Abstract
BackgroundThe efficient derivation of mature (Hb9+) motor neurons from embryonic stem cells is a sought-after goal in the understanding, and potential treatment, of motor neuron diseases. Conditions that promote the robust generation of motor neuron progenitors from embryonic stem cells and that promote the survival of differentiated motor neurons ex vivo are likely, therefore, to be critical in future biological/therapeutic/screening approaches. Previous studies have shown that astrocytes have a protective effect on differentiated motor neurons (in vivo and ex vivo), but it remains unclear whether astrocytes also play a beneficial role in the support of motor neuron progenitors. Here we explore the effect of murine astrocyte-conditioned medium on monolayer cultures of mouse embryonic stem cell-derived motor neuron progenitors.ResultsOur data show that wild-type astrocyte-conditioned medium significantly increases the number of Olig2+/Hb9- progenitors, which subsequently differentiate into Hb9+/Islet1+ post-mitotic motor neurons. Intriguingly, while astrocyte-conditioned medium derived from mice transgenic for wild-type human SOD1 mimics the effect of wild-type astrocytes, conditioned medium derived from astrocytes carrying an amyotrophic lateral sclerosis-related SOD1-G93A mutation shows no such beneficial effect. The effect of astrocyte-conditioned medium, moreover, is specific to motor neurons: we find that interneurons generated from mouse embryonic stem cells are unaffected by conditioned media from any type of astrocyte.ConclusionsOur study indicates that conditioned medium derived from wild type astrocytes enhances the efficient generation of motor neurons from mouse embryonic stem cells by enhancing motor neuron progenitors. In contrast, conditioned medium from SOD1-G93A astrocytes does not show a similar enhancing effect.
Highlights
The efficient derivation of mature (Hb9+) motor neurons from embryonic stem cells is a sought-after goal in the understanding, and potential treatment, of motor neuron diseases
Studies in mouse have shown that astrocytes expressing mutant forms of SOD1-G37R, SOD1-G85R, and SOD1-G93A, release soluble factors that can selectively kill embryonic stem (ES) cell-derived or primary Motor neuron (MN) in vitro, and have demonstrated that neurotoxicity by SOD1-G93A astrocytes is mediated through the recruitment of the Bax-dependent death machinery
Double-labelling for Olig2 and Hb9/ MNR2 reveals that the majority of Olig2+ cells do not co-express Hb9/MNR2 and are largely restricted to the ventricular zone and subventricular zone (VZ/SVZ), the region of the developing neural tube that harbours proliferating progenitor cells
Summary
The efficient derivation of mature (Hb9+) motor neurons from embryonic stem cells is a sought-after goal in the understanding, and potential treatment, of motor neuron diseases. Conditions that promote the robust generation of motor neuron progenitors from embryonic stem cells and that promote the survival of differentiated motor neurons ex vivo are likely, to be critical in future biological/therapeutic/screening approaches. We explore the effect of murine astrocyte-conditioned medium on monolayer cultures of mouse embryonic stem cell-derived motor neuron progenitors. Studies in mouse have shown that astrocytes expressing mutant forms of SOD1-G37R (change of arginine to glycine at position 37), SOD1-G85R (change of arginine to glycine at position 85), and SOD1-G93A (change of alanine to glycine at position 93), release soluble factors that can selectively kill embryonic stem (ES) cell-derived or primary MNs in vitro, and have demonstrated that neurotoxicity by SOD1-G93A astrocytes is mediated through the recruitment of the Bax-dependent death machinery. The evidence from these studies suggests that astrocytes are critically involved in MN depletion in ALS, most likely acting through multiple mechanisms
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