Genomic instability in pluripotent stem cells: implications for clinical applications

Assessment of Genetic Stability in Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes by Using Droplet Digital PCR

Unintended genetic modifications that occur during the differentiation and proliferation of human induced pluripotent stem cells (hiPSCs) can lead to tumorigenicity. This is a crucial concern in the development of stem cell-based therapies to ensure the safety and efficacy of the final product. Moreover, conventional genetic stability testing methods are limited by low sensitivity, which is an issue that remains unsolved. In this study, we assessed the genetic stability of hiPSCs and hiPSC-derived cardiomyocytes using various testing methods, including karyotyping, CytoScanHD chip analysis, whole-exome sequencing, and targeted sequencing. Two specific genetic mutations in KMT2C and BCOR were selected from the 17 gene variants identified by whole-exome and targeted sequencing methods, which were validated using droplet digital PCR. The applicability of this approach to stem cell-based therapeutic products was further demonstrated with associated validation according to the International Council for Harmonisation (ICH) guidelines, including specificity, precision, robustness, and limit of detection. Our droplet digital PCR results showed high sensitivity and accuracy for quantitatively detecting gene mutations, whereas conventional qPCR could not avoid false positives. In conclusion, droplet digital PCR is a highly sensitive and precise method for assessing the expression of mutations with tumorigenic potential for the development of stem cell-based therapeutics.

Avian iPSC Derivation to Recover Threatened Wild Species: A Comprehensive Review in Light of Well-Established Protocols

Induced pluripotent stem cells (iPSCs) were first generated by Yamanaka in 2006, revolutionizing research by overcoming limitations imposed by the use of embryonic stem cells. In terms of the conservation of endangered species, iPSC technology presents itself as a viable alternative for the manipulation of target genetics without compromising specimens. Although iPSCs have been successfully generated for various species, their application in nonmammalian species, particularly avian species, requires further in-depth investigation to cover the diversity of wild species at risk and their different protocol requirements. This study aims to provide an overview of the workflow for iPSC induction, comparing well-established protocols in humans and mice with the limited information available for avian species. Here, we discuss the somatic cell sources to be reprogrammed, genetic factors, delivery methods, enhancers, a brief history of achievements in avian iPSC derivation, the main approaches for iPSC characterization, and the future perspectives and challenges for the field. By examining the current protocols and state-of-the-art techniques employed in iPSC generation, we seek to contribute to the development of efficient and species-specific iPSC methodologies for at-risk avian species. The advancement of iPSC technology holds great promise for achieving in vitro germline competency and, consequently, addressing reproductive challenges in endangered species, providing valuable tools for basic research, bird genetic preservation and rescue, and the establishment of cryobanks for future conservation efforts.

Advances in Genetic Reprogramming: Prospects from Developmental Biology to Regenerative Medicine

The foundations of cell reprogramming were laid by Yamanaka and co-workers, who showed that somatic cells can be reprogrammed into pluripotent cells (induced pluripotency). Since this discovery, the field of regenerative medicine has seen advancements. For example, because they can differentiate into multiple cell types, pluripotent stem cells are considered vital components in regenerative medicine aimed at the functional restoration of damaged tissue. Despite years of research, both replacement and restoration of failed organs/ tissues have remained elusive scientific feats. However, with the inception of cell engineering and nuclear reprogramming, useful solutions have been identified to counter the need for compatible and sustainable organs. By combining the science underlying genetic engineering and nuclear reprogramming with regenerative medicine, scientists have engineered cells to make gene and stem cell therapies applicable and effective. These approaches have enabled the targeting of various pathways to reprogramme cells, i.e., make them behave in beneficial ways in a patient-specific manner. Technological advancements have clearly supported the concept and realization of regenerative medicine. Genetic engineering is used for tissue engineering and nuclear reprogramming and has led to advances in regenerative medicine. Targeted therapies and replacement of traumatized , damaged, or aged organs can be realized through genetic engineering. Furthermore, the success of these therapies has been validated through thousands of clinical trials. Scientists are currently evaluating induced tissue-specific stem cells (iTSCs), which may lead to tumour-free applications of pluripotency induction. In this review, we present state-of-the-art genetic engineering that has been used in regenerative medicine. We also focus on ways that genetic engineering and nuclear reprogramming have transformed regenerative medicine and have become unique therapeutic niches.

Recent advances in the application of induced pluripotent stem cell technology to the study of myeloid malignancies

Acquired myeloid malignancies are a spectrum of clonal disorders known to be caused by sequential acquisition of genetic lesions in hematopoietic stem and progenitor cells, leading to their aberrant self-renewal and differentiation. The increasing use of induced pluripotent stem cell (iPSC) technology to study myeloid malignancies has helped usher a paradigm shift in approaches to disease modeling and drug discovery, especially when combined with gene-editing technology. The process of reprogramming allows for the capture of the diversity of genetic lesions and mutational burden found in primary patient samples into individual stable iPSC lines. Patient-derived iPSC lines, owing to their self-renewal and differentiation capacity, can thus be a homogenous source of disease relevant material that allow for the study of disease pathogenesis using various functional read-outs. Furthermore, genome editing technologies like CRISPR/Cas9 enable the study of the stepwise progression from normal to malignant hematopoiesis through the introduction of specific driver mutations, individually or in combination, to create isogenic lines for comparison. In this review, we survey the current use of iPSCs to model acquired myeloid malignancies including myelodysplastic syndromes (MDS), myeloproliferative neoplasms (MPN), acute myeloid leukemia and MDS/MPN overlap syndromes. The use of iPSCs has enabled the interrogation of the underlying mechanism of initiation and progression driving these diseases. It has also made drug testing, repurposing, and the discovery of novel therapies for these diseases possible in a high throughput setting.

SeqVerify: An accessible analysis tool for cell line genomic integrity, contamination, and gene editing outcomes

1Over the last decade, advances in genome editing and pluripotent stem cell (PSC) culture have let researchers generate edited PSC lines to study a wide variety of biological questions. However, abnormalities in cell lines such as aneuploidy, on-target and off-target editing errors, and microbial contamination can arise during PSC culture or due to undesired editing outcomes. Any of these abnormalities can invalidate experiments, so detecting them is crucial. The ongoing decline of next-generation sequencing prices has made whole genome sequencing (WGS) an effective quality control option, since WGS can detect any abnormality involving changes to DNA sequences or presence of unwanted sequences. However, this approach has suffered from a lack of easily usable data analysis software. Here, we present SeqVerify, a computational pipeline designed to take raw WGS data and a list of intended edits, and verify that the edits are present and that there are no abnormalities. We anticipate that SeqVerify will be a useful tool for researchers generating edited PSCs, and more broadly, for cell line quality control in general.

