Preclinical Efficacy and Safety of a Human Embryonic Stem Cell-Derived Midbrain Dopamine Progenitor Product, MSK-DA01

Recent advances and applications of human brain models

Recent advances in human pluripotent stem cell (hPSC) technologies have prompted the emergence of new research fields and applications for human neurons and brain organoids. Brain organoids have gained attention as an in vitro model system that recapitulates the higher structure, cellular diversity and function of the brain to explore brain development, disease modeling, drug screening, and regenerative medicine. This progress has been accelerated by abundant interactions of brain organoid technology with various research fields. A cross-disciplinary approach with human brain organoid technology offers a higher-ordered advance for more accurately understanding the human brain. In this review, we summarize the status of neural induction in two- and three-dimensional culture systems from hPSCs and the modeling of neurodegenerative diseases using brain organoids. We also highlight the latest bioengineered technologies for the assembly of spatially higher-ordered neural tissues and prospects of brain organoid technology toward the understanding of the potential and abilities of the human brain.

Stem cell therapeutics and gene therapy for neurologic disorders

Rapid advances in biological knowledge and technological innovation have greatly advanced the fields of stem cell and gene therapies to combat a broad spectrum of neurologic disorders. Researchers are currently exploring a variety of stem cell types (e.g., embryonic, progenitor, induced pluripotent) and various transplantation strategies, each with its own advantages and drawbacks. Similarly, various gene modification techniques (zinc finger, TALENs, CRISPR-Cas9) are employed with various delivery vectors to modify underlying genetic contributors to neurologic disorders. While these two individual fields continue to blaze new trails, it is the combination of these technologies which enables genetically engineered stem cells and vastly increases investigational and therapeutic opportunities. The capability to culture and expand stem cells outside the body, along with their potential to correct genetic abnormalities in patient-derived cells or enhance cells with extra gene products, unleashes the full biological potential for innovative, multifaceted approaches to treat complex neurological disorders. In this review, we provide an overview of stem cell and gene therapies in the context of neurologic disorders, highlighting recent advances and current shortcomings, and discuss prospects for future therapies in clinical settings.

Precision Medicine in Parkinson's Disease Using Induced Pluripotent Stem Cells

Parkinson's disease (PD) is one of the most devastating neurological diseases; however, there is no effective cure yet. The availability of human induced pluripotent stem cells (iPSCs) provides unprecedented opportunities to understand the pathogenic mechanism and identification of new therapy for PD. Here a new model system of PD, including 2D human iPSC-derived midbrain dopaminergic (mDA) neurons, 3D iPSC-derived midbrain organoids (MOs) with cellular complexity, and more advanced microphysiological systems (MPS) with 3D organoids, is introduced. It is believed that successful integrations and applications of iPSC, organoid, and MPS technologies can bring new insight on PD's pathogenesis that will lead to more effective treatments for this debilitating disease.

TNF-NF-κB-p53 axis restricts in vivo survival of hPSC-derived dopamine neurons

Ongoing, early-stage clinical trials illustrate the translational potential of human pluripotent stem cell (hPSC)-based cell therapies in Parkinson's disease (PD). However, an unresolved challenge is the extensive cell death following transplantation. Here, we performed a pooled CRISPR-Cas9 screen to enhance postmitotic dopamine neuron survival in vivo. We identified p53-mediated apoptotic cell death as a major contributor to dopamine neuron loss and uncovered a causal link of tumor necrosis factor alpha (TNF-α)-nuclear factor κB (NF-κB) signaling in limiting cell survival. As a translationally relevant strategy to purify postmitotic dopamine neurons, we identified cell surface markers that enable purification without the need for genetic reporters. Combining cell sorting and treatment with adalimumab, a clinically approved TNF-α inhibitor, enabled efficient engraftment of postmitotic dopamine neurons with extensive reinnervation and functional recovery in a preclinical PD mouse model. Thus, transient TNF-α inhibition presents a clinically relevant strategy to enhance survival and enable engraftment of postmitotic hPSC-derived dopamine neurons in PD.

Accelerating Diverse Cell-Based Therapies Through Scalable Design

Augmenting cells with novel, genetically encoded functions will support therapies that expand beyond natural capacity for immune surveillance and tissue regeneration. However, engineering cells at scale with transgenic cargoes remains a challenge in realizing the potential of cell-based therapies. In this review, we introduce a range of applications for engineering primary cells and stem cells for cell-based therapies. We highlight tools and advances that have launched mammalian cell engineering from bioproduction to precision editing of therapeutically relevant cells. Additionally, we examine how transgenesis methods and genetic cargo designs can be tailored for performance. Altogether, we offer a vision for accelerating the translation of innovative cell-based therapies by harnessing diverse cell types, integrating the expanding array of synthetic biology tools, and building cellular tools through advanced genome writing techniques.

Biocompatible hydroxyapatite-based nano vehicle bypasses viral transduction and enables sustained silencing of a pluripotency marker gene, demonstrating desired differentiation in mouse embryonic stem cells

BACKGROUND

Differentiation of pluripotent stem cells into desired lineages is the key aspect of regenerative medicine and cell-based therapy. Although RNA interference (RNAi) technology is exploited extensively for this, methods for long term silencing of the target genes leading to differentiation remain a challenge. Sustained knockdown of the target gene by RNAi is often inefficient as a result of low delivery efficiencies, protocol induced toxicity and safety concerns related to viral vectors. Earlier, we established octa-arginine functionalized hydroxyapatite nano vehicles (R8HNPs) for delivery of small interfering RNA (siRNA) against a pluripotency marker gene in mouse embryonic stem cells. Although we demonstrated excellent knockdown efficiency of the target gene, sustained gene silencing leading to differentiation was yet to be achieved.

METHODS

To establish a sustained non-viral gene silencing protocol using R8HNP, we investigated various methods of siRNA delivery: double delivery of adherent cells (Adh-D), suspension delivery followed by adherent delivery (Susp + Adh), single delivery in suspension (Susp-S) and multiple deliveries in suspension (Susp-R). Sustained knockdown of a pluripotent marker gene followed by differentiation was analysed by reverse transcriptase-PCR, fluoresence-activated cell sorting and immunofluorescence techniques. Impact on cell viability as a result of repeated exposure of the R8HNP was also tested.

RESULTS

Amongst the protocols tested, the most efficient knockdown of the target gene for a prolonged period of time was obtained by repeated suspension delivery of the R8HNP-siRNA conjugate. The long-term silencing of a pluripotency marker gene resulted in differentiation of R1 ESCs predominantly towards the extra embryonic and ectodermal lineages. Cells displayed excellent tolerance to repeated exposures of R8HNPs.

CONCLUSIONS

The results demonstrate that R8HNPs are promising, biocompatible, non-viral alternatives for prolonged gene silencing and obtaining differentiated cells for therapeutics.

