Efficient episomal reprogramming of blood mononuclear cells and differentiation to hepatocytes with functional drug metabolism

Gene delivery in adherent and suspension cells using the combined physical methods

Physical methods are widely utilized to deliver nucleic acids into cells such as electro-transfection or heat shock. An efficient gene electro-transfection requires the best conditions including voltage, the pulse length or number, buffer, incubation time and DNA form. In this study, the delivery of pEGFP-N1 vector into two adherent cell lines (HEK-293 T and COS-7) with the same origin (epithelial cells), and also mouse bone marrow-derived dendritic cells (DCs) was evaluated using electroporation under different conditions alone and along with heat treatment. Our data showed that the highest green fluorescent protein (GFP) expression in HEK-293 T and COS-7 cells was observed in serum-free RPMI cell culture medium as electroporation buffer, voltage (200 V), the pulse number (2), the pulse length (15 ms), the circular form of DNA, and 48 h after electro-transfection. In addition, the highest GFP expression in DCs was detected in serum-free RPMI, voltage (300 V), the pulse number (1), the pulse length (5 ms), and 48 h after electro-transfection. The use of sucrose as electroporation buffer, the pulse number (2), and the pulse length (25 ms) led to further cytotoxicity and lower transfection in HEK293T and COS-7 cells than other conditions. Moreover, the high voltage (700 V) increased the cell cytotoxicity, and decreased electro-transfection efficiency in DCs. On the other hand, the best conditions of electroporation along with heat treatment could significantly augment the transfection efficiency in all the cells. These data will be useful for gene delivery in other cells with the same properties using physical methods.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10616-022-00524-4.

Induced pluripotent stem cells as an innovative model to study drug induced pancreatitis

Drug-induced pancreatitis is a gastrointestinal adverse effect concerning about 2% of drugs. The majority of cases are mild to moderate but severe episodes can also occur, leading to hospitalization or even death. Unfortunately, the mechanisms of this adverse reaction are still not clear, hindering its prevention, and the majority of data available of this potentially life-threatening adverse effect are limited to case reports leading to a probable underestimation of this event. In particular, in this editorial, special attention is given to thiopurine-induced pancreatitis (TIP), an idiosyncratic adverse reaction affecting around 5% of inflammatory bowel disease (IBD) patients taking thiopurines as immunosuppressants, with a higher incidence in the pediatric population. Validated biomarkers are not available to assist clinicians in the prevention of TIP, also because of the inaccessibility of the pancreatic tissue, which limits the possibility to perform dedicated cellular and molecular studies. In this regard, induced pluripotent stem cells (iPSCs) and the exocrine pancreatic differentiated counterpart could be a great tool to investigate the cellular and molecular mechanisms underlying the development of this undesirable event. This particular type of stem cells is obtained by reprogramming adult cells, including fibroblasts and leukocytes, with a set of transcription factors known as the Yamanaka’s factors. Maintaining unaltered the donors’ genetic heritage, iPSCs represent an innovative model to study the mechanisms of adverse drug reactions in individual patients’ tissues not easily obtainable from human probands. Indeed, iPSCs can differentiate under adequate stimuli into almost any somatic lineage, opening a new world of opportunities for researchers. Several works are already available in the literature studying liver, central nervous system and cardiac cells derived from iPSCs and adverse drug effects. However, to our knowledge no studies have been performed on exocrine pancreas differentiated from iPSCs and drug-induced pancreatitis, so far. Hence, in this editorial we focus specifically on the description of the study of the mechanisms of TIP by using IBD patient-specific iPSCs and exocrine pancreatic differentiated cells as innovative in vitro models.