Enhanced Expansion of Human Pluripotent Stem Cells and Somatic Cell Reprogramming Using Defined and Xeno-Free Culture Conditions

Human embryonic stem cells and induced pluripotent stem cells (hPSC) have an unprecedented opportunity to revolutionize the fields of developmental biology as well as tissue engineering and regenerative medicine. However, their applications have been significantly limited by the lack of chemically defined and xeno-free culture conditions. The demand for the high-quality and scaled-up production of cells for use in both research and clinical studies underscores the need to develop tools that will simplify the in vitro culture process while reducing the variables. Here, we describe a systematic study to identify the optimal conditions for the initial cell attachment of hPSC to tissue culture dishes grafted with polymers of N-(3-Sulfopropyl)-N-Methacryloxyethyl-N, N-Dimethylammoniun Betaine (PMEDSAH) in combination with chemically defined and xeno-free culture media. After testing multiple supplements and chemicals, we identified that pre-conditioning of PMEDSAH grafted plates with 10% human serum (HS) supported the initial cell attachment, which allowed for the long-term culture and maintenance of hPSC compared to cells cultured on Matrigel-coated plates. Using this culture condition, a 2.1-fold increase in the expansion of hPSC was observed without chromosomal abnormalities. Furthermore, this culture condition supported a higher reprogramming efficiency (0.37% vs. 0.22%; p < 0.0068) of somatic cells into induced pluripotent stem cells compared to the non-defined culture conditions. This defined and xeno-free hPSC culture condition may be used in obtaining the large populations of hPSC and patient-derived iPSC required for many applications in regenerative and translational medicine.

Xeno-free generation of human induced pluripotent stem cells from donor-matched fibroblasts isolated from dermal and oral tissues

BACKGROUND

Induced pluripotent stem cells (iPS) can be generated from various somatic cells and can subsequently be differentiated to multiple cell types of the body. This makes them highly promising for cellular therapy in regenerative medicine. However, to facilitate their clinical use and to ensure safety, iPS culturing protocols must be compliant with good manufacturing practice guidelines and devoid of xenogenic products. Therefore, we aimed to compare the efficiency of using humanized culture conditions, specifically human platelet lysate to fetal bovine serum, for iPS generation from different sources, and to evaluate their stemness.

METHODS

iPS were generated via a platelet lysate or fetal bovine serum-based culturing protocol from matched dermal, buccal and gingival human fibroblasts, isolated from healthy donors (n = 2) after informed consent, via episomal plasmid transfection. Pluripotency, genotype and phenotype of iPS, generated by both protocols, were then assessed by various methods.

RESULTS

More attempts were generally required to successfully reprogram xeno-free fibroblasts to iPS, as compared to xenogenic cultured fibroblasts. Furthermore, oral fibroblasts generally required more attempts for successful iPS generation as opposed to dermal fibroblasts. Morphologically, all iPS generated from fibroblasts formed tight colonies surrounded by a reflective "whitish" outer rim, typical for iPS. They also expressed pluripotency markers at both gene (SOX2, OCT4, NANOG) and protein level (SOX2, OCT4). Upon stimulation, all iPS showed ability to differentiate into the three primary germ layers via expression of lineage-specific markers for mesoderm (MESP1, OSR1, HOPX), endoderm (GATA4) and ectoderm (PAX6, RAX). Genome analysis revealed several amplifications and deletions within the chromosomes of each iPS type.

CONCLUSIONS

The xeno-free protocol had a lower reprogramming efficiency compared to the standard xenogenic protocol. The oral fibroblasts generally proved to be more difficult to reprogram than dermal fibroblasts. Xeno-free dermal, buccal and gingival fibroblasts can successfully generate iPS with a comparable genotype/phenotype to their xenogenic counterparts.

Allogenic Synovia-Derived Mesenchymal Stem Cells for Treatment of Equine Tendinopathies and Desmopathies-Proof of Concept

Tendon and ligament injuries are frequent in sport horses and humans, and such injuries represent a significant therapeutic challenge. Tissue regeneration and function recovery are the paramount goals of tendon and ligament lesion management. Nowadays, several regenerative treatments are being developed, based on the use of stem cell and stem cell-based therapies. In the present study, the preparation of equine synovial membrane mesenchymal stem cells (eSM-MSCs) is described for clinical use, collection, transport, isolation, differentiation, characterization, and application. These cells are fibroblast-like and grow in clusters. They retain osteogenic, chondrogenic, and adipogenic differentiation potential. We present 16 clinical cases of tendonitis and desmitis, treated with allogenic eSM-MSCs and autologous serum, and we also include their evaluation, treatment, and follow-up. The concerns associated with the use of autologous serum as a vehicle are related to a reduced immunogenic response after the administration of this therapeutic combination, as well as the pro-regenerative effects from the growth factors and immunoglobulins that are part of its constitution. Most of the cases (14/16) healed in 30 days and presented good outcomes. Treatment of tendon and ligament lesions with a mixture of eSM-MSCs and autologous serum appears to be a promising clinical option for this category of lesions in equine patients.

TPX2 Amplification-Driven Aberrant Mitosis in Culture Adapted Human Embryonic Stem Cells with gain of 20q11.21

BACKGROUND

Despite highly effective machinery for the maintenance of genome integrity in human embryonic stem cells (hESCs), the frequency of genetic aberrations during in-vitro culture has been a serious issue for future clinical applications.

METHOD

By passaging hESCs over a broad range of timepoints (up to 6 years), the isogenic hESC lines with different passage numbers with distinct cellular characteristics, were established.

RESULT

We found that mitotic aberrations, such as the delay of mitosis, multipolar centrosomes, and chromosome mis-segregation, were increased in parallel with polyploidy compared to early-passaged hESCs (EP-hESCs) with normal copy number. Through high-resolution genome-wide approaches and transcriptome analysis, we found that culture adapted-hESCs with a minimal amplicon in chromosome 20q11.21 highly expressed TPX2, a key protein for governing spindle assembly and cancer malignancy. Consistent with these findings, the inducible expression of TPX2 in EP-hESCs reproduced aberrant mitotic events, such as the delay of mitotic progression, spindle stabilization, misaligned chromosomes, and polyploidy.

CONCLUSION

These studies suggest that the increased transcription of TPX2 in culture adapted hESCs could contribute to an increase in aberrant mitosis due to altered spindle dynamics.

In vitro germ cell induction from fertile and infertile monozygotic twin research participants

Human induced pluripotent stem cells (hiPSCs) enable reproductive diseases to be studied when the reproductive health of the participant is known. In this study, monozygotic (MZ) monoamniotic (MA) twins discordant for primary ovarian insufficiency (POI) consent to research to address the hypothesis that discordant POI is due to a shared primordial germ cell (PGC) progenitor pool. If this is the case, reprogramming the twin's skin cells to hiPSCs is expected to restore equivalent germ cell competency to the twins hiPSCs. Following reprogramming, the infertile MA twin's cells are capable of generating human PGC-like cells (hPGCLCs) and amniotic sac-like structures equivalent to her fertile twin sister. Using these hiPSCs together with genome sequencing, our data suggest that POI in the infertile twin is not due to a genetic barrier to amnion or germ cell formation and support the hypothesis that during gestation, amniotic PGCs are likely disproportionately allocated to the fertile twin with embryo splitting.

Treating intrauterine adhesion using conditionally reprogrammed physiological endometrial epithelial cells

Background

There is unmet need for effective therapies of intrauterine adhesions (IUAs) that are common cause of menstrual disturbance and infertility, since current clinical procedures do not improve prognosis for patients with moderate to severe IUA, with a recurrence rate of 23–50%. Stem cell-based therapy has emerged as a therapeutic option with unsolved issues for IUA patients in the past few years. Primary endometrial epithelial cells for cell therapy are largely hampered with the extremely limited proliferation capacity of uterine epithelial cells. This study was to evaluate whether IUA is curable with conditionally reprogrammed (CR) endometrial epithelial cells.

