Induced pluripotent stem cells: past, present, and future

Mechanical Control of Cell Differentiation: Insights from the Early Embryo

Differentiation is the process by which a cell activates the expression of tissue-specific genes, downregulates the expression of potency markers, and acquires the phenotypic characteristics of its mature fate. The signals that regulate differentiation include biochemical and mechanical factors within the surrounding microenvironment. We describe recent breakthroughs in our understanding of the mechanical control mechanisms that regulate differentiation, with a specific emphasis on the differentiation events that build the early mouse embryo. Engineering approaches to reproducibly mimic the mechanical regulation of differentiation will permit new insights into early development and applications in regenerative medicine. Expected final online publication date for the Annual Review of Biomedical Engineering, Volume 24 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Computational and Experimental Analysis of Genetic Variants

Genomics has grown exponentially over the last decade. Common variants are associated with physiological changes through statistical strategies such as Genome-Wide Association Studies (GWAS) and quantitative trail loci (QTL). Rare variants are associated with diseases through extensive filtering tools, including population genomics and trio-based sequencing (parents and probands). However, the genomic associations require follow-up analyses to narrow causal variants, identify genes that are influenced, and to determine the physiological changes. Large quantities of data exist that can be used to connect variants to gene changes, cell types, protein pathways, clinical phenotypes, and animal models that establish physiological genomics. This data combined with bioinformatics including evolutionary analysis, structural insights, and gene regulation can yield testable hypotheses for mechanisms of genomic variants. Molecular biology, biochemistry, cell culture, CRISPR editing, and animal models can test the hypotheses to give molecular variant mechanisms. Variant characterizations can be a significant component of educating future professionals at the undergraduate, graduate, or medical training programs through teaching the basic concepts and terminology of genetics while learning independent research hypothesis design. This article goes through the computational and experimental analysis strategies of variant characterization and provides examples of these tools applied in publications. © 2022 American Physiological Society. Compr Physiol 12:3303-3336, 2022.

Analysing bio-art’s epistemic landscape: from metaphoric to post-metaphoric structure

Since its emergence, bio-art has developed numerous metaphors central to the transfer of concepts of modern biology, genetics, and genomics to the public domain that reveal several cultural, ethical, and social variations in their related themes. This article assumes that a general typology of metaphors developed by practices related to bio-art can be categorised into two categories: pictorial and operational metaphors. Through these, information regarding several biological issues is transferred to the public arena. Based on the analysis, this article attempts to answer the following questions: How does bio-art develop metaphors to advance epistemic and discursive agendas that constitute public understanding of a set of deeply problematic assumptions regarding how today’s biology operates? Under the influence of today’s synthetic biology, could bio-media operationally reframe these epistemic agendas by reframing complex and multi-layered metaphors towards post-metaphoric structures? Finally, what are the scientific, cultural, and social implications of reframing?

Current Concepts of Neural Stem/Progenitor Cell Therapy for Chronic Spinal Cord Injury

Chronic spinal cord injury (SCI) is a devastating condition that results in major neurological deficits and social burden. It continues to be managed symptomatically, and no real therapeutic strategies have been devised for its treatment. Neural stem/neural progenitor cells (NSCs/NPCs) being used for the treatment of chronic SCI in experimental SCI models can not only replace the lost cells and remyelinate axons in the injury site but also support their growth and provide neuroprotective factors. Currently, several clinical studies using NSCs/NPCs are underway worldwide. NSCs/NPCs also have the potential to differentiate into all three neuroglial lineages to regenerate neural circuits, demyelinate denuded axons, and provide trophic support to endogenous cells. This article explains the challenging pathophysiology of chronic SCI and discusses key NSC/NPC-based techniques having the greatest potential for translation over the next decade.

Direct reprogramming as a route to cardiac repair

Ischemic heart disease is the leading cause of morbidity, mortality, and healthcare expenditure worldwide due to an inability of the heart to regenerate following injury. Thus, novel heart failure therapies aimed at promoting cardiomyocyte regeneration are desperately needed. In recent years, direct reprogramming of resident cardiac fibroblasts to induced cardiac-like myocytes (iCMs) has emerged as a promising therapeutic strategy to repurpose the fibrotic response of the injured heart toward a functional myocardium. Direct cardiac reprogramming was initially achieved through the overexpression of the transcription factors (TFs) Gata4, Mef2c, and Tbx5 (GMT). However, this combination of TFs and other subsequent cocktails demonstrated limited success in reprogramming adult human and mouse fibroblasts, constraining the clinical translation of this therapy. Over the past decade, significant effort has been dedicated to optimizing reprogramming cocktails comprised of cardiac TFs, epigenetic factors, microRNAs, or small molecules to yield efficient cardiac cell fate conversion. Yet, efficient reprogramming of adult human fibroblasts remains a significant challenge. Underlying mechanisms identified to accelerate this process have been centered on epigenetic remodeling at cardiac gene regulatory regions. Further studies to achieve a refined understanding and directed means of overcoming epigenetic barriers are merited to more rapidly translate these promising therapies to the clinic.

Inducing somatic cells into pluripotent stem cells is an important platform to study the mechanism of early embryonic development

The early embryonic development starts with the totipotent zygote upon fertilization of differentiated sperm and egg, which undergoes a range of reprogramming and transformation to acquire pluripotency. Induced pluripotent stem cells (iPSCs), a nonclonal technique to produce stem cells, are originated from differentiated somatic cells via accomplishment of cell reprogramming, which shares common reprogramming process with early embryonic development. iPSCs are attractive in recent years due to the potentially significant applications in disease modeling, potential value in genetic improvement of husbandry animal, regenerative medicine, and drug screening. This review focuses on introducing the research advance of both somatic cell reprogramming and early embryonic development, indicating that the mechanisms of iPSCs also shares common features with that of early embryonic development in several aspects, such as germ cell factors, DNA methylation, histone modification, and/or X chromosome inactivation. As iPSCs can successfully avoid ethical concerns that are naturally present in the embryos and/or embryonic stem cells, the practicality of somatic cell reprogramming (iPSCs) could provide an insightful platform to elucidate the mechanisms underlying the early embryonic development.

Homologous Recombination-Enhancing Factors Identified by Comparative Transcriptomic Analyses of Pluripotent Stem Cell of Human and Common Marmoset

A previous study assessing the efficiency of the genome editing technology CRISPR-Cas9 for knock-in gene targeting in common marmoset (marmoset; Callithrix jacchus) embryonic stem cells (ESCs) unexpectedly identified innately enhanced homologous recombination activity in marmoset ESCs. Here, we compared gene expression in marmoset and human pluripotent stem cells using transcriptomic and quantitative PCR analyses and found that five HR-related genes (BRCA1, BRCA2, RAD51C, RAD51D, and RAD51) were upregulated in marmoset cells. A total of four of these upregulated genes enhanced HR efficiency with CRISPR-Cas9 in human pluripotent stem cells. Thus, the present study provides a novel insight into species-specific mechanisms for the choice of DNA repair pathways.