An iPSC model of hereditary sensory neuropathy-1 reveals L-serine-responsive deficits in neuronal ganglioside composition and axoglial interactions

Hereditary sensory neuropathy type 1 (HSN1) is caused by mutations in the SPTLC1 or SPTLC2 sub-units of the enzyme serine palmitoyltransferase, resulting in the production of toxic 1-deoxysphingolipid bases (DSBs). We used induced pluripotent stem cells (iPSCs) from patients with HSN1 to determine whether endogenous DSBs are neurotoxic, patho-mechanisms of toxicity and response to therapy. HSN1 iPSC-derived sensory neurons (iPSCdSNs) endogenously produce neurotoxic DSBs. Complex gangliosides, which are essential for membrane micro-domains and signaling, are reduced, and neurotrophin signaling is impaired, resulting in reduced neurite outgrowth. In HSN1 myelinating cocultures, we find a major disruption of nodal complex proteins after 8 weeks, which leads to complete myelin breakdown after 6 months. HSN1 iPSC models have, therefore, revealed that SPTLC1 mutation alters lipid metabolism, impairs the formation of complex gangliosides, and reduces axon and myelin stability. Many of these changes are prevented by l-serine supplementation, supporting its use as a rational therapy.

An Overview on Promising Somatic Cell Sources Utilized for the Efficient Generation of Induced Pluripotent Stem Cells

Human induced Pluripotent Stem Cells (iPSCs) have enormous potential in understanding developmental biology, disease modeling, drug discovery, and regenerative medicine. The initial human iPSC studies used fibroblasts as a starting cell source to reprogram them; however, it has been identified to be a less appealing somatic cell source by numerous studies due to various reasons. One of the important criteria to achieve efficient reprogramming is determining an appropriate starting somatic cell type to induce pluripotency since the cellular source has a major influence on the reprogramming efficiency, kinetics, and quality of iPSCs. Therefore, numerous groups have explored various somatic cell sources to identify the promising sources for reprogramming into iPSCs with different reprogramming factor combinations. This review provides an overview of promising easily accessible somatic cell sources isolated in non-invasive or minimally invasive manner such as keratinocytes, urine cells, and peripheral blood mononuclear cells used for the generation of human iPSCs derived from healthy and diseased subjects. Notably, iPSCs generated from one of these cell types derived from the patient will offer ethical and clinical advantages. In addition, these promising somatic cell sources have the potential to efficiently generate bona fide iPSCs with improved reprogramming efficiency and faster kinetics. This knowledge will help in establishing strategies for safe and efficient reprogramming and the generation of patient-specific iPSCs from these cell types.

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.

Evaluation of a Novel Plasmid for Simultaneous Gene Electrotransfer-Mediated Silencing of CD105 and CD146 in Combination with Irradiation

Targeting tumor vasculature through specific endothelial cell markers represents a promising approach for cancer treatment. Here our aim was to construct an antibiotic resistance gene-free plasmid encoding shRNAs to simultaneously target two endothelial cell markers, CD105 and CD146, and to test its functionality and therapeutic potential in vitro when delivered by gene electrotransfer (GET) and combined with irradiation (IR). Functionality of the plasmid was evaluated by determining the silencing of the targeted genes using qRT-PCR. Antiproliferative and antiangiogenic effects were determined by the cytotoxicity assay tube formation assay and wound healing assay in murine endothelial cells 2H-11. The functionality of the plasmid construct was also evaluated in malignant melanoma tumor cell line B16F10. Additionally, potential activation of immune response was measured by induction of DNA sensor STING and proinflammatory cytokines by qRT-PCR in endothelial cells 2H-11. We demonstrated that the plasmid construction was successful and can efficiently silence the expression of the two targeted genes. As a consequence of silencing, reduced migration rate and angiogenic potential was confirmed in 2H-11 endothelial cells. Furthermore, induction of DNA sensor STING and proinflammatory cytokines were determined, which could add to the therapeutic effectiveness when used in vivo. To conclude, we successfully constructed a novel plasmid DNA with two shRNAs, which holds a great promise for further in vivo testing.