Methods

Mouse endometrial epithelial cells (MEECs) were isolated from C57BL female mice, and long-term cultures of MEECs were established and maintained with conditional reprogramming (CR) method. DNA damage response analysis, soft agar assay, and matrigel 3D culture were carried out to determine the normal biological characteristics of CR-MEECs. The tissue-specific differentiation potential of MEECs was analyzed with air–liquid interface (ALI) 3D culture, hematoxylin and eosin (H&E) staining, Masson’s trichrome and DAB staining, immunofluorescence assay. IUA mice were constructed and transplanted with CR-MEECs. Repair and mechanisms of MEECs transplantation in IUA mice were measured with qRT-PCR, Masson’s trichrome, and DAB staining.

Results

We first successfully established long-term cultures of MEECs using CR approach. CR-MEECs maintained a rapid and stable proliferation in this co-culture system. Our data confirmed that CR-MEECs retained normal biological characteristics and endometrium tissue-specific differentiation potential. CR-MEECs also expressed estrogen and progesterone receptors and maintained the exquisite sensitivity to sex hormones in vitro. Most importantly, allogeneic transplantation of CR-MEECs successfully repaired the injured endometrium and significantly improved the pregnancy rate of IUA mice.

Conclusions

Conditionally reprogrammed physiological endometrial epithelial cells provide a novel strategy in IUA clinics in a personalized or generalized manner and also serve as a physiological model to explore biology of endometrial epithelial cells and mechanisms of IUA.

Neural is Fundamental: Neural Stemness as the Ground State of Cell Tumorigenicity and Differentiation Potential

Tumorigenic cells are similar to neural stem cells or embryonic neural cells in regulatory networks, tumorigenicity and pluripotent differentiation potential. By integrating the evidence from developmental biology, tumor biology and evolution, I will make a detailed discussion on the observations and propose that neural stemness underlies two coupled cell properties, tumorigenicity and pluripotent differentiation potential. Neural stemness property of tumorigenic cells can hopefully integrate different observations/concepts underlying tumorigenesis. Neural stem cells and tumorigenic cells share regulatory networks; both exhibit neural stemness, tumorigenicity and pluripotent differentiation potential; both depend on expression or activation of ancestral genes; both rely primarily on aerobic glycolytic metabolism; both can differentiate into various cells/tissues that are derived from three germ layers, leading to tumor formation resembling severely disorganized or more degenerated process of embryonic tissue differentiation; both are enriched in long genes with more splice variants that provide more plastic scaffolds for cell differentiation, etc. Neural regulatory networks, which include higher levels of basic machineries of cell physiological functions and developmental programs, work concertedly to define a basic state with fast cell cycle and proliferation. This is predestined by the evolutionary advantage of neural state, the ground or initial state for multicellularity with adaptation to an ancient environment. Tumorigenesis might represent a process of restoration of neural ground state, thereby restoring a state with fast proliferation and pluripotent differentiation potential in somatic cells. Tumorigenesis and pluripotent differentiation potential might be better understood from understanding neural stemness, and cancer therapy should benefit more from targeting neural stemness.

A library of induced pluripotent stem cells from clinically well-characterized, diverse healthy human individuals

A library of well-characterized human induced pluripotent stem cell (hiPSC) lines from clinically healthy human subjects could serve as a useful resource of normal controls for in vitro human development, disease modeling, genotype-phenotype association studies, and drug response evaluation. We report generation and extensive characterization of a gender-balanced, racially/ethnically diverse library of hiPSC lines from 40 clinically healthy human individuals who range in age from 22 to 61 years. The hiPSCs match the karyotype and short tandem repeat identities of their parental fibroblasts, and have a transcription profile characteristic of pluripotent stem cells. We provide whole-genome sequencing data for one hiPSC clone from each individual, genomic ancestry determination, and analysis of mendelian disease genes and risks. We document similar transcriptomic profiles, single-cell RNA-sequencing-derived cell clusters, and physiology of cardiomyocytes differentiated from multiple independent hiPSC lines. This extensive characterization makes this hiPSC library a valuable resource for many studies on human biology.

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A library of induced pluripotent stem cells from 40 healthy human subjects

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Racially/ethnically diverse subjects of clinically well-characterized health

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Whole-genome sequencing identifies variants of mild common phenotypes or incomplete penetrance

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Similar physiology of cardiomyocytes from independent hiPSC clones and individuals

RARG variant predictive of doxorubicin-induced cardiotoxicity identifies a cardioprotective therapy

Doxorubicin is an anthracycline chemotherapy agent effective in treating a wide range of malignancies, but its use is limited by dose-dependent cardiotoxicity. A recent genome-wide association study identified a SNP (rs2229774) in retinoic acid receptor-γ (RARG) as statistically associated with increased risk of anthracycline-induced cardiotoxicity. Here, we show that human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) from patients with rs2229774 and who suffered doxorubicin-induced cardiotoxicity (DIC) are more sensitive to doxorubicin. We determine that the mechanism of this RARG variant effect is mediated via suppression of topoisomerase 2β (TOP2B) expression and activation of the cardioprotective extracellular regulated kinase (ERK) pathway. We use patient-specific hiPSC-CMs as a drug discovery platform, determining that the RARG agonist CD1530 attenuates DIC, and we confirm this cardioprotective effect in an established in vivo mouse model of DIC. This study provides a rationale for clinical prechemotherapy genetic screening for rs2229774 and a foundation for the clinical use of RARG agonist treatment to protect cancer patients from DIC.

Novel cell sources for bone regeneration

A plethora of both acute and chronic conditions, including traumatic, degenerative, malignant, or congenital disorders, commonly induce bone disorders often associated with severe persisting pain and limited mobility. Over 1 million surgical procedures involving bone excision, bone grafting, and fracture repair are performed each year in the U.S. alone, resulting in immense levels of public health challenges and corresponding financial burdens. Unfortunately, the innate self-healing capacity of bone is often inadequate for larger defects over a critical size. Moreover, as direct transplantation of committed osteoblasts is hindered by deficient cell availability, limited cell spreading, and poor survivability, an urgent need for novel cell sources for bone regeneration is concurrent. Thanks to the development in stem cell biology and cell reprogramming technology, many multipotent and pluripotent cells that manifest promising osteogenic potential are considered the regenerative remedy for bone defects. Considering these cells' investigation is still in its relative infancy, each of them offers their own particular challenges that must be conquered before the large-scale clinical application.

Regulatory considerations for developing a phase I investigational new drug application for autologous induced pluripotent stem cells-based therapy product

Induced pluripotent stem cells (iPSC)-based therapies have been hailed as the future of regenerative medicine because of their potential to provide treatment options for most degenerative diseases. A key promise of iPSC-based therapies is the possibility of an autologous transplant that may engraft better in the longer-term due to its compatibility with the patient's immune system. Despite over a decade of research, clinical translation of autologous iPSC-based therapies has been slow-partly due to a lacking pre-defined regulatory path. Here, we outline regulatory considerations for developing an autologous iPSC-based product and challenges associated with the clinical manufacturing of autologous iPSCs and their derivatives. These challenges include donor tissue source, reprogramming methods, heterogeneity of differentiated cells, controls for the manufacturing process, and preclinical considerations. A robust manufacturing process with appropriate quality controls and well-informed, prospectively designed preclinical studies provide a path toward successful approval of autologous iPSC-based therapies.

