Adult Stem Cell Biology Research Articles

Neutralization of nerve growth factor impairs proliferation and differentiation of adult neural progenitors in the subventricular zone.

Adult neurogenesis is a multistep process regulated by several extrinsic factors, including neurotrophins. Among them, little is known about the role of nerve growth factor (NGF) in the neurogenic niches of the mouse. Here we analyzed the biology of adult neural stem cells (NSCs) from the subventricular zone (SVZ) of AD11 anti-NGF transgenic mice, in which the expression of the recombinant antibody aD11 leads to a chronic postnatal neutralization of endogenous NGF. We showed that AD11-NSCs proliferate 10-fold less, with respect to their control counterparts, and display a significant impairment in their ability to differentiate into β-tubulin positive neurons. We found a considerable reduction in the number of SVZ progenitors and neuroblasts also in vivo, which correlates with a lower number of newborn neurons in the olfactory bulbs of AD11 mice and a severe deficit in the ability of these mice to discriminate between different odors. We also demonstrated that, in AD11 mice, the morphology of both SVZ-resident and neurosphere-derived astrocytes is significantly altered. We were able to reproduce the AD11 phenotype in vitro, by acutely treating wild type NSCs with the anti-NGF antibody, further demonstrating that both the proliferation and the differentiation defects are due to the NGF deprivation. Consistently, the proliferative impairment of AD11 progenitors, as well as the atrophic morphology of AD11 astrocytes, can be partly rescued in vitro and in vivo by exogenous NGF addition. Altogether, our results demonstrate a causal link between NGF signaling and proper proliferation and differentiation of neural stem cells from the SVZ.

R-Spondine: Einblicke in die Potenzierung der Wnt-Signaltransduktion

Intercellular signalling by Wnt morphogenetic proteins is subject to a multi-layered system of regulation. The four secreted R-spondin proteins potentiate Wnt signalling in vertebrates. They are involved in embryogenesis, adult stem cell biology and cancer progression and have been proven essential for ex vivo culturing of organoids. Recent research has generated profound new insights into how R-spondins function to stabilize Wnt receptors of the Frizzled family at the cell surface.

Distinct and separable roles for EZH2 in neurogenic astroglia

The epigenetic mechanisms that enable specialized astrocytes to retain neurogenic competence throughout adult life are still poorly understood. Here we show that astrocytes that serve as neural stem cells (NSCs) in the adult mouse subventricular zone (SVZ) express the histone methyltransferase EZH2. This Polycomb repressive factor is required for neurogenesis independent of its role in SVZ NSC proliferation, as Ink4a/Arf-deficiency in Ezh2-deleted SVZ NSCs rescues cell proliferation, but neurogenesis remains defective. Olig2 is a direct target of EZH2, and repression of this bHLH transcription factor is critical for neuronal differentiation. Furthermore, Ezh2 prevents the inappropriate activation of genes associated with non-SVZ neuronal subtypes. In the human brain, SVZ cells including local astroglia also express EZH2, correlating with postnatal neurogenesis. Thus, EZH2 is an epigenetic regulator that distinguishes neurogenic SVZ astrocytes, orchestrating distinct and separable aspects of adult stem cell biology, which has important implications for regenerative medicine and oncogenesis.DOI: http://dx.doi.org/10.7554/eLife.02439.001.

Very Small Embryonic-Like Stem Cells: A Scientific Debate?

