Induced pluripotent stem cell research: A revolutionary approach to face the challenges in drug screening

iPSCs: A Preclinical Drug Research Tool for Neurological Disorders

The development and commercialization of new drugs is an articulated, lengthy, and very expensive process that proceeds through several steps, starting from target identification, screening new leading compounds for testing in preclinical studies, and subsequently in clinical trials to reach the final approval for therapeutic use. Preclinical studies are usually performed using both cell cultures and animal models, although they do not completely resume the complexity of human diseases, in particular neurodegenerative conditions. To this regard, stem cells represent a powerful tool in all steps of drug discovery. The recent advancement in induced Pluripotent Stem Cells (iPSCs) technology has opened the possibility to obtain patient-specific disease models for drug screening and development. Here, we report the use of iPSCs as a disease model for drug development in the contest of neurological disorders, including Alzheimer’s (AD) and Parkinson’s disease (PD), Amyotrophic lateral Sclerosis (ALS), and Fragile X syndrome (FRAX).

Integrated Genomic Medicine: A Paradigm for Rare Diseases and Beyond

Individualized medicine, or the tailoring of therapeutic interventions to a patient's unique genetic, biochemical, physiological, exposure and behavioral profile, has been enhanced, if not enabled, by modern biomedical technologies such as high-throughput DNA sequencing platforms, induced pluripotent stem cell assays, biomarker discovery protocols, imaging modalities, and wireless monitoring devices. Despite successes in the isolated use of these technologies, however, it is arguable that their combined and integrated use in focused studies of individual patients is the best way to not only tailor interventions for those patients, but also shed light on treatment strategies for patients with similar conditions. This is particularly true for individuals with rare diseases since, by definition, they will require study without recourse to other individuals, or at least without recourse to many other individuals. Such integration and focus will require new biomedical scientific paradigms and infrastructure, including the creation of databases harboring study results, the formation of dedicated multidisciplinary research teams and new training programs. We consider the motivation and potential for such integration, point out areas in need of improvement, and argue for greater emphasis on improving patient health via technological innovations, not merely improving the technologies themselves. We also argue that the paradigm described can, in theory, be extended to the study of individuals with more common diseases.

The potential of nanoparticles in stem cell differentiation and further therapeutic applications

Tissue regeneration could offer therapeutic advantages for individuals experiencing organ or tissue damage. Recently, advances in nanotechnology have provided various nanomaterials, with a wide range of applications, for modulating stem cell behavior and for further therapeutic applications in tissue regeneration. Defects in cell proliferation and differentiation, a low mechanical strength of scaffolds, and inefficient production of factors that are essential for stem cell differentiation are the current challenges in tissue regeneration. This review provides a brief explanation about the link between nanotechnology and tissue engineering, highlighting the current literature about the interaction between nanoparticles (NPs) and stem cells, the promotional effect of NPs on stem cell differentiation into various lineages, and their possible therapeutic applications. We also tried to describe the mechanism through which NPs regulate the spatial-temporal release and kinetics of vital growth and differentiation factors, enhance stem cell differentiation, and improve culture conditions for in vivo tissue regeneration. The field of nanotechnology is promising and provides novel nanomaterials and methods with valuable clinical applications in the regenerative medicine. Understanding the mechanism, as well as the toxic effects of NPs in stem cell biology will undoubtedly provide valuable insight into their clinical application in the regenerative medicine.

Efficient mRNA delivery with graphene oxide-polyethylenimine for generation of footprint-free human induced pluripotent stem cells

