Distinct Stem Cell Types Research Articles

Unraveling Epilepsy: Investigating stem cell approaches for innovative treatment and future cure

Epilepsy is a persistent neurological disorder characterized by repeated, spontaneous seizures that arise without a specific cause. These seizures result from abnormal electrical activity in the brain, leading to a range of symptoms, from brief periods of unconsciousness or minor sensory disturbances to severe convulsions. The management of epilepsy remains a significant challenge, as current treatment modalities, primarily involving antiepileptic drugs and surgical interventions to remove seizure foci, often provide adequate control for a substantial portion of patients. For this reason, stem cell therapies have become a hopeful approach because of their ability to potentially restore and renew impaired neural networks, which is particularly relevant for neurological disorders like epilepsy. This review investigates the present state of stem cell therapies in epilepsy, analyzing distinct types of stem cells, their mode of action, preclinical and clinical trials, as well as future research prospects.

Enhancement strategy for effective vascular regeneration following myocardial infarction through a dual stem cell approach

Since an impaired coronary blood supply following myocardial infarction (MI) negatively affects heart function, therapeutic neovascularization is considered one of the major therapeutic strategies for cell-based cardiac repair. Here, to more effectively achieve therapeutic neovascularization in ischemic hearts, we developed a dual stem cell approach for effective vascular regeneration by utilizing two distinct types of stem cells, CD31+-endothelial cells derived from human induced pluripotent stem cells (hiPSC-ECs) and engineered human mesenchymal stem cells that continuously secrete stromal derived factor-1α (SDF-eMSCs), to simultaneously promote natal vasculogenesis and angiogenesis, two core mechanisms of neovascularization. To induce more comprehensive vascular regeneration, we intramyocardially injected hiPSC-ECs to produce de novo vessels, possibly via vasculogenesis, and a 3D cardiac patch encapsulating SDF-eMSCs (SDF-eMSC-PA) to enhance angiogenesis through prolonged secretion of paracrine factors, including SDF-1α, was implanted into the epicardium of ischemic hearts. We verified that hiPSC-ECs directly contribute to de novo vessel formation in ischemic hearts, resulting in enhanced cardiac function. In addition, the concomitant implantation of SDF1α-eMSC-PAs substantially improved the survival, retention, and vasculogenic potential of hiPSC-ECs, ultimately achieving more comprehensive neovascularization in the MI hearts. Of note, the newly formed vessels through the dual stem cell approach were significantly larger and more functional than those formed by hiPSC-ECs alone. In conclusion, these results provide compelling evidence that our strategy for effective vascular regeneration can be an effective means to treat ischemic heart disease.

Two distinct trophectoderm lineage stem cells from human pluripotent stem cells

The trophectoderm layer of the blastocyst-stage embryo is the precursor for all trophoblast cells in the placenta. Human trophoblast stem (TS) cells have emerged as an attractive tool for studies on early trophoblast development. However, the use of TS cell models is constrained by the limited genetic diversity of existing TS cell lines and restrictions on using human fetal tissue or embryos needed to generate additional lines. Here we report the derivation of two distinct stem cell types of the trophectoderm lineage from human pluripotent stem cells. Analogous to villous cytotrophoblasts in vivo, the first is a CDX2- stem cell comparable with placenta-derived TS cells—they both exhibit identical expression of key markers, are maintained in culture and differentiate under similar conditions, and share high transcriptome similarity. The second is a CDX2+ stem cell with distinct cell culture requirements, and differences in gene expression and differentiation, relative to CDX2- stem cells. Derivation of TS cells from pluripotent stem cells will significantly enable construction of in vitro models for normal and pathological placental development.

Heparan Sulfate Proteoglycans: Key Mediators of Stem Cell Function.

Heparan sulfate proteoglycans (HSPGs) are an evolutionarily ancient subclass of glycoproteins with exquisite structural complexity. They are ubiquitously expressed across tissues and have been found to exert a multitude of effects on cell behavior and the surrounding microenvironment. Evidence has shown that heterogeneity in HSPG composition is crucial to its functions as an essential scaffolding component in the extracellular matrix as well as a vital cell surface signaling co-receptor. Here, we provide an overview of the significance of HSPGs as essential regulators of stem cell function. We discuss the various roles of HSPGs in distinct stem cell types during key physiological events, from development through to tissue homeostasis and regeneration. The contribution of aberrant HSPG production to altered stem cell properties and dysregulated cellular homeostasis characteristic of cancer is also reviewed. Finally, we consider approaches to better understand and exploit the multifaceted functions of HSPGs in influencing stem cell characteristics for cell therapy and associated culture expansion strategies.

