Stem cells, cancer stem-like cells, and natural products

Somatic stem cells can be found in many rapidly regenerating tissues, e.g., the skin, gastrointestinal mucosa, and hematopoietic system, but are also present at low numbers in non-regenerative organs such as the heart and brain. In these organs, somatic stem cells aid in normal tissue homeostasis and repair after injury as well as self-renewal and the generation of specific progenitor cells during differentiation. Cancer stem-like cells are a small subpopulation of self-renewing cells that are able to proliferate upon appropriate stimulation and differentiate into heterogeneous lineages in tumors. Modulation of the behavior of normal tissue stem cells and cancer stem-like cells is an emerging and thriving new field of research. The present review gives an overview of the state-of-the-art findings and highlights perspectives for future scientific developments and clinical application.

Productive hepatitis C virus infection of stem cell-derived hepatocytes reveals a critical transition to viral permissiveness during differentiation

Primary human hepatocytes isolated from patient biopsies represent the most physiologically relevant cell culture model for hepatitis C virus (HCV) infection, but these primary cells are not readily accessible, display individual variability, and are largely refractory to genetic manipulation. Hepatocyte-like cells differentiated from pluripotent stem cells provide an attractive alternative as they not only overcome these shortcomings but can also provide an unlimited source of noncancer cells for both research and cell therapy. Despite its promise, the permissiveness to HCV infection of differentiated human hepatocyte-like cells (DHHs) has not been explored. Here we report a novel infection model based on DHHs derived from human embryonic (hESCs) and induced pluripotent stem cells (iPSCs). DHHs generated in chemically defined media under feeder-free conditions were subjected to infection by both HCV derived in cell culture (HCVcc) and patient-derived virus (HCVser). Pluripotent stem cells and definitive endoderm were not permissive for HCV infection whereas hepatic progenitor cells were persistently infected and secreted infectious particles into culture medium. Permissiveness to infection was correlated with induction of the liver-specific microRNA-122 and modulation of cellular factors that affect HCV replication. RNA interference directed toward essential cellular cofactors in stem cells resulted in HCV-resistant hepatocyte-like cells after differentiation. The ability to infect cultured cells directly with HCV patient serum, to study defined stages of viral permissiveness, and to produce genetically modified cells with desired phenotypes all have broad significance for host-pathogen interactions and cell therapy.

Physiologically relevant cell-culture models for infection with hepatitis C virus (HCV) are scarce, and infection by viruses derived from patient serum has been inefficient. Differentiated human hepatocyte-like cells derived from pluripotent stem cells demonstrate hepatic functions but have not been explored for HCV infection studies. Here we report a novel infection model based on these hepatocyte-like cells. Stem cells and definitive endoderm successfully resisted HCV infection, whereas hepatic progenitor cells derived from the stem cells were productively infected by both human- and cell-culture-derived HCV. We determined the point of transition from resistance to susceptibility and, by comparative gene profiling, identified the host factors that were correlated with susceptibility. Genetic modification of human embryonic stem cells, coupled with hepatic differentiation, generated hepatocyte-like cells that were resistant to HCV infection. Our study establishes a new noncancerous and renewable cell-culture system for HCV infection, permits direct infection of cells by patient sera in vitro, identifies a defined transition to HCV susceptibility during hepatocyte differentiation, and demonstrates the feasibility of generating virus-resistant human hepatocyte-like cells in vitro.

Adrenocortical stem and progenitor cells: implications for adrenocortical carcinoma

