Gene expression pattern of functional neuronal cells derived from human bone marrow mesenchymal stromal cells

Central nervous system gene expression changes in a transgenic mouse model for bovine spongiform encephalopathy

Gene expression analysis has proven to be a very useful tool to gain knowledge of the factors involved in the pathogenesis of diseases, particularly in the initial or preclinical stages. With the aim of finding new data on the events occurring in the Central Nervous System in animals affected with Bovine Spongiform Encephalopathy, a comprehensive genome wide gene expression study was conducted at different time points of the disease on mice genetically modified to model the bovine species brain in terms of cellular prion protein. An accurate analysis of the information generated by microarray technique was the key point to assess the biological relevance of the data obtained in terms of Transmissible Spongiform Encephalopathy pathogenesis. Validation of the microarray technique was achieved by RT-PCR confirming the RNA change and immunohistochemistry techniques that verified that expression changes were translated into variable levels of protein for selected genes. Our study reveals changes in the expression of genes, some of them not previously associated with prion diseases, at early stages of the disease previous to the detection of the pathological prion protein, that might have a role in neuronal degeneration and several transcriptional changes showing an important imbalance in the Central Nervous System homeostasis in advanced stages of the disease. Genes whose expression is altered at early stages of the disease should be considered as possible therapeutic targets and potential disease markers in preclinical diagnostic tool development. Genes non-previously related to prion diseases should be taken into consideration for further investigations.

A novel xenogeneic co-culture system to examine neuronal differentiation capability of various adult human stem cells

Background

Targeted differentiation of stem cells is mainly achieved by the sequential administration of defined growth factors and cytokines, although these approaches are quite artificial, cost-intensive and time-consuming. We now present a simple xenogeneic rat brain co-culture system which supports neuronal differentiation of adult human stem cells under more in vivo-like conditions.

Methods and Findings

This system was applied to well-characterized stem cell populations isolated from human skin, parotid gland and pancreas. In addition to general multi-lineage differentiation potential, these cells tend to differentiate spontaneously into neuronal cell types in vitro and are thus ideal candidates for the introduced co-culture system. Consequently, after two days of co-culture up to 12% of the cells showed neuronal morphology and expressed corresponding markers on the mRNA and protein level. Additionally, growth factors with the ability to induce neuronal differentiation in stem cells could be found in the media supernatants of the co-cultures.

Conclusions

The co-culture system described here is suitable for testing neuronal differentiation capability of numerous types of stem cells. Especially in the case of human cells, it may be of clinical relevance for future cell-based therapeutic applications.

Bone marrow mesenchymal stem cells differentiate into urothelial cells and the implications for reconstructing urinary bladder mucosa

To determine the ability of cultured bone marrow-derived mesenchymal stem cells (BMSCs) to differentiate into functional urothelium. BMSCs were isolated from the long bones of aborted fetal limbs by Percoll density gradient centrifugation and characterized by flow cytometry. Human fetal urinary bladders were cut into small pieces and cultured for 3-5 days until the growth of urothelial cells was established. BMSCs were then cocultured with neonatal urothelial cells and subsequently evaluated for antigen expression and ultramicrostructure, by immunocytochemistry and electron microscopy, respectively. A subset of BMSCs expressed the differentiation marker CD71. The BMSC markers CD34, CD45, and HLA-DR were barely detectable, confirming that these cells were not derived from hematopoietic stem cells or differentiated cells. In contrast, the stem cell markers CD29, CD44, CD105, and CD90 were highly expressed. BMSCs possessed the ability to differentiate into a variety of cellular subtypes, including osteocytes, adipocytes, and chondrocytes. The shapes of BMSCs changed, and the size of the cells increased, following in vitro coculture with urothelial cells. After 2 weeks of coculture, immunostaining of the newly differentiated BMSCs positively displayed the urothelial-specific keratin marker. Electron microscopy revealed that the cocultured BMSCs had microstructural features characteristic of epithelial cells. Pluripotent BMSCs can transdifferentiate into urothelial cells in response to an environment conditioned by neonatal urothelial cells, providing a means for the time-, labor- and cost-effective reconstruction of urinary bladder mucosa.

