The cells that are involved in our sense of smell (olfaction) possess
characteristics that could also be very useful for repair of the damaged spinal
cord. Olfactory neurons (nerve cells) are unique in that they are the only known
neurons to replace themselves throughout adult life. The nerve fibres of these
cells are surrounded by cells called olfactory ensheathing cells (OECs). When
new neurons are born, the nerve fibres are guided from the nasal tissue up
through holes in the bone in the roof of the nasal cavity and into the olfactory
bulb (part of the brain) by the OECs. Although not technically stem cells, OECs
have considerable regenerative potential and have been the focus of much
attention in the spinal cord injury research community.
When OECs are transplanted into the injured spinal cord of animals they promote
axonal (nerve fiber) regeneration and some functional recovery. Exactly how this
occurs is theoretical but could be due to a number of different things happening
within the injury site. These include, OECs guiding the growth of nerve fibres
or wrapping around (and insulating) intact but non-functional nerve fibres, thus
making them functional again; OECs secreting growth factors, or generating a
matrix that cells can attach to and grow along, thus enabling re-growth and
repair.
The olfactory (nasal) tissue has many specialised cells, including a type of
stem cell. These stem cells are thought to be the origin of the new neurons
(nerve cells) and also possibly the origin of replacement OECs and other support
cells with the olfactory tissues.
Some researchers believe that the transplantation of more than one cell type
will be required in order to induce sufficient repair and produce functional
recovery.
One such researcher is Dr Carlos Lima of Lisbon Portugal. Dr Lima has developed
a method of transplanting olfactory mucosa (nasal lining), obtained from high in
nasal passages (roof of the nose), into the site of damage within the spinal
cord. Dr Lima and his surgical team, harvest OECs and stem cells from the
olfactory mucosa and transplant them into the injured spinal cord in a single
operation. This procedure has been performed on 70 participants, with many of
the latest cases including people from the United States.
We have also been granted Ethics approval to obtain and study the nasal tissue
from SCI volunteers and patients having nasal surgery. The aim of this study is
to study the OECs and establish a cell culture protocol to enhance the numbers.