CardioClusters: Enhancing Stem Cell Engraftment and Myocardial Repair

Introduction: Stem cells are routinely utilized to blunt damage and enhance repair following pathologic injury to the heart, but marginal engraftment, persistence, and cell communication remain significant challenges. Combinatorial stem cell delivery to enhance repair only partially addresses these issues. A novel approach has been developed by creating “CardioClusters”: three dimensional microenvironments consisting of three distinct types of stem cells isolated from the human heart and tested for intramyocardial injection into infarcted myocardium.

Intestinal Stem Cell Pool Regulation in Drosophila.

SummaryIntestinal epithelial renewal is mediated by intestinal stem cells (ISCs) that exist in a state of neutral drift, wherein individual ISC lineages are regularly lost and born but ISC numbers remain constant. To test whether an active mechanism maintains stem cell pools in the Drosophila midgut, we performed partial ISC depletion. In contrast to the mouse intestine, Drosophila ISCs failed to repopulate the gut after partial depletion. Even when the midgut was challenged to regenerate by infection, ISCs retained normal proportions of asymmetric division and ISC pools did not increase. We discovered, however, that the loss of differentiated midgut enterocytes (ECs) slows when ISC division is suppressed and accelerates when ISC division increases. This plasticity in rates of EC turnover appears to facilitate epithelial homeostasis even after stem cell pools are compromised. Our study identifies unique behaviors of Drosophila midgut cells that maintain epithelial homeostasis.

Argonaute and Argonaute-Bound Small RNAs in Stem Cells.

Small RNAs are essential for a variety of cellular functions. Argonaute (AGO) proteins are associated with all of the different classes of small RNAs, and are indispensable in small RNA-mediated regulatory pathways. AGO proteins have been identified in various types of stem cells in diverse species from plants and animals. This review article highlights recent progress on how AGO proteins and AGO-bound small RNAs regulate the self-renewal and differentiation of distinct stem cell types, including pluripotent, germline, somatic, and cancer stem cells.

Cell-specific transcriptomic analyses of three-dimensional shoot development in the moss Physcomitrella patens.

Haploid moss gametophytes harbor distinct stem cell types, including tip cells that divide in single planes to generate filamentous protonemata, and bud cells that divide in three planes to yield axial gametophore shoots. This transition from filamentous to triplanar growth occurs progressively during the moss life cycle, and is thought to mirror evolution of the first terrestrial plants from Charophycean green algal ancestors. The innovation of morphologically complex plant body plans facilitated colonization of the vertical landscape, and enabled development of complex vegetative and reproductive plant morphologies. Despite its profound evolutionary significance, the molecular programs involved in this transition from filamentous to triplanar meristematic plant growth are poorly understood. In this study, we used single-cell type transcriptomics to identify more than 4000 differentially expressed genes that distinguish uniplanar protonematal tip cells from multiplanar gametophore bud cells in the moss Physcomitrella patens. While the transcriptomes of both tip and bud cells show molecular signatures of proliferative cells, the bud cell transcriptome exhibits a wider variety of genes with significantly increased transcript abundances. Our data suggest that combined expression of genes involved in shoot patterning and asymmetric cell division accompanies the transition from uniplanar to triplanar meristematic growth in moss.

PrP(C) from stem cells to cancer.

The cellular prion protein PrPC was initially discovered as the normal counterpart of the pathological scrapie prion protein PrPSc, the main component of the infectious agent of Transmissible Spongiform Encephalopathies. While clues as to the physiological function of this ubiquitous protein were greatly anticipated from the development of knockout animals, PrP-null mice turned out to be viable and to develop without major phenotypic abnormalities. Notwithstanding, the discovery that hematopoietic stem cells from PrP-null mice have impaired long-term repopulating potential has set the stage for investigating into the role of PrPC in stem cell biology. A wealth of data have now exemplified that PrPC is expressed in distinct types of stem cells and regulates their self-renewal as well as their differentiation potential. A role for PrPC in the fate restriction of embryonic stem cells has further been proposed. Paralleling these observations, an overexpression of PrPC has been documented in various types of tumors. In line with the contribution of PrPC to stemness and to the proliferation of cancer cells, PrPC was recently found to be enriched in subpopulations of tumor-initiating cells. In the present review, we summarize the current knowledge of the role played by PrPC in stem cell biology and discuss how the subversion of its function may contribute to cancer progression.