Stem Cells and DevelopmentVol. 23, No. 7 EditorialVery Small Embryonic-Like Stem Cells: A Scientific Debate?Graham C. ParkerGraham C. ParkerSearch for more papers by this authorPublished Online:28 Mar 2014https://doi.org/10.1089/scd.2014.1500AboutSectionsView articleView Full TextPDF/EPUB ToolsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail View article"Very Small Embryonic-Like Stem Cells: A Scientific Debate?." Stem Cells and Development, 23(7), pp. 687–688FiguresReferencesRelatedDetailsCited ByCharacterization and Isolation of Very Small Embryonic-like (VSEL) Stem Cells Obtained from Various Human Hematopoietic Cell Sources6 June 2019 | Stem Cell Reviews and Reports, Vol. 15, No. 5Novel Insights into Adult and Cancer Stem Cell Biology Deepa Bhartiya, Hiren Patel, Ranita Ganguly, Ambreen Shaikh, Yashvi Shukla, Diksha Sharma, and Pushpa Singh7 November 2018 | Stem Cells and Development, Vol. 27, No. 22Mouse Bone Marrow VSELs Exhibit Differentiation into Three Embryonic Germ Lineages and Germ & Hematopoietic Cells in Culture9 January 2017 | Stem Cell Reviews and Reports, Vol. 13, No. 2Reply: An update on endometrial stem cells and progenitors by Deepa Bhartiya24 March 2016 | Human Reproduction Update, Vol. 22, No. 4 Volume 23Issue 7Apr 2014 InformationCopyright 2014, Mary Ann Liebert, Inc.To cite this article:Graham C. Parker.Very Small Embryonic-Like Stem Cells: A Scientific Debate?.Stem Cells and Development.Apr 2014.687-688.http://doi.org/10.1089/scd.2014.1500Published in Volume: 23 Issue 7: March 28, 2014PDF download

Induction of iPS Cells and of Cancer Stem Cells: The Stem Cell or Reprogramming Hypothesis of Cancer?

This article as designed to examine whether the "stoichiometric" or "elite models" of the origin of the "induced pluripotent stem" (iPS) cells fits some experiment facts from the developmental biology of adult stem cells and from the field of cancer research. In brief, since the evidence presented to support the stoichiometric model failed to recognize the factual existence of adult organ specific stem cells, the model has not been rigorously tested. In addition, the demonstration of a subset of cells (MUSE cells) in normal primary in vitro cultures of human fibroblasts (the usual source of iPS cells) seems to be the origin of the iPS cells. Moreover, from the field of carcinogenesis, the "stem cell" versus "de-differentiation" or "reprogramming" hypotheses were examined. Again, using the role of glycolysis, known to be associated with the Warburg effect in cancer cells, a list of experiments showing that (a) normal stem cells, which have few mitochondria, metabolize via glycolysis; (b) the stem cells are targets for "initiation" or "immortalization" or the blockage of differentiation and apoptosis of the stem cells by "immortalizing viruses"; (c) Lactate dehydrogenase A (LDHA), when expressed, is associated with glycolysis and therefore, must be expressed in normal adult stem cells, as well as in cancer cells; and (d) p53, depleted or rendered dysfunctional by SV40 Large T antigen, is associated with the reduction of mitochondrial function and mass and is associated with the Warburg effect. Together, these observations from the iPS and "cancer stem cell" fields support the idea that both iPS cells and cancer stem cell are derived from adult organ-specific stem cells that do not restore or switch their metabolism of glucose from oxidative metabolism to glycolysis but, rather, in both cases, the adult stem cell, which metabolizes by glycolysis, is prevented from differentiation or from metabolizing by oxidative phosphorylation.

Structural and molecular basis of ZNRF3/RNF43 transmembrane ubiquitin ligase inhibition by the Wnt agonist R-spondin

The four R-spondin (Rspo) proteins are secreted agonists of Wnt signalling in vertebrates, functioning in embryogenesis and adult stem cell biology. Through ubiquitination and degradation of Wnt receptors, the transmembrane E3 ubiquitin ligase ZNRF3 and related RNF43 antagonize Wnt signalling. Rspo ligands have been reported to inhibit the ligase activity through direct interaction with ZNRF3 and RNF43. Here we report multiple crystal structures of the ZNRF3 ectodomain (ZNRF3ecto), a signalling-competent Furin1–Furin2 (Fu1–Fu2) fragment of Rspo2 (Rspo2Fu1–Fu2), and Rspo2Fu1–Fu2 in complex with ZNRF3ecto, or RNF43ecto. A prominent loop in Fu1 clamps into equivalent grooves in the ZNRF3ecto and RNF43ecto surface. Rspo binding enhances dimerization of ZNRF3ecto but not of RNF43ecto. Comparison of the four Rspo proteins, mutants and chimeras in biophysical and cellular assays shows that their signalling potency depends on their ability to recruit ZNRF3 or RNF43 via Fu1 into a complex with LGR receptors, which interact with Rspo via Fu2.