Motor neuron replacement therapy for amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is a motor neuron degenerative disease that is also known as Lou Gehrig's disease in the United States, Charcot's disease in France, and motor neuron disease in the UK. The loss of motor neurons causes muscle wasting, paralysis, and eventually death, which is commonly related to respiratory failure, within 3-5 years after onset of the disease. Although there are a limited number of drugs approved for amyotrophic lateral sclerosis, they have had little success at treating the associated symptoms, and they cannot reverse the course of motor neuron degeneration. Thus, there is still a lack of effective treatment for this debilitating neurodegenerative disorder. Stem cell therapy for amyotrophic lateral sclerosis is a very attractive strategy for both basic and clinical researchers, particularly as transplanted stem cells and stem cell-derived neural progenitor/precursor cells can protect endogenous motor neurons and directly replace the lost or dying motor neurons. Stem cell therapies may also be able to re-establish the motor control of voluntary muscles. Here, we review the recent progress in the use of neural stem cells and neural progenitor cells for the treatment of amyotrophic lateral sclerosis. We focus on MN progenitor cells derived from fetal central nervous system tissue, embryonic stem cells, and induced pluripotent stem cells. In our recent studies, we found that transplanted human induced pluripotent stem cell-derived motor neuron progenitors survive well, differentiate into motor neurons, and extend axons into the host white matter, not only in the rostrocaudal direction, but also along motor axon tracts towards the ventral roots in the immunodeficient rat spinal cord. Furthermore, the significant motor axonal extension after neural progenitor cell transplantation in amyotrophic lateral sclerosis models demonstrates that motor neuron replacement therapy could be a promising therapeutic strategy for amyotrophic lateral sclerosis, particularly as a variety of stem cell derivatives, including induced pluripotent stem cells, are being considered for clinical trials for various diseases.

Emerging Trajectories for Next Generation Tissue Engineers

The field of tissue engineering has evolved from its early days of engineering tissue substitutes to current efforts at building human tissues for regenerative medicine and mechanistic studies of tissue disease, injury, and regeneration. Advances in bioengineering, material science, and stem cell biology have enabled major developments in the field. In this perspective, we reflect on the September 2021 virtual Next Generation Tissue Engineering symposium and trainee workshop, as well as our projections for the field over the next 15 years.

Optogenetically controlled human functional motor endplate for testing botulinum neurotoxins

Background

The lack of physiologically relevant and predictive cell-based assays is one of the major obstacles for testing and developing botulinum neurotoxins (BoNTs) therapeutics. Human-induced pluripotent stem cells (hiPSCs)-derivatives now offer the opportunity to improve the relevance of cellular models and thus the translational value of preclinical data.

Methods

We investigated the potential of hiPSC-derived motor neurons (hMNs) optical stimulation combined with calcium imaging in cocultured muscle cells activity to investigate BoNT-sensitivity of an in vitro model of human muscle-nerve system.

Results

Functional muscle-nerve coculture system was developed using hMNs and human immortalized skeletal muscle cells. Our results demonstrated that hMNs can innervate myotubes and induce contractions and calcium transient in muscle cells, generating an in vitro human motor endplate showing dose-dependent sensitivity to BoNTs intoxication. The implementation of optogenetics combined with live calcium imaging allows to monitor the impact of BoNTs intoxication on synaptic transmission in human motor endplate model.

Conclusions

Altogether, our findings demonstrate the promise of optogenetically hiPSC-derived controlled muscle-nerve system for pharmaceutical BoNTs testing and development.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02665-3.

Induced Neurons From Germ Cells in Caenorhabditis elegans

Cell fate conversion by the forced overexpression of transcription factors (TFs) is a process known as reprogramming. It leads to de-differentiation or trans-differentiation of mature cells, which could then be used for regenerative medicine applications to replenish patients suffering from, e.g., neurodegenerative diseases, with healthy neurons. However, TF-induced reprogramming is often restricted due to cell fate safeguarding mechanisms, which require a better understanding to increase reprogramming efficiency and achieve higher fidelity. The germline of the nematode Caenorhabditis elegans has been a powerful model to investigate the impediments of generating neurons from germ cells by reprogramming. A number of conserved factors have been identified that act as a barrier for TF-induced direct reprogramming of germ cells to neurons. In this review, we will first summarize our current knowledge regarding cell fate safeguarding mechanisms in the germline. Then, we will focus on the molecular mechanisms underlying neuronal induction from germ cells upon TF-mediated reprogramming. We will shortly discuss the specific characteristics that might make germ cells especially fit to change cellular fate and become neurons. For future perspectives, we will look at the potential of C. elegans research in advancing our knowledge of the mechanisms that regulate cellular identity, and what implications this has for therapeutic approaches such as regenerative medicine.

Human iPSC-derived fallopian tube organoids with BRCA1 mutation recapitulate early-stage carcinogenesis

Germline pathogenic mutations in BReast CAncer (BRCA1) genes are thought to drive normal fallopian tube epithelial (FTE) cell transformation to high-grade serous ovarian cancer. No human models capture the sequence of events for disease initiation and progression. Here, we generate induced pluripotent stem cells (iPSCs) from healthy individuals and young ovarian cancer patients with germline pathogenic BRCA1 mutations (BRCA1^mut). Following differentiation into FTE organoids, BRCA1^mut lines exhibit cellular abnormalities consistent with neoplastic transformation compared to controls. BRCA1^mut organoids show an increased production of cancer-specific proteins and survival following transplantation into mice. Organoids from women with the most aggressive ovarian cancer show the greatest pathology, indicating the potential value to predict clinical severity prior to disease onset. These human FTE organoids from BRCA1^mut carriers provide a faithful physiological in vitro model of FTE lesion generation and early carcinogenesis. This platform can be used for personalized mechanistic and drug screening studies.

Yucer et al. generate a human BRCA1 mutant iPSC-derived fallopian tube organoid model, which recapitulates BRCA1 mutant ovarian carcinogenesis in vitro and shows tumors in vivo. This model provides a biologically relevant platform to validate drugs and a basis for personalized early detection and preventative strategies for women carrying BRCA1 mutations.

Articular cartilage and osteochondral tissue engineering techniques: Recent advances and challenges

In spite of the considerable achievements in the field of regenerative medicine in the past several decades, osteochondral defect regeneration remains a challenging issue among diseases in the musculoskeletal system because of the spatial complexity of osteochondral units in composition, structure and functions. In order to repair the hierarchical tissue involving different layers of articular cartilage, cartilage-bone interface and subchondral bone, traditional clinical treatments including palliative and reparative methods have showed certain improvement in pain relief and defect filling. It is the development of tissue engineering that has provided more promising results in regenerating neo-tissues with comparable compositional, structural and functional characteristics to the native osteochondral tissues. Here in this review, some basic knowledge of the osteochondral units including the anatomical structure and composition, the defect classification and clinical treatments will be first introduced. Then we will highlight the recent progress in osteochondral tissue engineering from perspectives of scaffold design, cell encapsulation and signaling factor incorporation including bioreactor application. Clinical products for osteochondral defect repair will be analyzed and summarized later. Moreover, we will discuss the current obstacles and future directions to regenerate the damaged osteochondral tissues.