Non-immunogenic Induced Pluripotent Stem Cells, a Promising Way Forward for Allogenic Transplantations for Neurological Disorders

Neurological disorder is a general term used for diseases affecting the function of the brain and nervous system. Those include a broad range of diseases from developmental disorders (e.g., Autism) over injury related disorders (e.g., stroke and brain tumors) to age related neurodegeneration (e.g., Alzheimer's disease), affecting up to 1 billion people worldwide. For most of those disorders, no curative treatment exists leaving symptomatic treatment as the primary mean of alleviation. Human induced pluripotent stem cells (hiPSC) in combination with animal models have been instrumental to foster our understanding of underlying disease mechanisms in the brain. Of specific interest are patient derived hiPSC which allow for targeted gene editing in the cases of known mutations. Such personalized treatment would include (1) acquisition of primary cells from the patient, (2) reprogramming of those into hiPSC via non-integrative methods, (3) corrective intervention via CRISPR-Cas9 gene editing of mutations, (4) quality control to ensure successful correction and absence of off-target effects, and (5) subsequent transplantation of hiPSC or pre-differentiated precursor cells for cell replacement therapies. This would be the ideal scenario but it is time consuming and expensive. Therefore, it would be of great benefit if transplanted hiPSC could be modulated to become invisible to the recipient's immune system, avoiding graft rejection and allowing for allogenic transplantations. This review will focus on the current status of gene editing to generate non-immunogenic hiPSC and how these cells can be used to treat neurological disorders by using cell replacement therapy. By providing an overview of current limitations and challenges in stem cell replacement therapies and the treatment of neurological disorders, this review outlines how gene editing and non-immunogenic hiPSC can contribute and pave the road for new therapeutic advances. Finally, the combination of using non-immunogenic hiPSC and in vivo animal modeling will highlight the importance of models with translational value for safety efficacy testing; before embarking on human trials.

Alagille Syndrome: Diagnostic Challenges and Advances in Management

Alagille syndrome (ALGS) is a multisystem disease characterized by cholestasis and bile duct paucity on liver biopsy in addition to variable involvement of the heart, eyes, skeleton, face, kidneys, and vasculature. The identification of JAG1 and NOTCH2 as disease-causing genes has deepened our understanding of the molecular mechanisms underlying ALGS. However, the variable expressivity of the clinical phenotype and the lack of genotype-phenotype relationships creates significant diagnostic and therapeutic challenges. In this review, we provide a comprehensive overview of the clinical characteristics and management of ALGS, and the molecular basis of ALGS pathobiology. We further describe unique diagnostic considerations that pose challenges to clinicians and outline therapeutic concepts and treatment targets that may be available in the near future.

Modeling HIV-1 neuropathogenesis using three-dimensional human brain organoids (hBORGs) with HIV-1 infected microglia

HIV-1 associated neurocognitive disorder (HAND) is characterized by neuroinflammation and glial activation that, together with the release of viral proteins, trigger a pathogenic cascade resulting in synaptodendritic damage and neurodegeneration that lead to cognitive impairment. However, the molecular events underlying HIV neuropathogenesis remain elusive, mainly due to lack of brain-representative experimental systems to study HIV-CNS pathology. To fill this gap, we developed a three-dimensional (3D) human brain organoid (hBORG) model containing major cell types important for HIV-1 neuropathogenesis; neurons and astrocytes along with incorporation of HIV-infected microglia. Both infected and uninfected microglia infiltrated into hBORGs resulting in a triculture system (MG-hBORG) that mirrors the multicellular network observed in HIV-infected human brain. Moreover, the MG-hBORG model supported productive viral infection and exhibited increased inflammatory response by HIV-infected MG-hBORGs, releasing tumor necrosis factor (TNF-α) and interleukin-1 (IL-1β) and thereby mimicking the chronic neuroinflammatory environment observed in HIV-infected individuals. This model offers great promise for basic understanding of how HIV-1 infection alters the CNS compartment and induces pathological changes, paving the way for discovery of biomarkers and new therapeutic targets.

Using High-Content Screening to Generate Single-Cell Gene-Corrected Patient-Derived iPS Clones Reveals Excess Alpha-Synuclein with Familial Parkinson's Disease Point Mutation A30P

The generation of isogenic induced pluripotent stem cell (iPSC) lines using CRISPR-Cas9 technology is a technically challenging, time-consuming process with variable efficiency. Here we use fluorescence-activated cell sorting (FACS) to sort biallelic CRISPR-Cas9 edited single-cell iPSC clones into high-throughput 96-well microtiter plates. We used high-content screening (HCS) technology and generated an in-house developed algorithm to select the correctly edited isogenic clones for continued expansion and validation. In our model we have gene-corrected the iPSCs of a Parkinson’s disease (PD) patient carrying the autosomal dominantly inherited heterozygous c.88G>C mutation in the SNCA gene, which leads to the pathogenic p.A30P form of the alpha-synuclein protein. Undertaking a PCR restriction-digest mediated clonal selection strategy prior to sequencing, we were able to post-sort validate each isogenic clone using a quadruple screening strategy prior to generating footprint-free isogenic iPSC lines, retaining a normal molecular karyotype, pluripotency and three germ-layer differentiation potential. Directed differentiation into midbrain dopaminergic neurons revealed that SNCA expression is reduced in the gene-corrected clones, which was validated by a reduction at the alpha-synuclein protein level. The generation of single-cell isogenic clones facilitates new insights in the role of alpha-synuclein in PD and furthermore is applicable across patient-derived disease models.

Selective elimination of human pluripotent stem cells by Anti-Dsg2 antibody-doxorubicin conjugates

The self-renewal properties of human pluripotent stem cells (hPSCs) contribute to their efficacy in tissue regeneration applications yet increase the likelihood of teratoma formation, thereby limiting their clinical utility. To address this issue, we developed a tool to specifically target and neutralize undifferentiated hPSCs, thereby minimizing tumorigenicity risk without negatively affecting regenerated and somatic tissues. Specifically, we conjugated a monoclonal antibody (K6-1) previously generated in our laboratory against desmoglein 2 (Dsg2), which is highly differentially expressed in undifferentiated hPSCs versus somatic tissues, to the chemotherapeutic agent doxorubicin (DOX). The K6-1-DOX conjugates were selectively targeted and incorporated into Dsg2-positive hPSCs, leading to pH-dependent endosomal release and nuclear localization of DOX with subsequent cytotoxicity via an apoptotic caspase cascade. Conversely, Dsg2-negative fibroblasts showed minimal conjugate uptake or cytotoxicity, suggesting that K6-1-DOX treatment would yield few side effects owing to off-target effects. Selective removal of undifferentiated stem cells was also supported by in vivo studies using a mouse xenograft model, wherein hIgG-DOX- but not K6-1-DOX-pretreated-hPSC injection led to teratoma development. Together, these results validated the ability of the Dsg2-targeted antibody-anticancer drug conjugate to facilitate the safety of stem cell therapies.

