Astrocytes, but not olfactory ensheathing cells or Schwann cells, promote myelination of CNS axons in vitro

Abstract

We have examined the interaction between olfactory ensheathing cells (OECs), Schwann cells (SC), oligodendrocytes, and CNS axons using cultures generated from embryonic rat spinal cord. Oligodendrocyte process extension and myelination in these cultures was poor if the cells were plated on OECs or SCs. Myelin internodes and nodes of Ranvier formed frequently if these cultures were plated onto monolayers of neurosphere-derived astrocytes (NsAs). In the myelinated fibers generated on NsAs, Nav channels, caspr, and neurofascin molecules were correctly assembled at the nodes of Ranvier. The density of neurites, survival, and antigenic differentiation of oligodendrocytes was similar on OEC and NsAs monolayers. However, on OEC monolayers, despite a transient increase in the number of endogenous oligodendrocytes, there was a decrease in oligodendrocyte process extension and axonal ensheathment when compared with cultures plated on NsAs monolayers. To determine if these changes were due to axonal or glial factors, spinal cord oligodendrocytes were plated onto monolayers of OECs, NsAs, and poly-L-lysine in the absence of neurons. In these cultures, process extension and myelin-like membrane formation by oligodendrocytes was improved on monolayers of OEC. This suggests that inhibition of process extension is mediated via cross-talk between OECs and neurites. In cultures containing axons plated on OEC monolayers, oligodendrocyte process formation, axonal ensheathment, and myelination occurred albeit lower if the cultures were supplemented with NsAs conditioned medium. These data suggest OECs can permit neurite extension and oligodendrocyte proliferation, but lack secreted factor(s) and possible cell-cell contact that is necessary for oligodendrocyte process extension and myelination.

CNS/PNS Boundary Transgression by Central Glia in the Absence of Schwann Cells or Krox20/Egr2 Function

“…In our models, oligodendrocytes are always colocalized with astrocytes, which may suggest their interdependence in terms of survival, migration, and/or differentiation. This latter observation is in agreement with a recent study highlighting the role of astrocytes in the promotion of myelination in the CNS (Sorensen et al, 2008). In our study, ectopic oligodendrocytes and astrocytes were never observed in more distal parts of peripheral nerves, although the DRGs were also colonized (data not shown).…”

Axonal abnormalities in vanishing white matter

“…Astrocytes or forebrain mixed cells were isolated from cerebral hemispheres of E18 mice and cultured following previously described methods with minor modifications 27, 28, 29, 30, 31. Cultures were kept in a humidified incubator at 37°C and 7.5% CO 2 at all times.…”

The Development of a ɛ-Polycaprolactone Scaffold for Central Nervous System Repair

“…Myelinating CNS cultures were set up as previously outlined, 24,25 with a couple of minor modifications. They comprise a monolayer of astrocytes on top of which are plated mixed rat spinal cord cells.…”

“…Astrocytes are essential for cell survival and myelination. 24 Briefly, striatum were collected from P1 Sprague-Dawley rats in Liebowitz (L15; Invitrogen) media and dissociated mechanically before suspension in neurosphere media (Dulbecco's modified Eagle's medium, DMEM/F12 (1:1), 0.6% glucose, 2 mM glutamine (Invitrogen), insulin (25 mg/mL; Sigma), 5 mM Hepes (Sigma), 0.105% NaHCO 3 (Sigma), 5000 IU/mL penicillin (Invitrogen), 5 mg/mL streptomycin (Invitrogen), 100 mg/mL apotransferrin, 20 nM progesterone, 60 mM putrescine, and 30 nM sodium selenite (all Sigma) supplemented with 20 ng/mL mouse submaxillary gland epidermal growth factor (EGF; R&D systems) and cultured as neurospheres for 7-10 days at 37°C, 7% CO 2, with supplementation of the media every alternate day.…”

“…These cells interact to mimic the complex cellular interactions of CNS cells in vivo. [24][25][26] Although many studies have primarily investigated biocompatibility, cytotoxicity, and the immune response following implantation, 27 we have focused on how the host CNS cells, including astrocytes, neurons, microglia, and their myelinating glia respond to the scaffold design with emphasis on differentiation as a read out, which indicates the potential effectiveness of the scaffold to support repair in the CNS.…”