Bone Morphogenetic Protein 4 (BMP4) Enhances the Differentiation of Human Induced Pluripotent Stem Cells into Limbal Progenitor Cells

Corneal epithelium maintains visual acuity and is regenerated by the proliferation and differentiation of limbal progenitor cells. Transplantation of human limbal progenitor cells could restore the integrity and functionality of the corneal surface in patients with limbal stem cell deficiency. However, multiple protocols are employed to differentiate human induced pluripotent stem (iPS) cells into corneal epithelium or limbal progenitor cells. The aim of this study was to optimize a protocol that uses bone morphogenetic protein 4 (BMP4) and limbal cell-specific medium. Human dermal fibroblast-derived iPS cells were differentiated into limbal progenitor cells using limbal cell-specific (PI) medium and varying doses (1, 10, and 50 ng/mL) and durations (1, 3, and 10 days) of BMP4 treatment. Differentiated human iPS cells were analyzed by real-time polymerase chain reaction (RT-PCR), Western blotting, and immunocytochemical studies at 2 or 4 weeks after BMP4 treatment. Culturing human dermal fibroblast-derived iPS cells in limbal cell-specific medium and BMP4 gave rise to limbal progenitor and corneal epithelial-like cells. The optimal protocol of 10 ng/mL and three days of BMP4 treatment elicited significantly higher limbal progenitor marker (ABCG2, ∆Np63α) expression and less corneal epithelial cell marker (CK3, CK12) expression than the other combinations of BMP4 dose and duration. In conclusion, this study identified a successful reprogramming strategy to induce limbal progenitor cells from human iPS cells using limbal cell-specific medium and BMP4. Additionally, our experiments indicate that the optimal BMP4 dose and duration favor limbal progenitor cell differentiation over corneal epithelial cells and maintain the phenotype of limbal stem cells. These findings contribute to the development of therapies for limbal stem cell deficiency disorders.

The Clinical Trials of Mesenchymal Stromal Cells Therapy

Mesenchymal stromal cells (MSCs) are a heterogeneous population of adult stem cells, which are multipotent and possess the ability to differentiate/transdifferentiate into mesodermal and nonmesodermal cell lineages. MSCs display broad immunomodulatory properties since they are capable of secreting growth factors and chemotactic cytokines. Safety, accessibility, and isolation from patients without ethical concern make MSCs valuable sources for cell therapy approaches in autoimmune, inflammatory, and degenerative diseases. Many studies have been conducted on the application of MSCs as a new therapy, but it seems that a low percentage of them is related to clinical trials, especially completed clinical trials. Considering the importance of clinical trials to develop this type of therapy as a new treatment, the current paper is aimed at describing characteristics of MSCs and reviewing relevant clinical studies registered on the NIH database during 2016-2020 to discuss recent advances on MSC-based therapeutic approaches being used in different diseases.

Aniridia and the ocular surface: Medical and surgical problems and solutions

Congenital aniridia is a multisystemic genetic disease due to a mutation in PAX6 gene which severely affects the development and functionality of the human eyes. In patients affected by the mutation, aside from the absence or defects of iris tissue formation, abnormalities in position or opacities of the crystalline lens, macular hypoplasia, ocular surface disease is the main cause of visual loss and the deterioration of the quality of life of most patients. Limbal stem cell deficiency combined with tear film instability and secondary dry eye cause aniridic keratopathy which, in advanced stages, ends up in corneal opacification. In this paper, the actual knowledge about congenital aniridia keratopathy physiopathology and medical and surgical treatment options and their efficacy are discussed. Indications and results of topical treatments with artificial tears and blood-derivatives in its initial stages, and different surgical techniques as limbal stem cell transplantation, keratoplasty and keratoprostheses are reviewed. Finally, recent advances and results in regenerative medicine techniques with ex vivo stem cell cultivation or other types of cultivated cells are presented.

Induced pluripotency in the context of stem cell expansion bioprocess development, optimization, and manufacturing: a roadmap to the clinic

The translation of laboratory-scale bioprocess protocols and technologies to industrial scales and the application of human induced pluripotent stem cell (hiPSC) derivatives in clinical trials globally presents optimism for the future of stem-cell products to impact healthcare. However, while many promising therapeutic approaches are being tested in pre-clinical studies, hiPSC-derived products currently account for a small fraction of active clinical trials. The complexity and volatility of hiPSCs present several bioprocessing challenges, where the goal is to generate a sufficiently large, high-quality, homogeneous population for downstream differentiation-the derivatives of which must retain functional efficacy and meet regulatory safety criteria in application. It is argued herein that one of the major challenges currently faced in improving the robustness of routine stem-cell biomanufacturing is in utilizing continuous, meaningful assessments of molecular and cellular characteristics from process to application. This includes integrating process data with biological characteristic and functional assessment data to model the interplay between variables in the search for global optimization strategies. Coupling complete datasets with relevant computational methods will contribute significantly to model development and automation in achieving process robustness. This overarching approach is thus crucially important in realizing the potential of hiPSC biomanufacturing for transformation of regenerative medicine and the healthcare industry.

Hurdles for the wide implementation of photoimmunotherapy

Near infrared photoimmunotherapy (NIR-PIT) is a molecularly targeted treatment for cancers achieved by injecting a conjugate of IRDye700DX^® (IR700), a water-soluble silicon phthalocyanine derivative in the near infrared, and a monoclonal antibody that targets cancer cell antigens. NIR-PIT is a highly specific treatment with few side effects that results in rapid immunogenic cell death. Despite it being a very effective and innovative therapy, there are a few challenges preventing full implementation in clinical practice. These include the limits of near infrared light penetration, selection of targets, concerns about tumor lysis syndrome and drug costs. However, NIR-PIT has been approved by the regulatory authorities in Japan, allowing for exploration of how to mitigate challenges while maximizing the benefits of this treatment modality.

A small molecule modulating monounsaturated fatty acids and Wnt signaling confers maintenance to induced pluripotent stem cells against endodermal differentiation

Background

Stearoyl-coenzyme A desaturase 1 (SCD1) is required for de novo synthesis of fatty acids. Through the fatty acid acylation process, this enzyme orchestrates post-translational modifications to proteins involved in cell development and differentiation. In this study, we used biochemical methods, immunostaining, and covalent labeling to evaluate whether a small molecule modulating unsaturated fatty acids can influence the early endodermal differentiation of human-induced pluripotent stem cells (iPSCs).

Methods

The hiPSCs were cultured in an endoderm-inducing medium containing activin A and defined fetal bovine serum in the presence of an SCD1 inhibitor at different time points. The cell cycles and the yields of the three germ layers (endoderm, mesoderm, and ectoderm) were assessed using flow cytometry. The expression of endoderm and pluripotency markers and the expressions of Wnt signaling pathway proteins were assessed using western blotting and RT-PCR. Total protein acylation was evaluated using a click chemistry reaction.

Results

When SCD1 was inhibited on the first day, the population of cells with endodermal features decreased at the end of differentiation. Moreover, early SCD1 inhibition preserved the properties of hiPSCs, preventing their shift toward mesodermal or ectodermal lineage. Also, first-day-only treatment of cells with the SCD1 inhibitor decreased β-catenin gene expression and the intensity of fluorescent emission in the click chemistry assay. The cells were effectively rescued from these effects by cotreatment with oleate. Late treatment with the inhibitor in the two subsequent days of endoderm induction did not have any significant effects on endoderm-specific markers or fluorescent intensity. Reproducible results were also obtained with human embryonic stem cells.