Mesenchymal stem cells for treatment of CNS injury

Brain and spinal cord injuries present significant therapeutic challenges. The treatments available for these conditions are largely ineffective, partly due to limitations in directly targeting the therapeutic agents to sites of pathology within the central nervous system (CNS). The use of stem cells to treat these conditions presents a novel therapeutic strategy. A variety of stem cell treatments have been examined in animal models of CNS trauma. Many of these studies have used stem cells as a cell-replacement strategy. These investigations have also highlighted the significant limitations of this approach. Another potential strategy for stem cell therapy utilises stem cells as a delivery mechanism for therapeutic molecules. This review surveys the literature relevant to the potential of mesenchymal stem cells for delivery of therapeutic agents in CNS trauma in humans.

Neuronal plasticity of human Wharton's jelly mesenchymal stromal cells to the dopaminergic cell type compared with human bone marrow mesenchymal stromal cells

BACKGROUND AIMS

Mesenchymal stromal cells (MSC) derived from Wharton's jelly (WJ) of the umbilical cord are increasingly gaining prominence as substitutes for bone marrow (BM) MSC. While MSC isolated from different tissue sources may share common mesenchymal properties, the difference in their plasticity to individual lineages is ill-defined. Thus the focus of this study was to estimate the neuronal plasticity of WJ MSC to the dopaminergic (DA) cell type in comparison with BM MSC.

METHODS

For neuronal differentiation, MSC were exposed to developmentally relevant cues for midbrain DA neurons: sonic hedgehog (SHH) and fibroblast growth factor 8 (FGF8), along with basic fibroblast growth factor (bFGF).

RESULTS

Naive MSC from both sources constitutively expressed neuronal markers. Flow cytometry data revealed that the control WJ MSC shared a signature similar to BM MSC for early neuronal markers (nestin, musashi12 and A2B5) and DA-specific markers [tyrosine hydroxylase (TH) and Nuclear Receptor related protein 1 (Nurr1) but differed for mature neuronal proteins [β-tubulin III and microtubule-associated protein 2 (Map2ab)]. Similar populations of cells in both sources of MSC were positive for the SHH receptors [patched (PTCH) and smoothened (SMO)]. In induced BM and WJ MSC, real-time reverse transcriptase (RT)-polymerase chain reaction (PCR) analysis showed similar levels of DA-related transcription factors Nurr1 and Engrailed (En) 1. Immunocytochemical and flow cytometry analysis showed an increase in mature neuronal marker Map2ab. Kv4.2, a K(+) channel marker, was observed only in the induced MSC. Induced MSC also expressed several DA-specific markers, TH, dopamine and cyclic AMP regulated phosphoprotein (DARPP) 32, paired-like homeodomain transcription factor (PitX) 3 and vesicular monoamine transporter (VMAT) 2, in comparable levels between the two sources. The efficiency (c. 65%) of transdifferentiation of WJ MSC to TH-positive cells was similar to that of induced BM MSC. Constitutive and inducible release of dopamine was found to be similar between induced BM and WJ MSC, as measured by dopamine enzyme-linked immunosorbent assay (ELISA). Interestingly, an adenosine triphosphate (ATP)-stimulated change in intracellular Ca(2+) was observed in both control and induced MSC, but only the induced MSC was capable of releasing dopamine.

CONCLUSIONS

Our data demonstrate that MSC from the two different sources respond similarly to inductive cues to differentiate terminally to a DA cell type, and the neuronal plasticity of human WJ MSC is comparable with that of BM MSC.

The multiple roles of amphiregulin in human cancer

Amphiregulin (AREG) is one of the ligands of the epidermal growth factor receptor (EGFR). AREG plays a central role in mammary gland development and branching morphogenesis in organs and is expressed both in physiological and in cancerous tissues. Various studies have highlighted the functional role of AREG in several aspects of tumorigenesis, including self-sufficiency in generating growth signals, limitless replicative potential, tissue invasion and metastasis, angiogenesis, and resistance to apoptosis. The oncogenic activity of AREG has already been described in the most common human epithelial malignancies, such as lung, breast, colorectal, ovary and prostate carcinomas, as well as in some hematological and mesenchymal cancers. Furthermore, AREG is also involved in resistance to several cancer treatments. In this review, we describe the various roles of AREG in oncogenesis and discuss its translational potential, such as the development of anti-AREG treatments, based on AREG activity. In the last decade, independent groups have reported successful but sometimes contradictory results in relation to the potential of AREG to serve as a prognostic and/or predictive marker for oncology, especially with regard to anti-EGFR therapies. Thus, we also discuss the potential usefulness of using AREG as a therapeutic target and validated biomarker for predicting cancer outcomes or treatment efficacy.