Generation of three human iPSC lines from a retinitis pigmentosa family with SLC7A14 mutation

Mutation in SLC7A14 gene causes autosomal recessive retinitis pigmentosa (arRP). Here we describe the generation and characterization of human induced pluripotent stem cell (hiPSC) lines of RP patient with SLC7A14 mutation and his healthy parents. hiPSCs were derived from peripheral blood mononuclear cells (PBMCs) reprogrammed with integration-free plasmids including the reprogramming factors OCT3/4, SOX2, MYC and KLF4. All the established hiPSC lines showed normal karyotype, pluripotency and differentiation capacity.

Validation of Reference Genes for Gene Expression Studies by RT-qPCR in HepaRG Cells during Toxicity Testing and Disease Modelling

Gene expression analysis by quantitative real-time polymerase chain reaction (RT-qPCR) is routinely used in biomedical studies. The reproducibility and reliability of the data fundamentally depends on experimental design and data interpretation. Despite the wide application of this assay, there is significant variation in the validation process of gene expression data from research laboratories. Since the validity of results depends on appropriate normalisation, it is crucial to select appropriate reference gene(s), where transcription of the selected gene is unaffected by experimental setting. In this study we have applied geNorm technology to investigate the transcription of 12 ‘housekeeping’ genes for use in the normalisation of RT-qPCR data acquired using a widely accepted HepaRG hepatic cell line in studies examining models of pre-clinical drug testing. geNorm data identified a number of genes unaffected by specific drug treatments and showed that different genes remained invariant in response to different drug treatments, whereas the transcription of ‘classical’ reference genes such as GAPDH (glyceralde- hyde-3-phosphate dehydrogenase) was altered by drug treatment. Comparing data normalised using the reference genes identified by geNorm with normalisation using classical housekeeping genes demonstrated substantial differences in the final results. In light of cell therapy application, RT-qPCR analyses has to be carefully evaluated to accurately interpret data obtained from dynamic cellular models undergoing sequential stages of phenotypic change.

Induced pluripotent stem cells for therapy personalization in pediatric patients: Focus on drug-induced adverse events

Adverse drug reactions (ADRs) are major clinical problems, particularly in special populations such as pediatric patients. Indeed, ADRs may be caused by a plethora of different drugs leading, in some cases, to hospitalization, disability or even death. In addition, pediatric patients may respond differently to drugs with respect to adults and may be prone to developing different kinds of ADRs, leading, in some cases, to more severe consequences. To improve the comprehension, and thus the prevention, of ADRs, the set-up of sensitive and personalized assays is urgently needed. Important progress is represented by the possibility of setting up groundbreaking patient-specific assays. This goal has been powerfully achieved using induced pluripotent stem cells (iPSCs). Due to their genetic and physiological species-specific differences and their ability to be differentiated ideally into all tissues of the human body, this model may be accurate in predicting drug toxicity, especially when this toxicity is related to individual genetic differences. This review is an up-to-date summary of the employment of iPSCs as a model to study ADRs, with particular attention to drugs used in the pediatric field. We especially focused on the intestinal, hepatic, pancreatic, renal, cardiac, and neuronal levels, also discussing progress in organoids creation. The latter are three-dimensional in vitro culture systems derived from pluripotent or adult stem cells simulating the architecture and functionality of native organs such as the intestine, liver, pancreas, kidney, heart, and brain. Based on the existing knowledge, these models are powerful and promising tools in multiple clinical applications including toxicity screening, disease modeling, personalized and regenerative medicine.

Episomal Induced Pluripotent Stem Cells: Functional and Potential Therapeutic Applications

The term episomal induced pluripotent stem cells (EiPSCs) refers to somatic cells that are reprogrammed into induced pluripotent stem cells (iPSCs) using non-integrative episomal vector methods. This reprogramming process has a better safety profile compared with integrative methods using viruses. There is a current trend toward using episomal plasmid reprogramming to generate iPSCs because of the improved safety profile. Clinical reports of potential human cell sources that have been successfully reprogrammed into EiPSCs are increasing, but no review or summary has been published. The functional applications of EiPSCs and their potential uses in various conditions have been described, and these may be applicable to clinical scenarios. This review summarizes the current direction of EiPSC research and the properties of these cells with the aim of explaining their potential role in clinical applications and functional restoration.