The continuous centripetal repopulation of the adrenal cortex is consistent with a population of cells endowed with the stem/progenitor cell properties of self-renewal and pluripotency. The adrenocortical capsule and underlying undifferentiated cortical cells are emerging as critical components of the stem/progenitor cell niche. Recent genetic analysis has identified various signaling pathways including Sonic Hedgehog (Shh) and Wnt as crucial mediators of adrenocortical lineage and organ homeostasis. Shh expression is restricted to the peripheral cortical cells that express a paucity of steroidogenic genes but give rise to the underlying differentiated cells of the cortex. Wnt/β-catenin signaling maintains the undifferentiated state and adrenal fate of adrenocortical stem/progenitor cells, in part through induction of its target genes Dax1 and inhibin-α, respectively. The pathogenesis of ACC, a rare yet highly aggressive cancer with an extremely poor prognosis, is slowly emerging from studies of the stem/progenitor cells of the adrenal cortex coupled with the genetics of familial syndromes in which ACC occurs. The frequent observation of constitutive activation of Wnt signaling due to loss-of-function mutations in the tumor suppressor gene APC or gain-of-function mutation in β-catenin in both adenomas and carcinomas, suggests perhaps that the Wnt pathway serves an early or initiating insult in the oncogenic process. Loss of p53 might be predicted to cooperate with additional genetic insults such as IGF2 as both are the most common genetic abnormalities in malignant versus benign adrenocortical neoplasms. It is unclear whether other factors such as Pod1 and Pref1, which are implicated in stem/progenitor cell biology in the adrenal and/or other organs, are also implicated in the etiology of adrenocortical carcinoma. The rarity and heterogeneous presentation of ACC makes it difficult to identify the cellular origin and the molecular progression to cancer. A more complete understanding of adrenocortical stem/progenitor cell biology will invariably aid in characterization of the molecular details of ACC tumorigenesis and may offer new options for therapeutic intervention.

A survey of parameters involved in the establishment of new lines of human embryonic stem cells

Since the derivation of the first human embryonic stem cell (hESC) lines by Thomson and coworkers in 1998, more than 1,200 different hESC lines have been established worldwide. Nevertheless, there is still a recognized interest in the establishment of new lines of hESC, particularly from HLA types and ethnic groups currently underrepresented among the available lines. The methodology of hESC derivation has evolved significantly since 1998, when human LIF (hLIF) was used for maintenance of pluripotency. However, there are a number of different strategies for the several steps involved in establishing a new line of hESC. Here we make a survey of the most relevant parameters used between 1998 and 2010 for the derivation of the 375 hESC lines deposited in two international stem cell registries, and able to form teratomas in immunocompromised mice. Although we identify some trends in the methodology for establishing hESC lines, our data reveal a much greater heterogeneity of strategies than what is used for derivation of murine ESC lines, indicating that optimum conditions have not been consolidated yet, and thus, hESC establishment is still an evolving field of research.

FoxO: a new addition to the ESC cartel

The forkhead box O (FoxO) family is involved in diverse cellular processes such as tumor suppression, stress response, and metabolism. In a recent Nature Cell Biology Letter, Zhang et al. (2011) uncover a novel role for FoxO proteins in regulating the identity of human ESCs.

Inhibition of Rho kinase regulates specification of early differentiation events in P19 embryonal carcinoma stem cells

BACKGROUND

The Rho kinase pathway plays a key role in many early cell/tissue determination events that take place in embryogenesis. Rho and its downstream effector Rho kinase (ROCK) play pivotal roles in cell migration, apoptosis (membrane blebbing), cell proliferation/cell cycle, cell-cell adhesion and gene regulation. We and others have previously demonstrated that inhibition of ROCK blocks endoderm differentiation in embryonal carcinoma stem cells, however, the effect of ROCK inhibition on mesoderm and ectoderm specification has not been fully examined. In this study, the role of ROCK within the specification and differentiation of all three germ layers was examined.

METHODOLOGY/PRINCIPAL FINDINGS

P19 cells were treated with the specific ROCK inhibitor Y-27623, and increase in differentiation efficiency into neuro-ectodermal and mesodermal lineages was observed. However, as expected a dramatic decrease in early endodermal markers was observed when ROCK was inhibited. Interestingly, within these ROCK-inhibited RA treated cultures, increased levels of mesodermal or ectodermal markers were not observed, instead it was found that the pluripotent markers SSEA-1 and Oct-4 remained up-regulated similar to that seen in undifferentiated cultures. Using standard and widely accepted methods for reproducible P19 differentiation into all three germ layers, an enhancement of mesoderm and ectoderm differentiation with a concurrent loss of endoderm lineage specification was observed with Y-27632 treatment. Evidence would suggest that this effect is in part mediated through TGF-β and SMAD signaling as ROCK-inhibited cells displayed aberrant SMAD activation and did not return to a 'ground' state after the inhibition had been removed.

CONCLUSIONS/SIGNIFICANCE

Given this data and the fact that only a partial rescue of normal differentiation capacity occurred when ROCK inhibition was alleviated, the effect of ROCK inhibition on the differentiation capacity of pluripotent cell populations should be further examined to elucidate the role of the Rho-ROCK pathway in early cellular 'fate' decision making processes.