Past, present, and future of cell replacement therapy for parkinson's disease: a novel emphasis on host immune responses

Parkinson's disease (PD) stands as the second most common neurodegenerative disorder after Alzheimer's disease, and its prevalence continues to rise with the aging global population. Central to the pathophysiology of PD is the specific degeneration of midbrain dopamine neurons (mDANs) in the substantia nigra. Consequently, cell replacement therapy (CRT) has emerged as a promising treatment approach, initially supported by various open-label clinical studies employing fetal ventral mesencephalic (fVM) cells. Despite the initial favorable results, fVM cell therapy has intrinsic and logistical limitations that hinder its transition to a standard treatment for PD. Recent efforts in the field of cell therapy have shifted its focus towards the utilization of human pluripotent stem cells, including human embryonic stem cells and induced pluripotent stem cells, to surmount existing challenges. However, regardless of the transplantable cell sources (e.g., xenogeneic, allogeneic, or autologous), the poor and variable survival of implanted dopamine cells remains a major obstacle. Emerging evidence highlights the pivotal role of host immune responses following transplantation in influencing the survival of implanted mDANs, underscoring an important area for further research. In this comprehensive review, building upon insights derived from previous fVM transplantation studies, we delve into the functional ramifications of host immune responses on the survival and efficacy of grafted dopamine cells. Furthermore, we explore potential strategic approaches to modulate the host immune response, ultimately aiming for optimal outcomes in future clinical applications of CRT for PD.

Dopamine synthesis and transport: current and novel therapeutics for parkinsonisms

Parkinsonism is the primary type of movement disorder in adults, encompassing a set of clinical symptoms, including rigidity, tremors, dystonia, bradykinesia, and postural instability. These symptoms are primarily caused by a deficiency in dopamine (DA), an essential neurotransmitter in the brain. Currently, the DA precursor levodopa (synthetic L-DOPA) is the standard medication to treat DA deficiency, but it only addresses symptoms rather than provides a cure. In this review, we provide an overview of disorders associated with DA dysregulation and deficiency, particularly Parkinson's disease and rare inherited disorders leading predominantly to dystonia and/or parkinsonism, even in childhood. Although levodopa is relatively effective for the management of motor dysfunctions, it is less effective for severe forms of parkinsonism and is also associated with side effects and a loss of efficacy over time. We present ongoing efforts to reinforce the effect of levodopa and to develop innovative therapies that target the underlying pathogenic mechanisms affecting DA synthesis and transport, increasing neurotransmission through disease-modifying approaches, such as cell-based therapies, nucleic acid- and protein-based biologics, and small molecules.

In and out: Benchmarking in vitro, in vivo, ex vivo, and xenografting approaches for an integrative brain disease modeling pipeline

Human cellular models and their neuronal derivatives have afforded unprecedented advances in elucidating pathogenic mechanisms of neuropsychiatric diseases. Notwithstanding their indispensable contribution, animal models remain the benchmark in neurobiological research. In an attempt to harness the best of both worlds, researchers have increasingly relied on human/animal chimeras by xenografting human cells into the animal brain. Despite the unparalleled potential of xenografting approaches in the study of the human brain, literature resources that systematically examine their significance and advantages are surprisingly lacking. We fill this gap by providing a comprehensive account of brain diseases that were thus far subjected to all three modeling approaches (transgenic rodents, in vitro human lineages, human-animal xenografting) and provide a critical appraisal of the impact of xenografting approaches for advancing our understanding of those diseases and brain development. Next, we give our perspective on integrating xenografting modeling pipeline with recent cutting-edge technological advancements.

Diminished Immune Cell Adhesion in Hypoimmune ICAM-1 Knockout Pluripotent Stem Cells

Hypoimmune gene edited human pluripotent stem cells (hPSCs) are a promising platform for developing reparative cellular therapies that evade immune rejection. Existing first-generation hypoimmune strategies have used CRISPR/Cas9 editing to modulate genes associated with adaptive (e.g., T cell) immune responses, but have largely not addressed the innate immune cells (e.g., monocytes, neutrophils) that mediate inflammation and rejection processes occurring early after graft transplantation. We identified the adhesion molecule ICAM-1 as a novel hypoimmune target that plays multiple critical roles in both adaptive and innate immune responses post-transplantation. In a series of studies, we found that ICAM-1 blocking or knock-out (KO) in hPSC-derived cardiovascular therapies imparted significantly diminished binding of multiple immune cell types. ICAM-1 KO resulted in diminished T cell proliferation responses in vitro and in longer in vivo retention/protection of KO grafts following immune cell encounter in NeoThy humanized mice. The ICAM-1 KO edit was also introduced into existing first-generation hypoimmune hPSCs and prevented immune cell binding, thereby enhancing the overall hypoimmune capacity of the cells. This novel hypoimmune editing strategy has the potential to improve the long-term efficacy and safety profiles of regenerative therapies for cardiovascular pathologies and a number of other diseases.

Preclinical efficacy and safety of encapsulated proliferating human hepatocyte organoids in treating liver failure

Alginate-encapsulated hepatocyte transplantation is a promising strategy to treat liver failure. However, its clinical application was impeded by the lack of primary human hepatocytes and difficulty in controlling their quality. We previously reported proliferating human hepatocytes (ProliHHs). Here, quality-controlled ProliHHs were produced in mass and engineered as liver organoids to improve their maturity. Encapsulated ProliHHs liver organoids (eLO) were intraperitoneally transplanted to treat liver failure animals. Notably, eLO treatment increased the survival of mice with post-hepatectomy liver failure (PHLF) and ameliorated hyperammonemia and hypoglycemia by providing liver functions. Additionally, eLO treatment protected the gut from PHLF-augmented permeability and normalized the increased serum endotoxin and inflammatory response, which facilitated liver regeneration. The therapeutic effect of eLO was additionally proved in acetaminophen-induced liver failure. Furthermore, we performed assessments of toxicity and biodistribution, demonstrating that eLO had no adverse effects on animals and remained non-tumorigenic.

Advancements in Human Embryonic Stem Cell Research: Clinical Applications and Ethical Issues

BACKGROUND

The development and use of human embryonic stem cells (hESCs) in regenerative medicine have been revolutionary, offering significant advancements in treating various diseases. These pluripotent cells, derived from early human embryos, are central to modern biomedical research. However, their application is mired in ethical and regulatory complexities related to the use of human embryos.

METHOD

This review utilized key databases such as ClinicalTrials.gov, EU Clinical Trials Register, PubMed, and Google Scholar to gather recent clinical trials and studies involving hESCs. The focus was on their clinical application in regenerative medicine, emphasizing clinical trials and research directly involving hESCs.

RESULTS

Preclinical studies and clinical trials in various areas like ophthalmology, neurology, endocrinology, and reproductive medicine have demonstrated the versatility of hESCs in regenerative medicine. These studies underscore the potential of hESCs in treating a wide array of conditions. However, the field faces ethical and regulatory challenges, with significant variations in policies and perspectives across different countries.

CONCLUSION

The potential of hESCs in regenerative medicine is immense, offering new avenues for treating previously incurable diseases. However, navigating the ethical, legal, and regulatory landscapes is crucial for the continued advancement and responsible application of hESC research in the medical field. Considering both scientific potential and ethical implications, a balanced approach is essential for successfully integrating hESCs into clinical practice.

Clinical translation of pluripotent stem cell-based therapies: successes and challenges

The translational stem cell research field has progressed immensely in the past decade. Development and refinement of differentiation protocols now allows the generation of a range of cell types, such as pancreatic β-cells and dopaminergic neurons, from human pluripotent stem cells (hPSCs) in an efficient and good manufacturing practice-compliant fashion. This has led to the initiation of several clinical trials using hPSC-derived cells to replace lost or dysfunctional cells, demonstrating evidence of both safety and efficacy. Here, we highlight successes from some of the hPSC-based trials reporting early signs of efficacy and discuss common challenges in clinical translation of cell therapies.