Stem cell therapies for retinal diseases: from bench to bedside

As the human retina has no regenerative ability, stem cell interventions represent potential therapies for various blinding retinal diseases. This type of therapy has been extensively studied in the human eyes through decades of preclinical studies. The safety profiles shown in clinical trials thus far have indicated that these strategies should be further explored. There are still challenges with regard to cell source, cell delivery, immuno-related adverse events and long-term maintenance of the therapeutic effects. Retinal stem cell therapy is likely to be most successful with a combination of multiple technologies, such as gene therapy. The purpose of this review is to present a synthetical and systematic coverage of stem cell therapies that target retinal diseases from bench to bedside, intending to appeal to both junior specialists and the broader community of clinical investigators alike. This review will only focus on therapies that have already been studied in clinical trials. This review summarizes key concepts, highlights the main studies in human patients and discusses the current challenges and potential methods to reduce safety concerns while enhancing the therapeutic effects.

Liver Buds and Liver Organoids: New Tools for Liver Development, Disease and Medical Application

The current understanding and effective treatment of liver disease is far from satisfactory. Liver organoids and liver buds (LBs) transforming cell culture from two dimensions(2D) to three dimensions(3D) has provided infinite possibilities for stem cells to use in clinic. Recent technological advances in the 3D culture have shown the potentiality of liver organoids and LBs as the promising tool to model in vitro liver diseases. The induced LBs and liver organoids provide a platform for cell-based therapy, liver disease models, liver organogenesis and drugs screening. And its genetic heterogeneity supplies a way for the realization of precision medicine.

DLL4 restores damaged liver by enhancing hBMSC differentiation into cholangiocytes

BACKGROUND & AIMS

Biliary injury is one of the main pathological mechanisms of fulminant hepatic failure (FHF). Delta-like ligand 4 (DLL4)-mediated Notch activation contributes to reversing biliary injury; however, the specific role of DLL4 in biliary restoration is still unclear. This study aimed to determine whether human bone marrow mesenchymal stem cells (hBMSCs) can differentiate into biliary epithelial cells (cholangiocytes) in vitro and in vivo and to clarify the role of DLL4 in restoring damaged liver by enhancing cholangiocyte differentiation.

METHODS

hBMSCs were transplanted into immunodeficient mice (FRGS) with FHF induced by the hamster-anti-mouse CD95 antibody JO2. The appearance of human cholangiocytes was evaluated in the generated hBMSC-FRGS mice by q-PCR expression, flow cytometry and immunohistochemistry. The potency of DLL4 in inducing cholangiocyte differentiation from hBMSCs was assessed by observing the cell morphology and measuring the expression of cholangiocyte-specific genes and proteins.

RESULTS

Human KRT19- and KRT7-double-positive cholangiocyte-like cells appeared in hBMSC-FRGS mice at 12 weeks after transplantation. After these cells were separated and collected by fluorescent-activated cell sorting (FACS), there were high levels of expression of eight typical human cholangiocyte-specific genes and proteins (e.g., KRT19 and KRT7). Furthermore, hBMSC-derived cholangiocytes induced by DLL4 had a better shape with higher nucleus/cytoplasm ratios and showed a specific increase in the expression of cholangiocyte-specific genes and proteins (e.g., KRT19, KRT7, SOX9 and CFTR).

CONCLUSIONS

Cholangiocytes can be efficiently differentiated from hBMSCs in vivo and in vitro. DLL4 restores damaged liver by enhancing cholangiocyte differentiation from hBMSCs and has the potential to be used in future clinical therapeutic applications.

Ultra-High-Frequency Reprogramming of Individual Long-Term Hematopoietic Stem Cells Yields Low Somatic Variant Induced Pluripotent Stem Cells

Efficiency of reprogramming of human cells into induced pluripotent stem cells (iPSCs) has remained low. We report that individual adult human CD49f⁺ long-term hematopoietic stem cells (LT-HSCs) can be reprogrammed into iPSCs at close to 50% efficiency using Sendai virus transduction. This exquisite sensitivity to reprogramming is specific to LT-HSCs, since it progressively decreases in committed progenitors. LT-HSC reprogramming can follow multiple paths and is most efficient when transduction is performed after the cells have exited G₀. Sequencing of 75 paired skin fibroblasts/LT-HSC samples collected from nine individuals revealed that LT-HSCs contain a lower load of somatic single-nucleotide variants (SNVs) and indels than skin fibroblasts and accumulate about 12 SNVs/year. Mutation analysis revealed that LT-HSCs and fibroblasts have very different somatic mutation signatures and that somatic mutations in iPSCs generally exist prior to reprogramming. LT-HSCs may become the preferred cell source for the production of clinical-grade iPSCs.

Wang et al. show that single adult human long-term hematopoietic stem cells can be reprogrammed into induced pluripotent stem cells at close to 50% efficiency and contain fewer somatic single-nucleotide variants and indels than skin fibroblasts. They may become the preferred source for the production of clinical-grade iPSCs.

Genomic integrity of human induced pluripotent stem cells across nine studies in the NHLBI NextGen program

Human induced pluripotent stem cell (hiPSC) lines have previously been generated through the NHLBI sponsored NextGen program at nine individual study sites. Here, we examined the structural integrity of 506 hiPSC lines as determined by copy number variations (CNVs). We observed that 149 hiPSC lines acquired 258 CNVs relative to donor DNA. We identified six recurrent regions of CNVs on chromosomes 1, 2, 3, 16 and 20 that overlapped with cancer associated genes. Furthermore, the genes mapping to regions of acquired CNVs show an enrichment in cancer related biological processes (IL6 production) and signaling cascades (JNK cascade & NFκB cascade). The genomic region of instability on chr20 (chr20q11.2) includes transcriptomic signatures for cancer associated genes such as ID1, BCL2L1, TPX2, PDRG1 and HCK. Of these HCK shows statistically significant differential expression between carrier and non-carrier hiPSC lines. Overall, while a low level of genomic instability was observed in the NextGen generated hiPSC lines, the observation of structural instability in regions with known cancer associated genes substantiates the importance of systematic evaluation of genetic variations in hiPSCs before using them as disease/research models.

Induced pluripotent stem cells and derivative photoreceptor precursors as therapeutic cells for retinal degenerations

The visual impairment associated with inherited retinal degeneration and age-related degeneration of photoreceptors is causing substantial challenges in finding effective therapies. However, induced pluripotent stem cell (iPSC)-derived therapeutic cells such as photoreceptor and retinal pigment epithelium (RPE) cells provide the ultimate options in the rescue of lost photoreceptors to improve the visual function in end-stage degeneration. Retinal cells derived from iPSC are therapeutic cells that could be promising in the field of cell replacement therapy and regenerative medicine. This review presents an overview of the photoreceptor degeneration, methods of iPSC generation, iPSC in retinal disease modeling, summarizes the photoreceptor differentiation protocols, and challenges remained with photoreceptor cell replacement for the treatment of retinal diseases. Thus, the burden and increased incidence of visual impairment emphasizes the need of novel therapy, where iPSC-derived photoreceptor and RPE cells proved to be promising for curing the retinal dysfunction and act as renovation in approach to improve visual function.