Detection of variable levels of RARα and RARγ proteins in pluripotent and differentiating mouse embryonal carcinoma and mouse embryonic stem cells

Pluripotent mouse embryonal carcinoma (mEC) and mouse embryonic stem (mES) cells differentiate into several cell lineages upon retinoic acid (RA) addition. Differentiation is facilitated, in part, by RA activation of nuclear RA receptors (RARs) that bind to DNA response elements located in the promoters of target genes. The purpose of the studies reported here was to immunolocalize RARα and RARγ protein in mEC and mES cells and in their RA-induced differentiated progeny. Fixed cells were reacted with three different RARα antibodies and one RARγ antibody. Pluripotent and differentiated mEC and mES cells showed positive nuclear immunoreactivity with all antibodies tested. Two RARα antibodies also showed positive reactivity in the cytoplasm. Surprisingly, our results revealed variability in immunofluorescence intensity and in RARα and RARγ distribution from one cell to the other, suggesting that RARα and RARγ protein levels were not synchronous throughout the cell population. The results indicate that RARα and RARγ are present in pluripotent and differentiating mEC and mES cells and suggest that the expression of these proteins is dynamic.

Short-term serum-free culture reveals that inhibition of Gsk3β induces the tumor-like growth of mouse embryonic stem cells

Here, we present evidence that the tumor-like growth of mouse embryonic stem cells (mESCs) is suppressed by short-term serum-free culture, which is reversed by pharmacological inhibition of Gsk3β. Mouse ESCs maintained under standard conditions using fetal bovine serum (FBS) were cultured in a uniquely formulated chemically-defined serum-free (CDSF) medium, namely ESF7, for three passages before being subcutaneously transplanted into immunocompromised mice. Surprisingly, the mESCs failed to produce teratomas for up to six months, whereas mESCs maintained under standard conditions generated well-developed teratomas in five weeks. Mouse ESCs cultured under CDSF conditions maintained the expression of Oct3/4, Nanog, Sox2 and SSEA1, and differentiated into germ cells in vivo. In addition, when mESCs were cultured under CDSF conditions supplemented with FBS, or when the cells were cultured under CDSF conditions followed by standard culture conditions, they consistently developed into teratomas. Thus, these results validate that the pluripotency of mESCs was not compromised by CDSF conditions. Mouse ESCs cultured under CDSF conditions proliferated significantly more slowly than mESCs cultured under standard conditions, and were reminiscent of Eras-null mESCs. In fact, their slower proliferation was accompanied by the downregulation of Eras and c-Myc, which regulate the tumor-like growth of mESCs. Remarkably, when mESCs were cultured under CDSF conditions supplemented with a pharmacological inhibitor of Gsk3β, they efficiently proliferated and developed into teratomas without upregulation of Eras and c-Myc, whereas mESCs cultured under standard conditions expressed Eras and c-Myc. Although the role of Gsk3β in the self-renewal of ESCs has been established, it is suggested with these data that Gsk3β governs the tumor-like growth of mESCs by means of a mechanism different from the one to support the pluripotency of ESCs.

Genetic correction and analysis of induced pluripotent stem cells from a patient with gyrate atrophy

Gene-corrected patient-specific induced pluripotent stem (iPS) cells offer a unique approach to gene therapy. Here, we begin to assess whether the mutational load acquired during gene correction of iPS cells is compatible with use in the treatment of genetic causes of retinal degenerative disease. We isolated iPS cells free of transgene sequences from a patient with gyrate atrophy caused by a point mutation in the gene encoding ornithine-δ-aminotransferase (OAT) and used homologous recombination to correct the genetic defect. Cytogenetic analysis, array comparative genomic hybridization (aCGH), and exome sequencing were performed to assess the genomic integrity of an iPS cell line after three sequential clonal events: initial reprogramming, gene targeting, and subsequent removal of a selection cassette. No abnormalities were detected after standard G-band metaphase analysis. However, aCGH and exome sequencing identified two deletions, one amplification, and nine mutations in protein coding regions in the initial iPS cell clone. Except for the targeted correction of the single nucleotide in the OAT locus and a single synonymous base-pair change, no additional mutations or copy number variation were identified in iPS cells after the two subsequent clonal events. These findings confirm that iPS cells themselves may carry a significant mutational load at initial isolation, but that the clonal events and prolonged cultured required for correction of a genetic defect can be accomplished without a substantial increase in mutational burden.