Robust and highly efficient hiPSC generation from patient non-mobilized peripheral blood-derived CD34+ cells using the auto-erasable Sendai virus vector

BACKGROUND

Disease modeling with patient-derived induced pluripotent stem cells (iPSCs) is a powerful tool for elucidating the mechanisms underlying disease pathogenesis and developing safe and effective treatments. Patient peripheral blood (PB) cells are used for iPSC generation in many cases since they can be collected with minimum invasiveness. To derive iPSCs that lack immunoreceptor gene rearrangements, hematopoietic stem and progenitor cells (HSPCs) are often targeted as the reprogramming source. However, the current protocols generally require HSPC mobilization and/or ex vivo expansion owing to their sparsity at the steady state and low reprogramming efficiencies, making the overall procedure costly, laborious, and time-consuming.

METHODS

We have established a highly efficient method for generating iPSCs from non-mobilized PB-derived CD34+ HSPCs. The source PB mononuclear cells were obtained from 1 healthy donor and 15 patients and were kept frozen until the scheduled iPSC generation. CD34+ HSPC enrichment was done using immunomagnetic beads, with no ex vivo expansion culture. To reprogram the CD34+-rich cells to pluripotency, the Sendai virus vector SeVdp-302L was used to transfer four transcription factors: KLF4, OCT4, SOX2, and c-MYC. In this iPSC generation series, the reprogramming efficiencies, success rates of iPSC line establishment, and progression time were recorded. After generating the iPSC frozen stocks, the cell recovery and their residual transgenes, karyotypes, T cell receptor gene rearrangement, pluripotency markers, and differentiation capability were examined.

RESULTS

We succeeded in establishing 223 iPSC lines with high reprogramming efficiencies from 15 patients with 8 different disease types. Our method allowed the rapid appearance of primary colonies (~ 8 days), all of which were expandable under feeder-free conditions, enabling robust establishment steps with less workload. After thawing, the established iPSC lines were verified to be pluripotency marker-positive and of non-T cell origin. A majority of the iPSC lines were confirmed to be transgene-free, with normal karyotypes. Their trilineage differentiation capability was also verified in a defined in vitro assay.

CONCLUSION

This robust and highly efficient method enables the rapid and cost-effective establishment of transgene-free iPSC lines from a small volume of PB, thus facilitating the biobanking of patient-derived iPSCs and their use for the modeling of various diseases.

iPSCs: A powerful tool for skeletal muscle tissue engineering

Both volumetric muscle loss (VML) and muscle degenerative diseases lead to an important decrease in skeletal muscle mass, condition that nowadays lacks an optimal treatment. This issue has driven towards an increasing interest in new strategies in tissue engineering, an emerging field that can offer very promising approaches. In addition, the discovery of induced pluripotent stem cells (iPSCs) has completely revolutionized the actual view of personalized medicine, and their utilization in skeletal muscle tissue engineering could, undoubtedly, add myriad benefits. In this review, we want to provide a general vision of the basic aspects to consider when engineering skeletal muscle tissue using iPSCs. Specifically, we will focus on the three main pillars of tissue engineering: the scaffold designing, the selection of the ideal cell source and the addition of factors that can enhance the resemblance with the native tissue.

Induced Pluripotent Stem Cells and Their Use in Human Models of Disease and Development

The discovery of somatic cell nuclear transfer proved that somatic cells can carry the same genetic code as the zygote, and that activating parts of this code are sufficient to reprogram the cell to an early developmental state. The discovery of induced pluripotent stem cells (iPSCs) nearly half a century later provided a molecular mechanism for the reprogramming. The initial creation of iPSCs was accomplished by the ectopic expression of four specific genes (OCT4, KLF4, SOX2, and c-Myc; OSKM). iPSCs have since been acquired from a wide range of cell types and a wide range of species, suggesting a universal molecular mechanism. Furthermore, cells have been reprogrammed to iPSCs using a myriad of methods, although OSKM remains the gold standard. The sources for iPSCs are abundant compared with those for other pluripotent stem cells; thus the use of iPSCs to model the development of tissues, organs, and other systems of the body is increasing. iPSCs also, through the reprogramming of patient samples, are being used to model diseases. Moreover, in the 10 years since the first report, human iPSCs are already the basis for new cell therapies and drug discovery that have reached clinical application. In this review, we examine the generation of iPSCs and their application to disease and development.