Survival and maturation of human induced pluripotent stem cell-derived dopaminergic progenitors in the parkinsonian rat brain is enhanced by transplantation in a neurotrophin-enriched hydrogel

Objective.Although human induced pluripotent stem cell (iPSC)-derived cell replacement for Parkinson's disease has considerable reparative potential, its full therapeutic benefit is limited by poor graft survival and dopaminergic maturation. Injectable biomaterial scaffolds, such as collagen hydrogels, have the potential to address these issues via a plethora of supportive benefits including acting as a structural scaffold for cell adherence, shielding from the host immune response and providing a reservoir of neurotrophic factors to aid survival and differentiation. Thus, the aim of this study was to determine if a neurotrophin-enriched collagen hydrogel could improve the survival and maturation of iPSC-derived dopaminergic progenitors (iPSC-DAPs) after transplantation into the rat parkinsonian brain.Approach.Human iPSC-DAPs were transplanted into the 6-hydroxydopamine-lesioned striatum either alone, with the neurotrophins GDNF and BDNF, in an unloaded collagen hydrogel, or in a neurotrophin-loaded collagen hydrogel.Post-mortem, human nuclear immunostaining was used to identify surviving iPSC-DAPs while tyrosine hydroxylase immunostaining was used to identify iPSC-DAPs that had differentiated into mature dopaminergic neurons.Main results.We found that iPSC-DAPs transplanted in the neurotrophin-enriched collagen hydrogel survived and matured significantly better than cells implanted without the biomaterial (8 fold improvement in survival and 16 fold improvement in dopaminergic differentiation). This study shows that transplantation of human iPSC-DAPs in a neurotrophin-enriched collagen hydrogel improves graft survival and maturation in the parkinsonian rat brain.Significance.The data strongly supports further investigation of supportive hydrogels for improving the outcome of iPSC-derived brain repair in Parkinson's disease.

Host-to-graft propagation of inoculated α-synuclein into transplanted human induced pluripotent stem cell-derived midbrain dopaminergic neurons

Introduction

Cell therapeutic clinical trials using fetal mesencephalic tissue provided a proof-of-concept for regenerative therapy in patients with Parkinson's disease. Postmortem studies of patients with fetal grafts revealed that α-synuclein+ Lewy body (LB)-like inclusions emerged in long-term transplantation and might worsen clinical outcomes even if the grafts survived and innervated in the recipients. Various studies aimed at addressing whether host-derived α-synuclein could be transferred to the grafted neurons to assess α-synuclein+ inclusion appearance in the grafts. However, determining whether α-synuclein in the grafted neurons has been propagated from the host is difficult due to the intrinsic α-synuclein expression.

Methods

We induced midbrain dopaminergic (mDA) neurons from human induced pluripotent stem cells (hiPSCs) and transplanted them into the striatum of immunodeficient rats. The recombinant human α-synuclein preformed fibrils (PFFs) were inoculated into the cerebral cortex after transplantation of SNCA-/- hiPSC-derived mDA neural progenitors into the striatum of immunodeficient rats to evaluate the host-to-graft propagation of human α-synuclein PFFs. Additionally, we examined the incorporation of human α-synuclein PFFs into SNCA-/- hiPSC-derived mDA neurons using in vitro culture system.

Results

We detected human α-synuclein-immunoreactivity in SNCA-/- hiPSC-derived mDA neurons that lacked endogenous α-synuclein expression in vitro. Additionally, we observed host-to-graft α-synuclein propagation into the grafted SNCA-/- hiPSC-derived mDA neurons.

Conclusion

We have successfully proven that intracerebral inoculated α-synuclein PFFs are propagated and incorporated from the host into grafted SNCA-/- hiPSC-derived mDA neurons. Our results contribute toward the basic understanding of the molecular mechanisms related to LB-like α-synuclein deposit formation in grafted mDA neurons.

Exploiting spatiotemporal regulation of FZD5 during neural patterning for efficient ventral midbrain specification

The Wnt/β-catenin signaling governs anterior-posterior neural patterning during development. Current human pluripotent stem cell (hPSC) differentiation protocols use a GSK3 inhibitor to activate Wnt signaling to promote posterior neural fate specification. However, GSK3 is a pleiotropic kinase involved in multiple signaling pathways and, as GSK3 inhibition occurs downstream in the signaling cascade, it bypasses potential opportunities for achieving specificity or regulation at the receptor level. Additionally, the specific roles of individual FZD receptors in anterior-posterior patterning are poorly understood. Here, we have characterized the cell surface expression of FZD receptors in neural progenitor cells with different regional identity. Our data reveal unique upregulation of FZD5 expression in anterior neural progenitors, and this expression is downregulated as cells adopt a posterior fate. This spatial regulation of FZD expression constitutes a previously unreported regulatory mechanism that adjusts the levels of β-catenin signaling along the anterior-posterior axis and possibly contributes to midbrain-hindbrain boundary formation. Stimulation of Wnt/β-catenin signaling in hPSCs, using a tetravalent antibody that selectively triggers FZD5 and LRP6 clustering, leads to midbrain progenitor differentiation and gives rise to functional dopaminergic neurons in vitro and in vivo.

Updates and Challenges in ENS Cell Therapy for the Treatment of Neurointestinal Diseases

Neurointestinal diseases represent a significant challenge in clinical management with current palliative approaches failing to overcome disease and treatment-related morbidity. The recent progress with cell therapy to restore missing or defective components of the gut neuromusculature offers new hope for potential cures. This review discusses the progress that has been made in the sourcing of putative stem cells and the studies into their biology and therapeutic potential. We also explore some of the practical challenges that must be overcome before cell-based therapies can be applied in the clinical setting. Although a number of obstacles remain, the rapid advances made in the enteric neural stem cell field suggest that such therapies are on the near horizon.

Recent approaches in regenerative medicine in the fight against neurodegenerative disease

Neurodegenerative diseases arise due to slow and gradual loss of structure and/or function of neurons and glial cells and cause different degrees of loss of cognition abilities and sensation. The little success in developing effective treatments imposes a high and regressive economic impact on society, patients and their families. In recent years, regenerative medicine has provided a great opportunity to research new innovative strategies with strong potential to treatleva these diseases. These effects are due to the ability of suitable cells and biomaterials to regenerate damaged nerves with differentiated cells, creating an appropriate environment for recovering or preserving existing healthy neurons and glial cells from destruction and damage. Ultimately, a better understanding and thus a further investigation of stem cell technology, tissue engineering, gene therapy, and exosomes allows progress towards practical and effective treatments for neurodegenerative diseases. Therefore, in this review, advances currently being developed in regenerative medicine using animal models and human clinical trials in neurological disorders are summarized.

iSCORE-PD: an isogenic stem cell collection to research Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative disorder caused by complex genetic and environmental factors. Genome-edited human pluripotent stem cells (hPSCs) offer the uniique potential to advance our understanding of PD etiology by providing disease-relevant cell-types carrying patient mutations along with isogenic control cells. To facilitate this experimental approach, we generated a collection of 55 cell lines genetically engineered to harbor mutations in genes associated with monogenic PD (SNCA A53T, SNCA A30P, PRKN Ex3del, PINK1 Q129X, DJ1/PARK7 Ex1-5del, LRRK2 G2019S, ATP13A2 FS, FBXO7 R498X/FS, DNAJC6 c.801 A>G+FS, SYNJ1 R258Q/FS, VPS13C A444P, VPS13C W395C, GBA1 IVS2+1). All mutations were generated in a fully characterized and sequenced female human embryonic stem cell (hESC) line (WIBR3; NIH approval number NIHhESC-10-0079) using CRISPR/Cas9 or prime editing-based approaches. We implemented rigorous quality controls, including high density genotyping to detect structural variants and confirm the genomic integrity of each cell line. This systematic approach ensures the high quality of our stem cell collection, highlights differences between conventional CRISPR/Cas9 and prime editing and provides a roadmap for how to generate gene-edited hPSCs collections at scale in an academic setting. We expect that our isogenic stem cell collection will become an accessible platform for the study of PD, which can be used by investigators to understand the molecular pathophysiology of PD in a human cellular setting.