‘From Death, Lead Me to Immortality’ – Mantra of Ageing Skeletal Muscle

Skeletal muscle is a post-mitotic tissue maintained by repair and regeneration through a population of stem cell-like satellite cells. Following muscle injury, satellite cell proliferation is mediated by local signals ensuring sufficient progeny for tissue repair. Age–related changes in satellite cells as well as to the local and systemic environment potentially impact on the capacity of satellite cells to generate sufficient progeny in an ageing organism resulting in diminished regeneration. ‘Rejuvenation’ of satellite cell progeny and regenerative capacity by environmental stimuli effectors suggest that a subset of age-dependent satellite cell changes may be reversible. Epigenetic regulation of satellite stem cells that include DNA methylation and histone modifications which regulate gene expression are potential mechanisms for such reversible changes and have been shown to control organismal longevity. The area of health and ageing that is likely to benefit soonest from advances in the biology of adult stem cells is the emerging field of regenerative medicine. Further studies are needed to elucidate the mechanisms by which epigenetic modifications regulate satellite stem cell function and will require an increased understanding of stem-cell biology, the environment of the aged tissue and the interaction between the two.

Lgr proteins in epithelial stem cell biology

The ultimate success of global efforts to exploit adult stem cells for regenerative medicine will depend heavily on the availability of robust, highly selective stem cell surface markers that facilitate the isolation of stem cells from human tissues. Any subsequent expansion or manipulation of isolated stem cells will also require an intimate knowledge of the mechanisms that regulate these cells, to ensure maintenance of their regenerative capacities and to minimize the risk of introducing undesirable growth traits that could pose health risks for patients. A subclass of leucine-rich repeat-containing G-protein-coupled receptor (Lgr) proteins has recently gained prominence as adult stem cell markers with crucial roles in maintaining stem cell functions. Here, we discuss the major impact that their discovery has had on our understanding of adult stem cell biology in various self-renewing tissues and in accelerating progress towards the development of effective stem cell therapies.

Secreted Frizzled-Related Protein 3 Regulates Activity-Dependent Adult Hippocampal Neurogenesis

Adult neurogenesis, the process of generating mature neurons from adult neural stem cells, proceeds concurrently with ongoing neuronal circuit activity and is modulated by various physiological and pathological stimuli. The niche mechanism underlying the activity-dependent regulation of the sequential steps of adult neurogenesis remains largely unknown. Here, we report that neuronal activity decreases the expression of secreted frizzled-related protein 3 (sFRP3), a naturally secreted Wnt inhibitor highly expressed by adult dentate gyrus granule neurons. Sfrp3 deletion activates quiescent radial neural stem cells and promotes newborn neuron maturation, dendritic growth, and dendritic spine formation in the adult mouse hippocampus. Furthermore, sfrp3 reduction is essential for activity-induced adult neural progenitor proliferation and the acceleration of new neuron development. Our study identifies sFRP3 as an inhibitory niche factor from local mature dentate granule neurons that regulates multiple phases of adult hippocampal neurogenesis and suggests an interesting activity-dependent mechanism governing adult neurogenesis via the acute release of tonic inhibition.

Prospective Technologies in Dental Tissues Regeneration

Interest in applications for dental tissues regeneration continues to increas as clinically relevant methods alternative to traditional treatments. Dental tissues engineering is an opportunity that dentistry cannot afford to miss. Recent progress in the studies of molecular basis of tooth development, adult stem cell biology, and regeneration will provide fundamental knowledge for that. We are now starting to understand at the level of genes and molecules how the development of dental tissues is regulated. For instance, specific signal molecules have been identified which regulate the development of teeth and bones from progenitor cells. This information is already being used for the generation of dentoalveolar tissues

