Origin of cells associated with nerve repair discovered

22 November 2010

Scientists have discovered the origin of a unique type of cell that can help the central nervous system regenerate. This may allow more of these cells to be produced and used to repair spinal cord injuries.

The cells with this remarkable ability are called olfactory ensheathing cells (OECs). Their normal role is to protect nerve fibres in the olfactory nerve, which transmits information about smell to the brain from receptors in the lining of the nose. OECs can be grown in dishes from pieces of nasal lining, but this method produces such small quantities that it would hamper their use in medicine.

Now, researchers from the University of Cambridge have found that, like all other cells that surround peripheral nerve fibres, OECs are derived from a group of embryonic stem cells called neural crest cells. These persist in adult skin and hair follicles, and previous research has shown that it is possible to isolate these stem cells and grow them in the lab.

Scientists had thought that OECs were formed from the nasal lining itself. This new research reveals a different origin that may enable OECs to be produced in large quantities from adult stem cells.

"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," said Dr Clare Baker, from the University of Cambridge, who led the study.

"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 are less effective at promoting spinal cord repair. As a result, it has thus proven difficult to purify sufficiently large numbers of OECs from the nasal lining for effective use in cell transplantation therapy."

Baker's team used embryonic neural crest cells tagged with green fluorescent protein to track their development in chicken and mouse embryos. Using this technique, only neural crest cells and their descendants glowed green under ultraviolet light, and the cells couldbe followed as the olfactory nerve developed. This showed that many green neural crest-derived cells were associated with the developing olfactory nerve fibres. The green cells expressed molecular markers characteristic of OECs, and they ensheathed bundles of the olfactory nerve fibres.

"The next step is to work out how to turn these stem cells into OECs," said Dr Baker. "To do this, we need to investigate how this process happens normally in a developing embryo."

She emphasised that it will take many years for the research to have any impact on therapy for people with damaged spinal cords. "However, we are hopeful that our discovery provides a fresh starting point for new research into ways of purifying large numbers of these cells for use in treatments."

The research was funded by the Isaac Newton Trust and the Wellcome Trust.

Image: Nerve regeneration in a dish. Credit: Jim Cohen, Wellcome Images.

Reference

Barraud P et al. Neural crest origin of olfactory ensheathing glia. Proc Natl Acad Sci U S A 2010 Nov 15 [Epub ahead of print].