Mouse embryonic stem cell adherent cell differentiation and cytotoxicity (ACDC) assay

An adherent cell differentiation and cytotoxicity (ACDC) assay was developed using pluripotent J1 mouse embryonic stem cells (mESCs). Adherent mESCs were used to evaluate chemical-induced effects on both stem cell viability and differentiation using an in-cell western technique after a 9-day culture. DRAQ5/Sapphire700 stains were used to quantify cell number. Myosin heavy chain protein was used as a marker of cardiomyocyte differentiation and was corrected for cell number, thereby separating cytotoxicity and effects on differentiation. Acetic acid, 5-fluorouracil and bromochloroacetic acid were evaluated using the embryonic stem cell test and ACDC assay. Both systems distinguish the relative potencies of these compounds. TaqMan low-density arrays were used to characterize the time course of differentiation and effects of chemical exposure on multiple differentiation gene markers. The ACDC assay is a technique that can be used to evaluate the effects of xenobiotics on mESC differentiation and cell number using a single assay.

Using human pluripotent stem cells to untangle neurodegenerative disease mechanisms

Human pluripotent stem cells, including embryonic (hES) and induced pluripotent stem cells (hiPS), retain the ability to self-renew indefinitely, while maintaining the capacity to differentiate into all cell types of the nervous system. While human pluripotent cell-based therapies are unlikely to arise soon, these cells can currently be used as an inexhaustible source of committed neurons to perform high-throughput screening and safety testing of new candidate drugs. Here, we describe critically the available methods and molecular factors that are used to direct the differentiation of hES or hiPS into specific neurons. In addition, we discuss how the availability of patient-specific hiPS offers a unique opportunity to model inheritable neurodegenerative diseases and untangle their pathological mechanisms, or to validate drugs that would prevent the onset or the progression of these neurological disorders.

Normal and pathological development of pluripotent stem cells

Pluripotent cells of the early embryo originate all types of somatic cells and germ cells of adult organism. Pluripotent stem cell lines were derived from mammalian embryos and adult tissues using different techniques and from different sources--inner cell mass of the blastocyst, primordial germ cells, parthenogenetic oocytes, and mature spermatogonia--as well as by transgenic modification of various adult somatic cells. Despite different origin, all pluripotent stem cell lines demonstrate considerable similarity of the major biological properties: unlimited self-renewal and differentiation into various somatic and germ cells in vitro and in vivo, similar gene expression profiles, and similar cell cycle structure. Their malignant counterpart embryonal teratocarcinoma stem cell lines have restricted developmental potentials caused by genetic disturbances that result in deregulation of proliferation and differentiation balance. Numerous studies on the stability of different pluripotent stem cell lines demonstrated that, irrespective of their origin, long-term in vitro cultivation leads to the accumulation of chromosomal and gene mutations as well as epigenetic changes that can cause oncogenic transformation of cells. Our research of signaling pathways and pattern of specific gene expression in pluripotent stem cells and teratocarcinoma cells is focused on discovery of fundamental mechanisms that regulate normal development of pluripotent cells into different lineages and are disrupted in cancer initiating cells. Analysis gene expression profiles, differentiation potentials and cell cycle of normal and mutant pluripotent stem cells provide new data to search molecular targets to eliminate malignant cells in tumors.

Current technology for the derivation of pluripotent stem cell lines from human embryos

Technology for the derivation, propagation, and characterization of pluripotent stem cell lines from the human embryo has undergone considerable refinement and improvement since the first published description of human embryonic stem cells in 1998. In particular, there has been extensive effort to optimize protocols and develop defined culture systems with a view toward future clinical applications of embryonic stem cell-derived products. Here, we review the current status of methodology for human embryonic stem cell derivation and culture, and we highlight the challenges that remain for workers in the field.