Multipotent to Pluripotent Properties of Adult Stem Cells

Stem cells have captured the attention of both researchers and the public alike because of the promise of tissue regeneration, drug screening, and organogenesis. Stem cells are broadly classified as embryonic or adult with differentiation capacities ranging from pluripotent and multipotent to unipotent. In general, pluripotent stem cells are ascribed to cells derived from the inner cell mass of blastocyst stage embryos or to those generated experimentally using reprogramming factors. Adult stem or progenitor cells are generally tissue-restricted but reside in most organs. While the use of pluripotent stem cells has been limited to a few clinical trials due to safety concerns, adult stem cells have shown evidence of safety and are broadly employed in both clinical trials (http://www.clinicaltrial.gov/) and clinical practice. Transplantation of adult bone marrow hematopoietic stem cells, for example, represents a standard method of clinical care for autoimmune diseases and hematological disorders. While hematopoietic stem cells cannot be expanded in vitro, other stem cells such as mesenchymal stem cells (MSCs) can be easily expanded from autologous and allogeneic sources for clinical testing. Moreover, adult-derived testicular spermatogonial stem cells (SSCs) have been reported to be the only cells in the body that can be dedifferentiated/reprogrammed to a pluripotent state in vitro and grown into ES-like colonies. It has been advocated that adult stem cells have remarkable plasticity, transdetermination, and transdifferentiation ability. These properties have raised hope that adult stem cells could become a universal source of stem cells for tissue/organ repair in lieu of embryonic stem cells, which can easily form tumors. MSCs, for example, can be isolated from various tissues like bone marrow, gut, lungs, liver, blood, adipose tissue, umbilical cord Wharton's jelly, dental pulp, amniotic fluid, and so forth and have the ability to form bone, cartilage, adipose tissue, skeletal muscle, liver, neurons, skin, pancreatic islets, endothelial cells, intestine, renal, epithelial, and germ cells. More importantly, MSCs can be given across allogeneic barriers. Nevertheless, many trials with MSCs have shown only marginal benefits and some have proposed that the effects may be more paracrine in nature than being regenerative. This special issue, comprised of 10 articles, focuses on adult stem cells that examine the following claims: Why are MSCs ubiquitous? Are they indeed stem cells or just stromal cells which constitute the somatic niche for tissue specific stem cells in various body organs? Have we looked carefully at MSCs growing in a culture dish? Are ES-like colonies observed only from testicular biopsy but also from ovarian and endometrial biopsies? The article by D. Bhartiya addresses these issues and reviews the available literature on the presence of novel pluripotent very small ES-like stem cells (VSELs) as a subgroup among MSCs. It also highlights that Oct-4A transcripts need to be studied to conclude pluripotent state rather than Oct-4. An article by Dr. P. Rameshwar's group studied the safety issue of MSCs since these stem cells have been shown to support tumor growth. Other papers have discussed various sources of adult stem cells including dental pulp stem cells (S. Arrifin et al.), satellite stem cells in skeletal muscles (S. Fujimaki et al.), and bone marrow stem cells (I. Catacchio et al.) and their multipotent properties and transdifferentiation potential. Further characterization of these stem cells and their functional potential is essential. The role of cannabinoid receptor type I in differentiation and survival of MSCs is discussed by A. Gowran et al. M. Akita et al. show that CD133 positive cells have the capacity to form endothelial capillary tubes in 3D culture. Cultures of cardiac explants result in the formation of cardiospheres which contain both stem and progenitor cells implicated in cardiac regeneration (L. Barile et al.). Y. Togo et al. have reviewed the literature on the use of MSCs as a nonviral gene carrier for gene transfer in vitro. Finally, N. Sakayori et al. discuss how neural stem/progenitor cells function is regulated by lipids. The diverse areas of the manuscripts in this issue underscore the wide field of adult stem cell biology. The papers indicate that more in-depth research and functional studies are required to take adult stem cells safely to the clinic for regenerative medicine. Deepa Bhartiya Kenneth R. Boheler Pranela Rameshwar

Chromatin-based epigenetics of adult subventricular zone neural stem cells.

