• Astrocytes grown in Alvetex® 3 dimensional scaffolds retain a non-reactive phenotype

      Ugbode, Christopher I.; Hirst, W.D.; Rattray, Marcus (2016)
      Protocols which permit the extraction of primary astrocytes from either embryonic or postnatal mice are well established however astrocytes in culture are different to those in the mature CNS. Three dimensional (3D) cultures, using a variety of scaffolds may enable better phenotypic properties to be developed in culture. We present data from embryonic (E15) and postnatal (P4) murine primary cortical astrocytes grown on coated coverslips or a 3D polystyrene scaffold, Alvetex. Growth of both embryonic and postnatal primary astrocytes in the 3D scaffold changed astrocyte morphology to a mature, protoplasmic phenotype. Embryonic-derived astrocytes in 3D expressed markers of mature astrocytes, namely the glutamate transporter GLT-1 with low levels of the chondroitin sulphate proteoglycans, NG2 and SMC3. Embroynic astrocytes derived in 3D show lower levels of markers of reactive astrocytes, namely GFAP and mRNA levels of LCN2, PTX3, Serpina3n and Cx43. Postnatal-derived astrocytes show few protein changes between 2D and 3D conditions. Our data shows that Alvetex is a suitable scaffold for growth of astrocytes, and with appropriate choice of cells allows the maintenance of astrocytes with the properties of mature cells and a non-reactive phenotype.
    • Astrocytic Transporters in Alzheimer’s disease

      Ugbode, Christopher I.; Yuhan, H.; Whalley, B.J.; Peers, C.; Rattray, Marcus; Dallas, M. (2017)
      Astrocytes play a fundamental role in maintaining the health and function of the central nervous system. Increasing evidence indicates that astrocytes undergo both cellular and molecular changes at an early stage in neurological diseases, including Alzheimer’s disease. These changes may reflect a change from a neuroprotective to a neurotoxic phenotype. Given the lack of current disease modifying therapies for Alzheimer’s disease, astrocytes have become an interesting and viable target for therapeutic intervention. The astrocyte transport system covers a diverse array of proteins involved in metabolic support, neurotransmission and synaptic architecture. Therefore, specific targeting of individual transporter families has the potential to suppress neurodegeneration, a characteristic hallmark of Alzheimer’s disease. A small number of the four hundred transporter superfamilies’ are expressed in astrocytes, with evidence highlighting a fraction of these are implicated in Alzheimer’s disease. Here we review the current evidence for six astrocytic transporter subfamilies involved in Alzheimer’s disease, as reported in both animal and human studies. This review confirms that astrocytes are indeed a viable target, highlights the complexities of studying astrocytes and provides future directives to exploit the potential of astrocytes in tackling Alzheimer’s disease.
    • Neuronal influences are necessary to produce mitochondrial co-localization with glutamate transporters in astrocytes.

      Ugbode, Christopher I.; Hirst, W.D.; Rattray, Marcus (2014-09)
      Abstract Recent evidence suggests that the predominant astrocyte glutamate transporter, GLT-1/ Excitatory Amino Acid Transporter 2 (EAAT2) is associated with mitochondria. We used primary cultures of mouse astrocytes to assess co-localization of GLT-1 with mitochondria, and tested whether the interaction was dependent on neurons, actin polymerization or the kinesin adaptor, TRAK2. Mouse primary astrocytes were transfected with constructs expressing V5-tagged GLT-1, pDsRed1-Mito with and without dominant negative TRAK2. Astrocytes were visualized using confocal microscopy and co-localization was quantified using Volocity software. Image analysis of confocal z-stacks revealed no co-localization between mitochondria and GLT-1 in pure astrocyte cultures. Co-culture of astrocytes with primary mouse cortical neurons revealed more mitochondria in processes and a positive correlation between mitochondria and GLT-1. This co-localization was not further enhanced after neuronal depolarization induced by 1 h treatment with 15 mM K+. In pure astrocytes, a rho kinase inhibitor, Y27632 caused the distribution of mitochondria to astrocyte processes without enhancing GLT-1/mitochondrial co-localization, however, in co-cultures, Y27632 abolished mitochondrial: GLT-1 co-localization. Disrupting potential mitochondrial: kinesin interactions using dominant negative TRAK2 did not alter GLT-1 distribution or GLT-1: mitochondrial co-localization. We conclude that the association between GLT-1 and mitochondria is modest, is driven by synaptic activity and dependent on polymerized actin filaments. Mitochondria have limited co-localization with the glutamate transporter GLT-1 in primary astrocytes in culture. Few mitochondria are in the fine processes where GLT-1 is abundant. It is necessary to culture astrocytes with neurones to drive a significant level of co-localization, but co-localization is not further altered by depolarization, manipulating sodium ion gradients or Na/K ATPase activity.
    • Neuronal-glial populations form functional networks in a biocompatible 3D scaffold.