Clinical application of stem cell in patients with end-stage liver disease: progress and challenges

End-stage liver disease (ESLD) is life-threatening disease worldwide, and patients with ESLD should be referred to liver transplantation (LT). However, the use of LT is limited by the lacking liver source, high cost and organ rejection. Thus, other alternative options have been explored. Stem cell therapy may be a potential alternative for ESLD treatment. With the potential of self-renewal and differentiation, both hepatic and extrahepatic stem cells have attracted a lot of attention. Among them, multipotent stem cells are most widely studies owing to their characteristics. Multipotent stem cells mainly consist of two subpopulations: hematopoietic stem cells (HSCs) and mesenchymal stem cells (MSCs). Accumulating evidences have proved that either bone marrow (BM)-derived HSCs mobilized by granulocyte colony-stimulating factor or MSCs transplantation can improve the biochemical indicators of patients with ESLD. However, there are some challenges to be resolved before stem cells widely used in clinic, including the best stem cell source, the optimal route for stem cells transplantation, and the dose and frequency of stem cell injected. The purpose of this review is to discuss the potential of stem cell in liver diseases, particularly, the clinical progress and challenges of multipotent stem cells in the field of ESLD.

Modeling Leukemia with Human Induced Pluripotent Stem Cells

The reprogramming of human somatic cells into induced pluripotent stem cells (iPSCs) a little over a decade ago raised exciting prospects to transform the study and potentially also the therapy of human diseases. iPSC models have now been created for a multitude of hematologic diseases, including malignancies. Here we discuss practical aspects of iPSC modeling of malignant diseases, review recent studies, and discuss the new opportunities that iPSC models offer, as well as their current limitations and prospects for future development.

Tissue inhibitor of metalloproteinase proteins inhibit teratoma growth in mice transplanted with pluripotent stem cells

Pluripotent stem cells (PSCs) can serve as an unlimited cell source for transplantation therapies for treating various devastating diseases, such as cardiovascular diseases, diabetes, and Parkinson's disease. However, PSC transplantation has some associated risks, including teratoma formation from the remaining undifferentiated PSCs. Thus, for successful clinical application, it is essential to ablate the proliferative PSCs before or after transplantation. In this study, neural stem cell-derived conditioned medium (NSC-CM) inhibited the proliferation of PSCs and PSC-derived neural precursor (NP) cells without influencing the potential of PSC-NP cells to differentiate into neurons in vitro and prevented teratoma growth in vivo. Moreover, we found that the NSC-CM remarkably decreased the expression levels of Oct4 and cyclin D1 that Oct4 directly binds to and increased the cleaved-caspase 3-positive cell death through the DNA damage response in PSCs and PSC-NPs. Interestingly, we found that NSCs distinctly secreted the tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 proteins. These proteins suppressed not only the proliferation of PSCs in cell culture but also teratoma growth in mice transplanted with PSCs through inhibition of matrix metalloproteinase (MMP)-2 and MMP-9 activity. Taken together, these results suggest that the TIMP proteins may improve the efficacy and safety of the PSC-based transplantation therapy.

Modeling blood diseases with human induced pluripotent stem cells

Induced pluripotent stem cells (iPSCs) are derived from somatic cells through a reprogramming process, which converts them to a pluripotent state, akin to that of embryonic stem cells. Over the past decade, iPSC models have found increasing applications in the study of human diseases, with blood disorders featuring prominently. Here, we discuss methodological aspects pertaining to iPSC generation, hematopoietic differentiation and gene editing, and provide an overview of uses of iPSCs in modeling the cell and gene therapy of inherited genetic blood disorders, as well as their more recent use as models of myeloid malignancies. We also discuss the strengths and limitations of iPSCs compared to model organisms and other cellular systems commonly used in hematology research.

Generation and comprehensive characterization of induced pluripotent stem cells for translational research

Induced pluripotent stem cells (iPSCs) hold immense potential in disease modeling, drug discovery and regenerative medicine. Despite advances in reprogramming methods, generation of clinical-grade iPSCs remains a challenge. Reported here is the first off-the-shelf reprogramming kit, CTS CytoTune-iPS 2.1, specifically designed for clinical and translational research. Workflow gaps were identified, and methods developed were used to consistently generate iPSC from multiple cell types. Resulting clones were subjected to characterization that included confirmation of pluripotency, preservation of genomic integrity and authentication of cell banks via an array of molecular methods including high resolution microarray and next-generation sequencing. Development of integrated xeno-free workflows combined with comprehensive characterization offers generation of high-quality iPSCs that are suited for clinical and translational research.

Characterization of new variant human ES line VH9 hESC (INSTEMe001-a): a tool for human stem cell and cancer research

Human pluripotent stem cells (hPSCs) acquire changes at the genomic level upon proliferation and differentiation (Peterson and Loring, 2014). Studies from International Stem Cell Initiative and independent laboratories identified a copy number variant (CNV) in hES cell lines displaying a normal karyotype, which provided a selective advantage to hES cells in culture. In our laboratory we have identified variant H9-hESC (derived from H9-hESC) with normal karyotype, pluripotency expression, differentiation profile but with altered traits of high cell survival and low E-CADHERIN expression.

Organoids of liver diseases: From bench to bedside

Understanding the occurrence, development, and treatment of liver diseases is the main goal of hepatopathology research. Liver diseases are not only diverse but also highly heterogeneous among individuals. At present, research on liver diseases is conducted mainly through cell culture, animal models, pathological specimens, etc. However, these methods cannot fully reveal the pathogenic mechanism and therapeutic characteristics of individualized liver diseases. Recent advances in three-dimensional cell culture technology (organoid culture techniques) include pluripotent stem cells and adult stem cells that are cultured in vitro to form self-organizing properties, making it possible to achieve individualized liver disease research. This review provides a comprehensive overview of the development of liver organoids, the existing and potential applications of liver regenerative medicine, the pathogenesis of liver disease heterogeneity, and drug screening.

iPS-Cell Technology and the Problem of Genetic Instability-Can It Ever Be Safe for Clinical Use?

The use of induced Pluripotent Stem Cells (iPSC) as a source of autologous tissues shows great promise in regenerative medicine. Nevertheless, several major challenges remain to be addressed before iPSC-derived cells can be used in therapy, and experience of their clinical use is extremely limited. In this review, the factors affecting the safe translation of iPSC to the clinic are considered, together with an account of efforts being made to overcome these issues. The review draws upon experiences with pluripotent stem-cell therapeutics, including clinical trials involving human embryonic stem cells and the widely transplanted mesenchymal stem cells. The discussion covers concerns relating to: (i) the reprogramming process; (ii) the detection and removal of incompletely differentiated and pluripotent cells from the resulting medicinal products; and (iii) genomic and epigenetic changes, and the evolutionary and selective processes occurring during culture expansion, associated with production of iPSC-therapeutics. In addition, (iv) methods for the practical culture-at-scale and standardization required for routine clinical use are considered. Finally, (v) the potential of iPSC in the treatment of human disease is evaluated in the light of what is known about the reprogramming process, the behavior of cells in culture, and the performance of iPSC in pre-clinical studies.

The Genomic Health of Human Pluripotent Stem Cells: Genomic Instability and the Consequences on Nuclear Organization

Human pluripotent stem cells (hPSCs) are increasingly used for cell-based regenerative therapies worldwide, with embryonic and induced pluripotent stem cells as potential treatments for debilitating and chronic conditions, such as age-related macular degeneration, Parkinson's disease, spinal cord injuries, and type 1 diabetes. However, with the level of genomic anomalies stem cells generate in culture, their safety may be in question. Specifically, hPSCs frequently acquire chromosomal abnormalities, often with gains or losses of whole chromosomes. This review discusses how important it is to efficiently and sensitively detect hPSC aneuploidies, to understand how these aneuploidies arise, consider the consequences for the cell, and indeed the individual to whom aneuploid cells may be administered.