Sham surgery for the trialing of cell-based therapies to the CNS may not be necessary

Sham surgery is often required for cell therapies adopting a randomized placebo-controlled double-blinded trial design. Using the case of dopamine neuron therapy for Parkinson's disease, we argue that alternative trial designs should be considered instead, for several reasons relating to ethics, patient burden, ease of unblinding, and cost.

A highly sensitive and specific Homo1-based real-time qPCR method for quantification of human umbilical cord mesenchymal stem cells in rats

BACKGROUND

Owing to the characteristics of easier access in vitro, low immunogenicity, and high plasticity, human umbilical cord-derived mesenchymal stem cells (UC-MSCs) are considered as a promising cell-based drugs for clinical application. No internationally recognized technology exists to evaluate the pharmacokinetics and distribution of cell-based drugs in vivo.

METHODS

We determined the human-specific gene sequence, Homo1, from differential fragments Homo sapiens mitochondrion and Rattus norvegicus mitochondrion. The expression of Homo1 was utilized to determine the distribution of UC-MSCs in the normal and diabetic nephropathy (DN) rats.

RESULTS

We observed a significant correlation between the number of UC-MSCs and the expression level of Homo1. Following intravenous transplantation, the blood levels of UC-MSCs peaked at 30 min. A large amount of intravenously injected MSCs were trapped in the lungs, but the number of them decreased rapidly after 24 h. Additionally, the distribution of UC-MSCs in the kidneys of DN rats was significantly higher than that of normal rats.

CONCLUSIONS

In this study, we establish a highly sensitive and specific Homo1-based real-time quantitative PCR method to quantify the distribution of human UC-MSCs in rats. The method provides guidelines for the safety research of cells in preclinical stages.

One-step cell biomanufacturing platform: porous gelatin microcarrier beads promote human embryonic stem cell-derived midbrain dopaminergic progenitor cell differentiation in vitro and survival after transplantation in vivo

Numerous studies have shown that cell replacement therapy can replenish lost cells and rebuild neural circuitry in animal models of Parkinson's disease. Transplantation of midbrain dopaminergic progenitor cells is a promising treatment for Parkinson's disease. However, transplanted cells can be injured by mechanical damage during handling and by changes in the transplantation niche. Here, we developed a one-step biomanufacturing platform that uses small-aperture gelatin microcarriers to produce beads carrying midbrain dopaminergic progenitor cells. These beads allow midbrain dopaminergic progenitor cell differentiation and cryopreservation without digestion, effectively maintaining axonal integrity in vitro. Importantly, midbrain dopaminergic progenitor cell bead grafts showed increased survival and only mild immunoreactivity in vivo compared with suspended midbrain dopaminergic progenitor cell grafts. Overall, our findings show that these midbrain dopaminergic progenitor cell beads enhance the effectiveness of neuronal cell transplantation.

Can pluripotent/multipotent stem cells reverse Parkinson's disease progression?

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by continuous and selective degeneration or death of dopamine neurons in the midbrain, leading to dysfunction of the nigrostriatal neural circuits. Current clinical treatments for PD include drug treatment and surgery, which provide short-term relief of symptoms but are associated with many side effects and cannot reverse the progression of PD. Pluripotent/multipotent stem cells possess a self-renewal capacity and the potential to differentiate into dopaminergic neurons. Transplantation of pluripotent/multipotent stem cells or dopaminergic neurons derived from these cells is a promising strategy for the complete repair of damaged neural circuits in PD. This article reviews and summarizes the current preclinical/clinical treatments for PD, their efficacies, and the advantages/disadvantages of various stem cells, including pluripotent and multipotent stem cells, to provide a detailed overview of how these cells can be applied in the treatment of PD, as well as the challenges and bottlenecks that need to be overcome in future translational studies.

Modeling the neuroimmune system in Alzheimer's and Parkinson's diseases

Parkinson's disease (PD) and Alzheimer's disease (AD) are neurodegenerative disorders caused by the interaction of genetic, environmental, and familial factors. These diseases have distinct pathologies and symptoms that are linked to specific cell populations in the brain. Notably, the immune system has been implicated in both diseases, with a particular focus on the dysfunction of microglia, the brain's resident immune cells, contributing to neuronal loss and exacerbating symptoms. Researchers use models of the neuroimmune system to gain a deeper understanding of the physiological and biological aspects of these neurodegenerative diseases and how they progress. Several in vitro and in vivo models, including 2D cultures and animal models, have been utilized. Recently, advancements have been made in optimizing these existing models and developing 3D models and organ-on-a-chip systems, holding tremendous promise in accurately mimicking the intricate intracellular environment. As a result, these models represent a crucial breakthrough in the transformation of current treatments for PD and AD by offering potential for conducting long-term disease-based modeling for therapeutic testing, reducing reliance on animal models, and significantly improving cell viability compared to conventional 2D models. The application of 3D and organ-on-a-chip models in neurodegenerative disease research marks a prosperous step forward, providing a more realistic representation of the complex interactions within the neuroimmune system. Ultimately, these refined models of the neuroimmune system aim to aid in the quest to combat and mitigate the impact of debilitating neuroimmune diseases on patients and their families.

Gains of 20q11.21 in human pluripotent stem cells: Insights from cancer research

The genetic abnormalities observed in hPSC cultures worldwide have been suggested to pose an important hurdle in their safe use in regenerative medicine due to the possibility of oncogenic transformation by mutant cells in the patient posttransplantation. One of the best-characterized genetic lesions in hPSCs is the gain of 20q11.21, found in 20% of hPSC lines worldwide, and strikingly, also amplified in 20% of human cancers. In this review, we have curated the existing knowledge on the incidence of this mutation in hPSCs and cancer, explored the significance of chromosome 20q11.21 amplification in cancer progression, and reviewed the oncogenic role of the genes in the smallest common region of gain, to shed light on the significance of this mutation in hPSC-based cell therapy. Lastly, we discuss the state-of-the-art strategies devised to detect aneuploidies in hPSC cultures, avoid genetic changes in vitro cultures of hPSCs, and strategies to eliminate genetically abnormal cells from culture.

Scaling up GMP-grade dopaminergic cells for Parkinson's disease

Stem cell therapy for Parkinson's disease requires demonstration of safety and efficacy of dopaminergic cells derived from a cell line, consideration of dose, and whether this is deliverable at scale. Park et al. demonstrate these requirements for a new hESC line and that their manufacturing methods allow for its scalability.