Grand challenges in the field of stem cell research.

DISCOVERY OF ADULT STEM CELLS In 1961, Mauro first discovered that skeletal muscle fibers of frogs contain mononuclear cells underneath the basal lamina by electron microscope and termed these “satellite cells” (Mauro, 1961). By contrast, they failed to find any satellite-like cells in cardiac muscle after thorough search of electron micrographs. Since then, satellite cells have been confirmed to be a true stem cell for skeletal muscle (von Maltzahn et al., 2013). Adult skeletal muscle possesses extraordinary regeneration capability (Seale and Rudnicki, 2000). After exercise or muscle injury, large numbers of new muscle fibers are normally formed within a week because of expansion and differentiation of muscle satellite cells as a stem cell population for muscle regeneration. In the same year, Till and McCulloch first established the concept of stem cells using bone marrow transplantation into irradiated mice (Till and McCulloch, 1961; Armstrong et al., 2012). They found that donorderived hematopoietic stem cells (HSCs) or progenitor cells can be colonized in the recipient spleen after transplantation. A single colony can give rise to multiple hematopoietic lineages as well as stem or progenitor cells, indicating the multipotent differentiation and self-renewal abilities for the HSCs or progenitor cells. In the last two decades, experiments have established the existence of adult stem cells in most tissues that appear to have the ability to differentiate into specific cell types following injury as a means of regeneration in vivo (Barker et al., 2010). For example, neural stem cells (NSCs) from the central nervous system can generate multiple neural cell types to respond (Gage and Temple, 2013). Bone marrow contains two distinct stem cell types: marrow stromal cells and HSCs. HSCs possess their ability to produce all blood cell lineages (Ugarte and Forsberg, 2013). Multipotent mesenchymal stem cells derived from marrow stromal cells can differentiate into a wide variety of cell lineages, including skeletal muscle, neurons, and hematopoietic cells in vitro and following transplantation (Pittenger et al., 1999; Dimarino et al., 2013). Therefore, many or all tissues may contain a population of stem cells that can differentiate in an appropriate manner in response to the growth factors and signals provided by their host tissues. The current challenge is to understand the molecular mechanisms of how these adult stem cells maintain their stem cell qualities: specific differentiation capability, self-renewal activity, and response to the microenvironments of the stem cell niche.

Roles of Reactive Oxygen Species in the Fate of Stem Cells

Stem cells are characterized by the properties of self-renewal and the ability to differentiate into multiple cell types, and thus maintain tissue homeostasis. Reactive oxygen species (ROS) are a natural byproduct of aerobic metabolism and have roles in cell signaling. Regulation of ROS has a vital role in maintaining "stemness" and differentiation of the stem cells, as well as in progression of stem-cell-associated diseases. As of late, much research has been done on the adverse effects of ROS in stem cells. However, recently it has become apparent that in some cases redox status of the stem cell does have a role in maintaining its identity as such. Both pluripotent and multipotent stem cell types have been reported to possess enzymatic and nonenzymatic mechanisms for detoxification of ROS and to correct oxidative damage to the genome as well as the proteome. Although context dependent and somewhat varied among different stem cell types, the correlation seems to exist between antioxidant defense level and stem cell fate change (i.e., proliferation, differentiation, and death). Changes in stem cell redox regulation may affect the pathogenesis of various human diseases. Dissecting the defined roles of ROS in distinct stem cell types will greatly enhance their basic and translational applications. Here, we discuss the various roles of ROS in adult, embryonic, and induced pluripotent stem cells.

