐derived process characteristics enabled predictive in silico modeling as a new rational for hPSC cultivation. Consequently, hPSC line‐independent maintenance of exponential cell proliferation was achieved. The strategy yielded 70‐fold cell expansion in 7 days achieving an unmatched density of 35 × 10⁶ cells/mL equivalent to 5.25 billion hPSC in 150 mL scale while pluripotency, differentiation potential, and karyotype stability was maintained. In parallel, media requirements were reduced by 75% demonstrating the outstanding increase in efficiency. Minimal input to our in silico model accurately predicts all main process parameters; combined with calculation‐controlled hPSC aggregation kinetics, linear process upscaling is also enabled and demonstrated for up to 500 mL scale in an independent bioreactor system. Thus, by merging applied stem cell research with recent knowhow from industrial cell fermentation, a new level of hPSC bioprocessing is revealed fueling their automated production for industrial and therapeutic applications.

Modeling the pathophysiology of Parkinson's disease in patient-specific neurons

The 30 trillion cells that self-assemble into a human being originate from the pluripotent stem cells in the inner cell mass of a human blastocyst. The discovery of induced pluripotent stem cells (iPSCs) makes it possible to approximate various aspects of this natural developmental process artificially by generating materials that can be used in invasive mechanistic studies of virtually all human conditions. In Parkinson's disease, instructions computed by the basal ganglia to control voluntary motor functions break down, leading to widespread rhythmic bursting activities in the basal ganglia and beyond. It is thought that these oscillatory neuronal activities, which disrupt aperiodic neurotransmission in a normal brain, may reduce information content in the instructions for motor control. Using midbrain neuronal cultures differentiated from iPSCs of Parkinson's disease patients with parkin mutations, we find that parkin mutations cause oscillatory neuronal activities when dopamine D1-class receptors are activated. This system makes it possible to study the molecular basis of rhythmic bursting activities in Parkinson's disease. Further development of stem cell models of Parkinson's disease will enable better approximation of the situation in the brain of Parkinson's disease patients. In this review, I will discuss what has been found in the past about the pathophysiology of motor dysfunction in Parkinson's disease, especially oscillatory neuronal activities and how stem cell technologies may transform our abilities to understand the pathophysiology of Parkinson's disease.

Transient inhibition of mTOR in human pluripotent stem cells enables robust formation of mouse-human chimeric embryos

It has not been possible to generate naïve human pluripotent stem cells (hPSCs) that substantially contribute to mouse embryos. We found that a brief inhibition of mTOR with Torin1 converted hPSCs from primed to naïve pluripotency. The naïve hPSCs were maintained in the same condition as mouse embryonic stem cells and exhibited high clonogenicity, rapid proliferation, mitochondrial respiration, X chromosome reactivation, DNA hypomethylation, and transcriptomes sharing similarities to those of human blastocysts. When transferred to mouse blastocysts, naïve hPSCs generated 0.1 to 4% human cells, of all three germ layers, including large amounts of enucleated red blood cells, suggesting a marked acceleration of hPSC development in mouse embryos. Torin1 induced nuclear translocation of TFE3; TFE3 with mutated nuclear localization signal blocked the primed-to-naïve conversion. The generation of chimera-competent naïve hPSCs unifies some common features of naïve pluripotency in mammals and may enable applications such as human organ generation in animals.

Unraveling correlative roles of dopamine transporter (DAT) and Parkin in Parkinson's disease (PD) - A road to discovery?

Parkinson's disease (PD) is a neurodegenerative disorder accompanied by depletion of dopamine(DA) and loss of dopaminergic (DAergic) neurons in the brain that is believed to be responsible for the motor and non-motor symptoms of PD. Dopamine Transporter (DAT) is essential for reuptake of DA into the presynaptic terminal, thereby controlling the availability and spatial activity of released DA. Parkin interacts with proteins involved in the endosomal pathway, suggesting that presynaptic Parkin could regulate the expression of DAT in the plasma membrane. Parkin mutations lead to early synaptic damage and it appears as a crucial gene having a vast functioning area. PD-specific induced pluripotent stem cells (iPSCs) derived DA neurons exist as a potential tool for in-vitro modeling of PD, as they can recapitulate the pathological features of PD. The exact mechanism of PARKIN influenced DAT variations and changes in DA reuptake by DAT remain unknown. Hence, DAT and PARKIN mutated PD-specific iPSCs-derived DA neurons could provide important clues for elucidating the pathogenesis and mechanism of PD. This mysterious and hidden connection may prove to be a boon in disguise, hence, here we review the influence of PARKIN and DAT on DA mechanism and will discuss how these findings underpin the concept of how downregulation or upregulation of DAT is influenced by PARKIN. We conclude that the establishment of new model for PD with a combination of DAT and PARKIN would have a high translational potential, which includes the identification of drug targets and testing of known and novel therapeutic agents.

