Characterisation of Embryonic Dermal Precursor Cells

Skin is an attractive organ for the acquisition of stem cells due to its accessibility, size and potential for autologous transplants. Research into skin development has implications for the isolation of stem cell populations, for example skin-derived precursors (SKPs), as well as the treatment of skin conditions, such as fibrosis. This study centred on the early development, differentiation and stem cell potential of the dermis in embryonic mouse skin. Based on microarray data, the expression of specific Wnt family members was examined using RT-PCR and immunohistochemistry. No evidence of Wnt protein expression was observed in the dermis, but more embryonic stages and Wnt family members need to be explored to better understand Wnt signalling and its role in dermal development. Our main focus was to investigate the plasticity of the common dermal fibroblast precursor population present at E13.5. We hypothesised that the dermis contains a common precursor capable of producing all cell types of the dermis and could harbour a high proportion of mesenchymal stem cell (MSC)-like precursors. This E13.5 dermal cell (DC) population was investigated by exploring its differentiation potential when cultured in adipogenic and osteogenic media. These experiments indicated the E13.5 DCs contained a small subpopulation of MSC-like progenitors. However, when E13.5 DCs were cultured to produce SKPs and, subsequently, pushed to adipogenic and osteogenic lineages, they differentiated less than expected. Most research regarding SKPs has used adult and older embryonic skin, therefore the findings here are novel in that SKPs were not expected at a younger age. However, RT-PCR revealed differences between the gene expression profiles of early and late embryonic dermal SKPs. Moreover, neither displayed the expected differentiation potential. The possible reasons for these unexpected findings include the potential role of hair follicle induction and/or a later migration of neural crest progenitors into the dermis

Synaptic Network Activity Induces Neuronal Differentiation of Adult Hippocampal Precursor Cells through BDNF Signaling

Adult hippocampal neurogenesis is regulated by activity. But how do neural precursor cells in the hippocampus respond to surrounding network activity and translate increased neural activity into a developmental program? Here we show that long-term potentiation (LTP)-like synaptic activity within a cellular network of mature hippocampal neurons promotes neuronal differentiation of newly generated cells. In co-cultures of precursor cells with primary hippocampal neurons, LTP-like synaptic plasticity induced by addition of glycine in Mg2+-free media for 5 min, produced synchronous network activity and subsequently increased synaptic strength between neurons. Furthermore, this synchronous network activity led to a significant increase in neuronal differentiation from the co-cultured neural precursor cells. When applied directly to precursor cells, glycine- and Mg2+-free solution did not induce neuronal differentiation. Synaptic plasticity-induced neuronal differentiation of precursor cells was observed in the presence of GABAergic neurotransmission blockers but was dependent on NMDA-mediated Ca2+ influx. Most importantly, neuronal differentiation required the release of brain-derived neurotrophic factor (BDNF) from the underlying substrate hippocampal neurons as well as TrkB receptor phosphorylation in precursor cells. This suggests that activity-dependent stem cell differentiation within the hippocampal network is mediated via synaptically evoked BDNF signaling

Mapping New Olfactory Bulb Neurons at the Single-Cell Level Using Iron Oxide- Assisted MRI

Mapping New Olfactory Bulb Neurons at the Single-Cell Level Using Iron Oxide- Assisted MRI Sarah Izabel, Dept. of Biology, with Dr. Jeffrey Dupree, Dept. of Anatomy and Neurobiology Neurogenesis in the subventricular zone (SVZ) of adult mammalian brains persists throughout life. Precursor cells that are continuously born in the SVZ migrate long-distance to the olfactory bulb (OB), where they differentiate into specific neurons. The distribution of new neurons in the OB has been studied via histological and intravital techniques, which are limited longitudinally and in depth of imaging. In the past decade, in vivo studies using magnetic resonance imaging (MRI) have shown the possibility of detecting single cells and tracking new neurons in the OB, where precursor cells can be labelled using iron oxide. In this study, neural progenitor cells in the SVZ were labeled using micro-sized iron oxide particles (MPIOs) and their migration to the OB was detected with MRI. MPIO was confirmed to be present in new neurons via immunohistochemistry and MRI signals were overlapped with MPIOs showing that MPIO-generated MRI contrast can be used to detect single neuronal cells in the OB.https://scholarscompass.vcu.edu/uresposters/1314/thumbnail.jp

Extracellular matrix and integrins influence in the regulation of myogenic precursor cells behaviour