Conclusion

The small molecule SCD1 inhibitor attenuates the Wnt/β-catenin signaling pathway, conferring the maintenance of hiPSCs by opposing the initiation of endoderm differentiation. The immediate requirement for SCD1 activity in the endoderm commitment of pluripotent stem cells may be of importance in disorders of endoderm-derived organs and dysregulated metabolism.

The schematic representation of the study design and main results. Activin A induces endoderm features through Smad2/3/4 and increases the expression of SCD1. SCD1 can produce MUFAs and subsequently modify the Wnt molecules. MUFA acylated/activated Wnts are secreted to interact with corresponding receptors on the target cells. β-catenin accumulates in the cytoplasm and is translocated into the nucleus after the interaction of Wnt with the receptor. Then, β-catenin increases the expression of the endoderm markers Sox17 and CXCR4.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02617-x.

Epigenome-Metabolome-Epigenome signaling cascade in cell biological processes

Cell fate determination as a fundamental question in cell biology has been extensively studied at different regulatory levels for many years. However, the mechanisms of multi-level regulation of cell fate determination remain unclear. Recently we have proposed an Epigenome-Metabolome-Epigenome (E-M-E) signaling cascade model to describe the crossover cooperation during mouse somatic cell reprogramming. In this review, we summarize the broad roles of E-M-E signaling cascade in different cell biological processes including cell differentiation and dedifferentiation, cell specialization, cell proliferation and cell pathological processes. Precise E-M-E signaling cascades are critical in these cell biological processes, and it is of worth to explore each step of E-M-E signaling cascade. E-M-E signaling cascade model sheds light on and may open a window to explore the mechanisms of multi-level regulation of cell biological processes.

In Search of a Unifying Concept in Human Diseases

Throughout the history of biological/medicine sciences, there has been opposing strategies to find solutions to complex human disease problems. Both empirical and deductive approaches have led to major insights and concepts that have led to practical preventive and therapeutic benefits for the human population. The classic definitions of "science" (to know) has been paired with the classic definition of technology (to do). One knew more as the technology developed, and that development was often based on science. In other words, one could do more if science could improve the technology. In turn, this made possible to know more science with improved technology. However, with the development of new technologies of today in biology and medicine, major advances have been made, such as the information from the Human Genome Project, genetic engineering techniques and the use of bioinformatic uses of sophisticated computer analyses. This has led to the renewed idea that Precision Medicine, while raising some serious ethical concerns, also raises the expectation of improved potential of risk predictions for prevention and treatment of various genetically and environmentally influenced human diseases. This new field Artificial Intelligence, as a major handmaiden to Precision Medicine, is significantly altering the fundamental means of biological discovery. However, can today's fundamental premise of "Artificial Intelligence", based on identifying DNA, as the primary nexus of human health and disease, provide the practical solutions to complex human diseases that involve the interaction of those genes with the broad spectrum of "environmental factors"? Will it be "precise" enough to provide practical solutions for prevention and treatments of diseases? In this "Commentary", with the example of human carcinogenesis, it will be challenged that, without the integration of mechanistic and hypothesis-driven approaches with the "unbiased" empirical analyses of large numbers of data, the Artificial Intelligence approach with fall short.

Stem cells' centrosomes: How can organelles identified 130 years ago contribute to the future of regenerative medicine?

At the core of regenerative medicine lies the expectation of repair or replacement of damaged tissues or whole organs. Donor scarcity and transplant rejection are major obstacles, and exactly the obstacles that stem cell-based therapy promises to overcome. These therapies demand a comprehensive understanding of the asymmetric division of stem cells, i.e. their ability to produce cells with identical potency or differentiated cells. It is believed that with better understanding, researchers will be able to direct stem cell differentiation. Here, we describe extraordinary advances in manipulating stem cell fate that show that we need to focus on the centrosome and the centrosome-derived primary cilium. This belief comes from the fact that this organelle is the vehicle that coordinates the asymmetric division of stem cells. This is supported by studies that report the significant role of the centrosome/cilium in orchestrating signaling pathways that dictate stem cell fate. We anticipate that there is sufficient evidence to place this organelle at the center of efforts that will shape the future of regenerative medicine.

Pre-clinical Investigation of Rett Syndrome Using Human Stem Cell-Based Disease Models

Rett syndrome (RTT) is an X-linked neurodevelopmental disorder, mostly caused by mutations in MECP2. The disorder mainly affects girls and it is associated with severe cognitive and physical disabilities. Modeling RTT in neural and glial cell cultures and brain organoids derived from patient- or mutation-specific human induced pluripotent stem cells (iPSCs) has advanced our understanding of the pathogenesis of RTT, such as disease-causing mechanisms, disease progression, and cellular and molecular pathology enabling the identification of actionable therapeutic targets. Brain organoid models that recapitulate much of the tissue architecture and the complexity of cell types in the developing brain, offer further unprecedented opportunity for elucidating human neural development, without resorting to conventional animal models and the limited resource of human neural tissues. This review focuses on the new knowledge of RTT that has been gleaned from the iPSC-based models as well as limitations of the models and strategies to refine organoid technology in the quest for clinically relevant disease models for RTT and the broader spectrum of neurodevelopmental disorders.

Process parameter development for the scaled generation of stem cell-derived pancreatic endocrine cells

Diabetes is a debilitating disease characterized by high blood glucose levels. The global prevalence of this disease has been projected to reach 700 million adults by the year 2045. Type 1 diabetes represents about 10% of the reported cases of diabetes. Although islet transplantation can be a highly effective method to treat type 1 diabetes, its widespread application is limited by the paucity of cadaveric donor islets. The use of pluripotent stem cells as an unlimited cell source to generate insulin‐producing cells for implant is a promising alternative for treating diabetes. However, to be clinically relevant, it is necessary to manufacture these stem cell‐derived cells at sufficient scales. Significant advances have been made in differentiation protocols used to generate stem cell‐derived cells capable of reversing diabetes in animal models and for testing in clinical trials. We discuss the potential of both stem cell‐derived pancreatic progenitors and more matured insulin‐producing cells to treat diabetes. We discuss the need for rigorous bioprocess parameter optimization and identify some critical process parameters and strategies that may influence the critical quality attributes of the cells with the goal of facilitating scalable manufacturing of human pluripotent stem cell‐derived pancreatic endocrine cells.

What Molecular Recognition Systems Do Mesenchymal Stem Cells/Medicinal Signaling Cells (MSC) Use to Facilitate Cell-Cell and Cell Matrix Interactions? A Review of Evidence and Options

Mesenchymal stem cells, also called medicinal signaling cells (MSC), have been studied regarding their potential to facilitate tissue repair for >30 years. Such cells, derived from multiple tissues and species, are capable of differentiation to a number of lineages (chondrocytes, adipocytes, bone cells). However, MSC are believed to be quite heterogeneous with regard to several characteristics, and the large number of studies performed thus far have met with limited or restricted success. Thus, there is more to understand about these cells, including the molecular recognition systems that are used by these cells to perform their functions, to enhance the realization of their potential to effect tissue repair. This perspective article reviews what is known regarding the recognition systems available to MSC, the possible systems that could be looked for, and alternatives to enhance their localization to specific injury sites and increase their subsequent facilitation of tissue repair. MSC are reported to express recognition molecules of the integrin family. However, there are a number of other recognition molecules that also could be involved such as lectins, inducible lectins, or even a MSC-specific family of molecules unique to these cells. Finally, it may be possible to engineer expression of recognition molecules on the surface of MSC to enhance their function in vivo artificially. Thus, improved understanding of recognition molecules on MSC could further their success in fostering tissue repair.