Transplantation of neuronal-primed human bone marrow mesenchymal stem cells in hemiparkinsonian rodents

Bone marrow-derived human mesenchymal stem cells (hMSCs) have shown promise in in vitro neuronal differentiation and in cellular therapy for neurodegenerative disorders, including Parkinson' disease. However, the effects of intracerebral transplantation are not well defined, and studies do not agreed on the optimal neuronal differentiation method. Here, we investigated three growth factor-based neuronal differentiation procedures (using FGF-2/EGF/PDGF/SHH/FGF-8/GDNF), and found all to be capable of eliciting an immature neural phenotype, in terms of cell morphology and gene/protein expression. The neuronal-priming (FGF-2/EGF) method induced neurosphere-like formation and the highest NES and NR4A2 expression by hMSCs. Transplantation of undifferentiated and neuronal-primed hMSCs into the striatum and substantia nigra of 6-OHDA-lesioned hemiparkinsonian rats revealed transient graft survival of 7 days, despite the reported immunosuppressive properties of MSCs and cyclosporine-immunosuppression of rats. Neither differentiation of hMSCs nor induction of host neurogenesis was observed at injection sites, and hMSCs continued producing mesodermal fibronectin. Strategies for improving engraftment and differentiation post-transplantation, such as prior in vitro neuronal-priming, nigral and striatal grafting, and co-transplantation of olfactory ensheathing cells that promote neural regeneration, were unable to provide advantages. Innate inflammatory responses (Iba-1-positive microglia/macrophage and GFAP-positive astrocyte activation and accumulation) were detected around grafts within 7 days. Our findings indicate that growth factor-based methods allow hMSC differentiation toward immature neuronal-like cells, and contrary to previous reports, only transient survival and engraftment of hMSCs occurs following transplantation in immunosuppressed hemiparkinsonian rats. In addition, suppression of host innate inflammatory responses may be a key factor for improving hMSC survival and engraftment.

X chromosome and suicide

Suicide completion rates are significantly higher in males than females in most societies. Although gender differences in suicide rates have been partially explained by environmental and behavioral factors, it is possible that genetic factors, through differential expression between genders, may also help explain gender moderation of suicide risk. This study investigated X-linked genes in suicide completers using a two-step strategy. We first took advantage of the genetic structure of the French-Canadian population and genotyped 722 unrelated French-Canadian male subjects, of whom 333 were suicide completers and 389 were non-suicide controls, using a panel of 37 microsatellite markers spanning the entire X chromosome. Nine haplotype windows and several individual markers were associated with suicide. Significant results aggregated primarily in two regions, one in the long arm and another in the short arm of chromosome X, limited by markers DXS8051 and DXS8102, and DXS1001 and DXS8106, respectively. The second stage of the study investigated differential brain expression of genes mapping to associated regions in Brodmann areas 8/9, 11, 44 and 46, in an independent sample of suicide completers and controls. Six genes within these regions, Rho GTPase-activating protein 6, adaptor-related protein complex 1 sigma 2 subunit, glycoprotein M6B, ribosomal protein S6 kinase 90  kDa polypeptide 3, spermidine/spermine N(1)-acetyltransferase 1 and THO complex 2, were found to be differentially expressed in suicide completers.

EZH2 regulates neuronal differentiation of mesenchymal stem cells through PIP5K1C-dependent calcium signaling