In specific regions of the adult mammalian brain, neural stem cells (NSCs) generate new neurons throughout life. Emerging evidence indicate that chromatin-based transcriptional regulation is a key epigenetic mechanism for the life-long function of adult NSCs. In the adult mouse brain, NSCs in the subventricular zone (SVZ) retain the ability to produce both neurons and glia for the life of the animal. In this review, we discuss the origin and function of SVZ NSCs as they relate to key epigenetic concepts of development and potential underlying mechanism of chromatin-based transcriptional regulation. A central point of discussion is how SVZ NSCs – which possess many characteristics of mature, non-neurogenic astrocytes – maintain a “youthful” ability to produce both neuronal and glial lineages. In addition to reviewing data regarding the function of chromatin-modifying factors in SVZ neurogenesis, we incorporate our growing understanding that long non-coding RNAs serve as an important element to chromatin-based transcriptional regulation, including that of SVZ NSCs. Discoveries regarding the epigenetic mechanisms of adult SVZ NSCs may provide key insights into fundamental principles of adult stem cell biology as well as the more complex and dynamic developmental environment of the embryonic brain.

Redox Signaling in Adult Stem Cell Biology: A New Target Controlling Pluripotency and Differentiation. What about Iron Chelators?.

AbstractAbstract 2299▪▪This icon denotes a clinically relevant abstract IntroductionHematopoietic stem cells (HSCs) constitute a reservoir of undifferentiated cells that can be committed, upon appropriate stimuli, in the haematic lineages. Although residing in a bone-marrow hypoxic microenvironment (niche) and mainly relying on anaerobic glycolysis, HSCs are endowed with mitochondria. Recently, specific interest has been focused on HSCs mitochondria and on their role as reactive oxygen species (ROS) generators during the early phases of commitment. Indeed, consolidated evidences highlight the importance of redox signalling in the homeostasis of fundamental processes in cell adaptive biology and particularly in controlling the balance between self-renewal and differentiation of stem cells. HSCs constitutively generate low levels of ROS produced by both mitochondrial respiratory chain and NADPH oxidases (NOXs). ROS would act as secondary messengers, modulating the expression of master transcription factors leading or (pre)conditioning stem cells towards differentiation. Myelodisplastic syndrome (MDS) is characterized by disturbance of the HSC differentiation and most MDS patients are treated with iron chelators to compensate for the iron overload consequent to the blood cell transfusion-based standard therapy. Intriguingly, a robust percentage of patients, treated with the iron chelator deferasirox (DFX), recover correct HSCs differentiation whereas other chelators, like deferoxamine (DFO) did not. In the presented study we investigated the effect of DFX and DFO on the redox homeostasis of hematopoietic stem/progenitor cells (HSPCs) in order to get insights on the differential effect of iron chelators in rescuing altered hematopoiesis. Materials and MethodsHuman HSPCs were isolated from peripheral blood (PB) or bone marrow (BM) of G-CSF-treated or untreated healthy donors, respectively, by immuno-selection against the specific markers CD133 and CD34 and resulted >99% immunophenotypically homogeneous. Mitochondrial respiratory activity was measured in intact HSPCs by high resolution oxymetry. Morpho-functional features of HSPC-mitochondria, expression of the HSPC-surface commitment markers and ROS level were analyzed by laser scanning confocal microscopy (LSCM) and flow cytometry using specific probes or antibodies. HSPCs were treated with 100 mM DFX or DFO for 24 hrs. ResultsMeasurement of oxygen consumption rate as well as molecular analyses in PB-HSPCs confirmed a poor mitochondrial oxidative phosphorylation phenotype. LSCM imaging of mitochondria in either PB- and BM-HSCs displayed a punctuate rather than interconnected network. However, co-staining of mitochondria and CD34/CD133 stemness-markers revealed a striking inverse correlation. Finally HSPCs produced DCF-detectable and DPI-inhibitable ROS attributable to constitutive NOX activity and related to stabilization of the hypoxia-inducibile factor (HIF1a) under normoxic condition. DFX treatment of HSPCs resulted in a significant up-regulation of ROS level whereas no significant change was observed following DFO treatment. Importantly, the DFX-mediated ROS production was insensitive to treatment with low NOX-inhibiting concentration of DPI but was abrogated by high concentration of DPI thus pointing to mitochondria as ROS source. ConclusionsOur results show that HSCs in the early phase of commitment undergo a progressive increase of mitochondrial mass indicating the need of a bioenergetic up-regulation to cope with the oncoming energy-demanding proliferative/differentiative phenotype. Redox signaling, mediated by ROS production and likely triggered by changes in the environmental oxygen tension, appears to be essential in regulating HSC self-renewal and preservation of pluripotency. DFX treatment, by modulating ROS production, might lead to activation of redox-sensitive key factors able to restore the hematopoietic function in MDS patients. This effect seemingly is independent on the iron-chelating property of DFX but pertains to additional pharmacological properties that warren further investigation. Disclosures:No relevant conflicts of interest to declare.