A compendious summary of Parkinson's disease patient-derived iPSCs in the first decade

The number of Parkinson's disease (PD) patients increases with aging, which brings heavy burden to families and society. The emergence of patient-derived induced pluripotent stem cells (iPSCs) has brought hope to the current situation of lacking new breakthroughs in diagnosis and treatment of PD. In this article, we reviewed and analyzed the current researches related to PD patient-derived iPSCs, in order to provide solid theoretical basis for future study of PD. In 2008, successful iPSCs derived from PD patients were reported. The current iPSCs research in PD mostly focused on the establishment of specific iPSCs models of PD patients carrying susceptible genes. The main source of PD patient-derived iPSCs is skin fibroblasts and the mainstream reprogramming methodology is the mature "four-factor" method, which introduces four totipotent correlation factors Oct4, Sox2, Klf4 and c-Myc into somatic cells. The main sources of iPSCs are patients with non-pedigrees and there have been no studies involving both PD patients and unaffected carriers within the same family. Most of the existing studies of PD patient-derived iPSCs started with the induction method for obtaining dopaminergic neurons in the first instance, but therapeutic applications are being increased. Although it is not the ultimate panacea, and there are still some unsolved problems (e.g., whether the mutated genes should be corrected or not), a better understanding of iPSCs may be a good gift for both PD patients and doctors due to their advantages in diagnosis and treatment of PD.

Safranal-promoted differentiation and survival of dopaminergic neurons in an animal model of Parkinson's disease

CONTEXT

Safranal (SAF) is verified to have potential effects in promoting nerve growth.

OBJECTIVES

This study verifies the role of SAF in promoting dopaminergic neurons growth in vitro and in vivo.

MATERIAL AND METHODS

Rat neural stem cells (NSC) were treated with 1, 20, or 100 ng/mL of SAF, and the expression levels of tyrosine hydroxylase (TH) and dopamine transporter (DAT) were assayed by flow cytometry and real-time PCR and the secretion of dopamine (DA) was assayed by ELISA. Then, 2 × 10⁶ cells of SAF-treated NSC was administrated into PD rat models induced by 6-OHDA. The differentiation and survival of dopaminergic neurons was identified by fluorescence microscope and TH⁺ cells by immunostaining and DA secretion by ELISA at week 2 and week 4, respectively.

RESULTS

After being treated with SAF at 20 and 100 ng/mL for 1 week, TH and DAT positive rates increased 1.4- and 1.7-fold (p < 0.01, respectively). TH and DAT mRNA also increased 8.05- and 4.41-fold, respectively. And the release of DA statistically increased 1.5-fold (p < 0.01). In vivo, the number of rotations decreased to 4.33 ± 0.97 rpm (p < 0.01) and the survival rates increased to 77.66 ± 7.87% (p < 0.05) at week 4 after transplantation of SAF-treated NSC. Moreover, the transplanted cells increased three-fold, TH fluorescence density increased four-fold and DA releases increased 1.4-fold (p < 0.01) at week 4 after transplantation.

CONCLUSIONS

SAF promoted the production of functional DA cells and alleviated PD, which may contribute to a new therapy for PD patients.

Using Patient-Derived Induced Pluripotent Stem Cells to Identify Parkinson's Disease-Relevant Phenotypes

PURPOSE OF REVIEW

Parkinson's disease (PD) is the second most common neurodegenerative disorder affecting older individuals. The specific cause underlying dopaminergic (DA) neuron loss in the substantia nigra, a pathological hallmark of PD, remains elusive. Here, we highlight peer-reviewed reports using induced pluripotent stem cells (iPSCs) to model PD in vitro and discuss the potential disease-relevant phenotypes that may lead to a better understanding of PD etiology. Benefits of iPSCs are that they retain the genetic background of the donor individual and can be differentiated into specialized neurons to facilitate disease modeling.

RECENT FINDINGS

Mitochondrial dysfunction, oxidative stress, ER stress, and alpha-synuclein accumulation are common phenotypes observed in PD iPSC-derived neurons. New culturing technologies, such as directed reprogramming and midbrain organoids, offer innovative ways of investigating intraneuronal mechanisms of PD pathology. PD patient-derived iPSCs are an evolving resource to understand PD pathology and identify therapeutic targets.