Methods for Automated Single Cell Isolation and Sub-Cloning of Human Pluripotent Stem Cells

Advances in human pluripotent stem cell (hPSC) techniques have led them to become a widely used and powerful tool for a vast array of applications, including disease modeling, developmental studies, drug discovery and testing, and emerging cell-based therapies. hPSC workflows that require clonal expansion from single cells, such as CRISPR/Cas9-mediated genome editing, face major challenges in terms of efficiency, cost, and precision. Classical sub-cloning approaches depend on limiting dilution and manual colony picking, which are both time-consuming and labor-intensive, and lack a real proof of clonality. Here we describe the application of three different automated cell isolation and dispensing devices that can enhance the single-cell cloning process for hPSCs. In combination with optimized cell culture conditions, these devices offer an attractive alternative compared to manual methods. We explore various aspects of each device system and define protocols for their practical application. Following the workflow described here, single cell-derived hPSC sub-clones from each system maintain pluripotency and genetic stability. Furthermore, the workflows can be applied to uncover karyotypic mosaicism prevalent in bulk hPSC cultures. Our robust automated workflow facilitates high-throughput hPSC clonal selection and expansion, urgently needed in the operational pipelines of hPSC applications. © 2020 The Authors. Basic Protocol: Efficient automated hPSC single cell seeding and clonal expansion using the iotaSciences IsoCell platform Alternate Protocol 1: hPSC single cell seeding and clonal expansion using the Cellenion CellenONE single-cell dispenser Alternate Protocol 2: hPSC single cell seeding and clonal expansion using the Cytena single-cell dispenser Support Protocol 1: Coating cell culture plates with Geltrex Support Protocol 2: hPSC maintenance in defined feeder-free conditions Support Protocol 3: hPSC passaging in clumps Support Protocol 4: Laminin 521 coating of IsoCell plates and 96-well/384-well plates Support Protocol 5: Preparation of medium containing anti-apoptotic small molecules Support Protocol 6: 96- and 384-well target plate preparation prior to single cell seeding Support Protocol 7: Single cell dissociation of hPSCs Support Protocol 8: IsoCell-, CellenONE-, and Cytena-derived hPSC clone subculture and expansion.

The Role of Mesenchymal Stem Cells (MSCs) in Veterinary Medicine and Their Use in Musculoskeletal Disorders

Regenerative medicine is a dynamically developing field of human and veterinary medicine. The animal model was most commonly used for mesenchymal stem cells (MSCs) treatment in experimental and preclinical studies with a satisfactory therapeutic effect. Year by year, the need for alternative treatments in veterinary medicine is increasing, and other applications for promising MSCs and their biological derivatives are constantly being sought. There is also an increase in demand for other methods of treating disease states, of which the classical treatment methods did not bring the desired results. Cell therapy can be a realistic option for treating human and animal diseases in the near future and therefore additional research is needed to optimize cell origins, numbers, or application methods in order to standardize the treatment process and assess its effects. The aim of the following work was to summarize available knowledge about stem cells in veterinary medicine and their possible application in the treatment of chosen musculoskeletal disorders in dogs and horses.

From Cells to Organs: The Present and Future of Regenerative Medicine

Regenerative medicine promises a bright future where damaged body parts can be restored, rejuvenated, and replaced. The application of regenerative medicine is interdisciplinary and covers nearly all fields of medical sciences and molecular engineering. This review provides a road map on how regenerative medicine is applied on the levels of cell, tissue, and organ and summarizes the advantages and limitation of human pluripotent stem cells in disease modeling and regenerative application.

Multicellular modeling of ciliopathy by combining iPS cells and microfluidic airway-on-a-chip technology

Mucociliary clearance is an essential lung function that facilitates the removal of inhaled pathogens and foreign matter unidirectionally from the airway tract and is innately achieved by coordinated ciliary beating of multiciliated cells. Should ciliary function become disturbed, mucus can accumulate in the airway causing subsequent obstruction and potentially recurrent pneumonia. However, it has been difficult to recapitulate unidirectional mucociliary flow using human-derived induced pluripotent stem cells (iPSCs) in vitro and the mechanism governing the flow has not yet been elucidated, hampering the proper humanized airway disease modeling. Here, we combine human iPSCs and airway-on-a-chip technology, to demonstrate the effectiveness of fluid shear stress (FSS) for regulating the global axis of multicellular planar cell polarity (PCP), as well as inducing ciliogenesis, thereby contributing to quantifiable unidirectional mucociliary flow. Furthermore, we applied the findings to disease modeling of primary ciliary dyskinesia (PCD), a genetic disease characterized by impaired mucociliary clearance. The application of an airway cell sheet derived from patient-derived iPSCs and their gene-edited counterparts, as well as genetic knockout iPSCs of PCD causative genes, made it possible to recapitulate the abnormal ciliary functions in organized PCP using the airway-on-a-chip. These findings suggest that the disease model of PCD developed here is a potential platform for making diagnoses and identifying therapeutic targets and that airway reconstruction therapy using mechanical stress to regulate PCP might have therapeutic value.

Stem Cell-Derived Exosomes: a New Strategy of Neurodegenerative Disease Treatment

Short-term symptomatic treatment and dose-dependent side effects of pharmacological treatment for neurodegenerative diseases have forced the medical community to seek an effective treatment for this serious global health threat. Therapeutic potential of stem cell for treatment of neurodegenerative disorders was identified in 1980 when fetal nerve tissue was used to treat Parkinson's disease (PD). Then, extensive studies have been conducted to develop this treatment strategy for neurological disease therapy. Today, stem cells and their secretion are well-known as a therapeutic environment for the treatment of neurodegenerative diseases. This new paradigm has demonstrated special characteristics related to this treatment, including neuroprotective and neurodegeneration, remyelination, reduction of neural inflammation, and recovery of function after induced injury. However, the exact mechanism of stem cells in repairing nerve damage is not yet clear; exosomes derived from them, an important part of their secretion, are introduced as responsible for an important part of such effects. Numerous studies over the past few decades have evaluated the therapeutic potential of exosomes in the treatment of various neurological diseases. In this review, after recalling the features and therapeutic history, we will discuss the latest stem cell-derived exosome-based therapies for these diseases.

Recent trends in stem cell-based therapies and applications of artificial intelligence in regenerative medicine

Stem cells are undifferentiated cells that can self-renew and differentiate into diverse types of mature and functional cells while maintaining their original identity. This profound potential of stem cells has been thoroughly investigated for its significance in regenerative medicine and has laid the foundation for cell-based therapies. Regenerative medicine is rapidly progressing in healthcare with the prospect of repair and restoration of specific organs or tissue injuries or chronic disease conditions where the body’s regenerative process is not sufficient to heal. In this review, the recent advances in stem cell-based therapies in regenerative medicine are discussed, emphasizing mesenchymal stem cell-based therapies as these cells have been extensively studied for clinical use. Recent applications of artificial intelligence algorithms in stem cell-based therapies, their limitation, and future prospects are highlighted.

