Mild electrical stimulation with heat shock guides differentiation of embryonic stem cells into Pdx1-expressing cells within the definitive endoderm

Bioelectric Potential in Next-Generation Organoids: Electrical Stimulation to Enhance 3D Structures of the Central Nervous System

Pluripotent stem cell-derived organoid models of the central nervous system represent one of the most exciting areas in in vitro tissue engineering. Classically, organoids of the brain, retina and spinal cord have been generated via recapitulation of in vivo developmental cues, including biochemical and biomechanical. However, a lesser studied cue, bioelectricity, has been shown to regulate central nervous system development and function. In particular, electrical stimulation of neural cells has generated some important phenotypes relating to development and differentiation. Emerging techniques in bioengineering and biomaterials utilise electrical stimulation using conductive polymers. However, state-of-the-art pluripotent stem cell technology has not yet merged with this exciting area of bioelectricity. Here, we discuss recent findings in the field of bioelectricity relating to the central nervous system, possible mechanisms, and how electrical stimulation may be utilised as a novel technique to engineer “next-generation” organoids.

Vertical Nanowire Electrode Array for Enhanced Neurogenesis of Human Neural Stem Cells via Intracellular Electrical Stimulation

Extracellular electrical stimulation (ES) can provide electrical potential from outside the cell membrane, but it is often ineffective due to interference from external factors such as culture medium resistance and membrane capacitance. To address this, we developed a vertical nanowire electrode array (VNEA) to directly provide intracellular electrical potential and current to cells through nanoelectrodes. Using this approach, the cell membrane resistivity and capacitance could be excluded, allowing effective ES. Human fetal neural stem cells (hfNSCs) were cultured on the VNEA for intracellular ES. Combining the structural properties of VNEA and VNEA-mediated ES, transient nanoscale perforation of the electrode was induced, promoting cell penetration and delivering current to the cell. Intracellular ES using VNEA improved the neuronal differentiation of hfNSCs more effectively than extracellular ES and facilitated electrophysiological functional maturation of hfNSCs because of the enhanced voltage-dependent ion-channel activity. The results demonstrate that VNEA with advanced nanoelectrodes serves as a highly effective culture and stimulation platform for stem-cell neurogenesis.

Response of Pluripotent Stem Cells to Environmental Stress and Its Application for Directed Differentiation

Simple Summary

Environmental changes in oxygen concentration, temperature, and mechanical stimulation lead to the activation of specific transcriptional factors and induce the expression of each downstream gene. In general, these responses are protective machinery against such environmental stresses, while these transcriptional factors also regulate cell proliferation, differentiation, and organ development in mammals. In the case of pluripotent stem cells, similar response mechanisms normally work and sometimes stimulate the differentiation cues. Up to now, differentiation protocols utilizing such environmental stresses have been reported to obtain various types of somatic cells from pluripotent stem cells. Basically, environmental stresses as hypoxia (low oxygen), hyperoxia, (high oxygen) and mechanical stress from cell culture plates are relatively safer than chemicals and gene transfers, which affect the genome irreversibly. Therefore, protocols designed with such environments in mind could be useful for the technology development of cell therapy and regenerative medicine. In this manuscript, we summarize recent findings of environmental stress-induced differentiation protocols and discuss their mechanisms.

Abstract

Pluripotent stem cells have unique characteristics compared to somatic cells. In this review, we summarize the response to environmental stresses (hypoxic, oxidative, thermal, and mechanical stresses) in embryonic stem cells (ESCs) and their applications in the differentiation methods directed to specific lineages. Those stresses lead to activation of each specific transcription factor followed by the induction of downstream genes, and one of them regulates lineage specification. In short, hypoxic stress promotes the differentiation of ESCs to mesodermal lineages via HIF-1α activation. Concerning mechanical stress, high stiffness tends to promote mesodermal differentiation, while low stiffness promotes ectodermal differentiation via the modulation of YAP1. Furthermore, each step in the same lineage differentiation favors each appropriate stiffness of culture plate; for example, definitive endoderm favors high stiffness, while pancreatic progenitor favors low stiffness during pancreatic differentiation of human ESCs. Overall, treatments utilizing those stresses have no genotoxic or carcinogenic effects except oxidative stress; therefore, the differentiated cells are safe and could be useful for cell replacement therapy. In particular, the effect of mechanical stress on differentiation is becoming attractive for the field of regenerative medicine. Therefore, the development of a stress-mediated differentiation protocol is an important matter for the future.