Utility of Induced Pluripotent Stem Cell-Derived Retinal Pigment Epithelium for an In Vitro Model of Proliferative Vitreoretinopathy

The advent of stem cell technology, including the technology to induce pluripotency in somatic cells, and direct differentiation of stem cells into specific somatic cell types, has created an exciting new field of scientific research. Much of the work with pluripotent stem (PS) cells has been focused on the exploration and exploitation of their potential as cells/tissue replacement therapies for personalized medicine. However, PS and stem cell-derived somatic cells are also proving to be valuable tools to study disease pathology and tissue-specific responses to injury. High-throughput drug screening assays using tissue-specific injury models have the potential to identify specific and effective treatments that will promote wound healing. Retinal pigment epithelium (RPE) derived from induced pluripotent stem cells (iPS-RPE) are well characterized cells that exhibit the phenotype and functions of in vivo RPE. In addition to their role as a source of cells to replace damaged or diseased RPE, iPS-RPE provide a robust platform for in vitro drug screening to identify novel therapeutics to promote healing and repair of ocular tissues after injury. Proliferative vitreoretinopathy (PVR) is an abnormal wound healing process that occurs after retinal tears or detachments. In this chapter, the role of iPS-RPE in the development of an in vitro model of PVR is described. Comprehensive analyses of the iPS-RPE response to injury suggests that these cells provide a physiologically relevant tool to investigate the cellular mechanisms of the three phases of PVR pathology: migration, proliferation, and contraction. This in vitro model will provide valuable information regarding cellular wound healing responses specific to RPE and enable the identification of effective therapeutics.

Virus-free and oncogene-free induced pluripotent stem cell reprogramming in cord blood and peripheral blood in patients with lung disease

AIM

A virus- and oncogene-free induced pluripotent stem cell (iPSC) reprogramming method was developed with cord blood-derived mononuclear cells (CBDMNC) and peripheral blood mononuclear cells (PBMNC) from patients with genetic lung diseases.

METHOD

iPSC reprogramming used small molecules, hematopoietic stem cell (HSC) expansion media and episomal vectors that lacked Myc and Lin28.

RESULTS

All iPSC colonies were fully reprogrammed based on SSEA4 expression. A total of 300,000 CBDMNC was the optimal cell number for cell reprogramming, which was associated with a 13-fold increase in CD34+ cells upon exposure to HSC media. Cell reprogramming was not observed in the absence of HSC expansion media. The method also reprogrammed PBMNC in patients with cystic fibrosis or α-1 antitrypsin deficiency. Oncogene-free iPSC cell lines differentiated into all three germ cell lineages.

CONCLUSION

This iPSC reprogramming approach satisfies an important regulatory requirement for iPSC-based cell therapies with lower clinical risk from CBDMNC and PBMNC.

Potential Strategies to Address the Major Clinical Barriers Facing Stem Cell Regenerative Therapy for Cardiovascular Disease: A Review

Importance

Although progress continues to be made in the field of stem cell regenerative medicine for the treatment of cardiovascular disease, significant barriers to clinical implementation still exist.

Objectives

To summarize the current barriers to the clinical implementation of stem cell therapy in patients with cardiovascular disease and to discuss potential strategies to overcome them.

Evidence Review

Information for this review was obtained through a search of PubMed and the Cochrane database for English-language studies published between January 1, 2000, and July 25, 2016. Ten randomized clinical trials and 8 systematic reviews were included.

Findings

One of the major clinical barriers facing the routine implementation of stem cell therapy in patients with cardiovascular disease is the limited and inconsistent benefit observed thus far. Reasons for this finding are unclear but may be owing to poor cell retention and survival, as suggested by numerous preclinical studies and a small number of human studies incorporating imaging to determine cell fate. Additional studies in humans using imaging to determine cell fate are needed to understand how these factors contribute to the limited efficacy of stem cell therapy. Treatment strategies to address poor cell retention and survival are under investigation and include the following: coadministration of immunosuppressive and prosurvival agents, delivery of cardioprotective factors packaged in exosomes rather than the cells themselves, and use of tissue-engineering strategies to provide structural support for cells. If larger grafts are achieved using these strategies, it will be imperative to carefully monitor for the potential risks of tumorigenicity, immunogenicity, and arrhythmogenicity.

Conclusions and Relevance

Despite important achievements to date, stem cell therapy is not yet ready for routine clinical implementation. Significant research is still needed to address the clinical barriers outlined herein before the next wave of large clinical trials is under way.

Parkinson's disease: what the model systems have taught us so far

Parkinson's disease (PD) is a debilitating neurodegenerative disorder, for which people above the age of 60 show an increased risk. Although there has been great advancement in understanding the disease-related abnormalities in brain circuitry and development of symptomatic treatments, a cure for PD remains elusive. The discovery of PD associated gene mutations and environmental toxins have yielded animal models of the disease. These models could recapitulate several key aspects of PD, and provide more insights into the disease pathogenesis. They have also revealed novel aspects of the disease mechanism including noncell autonomous events and spreading of pathogenic protein species across the brain. Nevertheless, none of these models so far can comprehensively represent all aspects of the human disease. While the field is still searching for the perfect model system, recent developments in stem cell biology have provided a new dimension to modelling PD, especially doing it in a patient-specific manner. In the current review, we attempt to summarize the key findings in the areas discussed above, and highlight how the core PD pathology distinguishes itself from other neurodegenerative disorders while also resembling them in many aspects.

Concise Review: The Regenerative Journey of Pericytes Toward Clinical Translation

Coronary artery disease (CAD) is the single leading cause of death worldwide. Advances in treatment and management have significantly improved patient outcomes. On the other hand, although mortality rates have decreased, more people are left with sequelae that require additional treatment and hospitalization. Moreover, patients with severe nonrevascularizable CAD remain with only the option of heart transplantation, which is limited by the shortage of suitable donors. In recent years, cell-based regenerative therapy has emerged as a possible alternative treatment, with several regenerative medicinal products already in the clinical phase of development and others emerging as competitive preclinical solutions. Recent evidence indicates that pericytes, the mural cells of blood microvessels, represent a promising therapeutic candidate. Pericytes are abundant in the human body, play an active role in angiogenesis, vessel stabilization and blood flow regulation, and possess the capacity to differentiate into multiple cells of the mesenchymal lineage. Moreover, early studies suggest a robustness to hypoxic insult, making them uniquely equipped to withstand the ischemic microenvironment. This review summarizes the rationale behind pericyte-based cell therapy and the progress that has been made toward its clinical application. We present the different sources of pericytes and the case for harvesting them from tissue leftovers of cardiovascular surgery. We also discuss the healing potential of pericytes in preclinical animal models of myocardial ischemia (MI) and current practices to upgrade the production protocol for translation to the clinic. Standardization of these procedures is of utmost importance, as lack of uniformity in cell manufacturing may influence clinical outcome. Stem Cells 2018;36:1295-1310.