Enhancer of zeste homolog 2 (EZH2) regulates stem cells renewal, maintenance, and differentiation into different cell lineages including neuron. Changes in intracellular Ca(2+) concentration play a critical role in the differentiation of neurons. However, whether EZH2 modulates intracellular Ca(2+) signaling in regulating neuronal differentiation from human mesenchymal stem cells (hMSCs) still remains unclear. When hMSCs were treated with a Ca(2+) chelator or a PLC inhibitor to block IP(3)-mediated Ca(2+) signaling, neuronal differentiation was disrupted. EZH2 bound to the promoter region of PIP5K1C to suppress its transcription in proliferating hMSCs. Interestingly, knockdown of EZH2 enhanced the expression of PIP5K1C, which in turn increased the amount of PI(4,5)P(2), a precursor of IP(3), and resulted in increasing the intracellular Ca(2+) level, suggesting that EZH2 negatively regulates intracellular Ca(2+) through suppression of PIP5K1C. Knockdown of EZH2 also enhanced hMSCs differentiation into functional neuron both in vitro and in vivo. In contrast, knockdown of PIP5K1C significantly reduced PI(4,5)P(2) contents and intracellular Ca(2+) release in EZH2-silenced cells and resulted in the disruption of neuronal differentiation from hMSCs. Here, we provide the first evidence to demonstrate that after induction to neuronal differentiation, decreased EZH2 activates the expression of PIP5K1C to evoke intracellular Ca(2+) signaling, which leads hMSCs to differentiate into functional neuron lineage. Activation of intracellular Ca(2+) signaling by repressing or knocking down EZH2 might be a potential strategy to promote neuronal differentiation from hMSCs for application to neurological dysfunction diseases.

Human cardiomyogenesis and the need for systems biology analysis

Cardiovascular disease remains the leading cause of death in the Western world and myocardial infarction is one of the primary facets of this disease. The limited natural self-renewal of cardiac muscle following injury and restricted supply of heart transplants has encouraged researchers to investigate other means to stimulate regeneration of damaged myocardium. The plasticity of stem cells toward multiple lineages offers the potential to repair the heart following injury. Embryonic stem cells have been extensively studied for their ability to differentiate into early cardiomyocytes, however, the pathway has only been partially defined and inadequate efficiency limits their clinical applicability. Some studies have shown cardiomyogenesis from adult mesenchymal stem cells, from both bone marrow and adipose tissue, but their differentiation pathway remains poorly detailed and these results remain controversial. Despite promising results using stem cells in animal models of cardiac injury, the driving mechanisms behind their differentiation down a cardiomyogenic pathway have yet to be determined. Currently, there is a paucity of information regarding cardiomyogenesis on the systemic level. Stem cell differentiation results from multiple signaling parameters operating in a tightly regulated spatiotemporal pattern. Investigating this phenomenon from a systems biology perspective could unveil the abstruse mechanisms controlling cardiomyogenesis that would otherwise require extensive in vitro testing.

Bone marrow mesenchymal stem cells: historical overview and concepts

This review describes the historical emergence of the concept of bone marrow mesenchymal stem cells (MSCs), summarizing data on Wolf and Trentin's hematopoietic inductive microenvironment; Dexter's hematopoiesis-supportive stromal cells; Friedenstein's osteogenic cells; and Pittenger's trilineal osteoblastic, chondrocytic, and adipocytic precursors; to finally introduce the specific bone marrow mesenchymal stem cells with differentiation potential to four lineages (mesenchymal and vascular smooth muscle lineages), and stromal and immunomodulatory capacities. Two points are the object of detailed discussion. The first point envisions the stem cell attributes (multipotentiality, self-renewal, tissue regeneration, population heterogeneity, plasticity, and lineage priming) compared with that of the paradigmatic hematopoietic stem cell. In the second point, we discuss the possible existence of bone marrow cells with greater differentiation potential, eventually pluripotential cells. The latter point raises the issues of cell fusion, reprogramming, or selection under nonstandardized conditions of rare populations of neuroectodermal origin, or of cells that had undergone mesenchymal-to-epithelial transition. In the last section, we review data on MSC senescence and possible malignant transformation secondary to extensive culture, gene transfer of telomerase, or mutations such as leading to Ewing's sarcoma. The set of data leads to the conclusion that bone marrow MSCs constitute a specific adult tissue stem cell population. The multiple characteristics of this stem cell type account for the versatility of the mechanisms of injured tissue repair. Although MSC administration may be extremely useful in a number of clinical applications, their transplantation is not without risks that must not be overlooked when developing cell therapy protocols.