From Stem Cells to Populations-Using hiPSC, Next-Generation Sequencing, and GWAS to Explore the Genetic and Molecular Mechanisms of Congenital Heart Defects

Congenital heart defects (CHD) are developmental malformations affecting the heart and the great vessels. Early heart development requires temporally regulated crosstalk between multiple cell types, signaling pathways, and mechanical forces of early blood flow. While both genetic and environmental factors have been recognized to be involved, identifying causal genes in non-syndromic CHD has been difficult. While variants following Mendelian inheritance have been identified by linkage analysis in a few families with multiple affected members, the inheritance pattern in most familial cases is complex, with reduced penetrance and variable expressivity. Furthermore, most non-syndromic CHD are sporadic. Improved sequencing technologies and large biobank collections have enabled genome-wide association studies (GWAS) in non-syndromic CHD. The ability to generate human to create human induced pluripotent stem cells (hiPSC) and further differentiate them to organotypic cells enables further exploration of genotype–phenotype correlations in patient-derived cells. Here we review how these technologies can be used in unraveling the genetics and molecular mechanisms of heart development.

Induced Tissue-Specific Stem Cells (iTSCs): Their Generation and Possible Use in Regenerative Medicine

Induced tissue-specific stem cells (iTSCs) are partially reprogrammed cells which have an intermediate state, such as progenitors or stem cells. They originate from the de-differentiation of differentiated somatic cells into pluripotent stem cells, such as induced pluripotent stem cells (iPSCs) and embryonic stem cells (ESCs), or from the differentiation of undifferentiated cells. They show a limited capacity to differentiate and a morphology similar to that of somatic cell stem cells present in tissues, but distinct from that of iPSCs and ESCs. iTSCs can be generally obtained 7 to 10 days after reprogramming of somatic cells with Yamanaka’s factors, and their fibroblast-like morphology remains unaltered. iTSCs can also be obtained directly from iPSCs cultured under conditions allowing cellular differentiation. In this case, to effectively induce iTSCs, additional treatment is required, as exemplified by the conversion of iPSCs into naïve iPSCs. iTSCs can proliferate continuously in vitro, but when transplanted into immunocompromised mice, they fail to generate solid tumors (teratomas), implying loss of tumorigenic potential. The low tendency of iTSCs to elicit tumors is beneficial, especially considering applications for regenerative medicine in humans. Several iTSC types have been identified, including iTS-L, iTS-P, and iTS-D, obtained by reprogramming hepatocytes, pancreatic cells, and deciduous tooth-derived dental pulp cells, respectively. This review provides a brief overview of iPSCs and discusses recent advances in the establishment of iTSCs and their possible applications in regenerative medicine.

Gene Therapy for Mucopolysaccharidosis Type II-A Review of the Current Possibilities

Mucopolysaccharidosis type II (MPS II) is a lysosomal storage disorder based on a mutation in the IDS gene that encodes iduronate 2-sulphatase. As a result, there is an accumulation of glycosaminoglycans-heparan sulphate and dermatan sulphate-in almost all body tissues, which leads to their dysfunction. Currently, the primary treatment is enzyme replacement therapy, which improves the course of the disease by reducing somatic symptoms, including hepatomegaly and splenomegaly. The enzyme, however, does not cross the blood-brain barrier, and no improvement in the function of the central nervous system has been observed in patients with the severe form of the disease. An alternative method of treatment that solves typical problems of enzyme replacement therapy is gene therapy, i.e., delivery of the correct gene to target cells through an appropriate vector. Much progress has been made in applying gene therapy for MPS II, from cellular models to human clinical trials. In this article, we briefly present the history and basics of gene therapy and discuss the current state of knowledge about the methods of this therapy in mucopolysaccharidosis type II.

Brain organoids: A promising model to assess oxidative stress-induced central nervous system damage

Oxidative stress (OS) is one of the most significant propagators of systemic damage with implications for widespread pathologies such as vascular disease, accelerated aging, degenerative disease, inflammation, and traumatic injury. OS can be induced by numerous factors such as environmental conditions, lifestyle choices, disease states, and genetic susceptibility. It is tied to the accumulation of free radicals, mitochondrial dysfunction, and insufficient antioxidant protection, which leads to cell aging and tissue degeneration over time. Unregulated systemic increase in reactive species, which contain harmful free radicals, can lead to diverse tissue-specific OS responses and disease. Studies of OS in the brain, for example, have demonstrated how this state contributes to neurodegeneration and altered neural plasticity. As the worldwide life expectancy has increased over the last few decades, the prevalence of OS-related diseases resulting from age-associated progressive tissue degeneration. Unfortunately, vital translational research studies designed to identify and target disease biomarkers in human patients have been impeded by many factors (e.g., limited access to human brain tissue for research purposes and poor translation of experimental models). In recent years, stem cell-derived three-dimensional tissue cultures known as "brain organoids" have taken the spotlight as a novel model for studying central nervous system (CNS) diseases. In this review, we discuss the potential of brain organoids to model the responses of human neural cells to OS, noting current and prospective limitations. Overall, brain organoids show promise as an innovative translational model to study CNS susceptibility to OS and elucidate the pathophysiology of the aging brain.

Pluripotent Stem Cell-Based Cell Therapy-Promise and Challenges

Human pluripotent stem cells such as embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) provide unprecedented opportunities for cell therapies against intractable diseases and injuries. Both ESCs and iPSCs are already being used in clinical trials. However, we continue to encounter practical issues that limit their use, including their inherent properties of tumorigenicity, immunogenicity, and heterogeneity. Here, I review two decades of research aimed at overcoming these three difficulties.

Reprogramming: Emerging Strategies to Rejuvenate Aging Cells and Tissues

Aging is associated with a progressive and functional decline of all tissues and a striking increase in many "age-related diseases". Although aging has long been considered an inevitable process, strategies to delay and potentially even reverse the aging process have recently been developed. Here, we review emerging rejuvenation strategies that are based on reprogramming toward pluripotency. Some of these approaches may eventually lead to medical applications to improve healthspan and longevity.

Pluripotent and Multipotent Stem Cells and Current Therapeutic Applications: Review

There is numerous evidence for the presence of stem cells, which is important for the treatment of a wide variety of disease conditions. Stem cells have a great therapeutic effect on different degenerative diseases through the development of specialized cells. Embryonic stem (ES) cells are derived from preimplantation embryos, which have a natural karyotype. This cell has the capacity of proliferation indefinitely and undifferentiated. Stem cells are very crucial for the treatment of different chronic and degenerative diseases. For instance, stem cell clinical trials have been done for ischemic heart disease. Also, the olfactory cells for spinal cord lesions and human fetal pancreatic cells for diabetes mellitus are the other clinical importance of stem cell therapy. Extracellular matrix (ECM) and other environmental factors influence the fate and activity of stem cells.