Mesoderm-Derived Stem Cells: The Link Between the Transcriptome and Their Differentiation Potential

Human adult stem cells (hASCs) have become an attractive source for autologous cell transplantation, tissue engineering, developmental biology, and the generation of human-based alternative in vitro models. Among the 3 germ cell layers, the mesoderm is the origin of today's most widely used and characterized hASC populations. A variety of isolated nonhematopoietic mesoderm-derived stem cell populations exist, and all of them show important differences in terms of function, efficacy, and differentiation potential both in vivo and in vitro. To better understand whether the intrinsic properties of these cells contribute to the overall differentiation potential of hASCs, we compared the global gene expression profiles of 4 mesoderm-derived stem cell populations: human adipose tissue-derived stromal cells, human bone marrow-derived stromal cells (hBMSCs), human (fore)skin-derived precursor cells (hSKPs), and human Wharton's jelly-derived mesenchymal stem cells (hWJs). Significant differences in gene expression profiles were detected between distinct stem cell types. hSKPs predominantly expressed genes involved in neurogenesis, skin, and bone development, whereas hWJs and, to some extent, hBMSCs showed an increased expression of genes involved in cardiovascular and liver development. Interestingly, the observed differential gene expression of distinct hASCs could be linked to existing differentiation data in which hASCs were differentiated toward specific cell types. As such, our data suggest that the intrinsic gene expression of the undifferentiated stem cells has an important impact on their overall differentiation potential as well as their application in stem cell-based research. Yet, the factors that define these intrinsic properties remain to be determined.

Stem cell therapy in retinal diseases?

term evidence based medicine (EBM) was first published in 1992, with the term defined in 1996 using a definition that is still widely used today: The conscientious, explicit and judicious use of current best evidence about individual patient care. practice of EBM allows the integration of available evidence from systematic research, specifically clinical research, and the best clinical judgment of the clinician(1,2). EBM is defined as the link between scientific research and good clinical practice(3,4). In other words, EBM trials use existing scientific data with good internal and external validity, to enforce the results in clinical practice. Evidence in this context is related to the effectiveness, efficiency, efficacy and safety of treatment. Effectiveness refers to how treatment functions in real-world conditions, efficiency to cheap and affordable treatment for patients, efficacy is how the treatment works in conditions of the ideal world, and safety means that an intervention is consistent and unlikely to cause any adverse effects(5). A study with high internal validity must comply with these characteristics(6). The concept of stem cell therapy has been advocated for more than 10 years and there has been a growing number of clinical reports documenting the use of stem cell therapies in humans in particular in respect to myocardial infarction(7-9). In respect to ophthalmology, several important cell types in the eye have little, if any, capacity for endogenous regeneration. As a result the only viable treatment option for patients with hereditary disorders that involve the loss of such cells is some type of cell replacement therapy. Although the replacement of highly differentiated cells, such as photoreceptors, poses challenges, a number of recent experiments suggest that the use of stem cells to achieve this goal is now feasible(10). Distinct stem cell types have been established from embryos and identified in fetal tissues and umbilical cord blood as well as in specific niches in many adult mammalian tissues and organs such as in the bone marrow, brain, skin, eyes, heart, kidneys, lungs, gastrointestinal tract, pancreas, liver, breast, ovaries, and prostate gland(11). Stem cell-based therapy has been tested in animal models for several diseases including neurodegenerative disorders, such as Parkinson disease, spinal cord injury, and multiple sclerosis. Replacing lost neurons which have not been physiologically replaced is pivotal to therapeutic success. Stem-cell therapy has the potential to treat a wide range of retinal diseases. neuroretina is a complex structure whose health depends on blood vessels and retinal pigment epithelium (RPE), each of which is affected differently in the spectrum of retinal disease. Therefore, three distinct cell types are conceivable targets for future cell therapy in the retina: the neuroretina (photoreceptors, bipolar cells, ganglion cells and glial cells), RPE and vascular endothelial cells. Depending on the type of retina disease, different cell replacement strategies will need to be developed(12). Degeneration of neural cells in the retina is a hallmark of such widespread ocular diseases as age-related macular degeneration (AMD) and retinitis pigmentosa (RP). In these cases the loss of photoreceptors that occurs as a primary event (as in RP) or secondary to loss of retinalpigment epithelium (in AMD) leads to blindness(11,13,14).