Cancer-related epigenome changes associated with reprogramming to induced pluripotent stem cells

The ability to induce pluripotent stem cells from committed, somatic human cells provides tremendous potential for regenerative medicine. However, there is a defined neoplastic potential inherent to such reprogramming that must be understood and may provide a model for understanding key events in tumorigenesis. Using genome-wide assays, we identify cancer-related epigenetic abnormalities that arise early during reprogramming and persist in induced pluripotent stem cell (iPS) clones. These include hundreds of abnormal gene silencing events, patterns of aberrant responses to epigenetic-modifying drugs resembling those for cancer cells, and presence in iPS and partially reprogrammed cells of cancer-specific gene promoter DNA methylation alterations. Our findings suggest that by studying the process of induced reprogramming, we may gain significant insight into the origins of epigenetic gene silencing associated with human tumorigenesis, and add to means of assessing iPS for safety.

Autism or autisms? Finding the lowest common denominator

Previous studies suggest the presence of a minicolumnopathy in autism. Minicolumnar abnormalities as well as certain migratory and proliferative defects, common to autism, may be rooted in the general mechanics of periventricular germinal cell division and maturation. Increased numbers of periventricular germinal cell/radial glia can be mimicked by a variety of different transgenic mouse models and environmental factors. These murine models and environmental factors illustrate how a fairly homogenous neuroanatomical phenotype can diverge at the genetic level. By first defining the lowest common denominator (i.e., the minicolumn) and then examining which pathways are vulnerable to involved genetic and environmental factors, we may gain a greater understanding of the pathophysiologic mechanisms underlying Autism Spectrum Conditions.

[Regulation of in vitro and in vivo differentiation of mouse embryonic stem cells, embryonic germ cells, and teratocarcinoma cells by TGFb family signaling factors]

The activity of specific signaling and transcription factors determines the cell fate in normal development and in tumor transformation. The transcriptional profiles of gene-components of different branches of TGFbeta family signaling pathways were studied in experimental models of initial stages of three-dimensional in vitro differentiation of embryonic stem cells, embryonic germ cells and teratocarcinoma cells and in teratomas and teratocarcinomas developed after their transplantation into immunodeficient Nude mice. Gene profile analysis of studied cell systems have revealed that expression patterns of ActivinA, Nodal, Lefty1, Lefty2, TGF TGFbeta1, BMP4, and GDF were identical in pluripotent stem cells whereas the mRNAs of all examined genes with the exception of Inhibin betaA/ActivinA were detected in the teratocarcinoma cells. These results indicate that differential activity of signaling pathways of the TGFbeta family factors regulates pluripotent state maintenance and pluripotent stem cell differentiation into the progenitors of three germ layers and extraembryonic structures and that normal expression pattern of TGFbeta family factors is rearranged in embryonic teratocarcinoma cells during tumor growth in vitro and in vivo.

Angiogenesis and vascular network of teratocarcinoma from embryonic stem cell transplant into seminiferous tubules

BACKGROUND

Carcinoma in situ (CIS) of the testis is considered to be a precancerous germinal cell lesion, but the precise cellular and molecular mechanisms underlying transformation of CIS into invasive pluripotent cancer cells remain to be elucidated. Moreover, a satisfactory animal model for the experimental study of germinal tumours has not been developed to date.

METHODS

We have developed a tumour model that involves the microinjection of green fluorescent protein-labelled embryonic stem (ES) cells (which are functionally equivalent to CIS cells) into syngenic mouse seminiferous tubules, a unique cell microenvironment in which germinal cells mature and CIS arise. To characterise the vascularisation of teratocarcinomas, which arise after cell transplant, we used immunohistochemistry, together with a qualitative and quantitative analysis of scanning electron microscopy images of corrosion casting samples.

RESULTS

Embryonic stem cells transplanted into seminiferous tubules did not differentiate into germinal cells, but rather they behaved as invasive embryonal carcinoma (EC) stem cells. The vascular pattern of the experimental teratocarcinomas showed a highly disorganised architecture, and some of the neoplastic capillaries were derived, at least in part, from the original transplanted ES cells.

CONCLUSION

The transplantation of pluripotent ES cells into seminiferous tubules efficiently recapitulates the early stages of development of teratocarcinomas. Consequently, this method constitutes a novel in vivo model to study the mechanisms of invasion and progression of experimental germinal tumours.

Emerging role of Notch in stem cells and cancer

The Notch signaling pathway is known to be responsible for maintaining a balance between cell proliferation and death and, as such, plays important roles in the formation of many types of human tumors. Recently, Notch signaling pathway has been shown to control stem cell self-renewal and multi-potency. As many cancers are thought to be developed from a number of cancer stem-like cells, which are also known to be linked with the acquisition of epithelial-mesenchymal transition (EMT); and thus suggesting an expanding role of Notch signaling in human tumor progression.