Preclinical and dose-ranging assessment of hESC-derived dopaminergic progenitors for a clinical trial on Parkinson's disease

Human embryonic stem cell (hESC)-derived midbrain dopaminergic (mDA) cell transplantation is a promising therapeutic strategy for Parkinson's disease (PD). Here, we present the derivation of high-purity mDA progenitors from clinical-grade hESCs on a large scale under rigorous good manufacturing practice (GMP) conditions. We also assessed the toxicity, biodistribution, and tumorigenicity of these cells in immunodeficient rats in good laboratory practice (GLP)-compliant facilities. Various doses of mDA progenitors were transplanted into hemi-parkinsonian rats, and a significant dose-dependent behavioral improvement was observed with a minimal effective dose range of 5,000-10,000 mDA progenitor cells. These results provided insights into determining a low cell dosage (3.15 million cells) for human clinical trials. Based on these results, approval for a phase 1/2a clinical trial for PD cell therapy was obtained from the Ministry of Food and Drug Safety in Korea, and a clinical trial for treating patients with PD has commenced.

Constructing human neural circuits in living systems by transplantation

Our understanding of how the brain assembles its circuits and how this goes awry in disease remains incomplete. There has been great progress in generating human neurons from stem cells in vitro and, more recently, in constructing circuits with human cells in vivo by transplantation. Here, I highlight approaches, promises, and challenges of growing human neurons in living animals to study human development and disease.

Unravelling the Parkinson's puzzle, from medications and surgery to stem cells and genes: a comprehensive review of current and future management strategies

Parkinson's disease (PD) is a neurodegenerative disorder, prevalent in the elderly population. Neuropathological hallmarks of PD include loss of dopaminergic cells in the nigro-striatal pathway and deposition of alpha-synuclein protein in the neurons and synaptic terminals, which lead to a complex presentation of motor and non-motor symptoms. This review focuses on various aspects of PD, from clinical diagnosis to currently accepted treatment options, such as pharmacological management through dopamine replacement and surgical techniques such as deep brain stimulation (DBS). The review discusses in detail the potential of emerging stem cell-based therapies and gene therapies to be adopted as a cure, in contrast to the present symptomatic treatment in PD. The potential sources of stem cells for autologous and allogeneic stem cell therapy have been discussed, along with the progress evaluation of pre-clinical and clinical trials. Even though recent techniques hold great potential to improve the lives of PD patients, we present the importance of addressing the safety, efficacy, ethical, cost, and regulatory concerns before scaling them to clinical use.

Stem Cell Therapy for the Treatment of Parkinson's Disease: What Promise Does it Hold?

Parkinson's disease (PD) is a common, progressive neurodegenerative disorder characterized by substantia nigra dopamine cell death and a varied clinical picture that affects older people. Although more than two centuries have passed since the earliest attempts to find a cure for PD, it remains an unresolved problem. With this in mind, cell replacement therapy is a new strategy for treating PD. This novel approach aims to replace degenerated dopaminergic (DAergic) neurons with new ones or provide a new source of cells that can differentiate into DAergic neurons. Induced pluripotent stem cells (iPSCs), mesenchymal stem cells (MSCs), neural stem cells (NSCs), and embryonic stem cells (ESCs) are among the cells considered for transplantation therapies. Recently disease-modifying strategies like cell replacement therapies combined with other therapeutic approaches, such as utilizing natural compounds or biomaterials, are proposed to modify the underlying neurodegeneration. In the present review, we discuss the current advances in cell replacement therapy for PD and summarize the existing experimental and clinical evidence supporting this approach.

Dopaminergic Cell Replacement for Parkinson's Disease: Addressing the Intracranial Delivery Hurdle

Parkinson's disease (PD) is an increasingly prevalent neurological disorder, affecting more than 8.5 million individuals worldwide. α-Synucleinopathy in PD is considered to cause dopaminergic neuronal loss in the substantia nigra, resulting in characteristic motor dysfunction that is the target for current medical and surgical therapies. Standard treatment for PD has remained unchanged for several decades and does not alter disease progression. Furthermore, symptomatic therapies for PD are limited by issues surrounding long-term efficacy and side effects. Cell replacement therapy (CRT) presents an alternative approach that has the potential to restore striatal dopaminergic input and ameliorate debilitating motor symptoms in PD. Despite promising pre-clinical data, CRT has demonstrated mixed success clinically. Recent advances in graft biology have renewed interest in the field, resulting in several worldwide ongoing clinical trials. However, factors surrounding the effective neurosurgical delivery of cell grafts have remained under-studied, despite their significant potential to influence therapeutic outcomes. Here, we focus on the key neurosurgical factors to consider for the clinical translation of CRT. We review the instruments that have been used for cell graft delivery, highlighting current features and limitations, while discussing how future devices could address these challenges. Finally, we review other novel developments that may enhance graft accessibility, delivery, and efficacy. Challenges surrounding neurosurgical delivery may critically contribute to the success of CRT, so it is crucial that we address these issues to ensure that CRT does not falter at the final hurdle.

Metabolic Changes during In Vivo Maturation of PSC-Derived Skeletal Myogenic Progenitors

In vitro-generated pluripotent stem cell (PSC)-derived Pax3-induced (iPax3) myogenic progenitors display an embryonic transcriptional signature, but upon engraftment, the profile of re-isolated iPax3 donor-derived satellite cells changes toward similarity with postnatal satellite cells, suggesting that engrafted PSC-derived myogenic cells remodel their transcriptional signature upon interaction within the adult muscle environment. Here, we show that engrafted myogenic progenitors also remodel their metabolic state. Assessment of oxygen consumption revealed that exposure to the adult muscle environment promotes overt changes in mitochondrial bioenergetics, as shown by the substantial suppression of energy requirements in re-isolated iPax3 donor-derived satellite cells compared to their in vitro-generated progenitors. Mass spectrometry-based metabolomic profiling further confirmed the relationship of engrafted iPax3 donor-derived cells to adult satellite cells. The fact that in vitro-generated myogenic progenitors remodel their bioenergetic signature upon in vivo exposure to the adult muscle environment may have important implications for therapeutic applications.

Identifying secreted biomarkers of dopaminergic ventral midbrain progenitor cells

BACKGROUND

Ventral midbrain (VM) dopaminergic progenitor cells derived from human pluripotent stem cells have the potential to replace endogenously lost dopamine neurons and are currently in preclinical and clinical development for treatment of Parkinson's Disease (PD). However, one main challenge in the quality control of the cells is that rostral and caudal VM progenitors are extremely similar transcriptionally though only the caudal VM cells give rise to dopaminergic (DA) neurons with functionality relevant for cell replacement in PD. Therefore, it is critical to develop assays which can rapidly and reliably discriminate rostral from caudal VM cells during clinical manufacturing.

METHODS

We performed shotgun proteomics on cell culture supernatants from rostral and caudal VM progenitor cells to search for novel secreted biomarkers specific to DA progenitors from the caudal VM. Key hits were validated by qRT-PCR and ELISA.

RESULTS

We identified and validated novel secreted markers enriched in caudal VM progenitor cultures (CPE, LGI1 and PDGFC), and found these markers to correlate strongly with the expression of EN1, which is a predictive marker for successful graft outcome in DA cell transplantation products. Other markers (CNTN2 and CORIN) were found to conversely be enriched in the non-dopaminergic rostral VM cultures. Key novel ELISA markers were further validated on supernatant samples from GMP-manufactured caudal VM batches.