Heat Shock Proteins and their Protective Roles in Stem Cell Biology

Stem cells (SCs) are discovered long back but the idea that SCs possess therapeutic potential came up just a few decades back. In a past decade stem cell therapy is highly emerged and displayed tremendous potential for the treatment of a wide range of diseases and disorders such as blindness and vision impairment, type I diabetes, infertility, HIV, etc. SCs are very susceptible to destruction after transplantation into the host because of the inability to sustain elevated stress conditions inside the damaged tissue/organ. Heat shock proteins (HSPs) are molecular chaperones/stress proteins expressed in response to stress (elevated temperature, harmful chemicals, ischemia, viruses, etc) inside a living cell. HSPs protect the cell from damage by assisting in the proper folding of cellular proteins. This review briefly summarises different types of HSPs, their classification, cellular functions as well as the role of HSPs in regulating SC self-renewal and survival in the transplanted host. Applications of HSP modulated SCs in regenerative medicine and for the treatment of ischemic heart disease, myocardial infarction (MI), osteoarthritis, ischemic stroke, spinocerebellar ataxia type 3 (SCA3), leukemia, hepatic ischemia-reperfusion injury, Graft-versus-host disease (GVHD) and Parkinson's disease (PD) are discussed. In order to provide potential insights in understanding molecular mechanisms related to SCs in vertebrates, correlations between HSPs and SCs in cnidarians and planarians are also reviewed. There is a need to advance research in order to validate the use of HSPs for SC therapy and establish effective treatment strategies.

Conductive electrospun scaffolds with electrical stimulation for neural differentiation of conjunctiva mesenchymal stem cells

An electrical stimulus is a new approach to neural differentiation of stem cells. In this work, the neural differentiation of conjunctiva mesenchymal stem cells (CJMSCs) on a new 3D conductive fibrous scaffold of silk fibroin (SF) and reduced graphene oxide (rGo) were examined. rGo (3.5% w/w) was dispersed in SF-acid formic solution (10% w/v) and conductive nanofibrous scaffold was fabricated using the electrospinning method. SEM and TEM microscopies were used for fibrous scaffold characterization. CJMSCs were cultured on the scaffold and 2 electrical impulse models (Current 1:115 V/m, 100-Hz frequency and current 2:115 v/m voltages, 0.1-Hz frequency) were applied for 7 days. Also, the effect of the fibrous scaffold and electrical impulses on cell viability and neural gene expression were examined using MTT assay and qPCR analysis. Fibrous scaffold with the 220 ± 20 nm diameter and good dispersion of graphene nanosheets at the surface of nanofibers were fabricated. The MTT result showed the viability of cells on the scaffold, with current 2 lower than current 1. qPCR analysis confirmed that the expression of β-tubulin (2.4-fold P ≤ 0.026), MAP-2 (1.48-fold; P ≤ 0.03), and nestin (1.5-fold; P ≤ 0.03) genes were higher in CJMSCs on conductive scaffold with 100-Hz frequency compared to 0.1-Hz frequency. Collectively, we proposed that SF-rGo fibrous scaffolds, as a new conductive fibrous scaffold with electrical stimulation are good strategies for neural differentiation of stem cells and the type of electrical pulses has an influence on neural differentiation and proliferation of CJMSCs.

Cardiomyocyte differentiation of mesenchymal stem cells from bone marrow: new regulators and its implications

In the past years, cardiac mortality has decreased, but cardiac diseases are still responsible for millions of deaths every year worldwide. Bone-marrow mesenchymal stem cells (BMSCs) transplantation may be a promising therapeutic strategy because of its capacity to differentiate into cardiac cells. Current research indicates that chemical substances, microRNAs, and cytokines have biological functions that regulate the cardiomyocytes differentiation of BMSCs. In this review, we chiefly summarize the regulatory factors that induce BMSCs to differentiate into cardiomyocytes.

Beta-cell replacement strategies for diabetes

Diabetes is characterized by elevated levels of blood glucose as a result of insufficient production of insulin from loss or dysfunction of pancreatic islet β-cells. Here, we review several approaches to replacing β-cells that were recently discussed at a symposium held in Kyoto, Japan. Transplant of donor human islets can effectively treat diabetes and eliminate the need for insulin injections, supporting research aimed at identifying abundant supplies of cells. Studies showing the feasibility of producing mouse islets in rats support the concept of generating pigs with human pancreas that can serve as donors of human islets, although scientific and ethical challenges remain. Alternatively, in vitro differentiation of both human embryonic stem cells and induced pluripotent stem cells is being actively pursued as an islet cell source, and embryonic stem cell-derived pancreatic progenitor cells are now in clinical trials in North America in patients with diabetes. Macro-encapsulation devices are being used to contain and protect the cells from immune attack, and alternate strategies of immune-isolation are being pursued, such as islets contained within long microfibers. Recent advancements in genetic engineering tools offer exciting opportunities to broaden therapeutic strategies and to probe the genetic involvement in β-cell failure that contributes to diabetes. Personalized medicine might eventually become a possibility with genetically edited patient-induced pluripotent stem cells, and the development of simplified robust differentiation protocols that ideally become standardized and automated. Additional efforts to develop a safe and effective β-cell replacement strategy to treat diabetes are warranted.