Clinical applications of induced pluripotent stem cells (iPSCs) require development of technologies for the production of "footprint-free" (gene integration-free) iPSCs, which avoid the potential risk of insertional mutagenesis in humans. Previously, several studies have shown that mRNA transfer can generate "footprint-free" iPSCs, but these studies did not use a delivery vehicle and thus repetitive daily transfection was required because of mRNA degradation. Here, we report an mRNA delivery system employing graphene oxide (GO)-polyethylenimine (PEI) complexes for the efficient generation of "footprint-free" iPSCs. GO-PEI complexes were found to be very effective for loading mRNA of reprogramming transcription factors and protection from mRNA degradation by RNase. Dynamic suspension cultures of GO-PEI/RNA complexes-treated cells dramatically increased the reprogramming efficiency and successfully generated rat and human iPSCs from adult adipose tissue-derived fibroblasts without repetitive daily transfection. The iPSCs showed all the hallmarks of pluripotent stem cells including expression of pluripotency genes, epigenetic reprogramming, and differentiation into the three germ layers. These results demonstrate that mRNA delivery using GO-PEI-RNA complexes can efficiently generate "footprint-free" iPSCs, which may advance the translation of iPSC technology into the clinical settings.

G protein-coupled receptors in stem cell maintenance and somatic reprogramming to pluripotent or cancer stem cells

G protein-coupled receptors (GPCRs) are a large class of transmembrane receptors categorized into five distinct families: rhodopsin, secretin, adhesion, glutamate, and frizzled. They bind and regulate 80% of all hormones and account for 20-50% of the pharmaceuticals currently on the market. Hundreds of GPCRs integrate and coordinate the functions of individual cells, mediating signaling between various organs. GPCRs are crucial players in tumor progression, adipogenesis, and inflammation. Several studies have also confirmed their central roles in embryonic development and stem cell maintenance. Recently, GPCRs have emerged as key players in the regulation of cell survival, proliferation, migration, and self-renewal in pluripotent (PSCs) and cancer stem cells (CSCs). Our study and other reports have revealed that the expression of many GPCRs is modulated during the generation of induced PSCs (iPSCs) or CSCs as well as during CSC sphere formation. These GPCRs may have crucial roles in the regulation of selfrenewal and other biological properties of iPSCs and CSCs. This review addresses the current understanding of the role of GPCRs in stem cell maintenance and somatic reprogramming to PSCs or CSCs.

Retinoid Processing in Induced Pluripotent Stem Cell-Derived Retinal Pigment Epithelium Cultures

Stem cell therapy for retinal degenerative diseases such as age-related macular degeneration is a promising clinical option for the replacement of photoreceptors and retinal pigment epithelium (RPE). Induced pluripotent stem cell technology has emerged as a viable potential source of cells for transplantation in retinal degenerative disorders. Induced pluripotent stem cells have been used to derive RPE and have been tested for their functional behavior. These cells have the ability to express RPE-specific proteins and morphologically resemble native RPE. Induced pluripotent stem cell-derived RPE are also able to contribute to the visual cycle by their ability to metabolize all-trans retinol, a critical function of RPE in maintaining visual function. Advances in induced pluripotent stem cell technology will contribute to the development of clinical therapies for retinal degenerative diseases as well as provide a tool to understand the pathology of these disorders.

Cultured Cells from the Human Oocyte Cumulus Niche Are Efficient Feeders to Propagate Pluripotent Stem Cells

Pluripotency is at the crossroads of stem cell research and biology of reproduction. The mature metaphase II oocyte contains the key factors for pluripotency induction and maintenance as assessed by its capacity to reprogram somatic nuclei. The cumulus cells (CCs) niche that surrounds the oocyte is crucial for its maturation and presumably for the oocyte to acquire its competence to confer pluripotency. In this study, we examined whether cells cultured from the human mature metaphase II oocyte CC niche (hCC) could be used as feeders for the propagation of human induced pluripotent stem cells. The induced pluripotent (iPS) cells cultured on hCC (hCC-iPS) were assessed for their pluripotency potential by their expression of pluripotency-associated genes such as Oct4, Nanog, and TRA1-60 and their competence to differentiate into the three germ layers in vitro (embryoid bodies) as well as in vivo (teratoma formation). We show that not only the hCC-iPS cells maintained their pluripotency potential, but they also exhibited much better self-renewal performance in terms of proliferation rate compared to the same cells cultured on human foreskin fibroblast (hFF) feeders (hFF-iPS). A comparative gene expression profile study of hCC and hFF revealed significant differences (P < 0.05) in expression of cellular matrix components and an upregulation in hCC of genes known to be important players in cell proliferation such as interleukin 6 gene (IL6).