CONCLUSION

As a non-invasive in-process quality control test for predicting correctly patterned batches of caudal VM DA cells during clinical manufacturing, we propose a dual ELISA panel measuring LGI1/CORIN ratios around day 16 of differentiation.

Enhanced production of mesencephalic dopaminergic neurons from lineage-restricted human undifferentiated stem cells

Current differentiation protocols for generating mesencephalic dopaminergic (mesDA) neurons from human pluripotent stem cells result in grafts containing only a small proportion of mesDA neurons when transplanted in vivo. In this study, we develop lineage-restricted undifferentiated stem cells (LR-USCs) from pluripotent stem cells, which enhances their potential for differentiating into caudal midbrain floor plate progenitors and mesDA neurons. Using a ventral midbrain protocol, 69% of LR-USCs become bona fide caudal midbrain floor plate progenitors, compared to only 25% of human embryonic stem cells (hESCs). Importantly, LR-USCs generate significantly more mesDA neurons under midbrain and hindbrain conditions in vitro and in vivo. We demonstrate that midbrain-patterned LR-USC progenitors transplanted into 6-hydroxydopamine-lesioned rats restore function in a clinically relevant non-pharmacological behavioral test, whereas midbrain-patterned hESC-derived progenitors do not. This strategy demonstrates how lineage restriction can prevent the development of undesirable lineages and enhance the conditions necessary for mesDA neuron generation.

In vitro modeling of the human dopaminergic system using spatially arranged ventral midbrain-striatum-cortex assembloids

Ventral midbrain dopaminergic neurons project to the striatum as well as the cortex and are involved in movement control and reward-related cognition. In Parkinson's disease, nigrostriatal midbrain dopaminergic neurons degenerate and cause typical Parkinson's disease motor-related impairments, while the dysfunction of mesocorticolimbic midbrain dopaminergic neurons is implicated in addiction and neuropsychiatric disorders. Study of the development and selective neurodegeneration of the human dopaminergic system, however, has been limited due to the lack of an appropriate model and access to human material. Here, we have developed a human in vitro model that recapitulates key aspects of dopaminergic innervation of the striatum and cortex. These spatially arranged ventral midbrain-striatum-cortical organoids (MISCOs) can be used to study dopaminergic neuron maturation, innervation and function with implications for cell therapy and addiction research. We detail protocols for growing ventral midbrain, striatal and cortical organoids and describe how they fuse in a linear manner when placed in custom embedding molds. We report the formation of functional long-range dopaminergic connections to striatal and cortical tissues in MISCOs, and show that injected, ventral midbrain-patterned progenitors can mature and innervate the tissue. Using these assembloids, we examine dopaminergic circuit perturbations and show that chronic cocaine treatment causes long-lasting morphological, functional and transcriptional changes that persist upon drug withdrawal. Thus, our method opens new avenues to investigate human dopaminergic cell transplantation and circuitry reconstruction as well as the effect of drugs on the human dopaminergic system.

Cell Replacement Therapy for Brain Repair: Recent Progress and Remaining Challenges for Treating Parkinson's Disease and Cortical Injury

Neural transplantation represents a promising approach to repairing damaged brain circuitry. Cellular grafts have been shown to promote functional recovery through "bystander effects" and other indirect mechanisms. However, extensive brain lesions may require direct neuronal replacement to achieve meaningful restoration of function. While fetal cortical grafts have been shown to integrate with the host brain and appear to develop appropriate functional attributes, the significant ethical concerns and limited availability of this tissue severely hamper clinical translation. Induced pluripotent stem cell-derived cells and tissues represent a more readily scalable alternative. Significant progress has recently been made in developing protocols for generating a wide range of neural cell types in vitro. Here, we discuss recent progress in neural transplantation approaches for two conditions with distinct design needs: Parkinson's disease and cortical injury. We discuss the current status and future application of injections of dopaminergic cells for the treatment of Parkinson's disease as well as the use of structured grafts such as brain organoids for cortical repair.

Safety and efficacy of human ESC-derived corneal endothelial cells for corneal endothelial dysfunction

BACKGROUND

Research on human pluripotent stem cells (hPSCs) has shown tremendous progress in cell-based regenerative medicine. Corneal endothelial dysfunction is associated with the loss and degeneration of corneal endothelial cells (CECs), rendering cell replacement a promising therapeutic strategy. However, comprehensive preclinical assessments of hPSC-derived CECs for this cell therapy remain a challenge.

RESULTS

Here we defined an adapted differentiation protocol to generate induced corneal endothelial cells (iCECs) consistently and efficiently from clinical-grade human embryonic stem cells (hESCs) with xeno-free medium and manufactured cryopreserved iCECs. Cells express high levels of typical CECs markers and exhibit transendothelial potential properties in vitro typical of iCECs. After rigorous quality control measures, cells meeting all release criteria were available for in vivo studies. We found that there was no overgrowth or tumorigenicity of grafts in immunodeficient mice. After grafting into rabbit models, the surviving iCECs ameliorated edema and recovered corneal opacity.

CONCLUSIONS

Our work provides an efficient approach for generating iCECs and demonstrates the safety and efficacy of iCECs in disease modeling. Therefore, clinical-grade iCECs are a reliable source for future clinical treatment of corneal endothelial dysfunction.

Challenges involved in cell therapy for Parkinson's disease using human pluripotent stem cells

Neurons derived from human pluripotent stem cells (hPSCs) provide a valuable tool for studying human neural development and neurodegenerative diseases. The investigation of hPSC-based cell therapy, involving the differentiation of hPSCs into target cells and their transplantation into affected regions, is of particular interest. One neurodegenerative disease that is being extensively studied for hPSC-based cell therapy is Parkinson's disease (PD), the second most common among humans. Various research groups are focused on differentiating hPSCs into ventral midbrain dopaminergic (vmDA) progenitors, which have the potential to further differentiate into neurons closely resembling DA neurons found in the substantia nigra pars compacta (SNpc) after transplantation, providing a promising treatment option for PD. In vivo experiments, where hPSC-derived vmDA progenitor cells were transplanted into the striatum or SNpc of animal PD models, the transplanted cells demonstrated stable engraftment and resulted in behavioral recovery in the transplanted animals. Several differentiation protocols have been developed for this specific cell therapy. However, the lack of a reliable live-cell lineage identification method presents a significant obstacle in confirming the precise lineage of the differentiated cells intended for transplantation, as well as identifying potential contamination by non-vmDA progenitors. This deficiency increases the risk of adverse effects such as dyskinesias and tumorigenicity, highlighting the importance of addressing this issue before proceeding with transplantation. Ensuring the differentiation of hPSCs into the target cell lineage is a crucial step to guarantee precise therapeutic effects in cell therapy. To underscore the significance of lineage identification, this review focuses on the differentiation protocols of hPSC-derived vmDA progenitors developed by various research groups for PD treatment. Moreover, in vivo experimental results following transplantation were carefully analyzed. The encouraging outcomes from these experiments demonstrate the potential efficacy and safety of hPSC-derived vmDA progenitors for PD cell therapy. Additionally, the results of clinical trials involving the use of hPSC-derived vmDA progenitors for PD treatment were briefly reviewed, shedding light on the progress and challenges faced in translating this promising therapy into clinical practice.