Advances in hepatic stellate cell-targeted treatment of hepatic fibrosis with bone marrow-derived mesenchymal stem cells

Hepatic fibrosis is one of the most serious diseases that pose a great threat to human health. Liver transplantation is currently the most effective treatment for these patients. However, the worldwide shortage of donor livers has greatly limited the use of this treatment. As a result, searching for alternative cell therapy has attracted great interest in preclinical studies. The transplantation of bone marrow-derived mesenchymal stem cells (BMSCs) holds great promise for treating hepatic fibrosis because experimental and clinical studies have shown that it has beneficial effects on hepatic fibrosis. However, the precise cellular and molecular mechanisms behind such treatment remain to be elucidated. In this article, we will review the advances in treatment of hepatic fibrosis with BMSCs using hepatic stellate cells (HSCs) as a target.

Microglia and neuroprotection: from in vitro studies to therapeutic applications

Microglia are the main immune cells in the brain, playing a role in both physiological and pathological conditions. Microglial involvement in neurodegenerative diseases is well-established, being microglial activation and neuroinflammation common features of these neuropathologies. Microglial activation has been considered harmful for neurons, but inflammatory state is not only associated with neurotoxic consequences, but also with neuroprotective effects, such as phagocytosis of dead neurons and clearance of debris. This brought to the idea of protective autoimmunity in the brain and to devise immunomodulatory therapies, aimed to specifically increase neuroprotective aspects of microglia. During the last years, several data supported the intrinsic neuroprotective function of microglia through the release of neuroprotective molecules. These data led to change the traditional view of microglia in neurodegenerative diseases: from the idea that these cells play an detrimental role for neurons due to a gain of their inflammatory function, to the proposal of a loss of microglial neuroprotective function as a causing factor in neuropathologies. This "microglial dysfunction hypothesis" points at the importance of understanding the mechanisms of microglial-mediated neuroprotection to develop new therapies for neurodegenerative diseases. In vitro models are very important to clarify the basic mechanisms of microglial-mediated neuroprotection, mainly for the identification of potentially effective neuroprotective molecules, and to design new approaches in a gene therapy set-up. Microglia could act as both a target and a vehicle for CNS gene delivery of neuroprotective factors, endogenously produced by microglia in physiological conditions, thus strengthening the microglial neuroprotective phenotype, even in a pathological situation.

Fatty Acid Desaturase 3 (Fads3) is a singular member of the Fads cluster

Since its identification in 2000, no function has been attributed to the Fatty Acid Desaturase 3 (Fads3) gene. This gene is located within the Fads cluster, which also contains Fads1 and Fads2, coding respectively for the Δ5- and Δ6- desaturases. Based on the sequence homology between these three genes, Fads3 may be a new fatty acid desaturase. It is thus essential to understand its involvement in Polyunsaturated Fatty Acid (PUFA) biosynthesis in order to improve our knowledge on lipid metabolism. Gene expression studies provided evidences on the specificity of Fads3 compared to Fads1 and Fads2, concerning the tissue distribution, alternative splicing and regulation. These works also identified possible physiological functions in which Fads3 could be involved. Thus, the Fads3 gene was transcripted in many tissues, and displayed a weak expression in the liver compared to other organs such as the lung or spleen. Fads3 was also showed to be a target gene for NK-κB, MYCN or p63 transcription factors and could consequently be involved in cell survival mechanisms. Polymorphism analysis underlined the possible implication of Fads3 in lipid homeostasis, particularly by modulating cholesterol and triglyceride plasma levels. In terms of proteins, FADS3 has been recently described in rodents. One of the identified isoforms may display the classical structure of a fatty acid desaturase but no enzymatic activity has been observed yet. Therefore, it is essential to consider the desaturase diversity in terms of catalysis and substrates to elucidate the FADS3 function.

Introducing transcription factors to multipotent mesenchymal stem cells: making transdifferentiation possible

Multipotent mesenchymal stem cells (MSCs) represent a promising autologous source for regenerative medicine. Because MSCs can be isolated from adult tissues, they represent an attractive cell source for autologous transplantation. A straightforward therapeutic strategy in the field of stem cell-based regenerative medicine is the transplantation of functional differentiated cells as cell replacement for the lost or defective cells affected by disease. However, this strategy requires the capacity to regulate stem cell differentiation toward the desired cell fate. This therapeutic approach assumes the capability to direct MSC differentiation toward diverse cell fates, including those outside the mesenchymal lineage, a process termed transdifferentiation. The capacity of MSCs to undergo functional transdifferentiation has been questioned over the years. Nonetheless, recent studies support that genetic manipulation can serve to promote transdifferentiation. Specifically, forced expression of certain transcription factors can lead to reprogramming and alter cell fate. Using such a method, fully differentiated lymphocytes have been reprogrammed to become macrophages and, remarkably, somatic cells have been reprogrammed to become embryonic stem-like cells. In this review, we discuss the past and current research aimed at transdifferentiating MSCs, a process with applications that could revolutionize regenerative medicine.