The Retinoblastoma pathway regulates stem cell proliferation in freshwater planarians

Freshwater planarians are flatworms of the Lophotrochozoan superphylum and are well known for their regenerative abilities, which rely on a large population of pluripotent adult stem cells. However, the mechanisms by which planarians maintain a precise population of adult stem cells while balancing proliferation and cell death, remain to be elucidated. Here we have identified, characterized, and functionally tested the core Retinoblastoma (Rb) pathway components in planarian adult stem cell biology. The Rb pathway is an ancient and conserved mechanism of proliferation control from plants to animals and is composed of three core components: an Rb protein, and a transcription factor heterodimer of E2F and DP proteins. Although the planarian genome contains all components of the Rb pathway, we found that they have undergone gene loss from the ancestral state, similar to other species in their phylum. The single Rb homolog (Smed-Rb) was highly expressed in planarian stem cells and was required for stem cell maintenance, similar to the Rb-homologs p107 and p130 in vertebrates. We show that planarians and their phylum have undergone the most severe reduction in E2F genes observed thus far, and the single remaining E2F was predicted to be a repressive-type E2F (Smed-E2F4-1). Knockdown of either Smed-E2F4-1 or its dimerization partner Dp (Smed-Dp) by RNAi resulted in temporary hyper-proliferation. Finally, we showed that known Rb-interacting genes in other systems, histone deacetylase 1 and cyclinD (Smed-HDAC1; Smed-cycD), were similar to Rb in expression and phenotypes when knocked down by RNAi, suggesting that these established interactions with Rb may also be conserved in planarians. Together, these results showed that planarians use the conserved components of the Rb tumor suppressor pathway to control proliferation and cell survival.

Fernando Camargo: No limits to learning about stem cells

Camargo studies the regulation of organ size and the biology of adult stem cells.

Clinical Applications and Biosafety of Human Adult Mesenchymal Stem Cells

Mesenchymal Stem Cells (MSCs) are a population of adherent cells that can differentiate into mesenchymal lineage populations (cartilage, bone and fat tissue). In addition, they seem to be able to differentiate also into a broader type of lineages other than the original mesodermal germ layer. Bone marrow MSCs are a standard in the field of adult stem cell biology and clinical applications; however adipose-derived MSCs are becoming an attractive alternative due to their minimally invasive accessibility and availability in the body. MSCs modulate several effector immune functions by interacting both with innate and adoptive immune responses. Several local signals from the tissue microenvironment, together with cytokine and soluble factors released by MSCs influence anti-inflammatory and tissue repair properties of infused MSCs. Therefore, cellular therapies utilizing ex vivo expanded MSCs may be an interesting approach for inflammatory and autoimmune diseases. Biosafety is still one of the most important aspects; therefore the production of clinical-grade MSCs requires the careful identification and control of all the phases of cell manipulation and release. Many clinical applications of adult MSCs are in progress and are using bone marrow or adipose tissue-derived MSCs for the treatment of Graft Versus Host Disease (GVHD), inflammatory joint diseases and osteocartilagineous defects, digestive tract, cardiovascular and neurological diseases.