A review of dynamical systems approaches for the detection of chaotic attractors in cancer networks

Cancers are complex dynamical systems. They remain the leading cause of disease-related pediatric mortality in North America. To overcome this burden, we must decipher the state-space attractor dynamics of gene expression patterns and protein oscillations orchestrated by cancer stemness networks. The review provides an overview of dynamical systems theory to steer cancer research in pattern science. While most of our current tools in network medicine rely on statistical correlation methods, causality inference remains primitively developed. As such, a survey of attractor reconstruction methods and machine algorithms for the detection of causal structures applicable in experimentally derived time series cancer datasets is presented. A toolbox of complex systems approaches are discussed for reconstructing the signaling state space of cancer networks, interpreting causal relationships in their time series gene expression patterns, and assisting clinical decision making in computational oncology. As a proof of concept, the applicability of some algorithms are demonstrated on pediatric brain cancer datasets and the requirement of their time series analysis is highlighted.

Non-viral Induction of Transgene-free iPSCs from Somatic Fibroblasts of Multiple Mammalian Species

Induced pluripotent stem cells (iPSCs) are capable of providing an unlimited source of cells from all three germ layers and germ cells. The derivation and usage of iPSCs from various animal models may facilitate stem cell-based therapy, gene-modified animal production, and evolutionary studies assessing interspecies differences. However, there is a lack of species-wide methods for deriving iPSCs, in particular by means of non-viral and non-transgene-integrating (NTI) approaches. Here, we demonstrate the iPSC derivation from somatic fibroblasts of multiple mammalian species from three different taxonomic orders, including the common marmoset (Callithrix jacchus) in Primates, the dog (Canis lupus familiaris) in Carnivora, and the pig (Sus scrofa) in Cetartiodactyla, by combinatorial usage of chemical compounds and NTI episomal vectors. Interestingly, the fibroblasts temporarily acquired a neural stem cell-like state during the reprogramming. Collectively, our method, robustly applicable to various species, holds a great potential for facilitating stem cell-based research using various animals in Mammalia.

A well plate-based multiplexed platform for incorporation of organoids into an organ-on-a-chip system with a perfusable vasculature

Owing to their high spatiotemporal precision and adaptability to different host cells, organ-on-a-chip systems are showing great promise in drug discovery, developmental biology studies and disease modeling. However, many current micro-engineered biomimetic systems are limited in technological application because of culture media mixing that does not allow direct incorporation of techniques from stem cell biology, such as organoids. Here, we describe a detailed alternative method to cultivate millimeter-scale functional vascularized tissues on a biofabricated platform, termed 'integrated vasculature for assessing dynamic events', that enables facile incorporation of organoid technology. Utilizing the 3D stamping technique with a synthetic polymeric elastomer, a scaffold termed 'AngioTube' is generated with a central microchannel that has the mechanical stability to support a perfusable vascular system and the self-assembly of various parenchymal tissues. We demonstrate an increase in user familiarity and content analysis by situating the scaffold on a footprint of a 96-well plate. Uniquely, the platform can be used for facile connection of two or more tissue compartments in series through a common vasculature. Built-in micropores enable the studies of cell invasion involved in both angiogenesis and metastasis. We describe how this protocol can be applied to create both vascularized cardiac and hepatic tissues, metastatic breast cancer tissue and personalized pancreatic cancer tissue through incorporation of patient-derived organoids. Platform assembly to populating the scaffold with cells of interest into perfusable functional vascularized tissue will require 12-14 d and an additional 4 d if pre-polymer and master molds are needed.

Photobiomodulation: An Effective Approach to Enhance Proliferation and Differentiation of Adipose-Derived Stem Cells into Osteoblasts

Osteoporosis is regarded as the most common chronic metabolic bone condition in humans. In osteoporosis, bone mesenchymal stem cells (MSCs) have reduced cellular function. Regenerative medicine using adipose-derived stem cell (ADSC) transplantation can promote the growth and strength of new bones, improve bone stability, and reduce the risk of fractures. Various methods have been attempted to differentiate ADSCs to functioning specialized cells for prospective clinical application. However, commonly used therapies have resulted in damage to the donor site and morbidity, immune reactions, carcinogenic generation, and postoperative difficulties. Photobiomodulation (PBM) improves ADSC differentiation and proliferation along with reducing clinical difficulties such as treatment failures to common drug therapies and late initiation of treatment. PBM is a noninvasive, nonthermal treatment that encourages cells to produce more energy and to undergo self-repair by using visible green and red and invisible near-infrared (NIR) radiation. The use of PBM for ADSC proliferation and differentiation has been widely studied with multiple outcomes observed due to laser fluence and wavelength dependence. In this article, the potential for differentiating ADSCs into osteoblasts and the various methods used, including biological induction, chemical induction, and PBM, will be addressed. Likewise, the optimal laser parameters that could improve the proliferation and differentiation of ADSC, translating into clinical success, will be commented on.

Neural Differentiation of Mouse Embryonic Stem Cells-An in vitro Approach to Profile DNA Methylation of Reprogramming Factor Sox2-SRR2

Sox2 is one of the core transcription factors maintaining the embryonic stem cells (ES) pluripotency and, also indispensable for cellular reprogramming. However, limited data is available about the DNA methylation of pluripotency genes during lineage-specific differentiations. This study investigated the DNA methylation of Sox2 regulatory region 2 (SRR2) during directed differentiation of mouse ES into neural lineage. ES cells were first grown to form embryoid bodies in suspension which were then dissociated, and cultured in defined medium to promote neural differentiation. Typical neuronal morphology together with the up-regulation of Pax6, neuroepithelial stem cell intermediate filament and β-tubulin III and, down-regulation of pluripotency genes Oct4, Nanog and Sox2 showed the existence of neural phenotype in cells undergoing differentiation. Three CpGs in the core enhancer region of neural-specific SRR2 were individually investigated by direct DNA sequencing post-bisulfite treatment and, found to be unmethylated in differentiated cells at time-points chosen for analysis. This analysis does not limit the possibility of methylation at other CpG sites than those profiled here and/or transient methylation. Hence, similar analyses exploring the DNA methylation at other regions of the Sox2 gene could unravel the onset and transitions of epigenetic signatures influencing the outcome of differentiation pathways and neural development. The data presented here shows that in vitro neural differentiation of embryonic stem cells can be employed to study and characterize molecular regulatory mechanisms governing neurogenesis by applying diverse pharmacological and toxicological agents.

Generation of high yield insulin-producing cells (IPCs) from various sources of stem cells

Type 1 diabetes mellitus occurs when beta cell mass is reduced to less than 20% of the normal level due to immune system destruction of beta cell resulting in an inability to secrete enough insulin. The prevalence of diabetes is expanding according to the American Diabetes Association and the World Health Organization (WHO), foretold to exceed 350 million by 2030. The current treatment does not cure many of the serious complications associated with the disease such as neuropathy, nephropathy, dyslipidemia, retinopathy and cardiovascular disease. Whole pancreas or isolated pancreatic islet transplantation as an alternative therapy can prevent or reduce some of the complications of diabetes. However, the shortage of matched organ or islets cells donor and alloimmune responses limit this therapeutic strategy. Recently, several reports have raised extremely promising results to use different sources of stem cells to differentiate insulin-producing cells and focus on the expansion of these alternative sources. Stem cells, due to their potential for multiple differentiation and self-renewal can differentiate into all cell types, including insulin-producing cells (IPCs). Generation of new beta cells can be achieved from various stem cell sources, including embryonic stem cells (ESCs), adult stem cells, such as mesenchymal stem cells (MSCs) and induced pluripotent stem cells (iPSCs). Thus, this chapter discusses on the assistance of cellular reprogramming of various stem cells as candidates for the generation of IPCs using transcription factors/miRNA, cytokines/small molecules and tissue engineering.