Development and characterization of human iPSC line NCCSi004-A from umbilical cord blood (UCB) derived CD34+cells obtained from donor belonging to Indian ethnic population

Here we report the reprogramming of CD34⁺ cells obtained from UCB of a healthy donor female child belonging to the Indian ethnic population. These CD34⁺cells were subjected to nucleofection for delivery of episomal vectors expressing Oct4, Sox2, L-Myc, Lin28, Klf4 and p53DD (negative mutation in p53). The iPSC colonies expressed pluripotency markers as detected by PCR, immunofluorescence and flow-cytometry. The removal of plasmid was confirmed by its absence in cells at higher passages. Karyotype analysis revealed a stable genome. The property of in vitro differentiation to tri-lineage was confirmed by expression of markers by immunofluorescence.

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.

Engineering the niche for hair regeneration - A critical review

Recent progress in hair follicle regeneration and alopecia treatment necessitates revisiting the concepts and approaches. In this sense, there is a need for shedding light on the clinical and surgical therapies benefitting from nanobiomedicine. From this perspective, this review attempts to recognize requirements upon which new hair therapies are grounded; to underline shortcomings and opportunities associated with recent advanced strategies for hair regeneration; and most critically to look over hair regeneration from nanomaterials and pluripotent stem cell standpoint. It is noteworthy that nanotechnology is able to illuminate a novel path for reprogramming cells and controlled differentiation to achieve the desired performance. Undoubtedly, this strategy needs further advancement and a lot of critical questions have yet to be answered. Herein, we introduce the salient features, the hurdles that must be overcome, the hopes, and practical constraints to engineer stem cell niches for hair follicle regeneration.

Current Progress in Electrotransfection as a Nonviral Method for Gene Delivery

Electrotransfection (ET) is a nonviral method for delivery of various types of molecules into cells both in vitro and in vivo. Close to 90 clinical trials that involve the use of ET have been performed, and approximately half of them are related to cancer treatment. Particularly, ET is an attractive technique for cancer immunogene therapy because treatment of cells with electric pulses alone can induce immune responses to solid tumors, and the responses can be further enhanced by ET of plasmid DNA (pDNA) encoding therapeutic genes. Compared to other gene delivery methods, ET has several unique advantages. It is relatively inexpensive, flexible, and safe in clinical applications, and introduces only naked pDNA into cells without the use of additional chemicals or viruses. However, the efficiency of ET is still low, partly because biological mechanisms of ET in cells remain elusive. In previous studies, it was believed that pDNA entered the cells through transient pores created by electric pulses. As a result, the technique is commonly referred to as electroporation. However, recent discoveries have suggested that endocytosis plays an important role in cellular uptake and intracellular transport of electrotransfected pDNA. This review will discuss current progresses in the study of biological mechanisms underlying ET and future directions of research in this area. Understanding the mechanisms of pDNA transport in cells is critical for the development of new strategies for improving the efficiency of gene delivery in tumors.

