Astroglial-axonal interactions during early stages of myelination in mixed cultures using in vitro and ex vivo imaging techniques.

Kalliopi Ioannidou,David Strachan,Susan C Barnett,Julia M Edgar,Kurt I Anderson

doi:10.1186/1471-2202-15-59

Kalliopi Ioannidou, David Strachan + Show 3 more

Open Access

https://doi.org/10.1186/1471-2202-15-59

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Abstract

BackgoundMyelination is a very complex process that requires the cross talk between various neural cell types. Previously, using cytosolic or membrane associated GFP tagged neurospheres, we followed the interaction of oligodendrocytes with axons using time-lapse imaging in vitro and ex vivo and demonstrated dynamic changes in cell morphology. In this study we focus on GFP tagged astrocytes differentiated from neurospheres and their interactions with axons.ResultsWe show the close interaction of astrocyte processes with axons and with oligodendrocytes in mixed mouse spinal cord cultures with formation of membrane blebs as previously seen for oligodendrocytes in the same cultures. When GFP-tagged neurospheres were transplanted into the spinal cord of the dysmyelinated shiverer mouse, confirmation of dynamic changes in cell morphology was provided and a prevalence for astrocyte differentiation compared with oligodendroglial differentiation around the injection site. Furthermore, we were able to image GFP tagged neural cells in vivo after transplantation and the cells exhibited similar membrane changes as cells visualised in vitro and ex vivo.ConclusionThese data show that astrocytes exhibit dynamic cell process movement and changes in their membrane topography as they interact with axons and oligodendrocytes during the process of myelination, with the first demonstration of bleb formation in astrocytes.

Highlights

Astrocytes are the most abundant cell type in the central nervous system (CNS) [1,2]
Differentiation of striatum-derived neurospheres to generate glial cells The multipotentiality of striatum-derived green fluorescent protein (GFP)-tagged neurospheres in differentiation medium was confirmed by determining their capacity to express astroglial and oligodendroglial markers in vitro
The GFP expressing neurospheres differentiated into GFAP positive astrocytes and O4 positive oligodendrocytes (Figure 1B,C) confirming the utility of these GFP expressing cells for the study of these cell types

Summary

Introduction

Astrocytes (from the Greek word “astro” meaning star) are the most abundant cell type in the central nervous system (CNS) [1,2]. Astrocytes are important in various physiological processes in the CNS, such as synapse maintenance, blood brain barrier formation and after injury, in the formation of the glial scar [1,3,4,5]. Astrocytes are important in facilitating CNS myelination [6,7,8]. The discovery of neural stem cells in the adult mammalian brain [11] has facilitated the generation of large their migration. They are believed to be instigated by hydrostatic pressure and depend on cellular mechanical properties and appear as spherical expansions of the membrane [20,21]

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