Negligible immunogenicity of induced pluripotent stem cells derived from human skin fibroblasts

Human induced pluripotent stem cells (hiPSCs) have potential applications in cell replacement therapy and regenerative medicine. However, limited information is available regarding the immunologic features of iPSCs. In this study, expression of MHC and T cell co-stimulatory molecules in hiPSCs, and the effects on activation, proliferation and cytokine production in allogeneic human peripheral blood mononuclear cells were examined. We found that no-integrate hiPSCs had no MHC-II and T cell co-stimulatory molecules expressions but had moderate level of MHC-I and HLA-G expressions. In contrast to human skin fibroblasts (HSFs) which significantly induced allogeneic T cell activation and proliferation, hiPSCs failed to induce allogeneic CD45⁺ lymphocyte and CD8⁺ T cell activation and proliferation but could induce a low level of allogeneic CD4⁺ T cell proliferation. Unlike HSFs which induced allogeneic lymphocytes to produce high levels of IFN-γ, TNF-α and IL-17, hiPSCs only induced allogeneic lymphocytes to produce IL-2 and IL-10, and promote IL-10-secreting regulatory T cell (Treg) generation. Our study suggests that the integration-free hiPSCs had low or negligible immunogenicity, which may result from their induction of IL-10-secreting Treg.

Direct reprogramming of fibroblasts into myocytes to reverse fibrosis

Heart disease is a major cause of morbidity and mortality worldwide. The low regenerative capacity of adult human hearts has thus far limited the available therapeutic approaches for heart failure. Therefore, new therapies that can regenerate damaged myocardium and improve heart function are urgently needed. Although cell transplantation-based therapies may hold great potential, direct reprogramming of endogenous cardiac fibroblasts, which represent more than half of the cells in the heart, into functional cardiomyocytes in situ may be an alternative strategy by which to regenerate the heart. We and others demonstrated that functional cardiomyocytes can be directly generated from fibroblasts by using several combinations of cardiac-enriched factors in mouse and human. In vivo gene delivery of cardiac reprogramming factors generates new cardiac muscle and improved heart function after myocardial infarction in mouse. This article reviews recent progress in cardiac reprogramming research and discusses the perspectives and challenges of this new technology for future regenerative therapy.

The hallmarks of Parkinson's disease

Since the discovery of dopamine as a neurotransmitter in the 1950s, Parkinson's disease (PD) research has generated a rich and complex body of knowledge, revealing PD to be an age-related multifactorial disease, influenced by both genetic and environmental factors. The tremendous complexity of the disease is increased by a nonlinear progression of the pathogenesis between molecular, cellular and organic systems. In this minireview, we explore the complexity of PD and propose a systems-based approach, organizing the available information around cellular disease hallmarks. We encourage our peers to adopt this cell-based view with the aim of improving communication in interdisciplinary research endeavors targeting the molecular events, modulatory cell-to-cell signaling pathways and emerging clinical phenotypes related to PD.

Direct reprogramming of mouse fibroblasts into cardiac myocytes

The potency of specific transcription factors as cell fate determinants was first demonstrated by the discovery of MyoD, a master gene for skeletal muscle transdifferentiation. More recently, the induction of pluripotency in somatic cells using a combination of stem cell-specific transcription factors has been reported. That elegant study altered the approach to regenerative medicine and inspired new strategies for generating specific cell types by introducing combinations of lineage-specific transcription factors. A diverse range of cell types, such as pancreatic β-cells, neurons, chondrocytes, and hepatocytes, can be induced from heterologous cells using lineage-specific reprogramming factors. Furthermore, functional cardiomyocytes can be generated directly from differentiated somatic cells using several combinations of cardiac-enriched defined factors in the mouse. The present article reviews the pioneering and recent studies in cellular reprogramming and discusses the perspectives and challenges of direct cardiac reprogramming in regenerative therapy.