Stem cell therapy for retinal diseases: update

Distinct stem cell types have been established from embryos and identified in the fetal tissues and umbilical cord blood as well as in specific niches in many adult mammalian tissues and organs such as bone marrow, brain, skin, eyes, heart, kidneys, lungs, gastrointestinal tract, pancreas, liver, breast, ovaries, and prostate. All stem cells are undifferentiated cells that exhibit unlimited self-renewal and can generate multiple cell lineages or more restricted progenitor populations that can contribute to tissue homeostasis by replenishing the cells or to tissue regeneration after injury. The remarkable progress of regenerative medicine in the last few years indicates promise for the use of stem cells in the treatment of ophthalmic disorders. Experimental and human studies with intravitreal bone marrow-derived stem cells have begun. This paper reviews recent advances and potential sources of stem cells for cell therapy in retinal diseases.

Selection of Stable Reference Genes for Quantitative RT-PCR Comparisons of Mouse Embryonic and Extra-Embryonic Stem Cells

Isolation and culture of both embryonic and tissue specific stem cells provide an enormous opportunity to study the molecular processes driving development. To gain insight into the initial events underpinning mammalian embryogenesis, pluripotent stem cells from each of the three distinct lineages present within the preimplantation blastocyst have been derived. Embryonic (ES), trophectoderm (TS) and extraembryonic endoderm (XEN) stem cells possess the developmental potential of their founding lineages and seemingly utilize distinct epigenetic modalities to program gene expression. However, the basis for these differing cellular identities and epigenetic properties remain poorly defined.Quantitative reverse transcription-polymerase chain reaction (qPCR) is a powerful and efficient means of rapidly comparing patterns of gene expression between different developmental stages and experimental conditions. However, careful, empirical selection of appropriate reference genes is essential to accurately measuring transcriptional differences. Here we report the quantitation and evaluation of fourteen commonly used references genes between ES, TS and XEN stem cells. These included: Actb, B2m, Hsp70, Gapdh, Gusb, H2afz, Hk2, Hprt, Pgk1, Ppia, Rn7sk, Sdha, Tbp and Ywhaz. Utilizing three independent statistical analysis, we identify Pgk1, Sdha and Tbp as the most stable reference genes between each of these stem cell types. Furthermore, we identify Sdha, Tbp and Ywhaz as well as Ywhaz, Pgk1 and Hk2 as the three most stable reference genes through the in vitro differentiation of embryonic and trophectoderm stem cells respectively.Understanding the transcriptional and epigenetic regulatory mechanisms controlling cellular identity within these distinct stem cell types provides essential insight into cellular processes controlling both embryogenesis and stem cell biology. Normalizing quantitative RT-PCR measurements using the geometric mean CT values obtained for the identified mRNAs, offers a reliable method to assess differing patterns of gene expression between the three founding stem cell lineages present within the mammalian preimplantation embryo.

Regulation of early trophoblast differentiation – Lessons from the mouse

The earliest stages of trophoblast differentiation are of tremendous importance to mediate implantation and to lay the anatomical foundations for normal placental development and function throughout gestation. Yet our molecular insights into these early developmental processes in humans have been limited by the inaccessibility of material and the unavailability of trophoblast cell lines that fully recapitulate the behaviour of early placental trophoblast. In this review we highlight recent advances that have come from the study of distinct stem cell types representative of the embryonic and extraembryonic lineages in the mouse, and from the study of mouse mutants. These models have revealed the presence of intricate transcriptional networks that are set up by signalling pathways, translating extracellular growth factor and cell positional information into distinct lineage-specific transcriptional programmes. The trophoblast specificity of these networks is ensured by epigenetic mechanisms including DNA methylation and histone modifications that complement each other to define trophoblast cell fate and differentiation. Despite the anatomical differences between mouse and human placentas, it seems that important aspects of early trophoblast specification are conserved between both species. Thus we may be able to build on our insights from the mouse to better understand early trophoblast differentiation in the human conceptus which is important for improving assisted reproductive technologies and may enable us in the future to derive human trophoblast stem cell lines. These advances will facilitate the investigation of genetic, epigenetic and environmental influences on early trophoblast differentiation in normal as well as in pathological conditions.