A self-renewal program controls the expansion of genetically unstable cancer stem cells in pluripotent stem cell-derived tumors

Human germ cell tumors are often metastatic, presumably due to distal site tumor growth by cancer stem cells. To determine whether cancer stem cells can be identified in a transplantation model of testicular germ cell tumor, we transplanted murine embryonic germ cells (EGCs) into the testis of adult severe combined immunodeficient mice. Transplantation resulted in a locally invasive solid tumor, with a cellular component that generated secondary tumors upon serial transplantation. The secondary tumors were invariably metastatic, a feature not observed in the primary tumors derived from EGCs. To characterize the differences between EGCs and the tumor-derived stem cells, we performed karyotype and microarray analysis. Our results show that generation of cancer stem cells is associated with the acquisition of nonclonal genomic rearrangements not found in the originating population. Furthermore, pretreatment of EGCs with a potent inhibitor of self-renewal, retinoic acid, prevented tumor formation and the emergence of these genetically unstable cancer stem cells. Microarray analysis revealed that EGCs and first- and second-generation cancer stem cells were highly similar; however, approximately 1,000 differentially expressed transcripts could be identified corresponding to alterations in oncogenes and genes associated with motility and development. Combined, the data suggest that the activation of oncogenic pathways in a cellular background of genetic instability, coupled with an inherent ability to self-renew, is involved in the acquisition of metastatic behavior in the cancer stem cell population of tumors derived from pluripotent cells.

The expression of pluripotency marker Oct 3/4 in prostate cancer and benign prostate hyperplasia

BACKGROUND

Oct 3/4 (Octamer 3/4), a member of POU family has been considered as an important stem cell marker and essential transcription factor during human embryogenesis. In recent years, there have also been reports on presence of Oct 3/4 in differentiated benign and malignant human cells. The objective of this study was to investigate the transcription and the protein expression of Oct 3/4 isoforms in prostate cancer and benign prostate tissue.

METHODS

Thirty sex adenocarcinomas and eight cases of benign prostate hyperplasia were studied. The transcription of Oct 3/4 was analyzed using RT-PCR approach associated with restriction digestion analysis. Oct 3/4 protein expression was studied by immunohistochemistry on paraffin sections using two different antibodies.

RESULTS

We identified only the transcript 2 of Oct 3/4 in prostate tumors and benign prostate hyperplasia. Immunohistochemistry verified these results, demonstrating only cytoplasmic localization of Oct 3/4. Transcription of type 1 of Oct 3/4 as well as protein expression with nuclear localization of Oct 3/4 isoform 1 were not detected. Oct 3/4 immunopositive tumors were also displayed neuroendocrine differentiation and showed androgen receptor immunopositivity. The stem cell markers CD44 and CD117 were not detected in Oct 3/4 immunopositive cells.

CONCLUSION

Our results indicate that only the cytoplasmic isoform 2 of Oct 3/4 is present in prostate cancer and benign prostate hyperplasia. The malignant and benign prostate cells, which are immunopositive for variant 2 of Oct 3/4, lack other stem cell markers supporting previously published data that variant 2 of Oct 3/4 is not a pluripotency marker.

DYRK1A-dosage imbalance perturbs NRSF/REST levels, deregulating pluripotency and embryonic stem cell fate in Down syndrome

Down syndrome (DS) is the most common cause of mental retardation. Many neural phenotypes are shared between DS individuals and DS mouse models; however, the common underlying molecular pathogenetic mechanisms remain unclear. Using a transchromosomic model of DS, we show that a 30%-60% reduced expression of Nrsf/Rest (a key regulator of pluripotency and neuronal differentiation) is an alteration that persists in trisomy 21 from undifferentiated embryonic stem (ES) cells to adult brain and is reproducible across several DS models. Using partially trisomic ES cells, we map this effect to a three-gene segment of HSA21, containing DYRK1A. We independently identify the same locus as the most significant eQTL controlling REST expression in the human genome. We show that specifically silencing the third copy of DYRK1A rescues Rest levels, and we demonstrate altered Rest expression in response to inhibition of DYRK1A expression or kinase activity, and in a transgenic Dyrk1A mouse. We reveal that undifferentiated trisomy 21 ES cells show DYRK1A-dose-sensitive reductions in levels of some pluripotency regulators, causing premature expression of transcription factors driving early endodermal and mesodermal differentiation, partially overlapping recently reported downstream effects of Rest +/-. They produce embryoid bodies with elevated levels of the primitive endoderm progenitor marker Gata4 and a strongly reduced neuroectodermal progenitor compartment. Our results suggest that DYRK1A-mediated deregulation of REST is a very early pathological consequence of trisomy 21 with potential to disturb the development of all embryonic lineages, warranting closer research into its contribution to DS pathology and new rationales for therapeutic approaches.