Combining NT3-overexpressing MSCs and PLGA microcarriers for brain tissue engineering: A potential tool for treatment of Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder that characterized by destruction of substantia nigrostriatal pathway due to the loss of dopaminergic (DA) neurons. Regardless of substantial efforts for treatment of PD in recent years, an effective therapeutic strategy is still missing. In a multidisciplinary approach, bone marrow derived mesenchymal stem cells (BMSCs) are genetically engineered to overexpress neurotrophin-3 (nt-3 gene) that protect central nervous system tissues and stimulates neuronal-like differentiation of BMSCs. Poly(lactic-co-glycolic acid) (PLGA) microcarriers are designed as an injectable scaffold and synthesized via double emulsion method. The surface of PLGA microcarriers are functionalized by collagen as a bioadhesive agent for improved cell attachment. The results demonstrate effective overexpression of NT-3. The expression of tyrosine hydroxylase (TH) in transfected BMSCs reveal that NT-3 promotes the intracellular signaling pathway of DA neuron differentiation. It is also shown that transfected BMSCs are successfully attached to the surface of microcarriers. The presence of dopamine in peripheral media of cell/microcarrier complex reveals that BMSCs are successfully differentiated into dopaminergic neuron. Our approach that sustains presence of growth factor can be suggested as a novel complementary therapeutic strategy for treatment of Parkinson disease.

Modeling Human Neurological and Neurodegenerative Diseases: From Induced Pluripotent Stem Cells to Neuronal Differentiation and Its Applications in Neurotrauma

With the help of several inducing factors, somatic cells can be reprogrammed to become induced pluripotent stem cell (iPSCs) lines. The success is in obtaining iPSCs almost identical to embryonic stem cells (ESCs), therefore various approaches have been tested and ultimately several ones have succeeded. The importance of these cells is in how they serve as models to unveil the molecular pathways and mechanisms underlying several human diseases, and also in its potential roles in the development of regenerative medicine. They further aid in the development of regenerative medicine, autologous cell therapy and drug or toxicity screening. Here, we provide a comprehensive overview of the recent development in the field of iPSCs research, specifically for modeling human neurological and neurodegenerative diseases, and its applications in neurotrauma. These are mainly characterized by progressive functional or structural neuronal loss rendering them extremely challenging to manage. Many of these diseases, including Parkinson's disease (PD), Huntington's disease (HD), Amyotrophic lateral sclerosis (ALS) and Alzheimer's disease (AD) have been explored in vitro. The main purpose is to generate patient-specific iPS cell lines from the somatic cells that carry mutations or genetic instabilities for the aim of studying their differentiation potential and behavior. This new technology will pave the way for future development in the field of stem cell research anticipating its use in clinical settings and in regenerative medicine in order to treat various human diseases, including neurological and neurodegenerative diseases.

Generation of disease-specific autopsy-confirmed iPSCs lines from postmortem isolated Peripheral Blood Mononuclear Cells

Understanding the molecular mechanisms that underlie neurodegenerative disorders has been hampered by a lack of readily available model systems that replicate the complexity of the human disease. Recent advances in stem cell technology have facilitated the derivation of patient-specific stem cells from a variety of differentiated cell types. These induced pluripotent stem cells (iPSCs) are attractive disease models since they can be grown and differentiated to produce large numbers of disease-relevant cell types. However, most iPSC lines are derived in advance of, and without the benefit of, neuropathological confirmation of the donor - the gold standard for many disease classifications and measurement of disease severity. While others have reported the generation of autopsy-confirmed iPSC lines from patient explants, these methods require outgrowth of cadaver tissue, which require additional time and is often only successful ∼50% of the time. Here we report the rapid generation of autopsy-confirmed iPSC lines from peripheral blood mononuclear cells (PBMCs) drawn postmortem. Since this approach doesn't require the propagation of previously frozen cadaver tissue, iPSC can be rapidly and efficiently produced from patients with autopsy-confirmed pathology. These matched iPSC-derived patient-specific neurons and postmortem brain tissue will support studies of specific mechanisms that drive the pathogenesis of neurodegenerative diseases.

Biological Effects of Culture Substrates on Human Pluripotent Stem Cells

In recent years, as human pluripotent stem cells (hPSCs) have been commonly cultured in feeder-free conditions, a number of cell culture substrates have been applied or developed. However, the functional roles of these substrates in maintaining hPSC self-renewal remain unclear. Here in this review, we summarize the types of these substrates and their effect on maintaining hPSC self-renewal. Endogenous extracellular matrix (ECM) protein expression has been shown to be crucial in maintaining hPSC self-renewal. These ECM molecules interact with integrin cell-surface receptors and transmit their cellular signaling. We discuss the possible effect of integrin-mediated signaling pathways on maintaining hPSC self-renewal. Activation of integrin-linked kinase (ILK), which transmits ECM-integrin signaling to AKT (also known as protein kinase B), has been shown to be critical in maintaining hPSC self-renewal. Also, since naïve pluripotency has been widely recognized as an alternative pluripotent state of hPSCs, we discuss the possible effects of culture substrates and integrin signaling on naïve hPSCs based on the studies of mouse embryonic stem cells. Understanding the role of culture substrates in hPSC self-renewal and differentiation enables us to control hPSC behavior precisely and to establish scalable or microfabricated culture technologies for regenerative medicine and drug development.