      Smith, I.; Haag, M.; Ugbode, Christopher I.; Tams, D.; Rattray, Marcus; Przyborski, S.; Bithell, A.; Whalley, B.J. (2015-11-16)
      Monolayers of neurons and glia have been employed for decades as tools for the study of cellular physiology and as the basis for a variety of standard toxicological assays. A variety of three dimensional (3D) culture techniques have been developed with the aim to produce cultures that recapitulate desirable features of intact. In this study, we investigated the effect of preparing primary mouse mixed neuron and glial cultures in the inert 3D scaffold, Alvetex. Using planar multielectrode arrays, we compared the spontaneous bioelectrical activity exhibited by neuroglial networks grown in the scaffold with that seen in the same cells prepared as conventional monolayer cultures. Two dimensional (monolayer; 2D) cultures exhibited a significantly higher spike firing rate than that seen in 3D cultures although no difference was seen in total signal power (<50 Hz) while pharmacological responsiveness of each culture type to antagonism of GABAAR, NMDAR and AMPAR was highly comparable. Interestingly, correlation of burst events, spike firing and total signal power (<50 Hz) revealed that local field potential events were associated with action potential driven bursts as was the case for 2D cultures. Moreover, glial morphology was more physiologically normal in 3D cultures. These results show that 3D culture in inert scaffolds represents a more physiologically normal preparation which has advantages for physiological, pharmacological, toxicological and drug development studies, particularly given the extensive use of such preparations in high throughput and high content systems.
    • SHH signalling mediates astrocyte crosstalk with neurons to confer neuroprotection

      Ugbode, Christopher I.; Smith, I.; Whalley, B.J.; Hirst, W.D.; Rattray, Marcus (2017)
      Sonic Hedgehog (SHH) is a glycoprotein associated with development that is also expressed in the adult CNS and released after brain injury. Since the SHH receptors PTCH1 (patched homolog-1) and SMO (Smoothened) are highly expressed on astrocytes, we hypothesised that SHH regulates astrocyte function. Primary mouse cortical astrocytes derived from embryonic (E15) Swiss mouse cortices, were treated with two chemically distinct agonists of the SHH pathway, which caused astrocytes to elongate and proliferate. These changes are accompanied by decreases in the major astrocyte glutamate transporter, GLT-1 and the astrocyte intermediate filament protein GFAP. Multi-site electrophysiological recordings revealed that the SHH agonist, SAG supressed neuronal firing in astrocyte-neuron co-cultures and this was abolished by the astrocyte metabolic inhibitor ethylfluoroacetate, revealing that SHH stimulation of metabolically-active astrocytes influences neuronal firing. Using 3D co-culture, MAP2 western blotting and immunohistochemistry, we show that SHH-stimulated astrocytes protect neurons from kainate induced cell death. Altogether the results show that SHH regulation of astrocyte function represents an endogenous neuroprotective mechanism.