Findings could one day lead to improved treatment of spinal cord injuries
Tuesday, 16 November 2010
Scientists have discovered the origin of a unique type of cell known for its ability to support regeneration in the central nervous system. Their findings, published this week in the journal Proceedings of the National Academy of Sciences USA (PNAS), raise the possibility of obtaining a more reliable source of these cells for use in cell transplantation therapy for spinal cord injuries.
Olfactory Nerve. The origin of cells
associated with nerve repair has been
discovered. The findings could one
day lead to improved treatment of
spinal cord injuries.
Credit: Dr. Perrine Barraud.
Dr Clare Baker, from the Department of Physiology, Development and Neuroscience at the University of Cambridge, lead author of the study, said: "In theory, one should be able to purify OECs from a patient's nose and transplant them into the damaged spinal cord to promote nerve repair, without any fear of graft rejection.”
"Unfortunately, there aren't very many OECs in the nasal lining, and this tissue also contains other peripheral nerve fibres, ensheathed by cells that look very similar to OECs but which are less effective at promoting spinal cord repair. As a result, it has thus far proven difficult to purify sufficiently large numbers of OECs from the nasal lining for effective use in cell transplantation therapy."
For the last 25 years, OECs have been thought to be formed by the nasal lining itself. The new research, however, reveals a different origin for OECs that may enable scientists in the future to produce them in large quantities from adult stem cells.
The researchers, funded by the Wellcome Trust and the Isaac Newton Trust, have discovered that, like all other cells ensheathing peripheral nerve fibres, OECs are actually derived from a group of embryonic stem cells called "neural crest cells". Neural crest stem cells persist in adult skin and hair follicles, and other researchers have already shown that it is possible to isolate these stem cells and grow them in the lab.
"The next step is to work out how to turn these stem cells into OECs. To do this, we need to investigate how this process happens normally in the developing embryo," Dr Baker said.
Cross-section of the embryonic chicken
olfactory bulb showing neural
crest-derived olfactory ensheathing
cells (green). (Blue, axons; red,
low-affinity neurotrophin receptor.)
Credit: Dr. Perrine Barraud.
In order to determine the origin of OECs, the scientists tagged embryonic neural crest cells with 'green fluorescent protein' (GFP), so that only neural crest cells and their descendants glowed green under ultraviolet light. They did this in chicken embryos by transplanting GFP-labelled neural crest cells into unlabelled host embryos; they also looked at mouse embryos in which, through a genetic trick, the only cells that expressed GFP were neural crest cells.
They were then able to follow what happened to neural crest cells and their descendants as the olfactory nerve developed. By analysing thin sections of these embryos under the microscope, they were able to see that lots of green neural crest-derived cells were associated with the developing olfactory nerve fibres. These green cells expressed molecular markers characteristic of OECs, and crucially, they ensheathed bundles of the olfactory nerve fibres, i.e., they were indeed olfactory ensheathing cells.
Source: University of Cambridge
Contact: Contact: Genevieve Maul
Neural crest origin of olfactory ensheathing glia
Perrine Barraud, Anastasia A. Seferiadis, Luke D. Tyson, Maarten F. Zwart, Heather L. Szabo-Rogers, Christiana Ruhrberg, Karen J. Liu, and Clare V. H. Baker
PNAS, 15 November 2010, doi:10.1073/pnas.1012248107
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