Mature dental pulp is similar to the embryonic tissue. It is a mixture of components such as nerves, blood vessels or lymphatic vessels, but importantly, it also contains Schwann cells, multipotent cells and neuropeptides that regulate growth and differentiation of neurons. Because of this unique composition of the tooth pulp, it has been recognized by numerous research teams involved in regenerative medicine. Japanese scientists have demonstrated the usefulness of the dental tissues in the regeneration of damaged nerves in a xeno-graft model.

Peripheral nerve injuries – a result of trauma or iatrogenic actions -lead to sensory or motor defect, hindering the patient’s life. The most commonly used procedure to regenerate the affected nerves is to create a “bridge” from patients’ own nervous tissue, connecting the broken fibers. Isogenic grafts taken from the sciatic nerve or minor superficial cutaneous nerves are the most widely used materials for bridging the broken nerve fibers. Harvesting isogenic material for transplantation is unfortunately combined with the danger of a serious damage of the donor nerve.

Obtaining a substitute for the problematic autogenous grafts has been the target of research in the recent years. Bioabsorbable materials such as chitosan have been manufactured. Such a material is is formed in the structure of a nanotube mesh and is an excellent for supporting the transplanted nerves.

The main objective of the research team from the University of Hokkaido was to find a way to increase the activity of Schwann cells, thus leading to improved axonal elongation in the damaged fibres. The pulp of the tooth for the experiment has been obtained from healthy human teeth, extracted for orthodontic reasons. The material was then frozen in liquid nitrogen and thawed in saline, in order to reduce antigenicity. Subsequently the material was placed in a chitosan tube allowing an enhanced integration with surrounding tissues. Pulp was then implanted in the rats’ broken sciatic nerve. For comparison, two other groups were created requiring the regeneration of the sciatic nerve: the first in which the chitosan tubes were filled with isogenic nerve graft , in the other, the tubes remained empty.

After four weeks Schwann cells and axons started to cross the border of the basement membrane which was clearly visible under the electron microscope. Twelve weeks after the surgery, enhanced axonal regeneration was observed under the light microscope. The regeneration was progressing constantly until the final evaluation in the thirty-second week after implantation. It turned out that the degree of regeneration in the group, in which the dental material was used, was similar to that in the isogenic group. Axons were mature, with a thick myelin layer. The only drawback was a slight delay in the regeneration in comparison to the isogenic group. The delay was most probably the effect of the presence of large amounts of tissue debris. The remains of the dead tissue induced a long lasting inflammation and a prolonged activity of macrophages eventually causing a delay in axon regeneration. According to the Japanese scientist the basal membrane of Schwann cells in the pulp is an excellent material to construct “bridges” in order to regenerate the axons of damaged peripheral nerves. This gives hope to avoid the complications associated with the isogenic nerves harvesting.

Promising discoveries of recent months allow the scientists to look at the future of regenerative medicine with new hopes. Researchers, thanks to pulps’ stem cells, are tempted to use this structure in the future to support the regeneration of damaged motor nerves in the spinal cord in the future.

Written by: Maria Bilińska

Source:
1.Dental pulp can be a good candidate for nerve grafting in a xeno-graft model; Journal of Neuroscience Methods Volume: 205, Issue: 2, April 15, 2012, pp. 245-251; Matasushita, Kazuhiro; Wang, Wei; Itoh, Soichiro; Domon, Takanori; Funahashi, Makoto; Tosuka, Yasunori
2. Peripheral nerve regeneration European Surgery Volume: 37, Issue: 4, August 2005, pp. 187 – 192 Sahni, V.; Qi, Y.; Frostick, S.

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