Tese de mestrado, Biologia (Biologia Molecular Humana), 2009, Universidade de Lisboa, Faculdade de CiênciasMyogenesis is the process by which undifferentiated dermomyotomal cells are specified for myogenesis, move towards the myotome where they differentiate into skeletal muscle cells that fuse into myotubes and later in development form myofibers which will constitute the skeletal muscles of the adult. The muscle precursor cells arise from the dermomyotome, an epithelial-like structure that is the source for skeletal muscle and dorsal dermis cells. Some cells, called satellite cells, go throughout part of this differentiation process but remain in a quiescent undifferentiated state (although committed to skeletal muscle fate). These cells are activated in the adult in case of muscle injury or enhanced exercise, for example. In this work we used a satellite cell-derived cell line, C2C12, and the mouse embryo to study the extracellular matrix (ECM) and integrins influence in myogenic determination and differentiation. Integrins are heterodimeric ECM receptors constituted by an α and a ß subunit that can induce, for example, migration or differentiation. The integrin ligand specificity is acquired by the combination of both subunits. Our studies have addressed that laminin-α6ß1 integrin interaction may be coordinating with Notch signaling the maintenance of undifferentiated dermomyotomal cells. By inhibiting Notch signaling, we observed precocious myogenic differentiation of dermomyotomal cells (by Myf5 expression) and the assembly of a laminin matrix around these cells. This result suggests that Myf5 induces laminin assembly. In vitro, fibronectin enhances C2C12 myoblasts alignment and migration. When we observed the myotubes of cells grown on fibronectin, we believe that the enhanced cell alignment imposed by fibronectin-α5ß1 integrin interaction will facilitate cell fusion. In vivo, we found that fibronectin is important for dermomyotome epithelial-integrity, especially through the polarization of N-cadherin, and that α5ß1 integrin signaling may also contribute to myogenic repression in the dermomyotome. These observations show that the ECM and integrins are of paramount importance in myoblast cell behaviour.Resumo alargado em português disponível no document

Characterization of Cre recombinase activity for in vivo targeting of adipocyte precursor cells.

The increased incidence of obesity and metabolic disease underscores the importance of elucidating the biology of adipose tissue development. The recent discovery of cell surface markers for prospective identification of adipose precursor cells (APCs) in vivo will greatly facilitate these studies, yet tools for specifically targeting these cells in vivo have not been identified. Here, we survey three transgenic mouse lines, Fabp4-Cre, PdgfRα-Cre, and Prx1-Cre, precisely assessing Cre-mediated recombination in adipose stromal populations and mature tissues. Our data provide key insights into the utility of these tools to modulate gene expression in adipose tissues. In particular, Fabp4-Cre is not effective to target APCs, nor is its activity restricted to these cells. PdgfRα-Cre directs recombination in the vast majority of APCs, but also targets other populations. In contrast, adipose expression of Prx1-Cre is chiefly limited to subcutaneous inguinal APCs, which will be valuable for dissection of APC functions among adipose depots

CD133 (Prominin) Negative Human Neural Stem Cells Are Clonogenic and Tripotent

CD133 (Prominin) is widely used as a marker for the identification and isolation of neural precursor cells from normal brain or tumor tissue. However, the assumption that CD133 is expressed constitutively in neural precursor cells has not been examined

The roles of cis-inactivation by Notch ligands and of neuralized during eye and bristle patterning in Drosophila

BACKGROUND: The receptor protein Notch and its ligand Delta are expressed throughout proneural regions yet non-neural precursor cells are defined by Notch activity and neural precursor cells by Notch inactivity. Not even Delta overexpression activates Notch in neural precursor cells. It is possible that future neural cells are protected by cis-inactivation, in which ligands block activation of Notch within the same cell. The Delta-ubiquitin ligase Neuralized has been proposed to antagonize cis-inactivation, favoring Notch activation. Cis-inactivation and role of Neuralized have not yet been studied in tissues where neural precursor cells are resistant to nearby Delta, however, such as the R8 cells of the eye or the bristle precursor cells of the epidermis. RESULTS: Overexpressed ligands could block Notch signal transduction cell-autonomously in non-neural cells of the epidermis and retina, but did not activate Notch nonautonomously in neural cells. High ligand expression levels were required for cis-inactivation, and Serrate was more effective than Delta, although Delta is the ligand normally regulating neural specification. Differences between Serrate and Delta depended on the extracellular domains of the respective proteins. Neuralized was found to act cell nonautonomously in signal-sending cells during eye development, inconsistent with the view that Neuralized antagonizes cis-inactivation in non-neural cells. CONCLUSIONS: Delta and Neuralized contribute cell nonautonomously to Notch signaling in neurogenesis, and the model that Neuralized antagonizes cis-inactivation to permit Notch activity and specification of non-neural cells is refuted. The molecular mechanism rendering Notch insensitive to paracrine activation in neural precursor cells remains uncertain