Preclinical quality, safety, and efficacy of a human embryonic stem cell-derived product for the treatment of Parkinson's disease, STEM-PD

Cell replacement therapies for Parkinson's disease (PD) based on transplantation of pluripotent stem cell-derived dopaminergic neurons are now entering clinical trials. Here, we present quality, safety, and efficacy data supporting the first-in-human STEM-PD phase I/IIa clinical trial along with the trial design. The STEM-PD product was manufactured under GMP and quality tested in vitro and in vivo to meet regulatory requirements. Importantly, no adverse effects were observed upon testing of the product in a 39-week rat GLP safety study for toxicity, tumorigenicity, and biodistribution, and a non-GLP efficacy study confirmed that the transplanted cells mediated full functional recovery in a pre-clinical rat model of PD. We further observed highly comparable efficacy results between two different GMP batches, verifying that the product can be serially manufactured. A fully in vivo-tested batch of STEM-PD is now being used in a clinical trial of 8 patients with moderate PD, initiated in 2022.

Paradigm Shift: Multiple Potential Pathways to Neurodegenerative Dementia

Neurodegenerative dementia can result from multiple underlying abnormalities, including neurotransmitter imbalances, protein aggregation, and other neurotoxic events. A major complication in identifying effective treatment targets is the frequent co-occurrence of multiple neurodegenerative processes, occurring either in parallel or sequentially. The path towards developing effective treatments for Alzheimer's disease (AD) and other dementias has been relatively slow and until recently has focused on disease symptoms. Aducanumab and lecanemab, recently approved by the FDA, are meant to target disease structures but have only modest benefit on symptom progression and remain unproven in reversing or preventing dementia. A third, donanemab, appears more promising but awaits FDA approval. Ongoing trials include potential cognition enhancers, new combinations of known drugs for synergistic effects, prodrugs with less toxicity, and increasing interest in drugs targeting neuroinflammation or microbiome. Scientific and technological advances offer the opportunity to move in new therapy directions, such as modifying microglia to prevent or suppress underlying disease. A major challenge, however, is that underlying comorbidities likely influence the effectiveness of therapies. Indeed, the full range of comorbidity, today only definitively identified postmortem, likely contributes to failed clinical trials and overmedication of older adults, since it is difficult to exclude (during life) people unlikely to respond. Our current knowledge thus signals that a paradigm shift towards individualized and multimodal treatments is necessary to effectively advance the field of dementia therapeutics.

Cryopreserved clinical-grade human embryonic stem cell-derived dopaminergic progenitors function in Parkinson's disease models

AIM

Parkinson's Disease (PD) is a common age-related neurodegenerative disorder with a rising prevalence. Human pluripotent stem cells have emerged as the most promising source of cells for midbrain dopaminergic (mDA) neuron replacement in PD. This study aimed to generate transplantable mDA progenitors for treatment of PD.

MATERIALS AND METHODS

Here, we optimized and fine-tuned a differentiation protocol using a combination of small molecules and growth factors to induce mDA progenitors to comply with good manufacturing practice (GMP) guidelines based on our clinical-grade human embryonic stem cell (hESC) line.

KEY FINDINGS

The resulting mDA progenitors demonstrated robust differentiation and functional properties in vitro. Moreover, cryopreserved mDA progenitors were transplanted into 6-hydroxydopamine-lesioned rats, leading to functional recovery.

SIGNIFICANCE

We demonstrate that our optimized protocol using a clinical hESC line is suitable for generating clinical-grade mDA progenitors and provides the ground work for future translational applications.

Expression and role of nicotinic acetylcholine receptors during midbrain dopaminergic neuron differentiation from human induced pluripotent stem cells

AIM

Nicotinic acetylcholine receptors (nAChRs) expressed in midbrain dopaminergic (mDA) neurons modulate mDA neuronal activity. However, their expression patterns and functional roles during mDA neuronal development remain unknown. Here, we profiled the expression and function of nAChR subtypes during mDA neuron differentiation from human induced pluripotent stem cells (hiPSCs).

METHODS

Midbrain dopaminergic neurons were differentiated from hiPSCs using a recently developed proprietary method that replicates midbrain development. The expression patterns of developmental marker proteins were monitored during mDA neuronal differentiation using immunohistochemical analysis. Gene expression of nAChR subtypes was analyzed by reverse transcription polymerase chain reaction. Pharmacological nAChR agonists and antagonists were used to reveal the role of the α6 nAChR subunit in the differentiation of mDA neurons from hiPSCs.

RESULTS

CHRNA4 expression was detected at the mDA neural progenitor stage, whereas CHRNA6 expression began during the mDA neuronal stage. CHRNA7 was expressed throughout the differentiation process, including in the undifferentiated hiPSCs. We also found that LMO3, a gene expressed in a subset of substantia nigra pars compacta (SNC) DA neurons in the midbrain, showed increased expression following nicotine treatment in a concentration-dependent manner. Additionally, 5-iodo A85380, a selective α6 nAChR agonist, also increased LMO3 expression in hiPSC-derived mDA neurons, and this increase was suppressed by simultaneous treatment with bPiDi, a selective α6 nAChR antagonist.

CONCLUSION

Our findings suggest that stimulating the α6 nAChR subunit on hiPSC-derived mDA neurons may induce neuronal maturation that is biased toward SNC DA neurons.

Reprogramming iPSCs to study age-related diseases: Models, therapeutics, and clinical trials

The unprecedented rise in life expectancy observed in the last decades is leading to a global increase in the ageing population, and age-associated diseases became an increasing societal, economic, and medical burden. This has boosted major efforts in the scientific and medical research communities to develop and improve therapies to delay ageing and age-associated functional decline and diseases, and to expand health span. The establishment of induced pluripotent stem cells (iPSCs) by reprogramming human somatic cells has revolutionised the modelling and understanding of human diseases. iPSCs have a major advantage relative to other human pluripotent stem cells as their obtention does not require the destruction of embryos like embryonic stem cells do, and do not have a limited proliferation or differentiation potential as adult stem cells. Besides, iPSCs can be generated from somatic cells from healthy individuals or patients, which makes iPSC technology a promising approach to model and decipher the mechanisms underlying the ageing process and age-associated diseases, study drug effects, and develop new therapeutic approaches. This review discusses the advances made in the last decade using iPSC technology to study the most common age-associated diseases, including age-related macular degeneration (AMD), neurodegenerative and cardiovascular diseases, brain stroke, cancer, diabetes, and osteoarthritis.

An engineered Sox17 induces somatic to neural stem cell fate transitions independently from pluripotency reprogramming

Advanced strategies to interconvert cell types provide promising avenues to model cellular pathologies and to develop therapies for neurological disorders. Yet, methods to directly transdifferentiate somatic cells into multipotent induced neural stem cells (iNSCs) are slow and inefficient, and it is unclear whether cells pass through a pluripotent state with full epigenetic reset. We report iNSC reprogramming from embryonic and aged mouse fibroblasts as well as from human blood using an engineered Sox17 (eSox17FNV). eSox17FNV efficiently drives iNSC reprogramming while Sox2 or Sox17 fail. eSox17FNV acquires the capacity to bind different protein partners on regulatory DNA to scan the genome more efficiently and has a more potent transactivation domain than Sox2. Lineage tracing and time-resolved transcriptomics show that emerging iNSCs do not transit through a pluripotent state. Our work distinguishes lineage from pluripotency reprogramming with the potential to generate more authentic cell models for aging-associated neurodegenerative diseases.