Cell and molecular regulation of the mouse blastocyst

Animals use diverse strategies to specify tissue lineages during development. A common strategy is to partition maternally supplied and localized lineage determinants into progenitor cells. The mouse embryo appears to use a different, more regulative strategy to specify the first three lineages: the epiblast (EPI: future embryo), the trophectoderm (TE: future placenta), and the primitive endoderm (PE: future yolk sac). These lineages are specified during two successive differentiation steps leading to formation of the blastocyst. Here, we review classic and contemporary models of early lineage specification in the mouse, and describe recent efforts to understand the molecular regulation of these events. We describe evidence that trophectoderm differentiation bears resemblance to the process of epithelialization and describe the importance of apical/basal protein complexes in regulating this process. Next, we present a revised model of PE specification, and describe evidence that PE cells in the inner cell mass sort out to occupy their ultimate position on the surface of the EPI. Finally, we describe factors that reinforce these lineages and three distinct stem cell types that can be isolated from them. Together, these mechanisms guide the differentiation of the first lineages of the mouse and thereby set up tissues that will be important for the first steps of embryonic body patterning.

Little evidence of transdifferentiation of bone marrow-derived cells into pancreatic beta cells.

Bone marrow cells contain at least two distinct types of stem cells which are haematopoietic stem cells and mesenchymal stem cells. Both cells have the ability to differentiate into a variety of cell types derived from all three germ layers. Thus, bone marrow stem cells could possibly be used to generate new pancreatic beta cells for the treatment of diabetes. In this study, we investigated the feasibility of bone marrow-derived cells to differentiate into beta cells in pancreas. Using green fluorescent protein transgenic mice as donors, the distribution of haematogenous cells in the pancreas was studied after bone marrow transplantation. In the pancreas of green fluorescent protein chimeric mice, green fluorescent protein-positive cells were found in the islets, but none of these cells expressed insulin. Previous data has suggested that tissue injury can recruit haematopoietic stem cells or their progeny to a non-haematopietic cell fate. Therefore, low-dose streptozotocin (30 or 50 mg/kg on five consecutive days) was injected into the mice 5 weeks after bone marrow transplantation, but no green fluorescent protein-positive cells expressing insulin were seen in the islets or around the ducts of the pancreas. Our data suggests that bone marrow-derived cells are a distinct cell population from islet cells and that transdifferentiation from bone marrow-derived cells to pancreatic beta cells is rarely observed.

Hemoglobin switching in the salamanderPleurodeles waltlii : Immunofluorescence detection of larval and adult hemoglobins in single erythrocytes.

In order to study the cellular distribution of larval and adult hemoglobins during larval development ofPleurodeles waltlii a double specific immunofluorescent labelling technique was developed.Rabbit antibodies specific for larval and adult hemoglobin components were prepared and conjugated with tetramethyl-rhodamine isothiocyanate for the anti-larval antibodies and fluorescein isothiocyanate for the anti-adult hemoglobin antibodies.Both simultaneous and sequential staining with the two types of fluorescent antibodies indicated that larval and adult hemoglobins were never observed within the same erythrocyte during development. The results provide evidence that two distinct cell populations exist, one synthesizing exclusively larval hemoglobins which is progressively replaced by the other one synthesizing exclusively adult hemoglobins. It remains to be determined if these two populations arise from two distinct types of stem cells (adult and larval) or from the same stem cell type.

The histogenesis of glandular neoplasia

Tissues in the organism may be divided according to their proliferative capacities into three categories: 1. Fast replicators (FR) e.g., epidermis; 2. Slow replicators (SR) e.g., liver and 3. Non replicators (NR) e.g., nerve cells. Evidence is presented that FR as well as SR tissues continuously proliferate exhibiting two distinct histomorphological structures; a progenitor region in which cells are formed and a functional region into which they enter. Throughout their displacement, the cells cover a typical path denominated as tissue radius. The SR tissues e.g., parotid gland, mammary gland, liver and prostate, exhibit similar ontogenies, and proceed during regeneration and neoplasia through similar stages. All are compound glands with two distinct stem cell types, one residing in the excretory duct epithelium and the second in the intercalated duct. Each stem cell gives rise to its typical neoplasm. Excretory duct originating neoplasms consist of papillomas, epidermal and adenocarcinomas, while intercalated stem cell bound neoplasms embrace the canalicular adenoma, oncocytoma acinic cell and lobular carcinomata. All tissues continuously stream along the tissue radius. Evidence is presented that even the liver cords are continuously displaced from the limiting lamina toward the terminal hepatic (or central) vein. The histological image of these tissues actually reflects an instantaneous picture of cells in a continuous flux.