BMP et cancer

In a normal context, bone morphogenetic proteins (BMPs), members of the TGFβ superfamily, are key players in adult stem cell biology. They are involved in the control of the overall functional and phenotypic properties of the stem cell population (self-renewal, proliferation, differentiation, apoptosis, quiescence, etc.). They can act directly on the stem cell or through its microenvironment, contributing to the tight balance of this system. In the tumorigenic context, alterations of the BMP signalling are involved in the deregulation of the interaction between stem cells and their microenvironment and, as such, participate to the different steps of the transformation process.

α‐6 Integrin Expression in Bovine Spermatogonial Cells Purified by Discontinuous Percoll Density Gradient

The study of spermatogonial stem cells (SSCs) provides a model to better understand adult stem cell biology. Besides the biomedical potential to perform studies of infertility in many species, SSCs hold a promising application at animal transgenesis. Because stem cells are thought to be associated with basement membranes, expression of α-6 integrin has been investigated as a marker of type A spermatogonial cells, which are considered SSCs because of their undifferentiated status and self-renewal ability. In this manner, the aim of this study was to isolate type A SSCs from adult bulls by a two-step enzymatic procedure followed by a discontinuous Percoll density gradient purification and verify the expression of α-6 integrin by flow cytometry and real-time RT-PCR before and after Percoll purification. Spermatogonial cells were successfully obtained using the two-step enzymatic digestion. An average of 1 × 10(5) viable cells per gram of testis was isolated. However, the discontinuous Percoll did not purify isolated cells regarding α-6 integrin expression. Flow cytometry analysis demonstrated no differences in the α-6 integrin expression between cell samples before and after Percoll purification (p = 0.5636). The same was observed in the real-time PCR analysis (p > 0.05). In addition to α-6 integrin, the expression of GFRa-1 and PGP9.5, known bovine SSCs markers, was detected in all samples studied. Considering that Percoll can reduce cell viability, it is possible to conclude that Percoll density gradient is not suitable to purify bovine SSC, according to α-6 integrin expression.

Differentiating human stem cells into neurons and glial cells for neural repair

Research on the biology of adult stem cells, embryonic stem cells and induced pluripotent stem cells, as well as cell-based strategies for treating nervous system disorders has begun to create the hope that these cells may be used for therapy in humans after injury or disease. In animal models of neurological diseases, transplantation of stem cells or their derivatives can improve function not only due to direct replacement of lost neurons or glia, but also by providing trophic support. Despite intense research efforts to translate these studies from the bench to bedside, critical problems remain at several steps in this process. Recent technological advancements in both the derivation of stem cells and their directed differentiation to lineage-committed progenitors have brought us closer to therapeutic applications. Several preclinical studies have already explored the behavior of transplanted cells with respect to proliferation, migration, differentiation and survival, especially in complex pathological disease environments. In this review, we examine the current status, progress, pitfalls, and potential of these stem cell technologies, focusing on directed differentiation of human stem cells into various neural lineages, including dopaminergic neurons, motor neurons, oligodendroglia, microglia, and astroglia, and on advancements in cell-based regenerative strategies for neural repair and criteria for successful therapeutic applications.

Tumor-stroma interactions in tumorigenesis lessons from stem cell biology

  Research in recent years has accumulated a wealth of novel insight into mechanisms by which tumor cells interact with activated fibroblasts, endothelial cells, inflammatory and immune cells and the extracellular matrix. Cancer and stromal cells co-evolve throughout tumorigenesis. As a result, the tumor stroma is now regarded as an essential contributor to tumor establishment, progression and dissemination. Moreover, the formation of suitable stroma niches has emerged as a prime determinant of metastasis. Notably, malignant tumors adopt numerous mechanisms that are also operative in embryonic and adult stem cell biology. Tumor sites show functional characteristics with striking similarities to stem cell niches. This review summarizes the current view of disease-relevant communication between tumor cells and the tumor stroma and relates it to interactions of stem cells and their respective niches. Progress in understanding the pivotal role of the microenvironment in both tumor and stem cell biology renders the tumor stroma an interesting potential future target for specific cancer therapies.