Antitumor in situ vaccination effect of TNFα and IL-12 plasmid DNA electrotransfer in a murine melanoma model

Gene electrotransfer (GET) is one of the most efficient non-viral gene therapy approaches for the localized transfer of multiple genes into tumors in vivo; therefore, it is especially promising for delivering different cytokines that are toxic if administered systemically. In this study, we used concomitant intratumoral GET of two cytokines: tumor necrosis factor alpha (TNFα), a potent cytotoxic cytokine to induce in situ vaccination, and interleukin 12 (IL-12), an immunostimulatory cytokine to boost the primed local immune response into a systemic one. After performing GET in murine melanoma tumors, both TNFα and IL-12 mRNA levels were significantly increased, which resulted in a pronounced delay in tumor growth of 27 days and a prolonged survival time of mice. An antitumor immune response was confirmed by extensive infiltration of immune cells in the tumor site, and expansion of the effector immune cells in the sentinel lymph nodes. Furthermore, the effect of in situ vaccination was indicated by the presence of vitiligo localized to the treatment area and resistance of the mice to secondary challenge with tumor cells. Intratumoral GET of two cytokines, one for in situ vaccination and one for an immune boost, proved feasible and effective in eliciting a potent and durable antitumor response; therefore, further studies of this approach are warranted.

Derivation of human iPSC line NCCSi002-A from umbilical cord blood (UCB) CD34+cells of donor from Indian ethnicity

We discuss the reprogramming of CD34⁺ cells isolated from UCB of a healthy female child of Indian ethnicity. The CD34⁺cells were nucleofected using episomal vectors expressing Oct4, Sox2, L-Myc, Klf4, Lin28 and p53DD (negative mutation in p53). The colonies were stained for alkaline phosphatase and evaluated for pluripotency marker expression by PCR, immunofluorescence and flow-cytometry. The safety of cells was confirmed by absence of plasmid in subsequent passages by PCR. G-banded karyotype demonstrated a stable genome. The ability of tri-lineage differentiation was confirmed by specific marker expression by immunofluorescence invitro and teratoma formation invivo.

Hepatic differentiation of human iPSCs in different 3D models: A comparative study

Human induced pluripotent stem cells (hiPSCs) are a promising source from which to derive distinct somatic cell types for in vitro or clinical use. Existent protocols for hepatic differentiation of hiPSCs are primarily based on 2D cultivation of the cells. In the present study, the authors investigated the generation of hiPSC-derived hepatocyte-like cells using two different 3D culture systems: A 3D scaffold-free microspheroid culture system and a 3D hollow-fiber perfusion bioreactor. The differentiation outcome in these 3D systems was compared with that in conventional 2D cultures, using primary human hepatocytes as a control. The evaluation was made based on specific mRNA expression, protein secretion, antigen expression and metabolic activity. The expression of α-fetoprotein was lower, while cytochrome P450 1A2 or 3A4 activities were higher in the 3D culture systems as compared with the 2D differentiation system. Cells differentiated in the 3D bioreactor showed an increased expression of albumin and hepatocyte nuclear factor 4α, as well as secretion of α-1-antitrypsin as compared with the 2D differentiation system, suggesting a higher degree of maturation. In contrast, the 3D scaffold-free microspheroid culture provides an easy and robust method to generate spheroids of a defined size for screening applications, while the bioreactor culture model provides an instrument for complex investigations under physiological-like conditions. In conclusion, the present study introduces two 3D culture systems for stem cell derived hepatic differentiation each demonstrating advantages for individual applications as well as benefits in comparison with 2D cultures.

Pluripotent stem cells to hepatocytes, the journey so far

Over the past several years, there has been substantial progress in the field of regenerative medicine, which has enabled new possibilities for research and clinical application. For example, there are ongoing efforts directed at generating functional hepatocytes from adult-derived pluripotent cells for toxicity screening, generating disease models or, in the longer term, for the treatment of liver failure. In the present review, the authors summarise recent developments in regenerative medicine and pluripotent stem cells, the methods and tissues used for reprogramming and the differentiation of induced pluripotent stem cells (iPSCs) into hepatocyte-like cells. In addition, the hepatic disease models developed using iPSC technologies are discussed, as well as the potential for gene editing.