Does the number or quality of pluripotent bone marrow stem cells decrease with age?

In the next 25 years, as the 37 million baby boomers age, we can expect a 400% increase in total joint arthroplasties that will challenge surgeons, the healthcare system, and the scientific community. The burden may be eased if we are able to manipulate side population stem cells and enhance peri-prosthetic bone remodeling thereby reducing the incidence of revisions. Therefore, as a preliminary question, we asked if the number and quality of side population stem cells, with the ability to proliferate into multiple cell lineages for long periods, correlates with age and can be evaluated in peripheral blood. Using flow cytometry we analyzed the quantity and quality of side population stem cells from bone marrow and peripheral blood in 54 patients (20 under 60 years of age, 34 over) undergoing THA. The total side population of stem cells decreased with age, but their long-term repopulating ability (quality) remained constant. The total count of side population stem cells in marrow correlated with the number found in peripheral blood. If these populations can be manipulated, periprosthetic remodeling may be beneficially enhanced.

An additional human chromosome 21 causes suppression of neural fate of pluripotent mouse embryonic stem cells in a teratoma model

BACKGROUND

Down syndrome (DS), caused by trisomy of human chromosome 21 (HSA21), is the most common genetic cause of mental retardation in humans. Among complex phenotypes, it displays a number of neural pathologies including smaller brain size, reduced numbers of neurons, reduced dendritic spine density and plasticity, and early Alzheimer-like neurodegeneration. Mouse models for DS show behavioural and cognitive defects, synaptic plasticity defects, and reduced hippocampal and cerebellar neuron numbers. Early postnatal development of both human and mouse-model DS shows the reduced capability of neuronal precursor cells to generate neurons. The exact molecular cause of this reduction, and the role played by increased dosage of individual HSA21 genes, remain unknown.

RESULTS

We have subcutaneously injected mouse pluripotent ES cells containing a single freely segregating supernumerary human chromosome 21 (HSA21) into syngeneic mice, to generate transchromosomic teratomas. Transchromosomic cells and parental control cells were injected into opposite flanks of thirty mice in three independent experiments. Tumours were grown for 30 days, a time-span equivalent to combined intra-uterine, and early post-natal mouse development. When paired teratomas from the same animals were compared, transchromosomic tumours showed a three-fold lower percentage of neuroectodermal tissue, as well as significantly reduced mRNA levels for neuron specific (Tubb3) and glia specific (Gfap) genes, relative to euploid controls. Two thirds of transchromosomic tumours also showed a lack of PCR amplification with multiple primers specific for HSA21, which were present in the ES cells at the point of injection, thus restricting a commonly retained trisomy to less than a third of HSA21 genes.

CONCLUSION

We demonstrate that a supernumerary chromosome 21 causes Inhibition of Neuroectodermal DIfferentiation (INDI) of pluripotent ES cells. The data suggest that trisomy of less than a third of HSA21 genes, in two chromosomal regions, might be sufficient to cause this effect.

The role of stem cells in fibrous dysplasia of bone and the Mccune-Albright syndrome

Stem cells have become a major area of interest in the treatment of human disease, but more recently, stem cells have come to be appreciated as the cause of disease. Fibrous dysplasia of bone and the McCune-Albright Syndrome evolve from activating missense mutations in Gsalpha in pluripotent embryonic stem cells. The legacy of these mutations remains in a population of mutated multipotent post-natal skeletal stem cells ("mesenchymal" stem cells), which direct the formation of abnormal bone and a fibrotic marrow in fibrous dysplasia. Future therapeutic approaches for the treatment of fibrous dysplasia, the most significant component of the McCune-Albright Syndrome, will depend on a greater understanding of post-natal skeletal stem cell biology and how skeletal stem cells can be manipulated for efficient bone regeneration.