Monitoring the genomic stability of in vitro cultured rat bone-marrow-derived mesenchymal stem cells

Bone-marrow-derived mesenchymal stem cells (MSCs) are multipotent cells capable of self-renewal and differentiation into multiple cell types. Accumulating preclinical and clinical evidence indicates that MSCs are good candidates to use as cell therapy in many degenerative diseases. For MSC clinical applications, an adequate number of cells are necessary so an extensive expansion is required. However, spontaneous immortalization and malignant transformation of MSCs after culture expansion have been reported in human and mouse, while very few data are present for rat MSCs (rMSCs). In this study, we monitored the chromosomal status of rMSCs at several passages in vitro, also testing the influence of four different cell culture conditions. We first used the conventional traditional cytogenetic techniques, in order to have the opportunity to observe even minor structural abnormalities and to identify low-degree mosaic conditions. Then, a more detailed genomic analysis was conducted by array comparative genomic hybridization. We demonstrated that, irrespective of culture conditions, rMSCs manifested a markedly aneuploid karyotype and a progressive chromosomal instability in all the passages we analyzed and that they are anything but stable during in vitro culture. Despite the fact that the risk of neoplastic transformation associated with this genomic instability needs to be further addressed and considering the apparent genomic stability reported for in vitro cultured human MSCs (hMSCs), our findings underline the fact that rMSCs may not in fact be a good model for effectively exploring the full clinical therapeutic potential of hMSCs.

The fatty acid desaturase 3 gene encodes for different FADS3 protein isoforms in mammalian tissues

In 2000, Marquardt et al. (A. Marquardt, H. Stöhr, K. White, and B. H. F. Weber. 2000. cDNA cloning, genomic structure, and chromosomal localization of three members of the human fatty acid desaturase family. Genomics. 66: 176-183.) described the genomic structure of the fatty acid desaturase (FADS) cluster in humans. This cluster includes the FADS1 and FADS2 genes encoding, respectively, for the Delta 5- and Delta 6-desaturases involved in polyunsaturated fatty acid biosynthesis. A third gene, named FADS3, has recently been identified but no functional role has yet been attributed to the putative FADS3 protein. In this study, we investigated the FADS3 occurrence in rat tissues by using two specific polyclonal antibodies directed against the N-terminal and C-terminal ends of rat FADS3. Our results showed three potential protein isoforms of FADS3 (75 kDa, 51 kDa, and 37 kDa) present in a tissue-dependent manner. The occurrence of these FADS3 isoforms did not depend on the mRNA level determined by real-time PCR. In parallel, mouse tissues were also tested and showed the same three FADS3 isoforms but with a different tissue distribution. Finally, we reported the existence of FADS3 in human cells and tissues but different new isoforms were identified. To conclude, we showed in this study that FADS3 does exist under multiple protein isoforms depending on the mammalian tissues. These results will help further investigations to determine the physiological function of FADS3.

Mesenchymal Stem Cell Therapy for Nonmusculoskeletal Diseases: Emerging Applications

Mesenchymal stem cells are stem/progenitor cells originated from the mesoderm and can different into multiple cell types of the musculoskeletal system. The vast differentiation potential and the relative ease for culture expansion have established mesenchymal stem cells as the building blocks in cell therapy and tissue engineering applications for a variety of musculoskeletal diseases, including repair of fractures and bone defects, cartilage regeneration, treatment of osteonecrosis of the femoral head, and correction of genetic diseases such as osteogenesis imperfect. However, research in the past decade has revealed differentiation potentials of mesenchymal stem cells beyond lineages of the mesoderm, suggesting broader applications than originally perceived. In this article, we review the recent developments in mesenchymal stem cell research with respect to their emerging properties and applications in nonmusculoskeletal diseases.