Stem cell-derived models to improve mechanistic understanding and prediction of human drug-induced liver injury

Current preclinical drug testing does not predict some forms of adverse drug reactions in humans. Efforts at improving predictability of drug-induced tissue injury in humans include using stem cell technology to generate human cells for screening for adverse effects of drugs in humans. The advent of induced pluripotent stem cells means that it may ultimately be possible to develop personalized toxicology to determine interindividual susceptibility to adverse drug reactions. However, the complexity of idiosyncratic drug-induced liver injury means that no current single-cell model, whether of primary liver tissue origin, from liver cell lines, or derived from stem cells, adequately emulates what is believed to occur during human drug-induced liver injury. Nevertheless, a single-cell model of a human hepatocyte which emulates key features of a hepatocyte is likely to be valuable in assessing potential chemical risk; furthermore, understanding how to generate a relevant hepatocyte will also be critical to efforts to build complex multicellular models of the liver. Currently, hepatocyte-like cells differentiated from stem cells still fall short of recapitulating the full mature hepatocellular phenotype. Therefore, we convened a number of experts from the areas of preclinical and clinical hepatotoxicity and safety assessment, from industry, academia, and regulatory bodies, to specifically explore the application of stem cells in hepatotoxicity safety assessment and to make recommendations for the way forward. In this short review, we particularly discuss the importance of benchmarking stem cell-derived hepatocyte-like cells to their terminally differentiated human counterparts using defined phenotyping, to make sure the cells are relevant and comparable between labs, and outline why this process is essential before the cells are introduced into chemical safety assessment. (Hepatology 2017;65:710-721).

Ten years of iPSC: clinical potential and advances in vitro hematopoietic differentiation

Ten years have passed since the first publication announcing the generation of induced pluripotent stem cells (iPSCs). Issues related to ethics, immune rejection, and cell availability seemed to be solved following this breakthrough. The development of iPSC technology allows advances in in vitro cell differentiation for cell therapy purpose and other clinical applications. This review provides a perspective on the iPSC potential for cell therapies, particularly for hematological applications. We discuss the advances in in vitro hematopoietic differentiation, the possibilities to employ iPSC in hematology studies, and their potential clinical application in hematologic diseases. The generation of red blood cells and functional T cells and the genome editing technology applied to mutation correction are also covered. We highlight some of the requirements and obstacles to be overcome before translating these cells from research to the clinic, for instance, iPSC variability, genotoxicity, the differentiation process, and engraftment. Also, we evaluate the patent landscape and compile the clinical trials in the field of pluripotent stem cells. Currently, we know much more about iPSC than in 2006, but there are still challenges that must be solved. A greater understanding of molecular mechanisms underlying the generation of hematopoietic stem cells is necessary to produce suitable and transplantable hematopoietic stem progenitor cells from iPSC.

Generation of Induced Pluripotent Stem Cells with Substitutes for Yamanaka's Four Transcription Factors

Induced pluripotent stem cells (iPSCs) share many characteristics with embryonic stem cells, but lack ethical controversy. They provide vast opportunities for disease modeling, pathogenesis understanding, therapeutic drug development, toxicology, organ synthesis, and treatment of degenerative disease. However, this procedure also has many potential challenges, including a slow generation time, low efficiency, partially reprogrammed colonies, as well as somatic coding mutations in the genome. Pioneered by Shinya Yamanaka's team in 2006, iPSCs were first generated by introducing four transcription factors: Oct 4, Sox 2, Klf 4, and c-Myc (OSKM). Of those factors, Klf 4 and c-Myc are oncogenes, which are potentially a tumor risk. Therefore, to avoid problems such as tumorigenesis and low throughput, one of the key strategies has been to use other methods, including members of the same subgroup of transcription factors, activators or inhibitors of signaling pathways, microRNAs, epigenetic modifiers, or even differentiation-associated factors, to functionally replace the reprogramming transcription factors. In this study, we will mainly focus on the advances in the generation of iPSCs with substitutes for OSKM. The identification and combination of novel proteins or chemicals, particularly small molecules, to induce pluripotency will provide useful tools to discover the molecular mechanisms governing reprogramming and ultimately lead to the development of new iPSC-based therapeutics for future clinical applications.