Direct cell reprogramming: approaches, mechanisms and progress

The reprogramming of somatic cells with defined factors, which converts cells from one lineage into cells of another, has greatly reshaped our traditional views on cell identity and cell fate determination. Direct reprogramming (also known as transdifferentiation) refers to cell fate conversion without transitioning through an intermediary pluripotent state. Given that the number of cell types that can be generated by direct reprogramming is rapidly increasing, it has become a promising strategy to produce functional cells for therapeutic purposes. This Review discusses the evolution of direct reprogramming from a transcription factor-based method to a small-molecule-driven approach, the recent progress in enhancing reprogrammed cell maturation, and the challenges associated with in vivo direct reprogramming for translational applications. It also describes our current understanding of the molecular mechanisms underlying direct reprogramming, including the role of transcription factors, epigenetic modifications, non-coding RNAs, and the function of metabolic reprogramming, and highlights novel insights gained from single-cell omics studies.

Enhanced differentiation of human induced pluripotent stem cells toward the midbrain dopaminergic neuron lineage through GLYPICAN-4 downregulation

Enhancing the differentiation potential of human induced pluripotent stem cells (hiPSC) into disease‐relevant cell types is instrumental for their widespread application in medicine. Here, we show that hiPSCs downregulated for the signaling modulator GLYPICAN‐4 (GPC4) acquire a new biological state characterized by increased hiPSC differentiation capabilities toward ventral midbrain dopaminergic (VMDA) neuron progenitors. This biological trait emerges both in vitro, upon exposing cells to VMDA neuronal differentiation signals, and in vivo, even when transplanting hiPSCs at the extreme conditions of floor‐plate stage in rat brains. Moreover, it is compatible with the overall neuronal maturation process toward acquisition of substantia nigra neuron identity. HiPSCs with downregulated GPC4 also retain self‐renewal and pluripotency in stemness conditions, in vitro, while losing tumorigenesis in vivo as assessed by flank xenografts. In conclusion, our results highlight GPC4 downregulation as a powerful approach to enhance generation of VMDA neurons. Outcomes may contribute to establish hiPSC lines suitable for translational applications.

Redox and Epigenetics in Human Pluripotent Stem Cells Differentiation

Significance: Since their discovery, induced pluripotent stem cells (iPSCs) had generated considerable interest in the scientific community for their great potential in regenerative medicine, disease modeling, and cell-based therapeutic approach, due to their unique characteristics of self-renewal and pluripotency. Recent Advances: Technological advances in iPSC genome-wide epigenetic profiling led to the elucidation of the epigenetic control of cellular identity during nuclear reprogramming. Moreover, iPSC physiology and metabolism are tightly regulated by oxidation-reduction events that mainly occur during the respiratory chain. In theory, iPSC-derived differentiated cells would be ideal for stem cell transplantation as autologous cells from donors, as the risks of rejection are minimal. Critical Issues: However, iPSCs experience high oxidative stress that, in turn, confers a high risk of increased genomic instability, which is most often linked to DNA repair deficiencies. Genomic instability has to be assessed before iPSCs can be used in therapeutic designs. Future Directions: This review will particularly focus on the links between redox balance and epigenetic modifications-in particular based on the histone variant macroH2A1-that determine DNA damage response in iPSCs and derived differentiated cells, and that might be exploited to decrease the teratogenic potential on iPSC transplantation. Antioxid. Redox Signal. 34, 335-349.

Generation of nonviral integration-free human iPS cell line KISCOi001-A from normal human fibroblasts, under defined xeno-free and feeder-free conditions

KISCOi001-A is a healthy feeder-free and fully characterized human induced pluripotent stem (iPS) cell line cultured under xeno-free and defined conditions. The cell line is generated from normal human foreskin fibroblasts with non-integrating episomal plasmid vectors encoding OCT4, SOX2, KLF4, NANOG, LIN28, nontransforming L-MYC and dominant negative p53. The generated iPS cells are transgene-free and their pluripotency is confirmed by the expression of stem cell markers and capacity to differentiate into the cells of ectoderm, endoderm and mesoderm while their identity and karyotype stability is confirmed with Genomic assays.

Hypothalamus and neuroendocrine diseases: The use of human-induced pluripotent stem cells for disease modeling

The hypothalamus, which is part of the brain of all vertebrate animals, is considered the link between the central nervous system (CNS) and (i) the endocrine system via the pituitary gland and (ii) with our organs via the autonomic nervous system. It synthesizes and releases neurohormones, which in turn stimulate or inhibit the secretion of other hormones within the CNS, and sends and receives signals to and from the peripheral nervous and endocrine systems. As the brain region responsible for energy homeostasis, the hypothalamus is the key regulator of thermoregulation, hunger and satiety, circadian rhythms, sleep and fatigue, memory and learning, arousal and reproductive cycling, blood pressure, and heart rate and thus orchestrates complex physiological responses in order to maintain metabolic homeostasis. These critical roles implicate the hypothalamus in neuroendocrine disorders such as obesity, diabetes, anorexia nervosa, bulimia, and others. In this chapter, we focus on the use of human-induced pluripotent stem cells (hiPSCs) and their differentiation into hypothalamic neurons in order to model neuroendocrine disorders such as extreme obesity in a dish. To do so, we discuss important steps of human hypothalamus development, neuroendocrine diseases related to the hypothalamus, multiple protocols to differentiate hiPSCs into hypothalamic neurons, and severe obesity modeling in vitro using hiPSCs-derived hypothalamic neurons.

Accentuating the sources of mesenchymal stem cells as cellular therapy for osteoarthritis knees-a panoramic review

The large economic burden on the global health care systems is due to the increasing number of symptomatic osteoarthritis (OA) knee patients whereby accounting for greater morbidity and impaired functional quality of life. The recent developments and impulses in molecular and regenerative medicine have paved the way for inducing the biological active cells such as stem cells, bioactive materials, and growth factors towards the healing and tissue regenerative process. Mesenchymal stem cells (MSCs) act as a minimally invasive procedure that bridges the gap between pharmacological treatment and surgical treatment for OA. MSCs are the ideal cell-based therapy for treating disorders under a minimally invasive environment in conjunction with cartilage regeneration. Due to the worldwide recognized animal model for such cell-based therapies, global researchers have started using the various sources of MSCs towards cartilage regeneration. However, there is a lacuna in literature on the comparative efficacy and safety of various sources of MSCs in OA of the knee. Hence, the identification of a potential source for therapeutic use in this clinical scenario remains unclear. In this article, we compared the therapeutic effects of various sources of MSCs in terms of efficacy, safety, differentiation potential, durability, accessibility, allogenic preparation and culture expandability to decide the optimal source of MSCs for OA knee.