Transcripts of unknown function in multiple-signaling pathways involved in human stem cell differentiation

Mammalian transcriptome analysis has uncovered tens of thousands of novel transcripts of unknown function (TUFs). Classical and recent examples suggest that the majority of TUFs may underlie vital intracellular functions as non-coding RNAs because of their low coding potentials. However, only a portion of TUFs have been studied to date, and the functional significance of TUFs remains mostly uncharacterized. To increase the repertoire of functional TUFs, we screened for TUFs whose expression is controlled during differentiation of pluripotent human mesenchymal stem cells (hMSCs). The resulting six TUFs, named transcripts related to hMSC differentiation (TMDs), displayed distinct transcriptional kinetics during hMSC adipogenesis and/or osteogenesis. Structural and comparative genomic characterization suggested a wide variety of biologically active structures of these TMDs, including a long nuclear non-coding RNA, a microRNA host gene and a novel small protein gene. Moreover, the transcriptional response to established pathway activators indicated that most of these TMDs were transcriptionally regulated by each of the two key pathways for hMSC differentiation: the Wnt and protein kinase A (PKA) signaling pathways. The present study suggests that not only TMDs but also other human TUFs may in general participate in vital cellular functions with different molecular mechanisms.

Cyclic AMP-dependent activation of rhodopsin gene transcription in cultured retinal precursor cells of chicken embryo

The present study describes a robust 50-fold increase in rhodopsin gene transcription by cAMP in cultured retinal precursor cells of chicken embryo. Retinal cells isolated at embryonic day 8 (E8) and cultured for 3 days in serum-supplemented medium differentiated mostly into red-sensitive cones and to a lesser degree into green-sensitive cones, as indicated by real-time RT-PCR quantification of each specific opsin mRNA. In contrast, both rhodopsin mRNA concentration and rhodopsin gene promoter activity required the presence of cAMP-increasing agents [forskolin and 3-isobutyl-1-methylxanthine (IBMX)] to reach significant levels. This response was rod-specific and was sufficient to activate rhodopsin gene transcription in serum-free medium. The increase in rhodopsin mRNA levels evoked by a series of cAMP analogs suggested the response was mediated by protein kinase A, not by EPAC. Membrane depolarization by high KCl concentration also increased rhodopsin mRNA levels and this response was strongly potentiated by IBMX. The rhodopsin gene response to cAMP-increasing agents was developmentally gated between E6 and E7. Rod-specific transducin alpha subunit mRNA levels also increased up to 50-fold in response to forskolin and IBMX, while rod-specific phosphodiesterase-VI and rod arrestin transcripts increased 3- to 10-fold. These results suggest a cAMP-mediated signaling pathway may play a role in rod differentiation.

Contributions of extracellular matrix signaling and tissue architecture to nuclear mechanisms and spatial organization of gene expression control

Post-translational modification of histones, ATP-dependent chromatin remodeling, and DNA methylation are interconnected nuclear mechanisms that ultimately lead to the changes in chromatin structure necessary to carry out epigenetic gene expression control. Tissue differentiation is characterized by a specific gene expression profile in association with the acquisition of a defined tissue architecture and function. Elements critical for tissue differentiation, like extracellular stimuli, adhesion and cell shape properties, and transcription factors all contribute to the modulation of gene expression and thus, are likely to impinge on the nuclear mechanisms of epigenetic gene expression control. In this review, we analyze how these elements modify chromatin structure in a hierarchical manner by acting on the nuclear machinery. We discuss how mechanotransduction via the structural continuum of the cell and biochemical signaling to the cell nucleus integrate to provide a comprehensive control of gene expression. The role of nuclear organization in this control is highlighted, with a presentation of differentiation-induced nuclear structure and the concept of nuclear organization as a modulator of the response to incoming signals.