A Scaled Framework for CRISPR Editing of Human Pluripotent Stem Cells to Study Psychiatric Disease

Scaling of CRISPR-Cas9 technology in human pluripotent stem cells (hPSCs) represents an important step for modeling complex disease and developing drug screens in human cells. However, variables affecting the scaling efficiency of gene editing in hPSCs remain poorly understood. Here, we report a standardized CRISPR-Cas9 approach, with robust benchmarking at each step, to successfully target and genotype a set of psychiatric disease-implicated genes in hPSCs and provide a resource of edited hPSC lines for six of these genes. We found that transcriptional state and nucleosome positioning around targeted loci was not correlated with editing efficiency. However, editing frequencies varied between different hPSC lines and correlated with genomic stability, underscoring the need for careful cell line selection and unbiased assessments of genomic integrity. Together, our step-by-step quantification and in-depth analyses provide an experimental roadmap for scaling Cas9-mediated editing in hPSCs to study psychiatric disease, with broader applicability for other polygenic diseases.

Pluripotent stem cell-based therapy for Parkinson's disease: Current status and future prospects

Parkinson's disease (PD) is one of the most common neurodegenerative disorders, which affects about 0.3% of the general population. As the population in the developed world ages, this creates an escalating burden on society both in economic terms and in quality of life for these patients and for the families that support them. Although currently available pharmacological or surgical treatments may significantly improve the quality of life of many patients with PD, these are symptomatic treatments that do not slow or stop the progressive course of the disease. Because motor impairments in PD largely result from loss of midbrain dopamine neurons in the substantia nigra pars compacta, PD has long been considered to be one of the most promising target diseases for cell-based therapy. Indeed, numerous clinical and preclinical studies using fetal cell transplantation have provided proof of concept that cell replacement therapy may be a viable therapeutic approach for PD. However, the use of human fetal cells as a standardized therapeutic regimen has been fraught with fundamental ethical, practical, and clinical issues, prompting scientists to explore alternative cell sources. Based on groundbreaking establishments of human embryonic stem cells and induced pluripotent stem cells, these human pluripotent stem cells have been the subject of extensive research, leading to tremendous advancement in our understanding of these novel classes of stem cells and promising great potential for regenerative medicine. In this review, we discuss the prospects and challenges of human pluripotent stem cell-based cell therapy for PD.

Human dental stem cell derived transgene-free iPSCs generate functional neurons via embryoid body-mediated and direct induction methods

Induced pluripotent stem cells (iPSCs) give rise to neural stem/progenitor cells, serving as a good source for neural regeneration. Here, we established transgene-free (TF) iPSCs from dental stem cells (DSCs) and determined their capacity to differentiate into functional neurons in vitro. Generated TF iPSCs from stem cells of apical papilla and dental pulp stem cells underwent two methods-embryoid body-mediated and direct induction, to guide TF-DSC iPSCs along with H9 or H9 Syn-GFP (human embryonic stem cells) into functional neurons in vitro. Using the embryoid body-mediated method, early stage neural markers PAX6, SOX1, and nestin were detected by immunocytofluorescence or reverse transcription-real time polymerase chain reaction (RT-qPCR). At late stage of neural induction measured at Weeks 7 and 9, the expression levels of neuron-specific markers Nav1.6, Kv1.4, Kv4.2, synapsin, SNAP25, PSD95, GAD67, GAP43, and NSE varied between stem cells of apical papilla iPSCs and H9. For direct induction method, iPSCs were directly induced into neural stem/progenitor cells and guided to become neuron-like cells. The direct method, while simpler, showed cell detachment and death during the differentiation process. At early stage, PAX6, SOX1 and nestin were detected. At late stage of differentiation, all five genes tested, nestin, βIII-tubulin, neurofilament medium chain, GFAP, and Nav, were positive in many cells in cultures. Both differentiation methods led to neuron-like cells in cultures exhibiting sodium and potassium currents, action potential, or spontaneous excitatory postsynaptic potential. Thus, TF-DSC iPSCs are capable of undergoing guided neurogenic differentiation into functional neurons in vitro, thereby may serve as a cell source for neural regeneration.

Generation of functional cardiomyocytes from rat embryonic and induced pluripotent stem cells using feeder-free expansion and differentiation in suspension culture

The possibility to generate cardiomyocytes from pluripotent stem cells in vitro has enormous significance for basic research, disease modeling, drug development and heart repair. The concept of heart muscle reconstruction has been studied and optimized in the rat model using rat primary cardiovascular cells or xenogeneic pluripotent stem cell derived-cardiomyocytes for years. However, the lack of rat pluripotent stem cells (rPSCs) and their cardiovascular derivatives prevented the establishment of an authentic clinically relevant syngeneic or allogeneic rat heart regeneration model. In this study, we comparatively explored the potential of recently available rat embryonic stem cells (rESCs) and induced pluripotent stem cells (riPSCs) as a source for cardiomyocytes (CMs). We developed feeder cell-free culture conditions facilitating the expansion of undifferentiated rPSCs and initiated cardiac differentiation by embryoid body (EB)-formation in agarose microwell arrays, which substituted the robust but labor-intensive hanging drop (HD) method. Ascorbic acid was identified as an efficient enhancer of cardiac differentiation in both rPSC types by significantly increasing the number of beating EBs (3.6 ± 1.6-fold for rESCs and 17.6 ± 3.2-fold for riPSCs). These optimizations resulted in a differentiation efficiency of up to 20% cTnT^pos rPSC-derived CMs. CMs showed spontaneous contractions, expressed cardiac markers and had typical morphological features. Electrophysiology of riPSC-CMs revealed different cardiac subtypes and physiological responses to cardio-active drugs. In conclusion, we describe rPSCs as a robust source of CMs, which is a prerequisite for detailed preclinical studies of myocardial reconstruction in a physiologically and immunologically relevant small animal model.

Human iPSC-Derived Posterior Gut Progenitors Are Expandable and Capable of Forming Gut and Liver Organoids

Early endoderm progenitors naturally possess robust propagating potential to develop a majority of meter-long gastrointestinal tracts and are therefore considered as a promising source for therapy. Here, we demonstrated the reproducible generation of human CDX2⁺ posterior gut endoderm cells (PGECs) from five induced pluripotent stem cell clones by manipulating FGF, TGF, and WNT signaling. Transcriptome analysis suggested that putative PGECs harbored an intermediate signature profile between definitive endoderm and organ-specific endoderm. We found that combinatorial EGF, VEGF, FGF2, Chir99021, and A83-01 treatments selectively amplify storable PGECs up to 10²¹ cell scale without any gene transduction or feeder use. PGECs, compared with induced pluripotent stem cells, showed stable differentiation propensity into multiple endodermal lineages without teratoma formation. Furthermore, transplantation of PGEC-derived liver bud organoids showed therapeutic potential against fulminant liver failure. Together, the robustly amplified PGECs may be a promising cellular source for endoderm-derived organoids in studying human development, modeling disease, and, ultimately, therapy.

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Successful activation of posteriorization program using human iPSC-derived endoderm

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CDX2⁺ PGECs exhibit a robust amplification potential after passaging and freezing

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PGECs with differentiation potential into hindgut and liver bud organoids

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PGEC liver bud transplant is therapeutically effective for acute liver failure