Current state of stem cell research in non-human primates: an overview

The remarkable similarity between non-human primates (NHPs) and humans establishes them as essential models for understanding human biology and diseases, as well as for developing novel therapeutic strategies, thereby providing more comprehensive reference data for clinical treatment. Pluripotent stem cells such as embryonic stem cells and induced pluripotent stem cells provide unprecedented opportunities for cell therapies against intractable diseases and injuries. As continue to harness the potential of these biotechnological therapies, NHPs are increasingly being employed in preclinical trials, serving as a pivotal tool to evaluate the safety and efficacy of these interventions. Here, we review the recent advancements in the fundamental research of stem cells and the progress made in studies involving NHPs.

hESC-derived striatal progenitors grafted into a Huntington's disease rat model support long-term functional motor recovery by differentiating, self-organizing and connecting into the lesioned striatum

BACKGROUND

Huntington's disease (HD) is a motor and cognitive neurodegenerative disorder due to prominent loss of striatal medium spiny neurons (MSNs). Cell replacement using human embryonic stem cells (hESCs) derivatives may offer new therapeutic opportunities to replace degenerated neurons and repair damaged circuits.

METHODS

With the aim to develop effective cell replacement for HD, we assessed the long-term therapeutic value of hESC-derived striatal progenitors by grafting the cells into the striatum of a preclinical model of HD [i.e., adult immunodeficient rats in which the striatum was lesioned by monolateral injection of quinolinic acid (QA)]. We examined the survival, maturation, self-organization and integration of the graft as well as its impact on lesion-dependent motor alterations up to 6 months post-graft. Moreover, we tested whether exposing a cohort of QA-lesioned animals to environmental enrichment (EE) could improve graft integration and function.

RESULTS

Human striatal progenitors survived up to 6 months after transplantation and showed morphological and neurochemical features typical of human MSNs. Donor-derived interneurons were also detected. Grafts wired in both local and long-range striatal circuits, formed domains suggestive of distinct ganglionic eminence territories and displayed emerging striosome features. Moreover, over time grafts improved complex motor performances affected by QA. EE selectively increased cell differentiation into MSN phenotype and promoted host-to-graft connectivity. However, when combined to the graft, the EE paradigm used in this study was insufficient to produce an additive effect on task execution.

CONCLUSIONS

The data support the long-term therapeutic potential of ESC-derived human striatal progenitor grafts for the replacement of degenerated striatal neurons in HD and suggest that EE can effectively accelerate the maturation and promote the integration of human striatal cells.

A defined method for differentiating human iPSCs into midbrain dopaminergic progenitors that safely restore motor deficits in Parkinson's disease

Background

Parkinson's disease (PD) is a progressive neurodegenerative condition that primarily affects motor functions; it is caused by the loss of midbrain dopaminergic (mDA) neurons. The therapeutic effects of transplanting human-induced pluripotent stem cell (iPSC)-derived mDA neural progenitor cells in animal PD models are known and are being evaluated in an ongoing clinical trial. However, However, improvements in the safety and efficiency of differentiation-inducing methods are crucial for providing a larger scale of cell therapy studies. This study aimed to investigate the usefulness of dopaminergic progenitor cells derived from human iPSCs by our previously reported method, which promotes differentiation and neuronal maturation by treating iPSCs with three inhibitors at the start of induction.

Methods

Healthy subject-derived iPS cells were induced into mDA progenitor cells by the CTraS-mediated method we previously reported, and their proprieties and dopaminergic differentiation efficiency were examined in vitro. Then, the induced mDA progenitors were transplanted into 6-hydroxydopamine-lesioned PD model mice, and their efficacy in improving motor function, cell viability, and differentiation ability in vivo was evaluated for 16 weeks.

Results

Approximately ≥80% of cells induced by this method without sorting expressed mDA progenitor markers and differentiated primarily into A9 dopaminergic neurons in vitro. After transplantation in 6-hydroxydopamine-lesioned PD model mice, more than 90% of the engrafted cells differentiated into the lineage of mDA neurons, and approximately 15% developed into mature mDA neurons without tumour formation. The grafted PD model mice also demonstrated significantly improved motor functions.

Conclusion

This study suggests that the differentiation protocol for the preparation of mDA progenitors is a promising option for cell therapy in patients with PD.

Astrocyte-to-neuron reprogramming and crosstalk in the treatment of Parkinson's disease

Parkinson's disease (PD) is currently the fastest growing disabling neurological disorder worldwide, with motor and non-motor symptoms being its main clinical manifestations. The primary pathological features include a reduction in the number of dopaminergic neurons in the substantia nigra and decrease in dopamine levels in the nigrostriatal pathway. Existing treatments only alleviate clinical symptoms and do not stop disease progression; slowing down the loss of dopaminergic neurons and stimulating their regeneration are emerging therapies. Preclinical studies have demonstrated that transplantation of dopamine cells generated from human embryonic or induced pluripotent stem cells can restore the loss of dopamine. However, the application of cell transplantation is limited owing to ethical controversies and the restricted source of cells. Until recently, the reprogramming of astrocytes to replenish lost dopaminergic neurons has provided a promising alternative therapy for PD. In addition, repair of mitochondrial perturbations, clearance of damaged mitochondria in astrocytes, and control of astrocyte inflammation may be extensively neuroprotective and beneficial against chronic neuroinflammation in PD. Therefore, this review primarily focuses on the progress and remaining issues in astrocyte reprogramming using transcription factors (TFs) and miRNAs, as well as exploring possible new targets for treating PD by repairing astrocytic mitochondria and reducing astrocytic inflammation.

Co-transplantation of autologous Treg cells in a cell therapy for Parkinson's disease

The specific loss of midbrain dopamine neurons (mDANs) causes major motor dysfunction in Parkinson's disease, which makes cell replacement a promising therapeutic approach1-4. However, poor survival of grafted mDANs remains an obstacle to successful clinical outcomes5-8. Here we show that the surgical procedure itself (referred to here as 'needle trauma') triggers a profound host response that is characterized by acute neuroinflammation, robust infiltration of peripheral immune cells and brain cell death. When midbrain dopamine (mDA) cells derived from human induced pluripotent stem (iPS) cells were transplanted into the rodent striatum, less than 10% of implanted tyrosine hydroxylase (TH)+ mDANs survived at two weeks after transplantation. By contrast, TH- grafted cells mostly survived. Notably, transplantation of autologous regulatory T (Treg) cells greatly modified the response to needle trauma, suppressing acute neuroinflammation and immune cell infiltration. Furthermore, intra-striatal co-transplantation of Treg cells and human-iPS-cell-derived mDA cells significantly protected grafted mDANs from needle-trauma-associated death and improved therapeutic outcomes in rodent models of Parkinson's disease with 6-hydroxydopamine lesions. Co-transplantation with Treg cells also suppressed the undesirable proliferation of TH- grafted cells, resulting in more compact grafts with a higher proportion and higher absolute numbers of TH+ neurons. Together, these data emphasize the importance of the initial inflammatory response to surgical injury in the differential survival of cellular components of the graft, and suggest that co-transplanting autologous Treg cells effectively reduces the needle-trauma-induced death of mDANs, providing a potential strategy to achieve better clinical outcomes for cell therapy in Parkinson's disease.