Analysis of Schwann-astrocyte Interactions Using In Vitro Assays
Summary
This article intends to describe in stepwise fashion the commonly used in vitro assays used in studying Schwann cell-asrtocyte interactions.
Abstract
Schwann cells are one of the commonly used cells in repair strategies following spinal cord injuries. Schwann cells are capable of supporting axonal regeneration and sprouting by secreting growth factors 1,2 and providing growth promoting adhesion molecules 3 and extracellular matrix molecules 4. In addition they myelinate the demyelinated axons at the site of injury 5.
However following transplantation, Schwann cells do not migrate from the site of implant and do not intermingle with the host astrocytes 6,7. This results in formation of a sharp boundary between the Schwann cells and astrocytes, creating an obstacle for growing axons trying to exit the graft back into the host tissue proximally and distally. Astrocytes in contact with Schwann cells also undergo hypertrophy and up-regulate the inhibitory molecules 8-13.
In vitro assays have been used to model Schwann cell-astrocyte interactions and have been important in understanding the mechanism underlying the cellular behaviour.
These in vitro assays include boundary assay, where a co-culture is made using two different cells with each cell type occupying different territories with only a small gap separating the two cell fronts. As the cells divide and migrate, the two cellular fronts get closer to each other and finally collide. This allows the behaviour of the two cellular populations to be analyzed at the boundary. Another variation of the same technique is to mix the two cellular populations in culture and over time the two cell types segregate with Schwann cells clumped together as islands in between astrocytes together creating multiple Schwann-astrocyte boundaries.
The second assay used in studying the interaction of two cell types is the migration assay where cellular movement can be tracked on the surface of the other cell type monolayer 14,15. This assay is commonly known as inverted coverslip assay. Schwann cells are cultured on small glass fragments and they are inverted face down onto the surface of astrocyte monolayers and migration is assessed from the edge of coverslip.
Both assays have been instrumental in studying the underlying mechanisms involved in the cellular exclusion and boundary formation. Some of the molecules identified using these techniques include N-Cadherins 15, Chondroitin Sulphate proteoglycans(CSPGs) 16,17, FGF/Heparin 18, Eph/Ephrins19.
This article intends to describe boundary assay and migration assay in stepwise fashion and elucidate the possible technical problems that might occur.
Protocol
Discussion
The assays described above have been used in various studies demonstrating the role of multiple factors involved in boundary formation between the Schwann-astrocytes and limited Schwann cell migration in astrocytic environment.
Understanding the mechanisms underlying these events is essential as it would allow development of strategies to optimise and enhance the integration of Schwann cell grafts following transplantation and in doing so facilitate the exit of the regenerating axons from the…
Divulgations
The authors have nothing to disclose.
Acknowledgements
We would like to thank Philippa Warren for her kind help.
Materials
| Material Name | Type | Company | Catalogue Number | Comment |
|---|---|---|---|---|
| DMEM | Invitrogen | 41966-029 | ||
| HBSS | Invitrogen | 14170-088 | ||
| FCS | Invitrogen | 10091-148 | ||
| PSF | Invitrogen | 15240-062 | ||
| BPE | Invitrogen | 13028-014 | ||
| Forskolin | Calbiochem | 344273 | ||
| Coverlips | VWR-International | 631-0149 | ||
| Coverlips(rectangle) | MENZEL-GLASER (Supplied by Thermo Scientifics) | BB022050A1 | ||
| Chamber slides | Nunc-LabTek | 177380 | ||
| 4 well plates, 6 well plates | Nunc | 4 well plates 6 well plates |
||
| rat p75 antibody | Millipore, Temecula,California | MAB365 | ||
| GFAP antibody | Dako | Z0334 | ||
| Secondary antibodies (Alexa-conjugated) | Invitrogen | A-11004 A-11034 |
Goat anti mouse 568 Goat anti Rabbit 488 |
|
| Secondary biotinylated | Vector | Goat anti mouse | ||
| DAB tablets | Sigma-aldrich | D4418 | ||
| ABC elite kit | Vector | PK-6100 | ||
| Fine Forceps | FST | 11295-10 | ||
| Paraformaldehyde | Sigma-Aldrich | P6168 | ||
| Fluorosave | Calbiochem | 345789 |
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