Identification of subpopulations in mesenchymal stem cell-like cultures from human umbilical cord

Background

A variety of cell types can be identified in the adherent fraction of bone marrow mononuclear cells including more primitive and embryonic-like stem cells, mesenchymal stem cells (MSC), lineage-committed progenitors as well as mature cells such as osteoblasts and fibroblasts. Different methods are described for the isolation of single bone marrow stem cell subpopulations – beginning from ordinary size sieving, long term cultivation under specific conditions to FACS-based approaches. Besides bone marrow-derived subpopulations, also other tissues including human umbilical cord (UC) have been recently suggested to provide a potential source for MSC. Although of clinical importance, these UC-derived MSC populations remain to be characterized. It was thus the aim of the present study to identify possible subpopulations in cultures of MSC-like cells obtained from UC. We used counterflow centrifugal elutriation (CCE) as a novel strategy to successfully address this question.

Results

UC-derived primary cells were separated by CCE and revealed differentially-sized populations in the fractions. Thus, a subpopulation with an average diameter of about 11 μm and a small flat cell body was compared to a large sized subpopulation of about 19 μm average diameter. Flow cytometric analysis revealed the expression of certain MSC stem cell markers including CD44, CD73, CD90 and CD105, respectively, although these markers were expressed at higher levels in the small-sized population. Moreover, this small-sized subpopulation exhibited a higher proliferative capacity as compared to the total UC-derived primary cultures and the large-sized cells and demonstrated a reduced amount of aging cells.

Conclusion

Using the CCE technique, we were the first to demonstrate a subpopulation of small-sized UC-derived primary cells carrying MSC-like characteristics according to the presence of various mesenchymal stem cell markers. This is also supported by the high proliferative capacity of these MSC-like cells as compared to whole primary culture or other UC-derived subpopulations. The accumulation of a self-renewing MSC-like subpopulation by CCE with low expression levels of the aging marker senescence-associated β-galactosidase provides a valuable tool in the regenerative medicine and an alternative to bone-marrow-derived MSC.

Identification of candidate genes for human pituitary development by EST analysis

Background

The pituitary is a critical neuroendocrine gland that is comprised of five hormone-secreting cell types, which develops in tandem during the embryonic stage. Some essential genes have been identified in the early stage of adenohypophysial development, such as PITX1, FGF8, BMP4 and SF-1. However, it is likely that a large number of signaling molecules and transcription factors essential for determination and terminal differentiation of specific cell types remain unidentified. High-throughput methods such as microarray analysis may facilitate the measurement of gene transcriptional levels, while Expressed sequence tag (EST) sequencing, an efficient method for gene discovery and expression level analysis, may no-redundantly help to understand gene expression patterns during development.

Results

A total of 9,271 ESTs were generated from both fetal and adult pituitaries, and assigned into 961 gene/EST clusters in fetal and 2,747 in adult pituitary by homology analysis. The transcription maps derived from these data indicated that developmentally relevant genes, such as Sox4, ST13 and ZNF185, were dominant in the cDNA library of fetal pituitary, while hormones and hormone-associated genes, such as GH1, GH2, POMC, LHβ, CHGA and CHGB, were dominant in adult pituitary. Furthermore, by using RT-PCR and in situ hybridization, Sox4 was found to be one of the main transcription factors expressed in fetal pituitary for the first time. It was expressed at least at E12.5, but decreased after E17.5. In addition, 40 novel ESTs were identified specifically in this tissue.

Conclusion

The significant changes in gene expression in both tissues suggest a distinct and dynamic switch between embryonic and adult pituitaries. All these data along with Sox4 should be confirmed to further understand the community of multiple signaling pathways that act as a cooperative network that regulates maturation of the pituitary. It was also suggested that EST sequencing is an efficient means of gene discovery.

Genomic profiling of mesenchymal stem cells

Mesenchymal stem/stromal cells (MSC) are an accessible source of precursor cells that can be expanded in vitro and used for tissue regeneration for different clinical applications. The advent of microarray technology has enabled the monitoring of individual and global gene expression patterns across multiple cell populations. Thus, genomic profiling has fundamentally changed our capacity to characterize MSCs, identify potential biomarkers and determined key molecules regulating biological processes involved in stem cell survival, growth and development. Numerous studies have now examined the genomic profiles of MSCs derived from different tissues that exhibit varying levels of differentiation and proliferation potentials. The knowledge gained from these studies will help improve our understanding of the cellular signalling pathways involved in MSC growth, survival and differentiation, and may aid in the development of strategies to improve the tissue regeneration potential of MSCs for different clinical indications. The present review summarizes studies characterizing the gene expression profile of MSCs.