Stem Cell Research

THE REGENERATION OF HUMAN SPINAL CORD INJURIES USING OLFACTORY GLIAL CELLS

HealThis project is a collaboration between clinicians at the Princess Alexandra Hospital and researchers at the Centre for Molecular Neurobiology, Griffith University.

The goal of our research is to repair the injured human spinal cord by autologous grafting of cells from the olfactory mucosa into the damaged spine. This work is based on sound animal studies. In summary, these animal studies show that grafted olfactory cells induce recovery after spinal cord transection. The grafted cells are the olfactory glia (“ensheathing “ cells) which normally assist in the continual regeneration of olfactory nerves occurring throughout life. Olfactory ensheathing cell grafts induced regrowth of axons across the region of damage. Electrophysiological and behavioural evidence of recovery, including use of the affected limbs, was also seen. Trials in monkey have been conducted, in which the spinal cord was hemisected, resulting in paralysis in one limb only. Recovery of spinal cord function was seen in both the transplanted monkeys and the control (which received no transplant). No explanation for this result can be given without further experimentation. Human olfactory ensheathing cells, proliferate and migrate when transplanted into rat spinal cord indicating they are likely to have the same power in human. Ethically we felt it was more appropriate to move onto a phase one human trial, particularly given the positive results in studies with rat.

BACKGROUND

image005The olfactory nerve ensheathing cells are specialised glia which have two interesting and useful properties. Like peripheral Schwann cells, they allow and promote axon growth, properties not seen in the glia of the central nervous system. Unlike Schwann cells, olfactory nerve ensheathing cells exist both within and outside the central nervous system. Transplants of olfactory nerve ensheathing cells promote regeneration of parts of the central nervous system which do not normally regenerate.

All published studies of ensheathing glial transplants have taken the glia from the exterior surface of the olfactory bulbs of a donor animal (rat or human) and transplanted them into an injured animal. Most studies have used olfactory ensheathing cells taken from foetuses or new-born rats. The two studies of human cells took ensheathing cells from the brain of patients undergoing tumour surgery.

As exciting as these recent results are, if olfactory ensheathing cells are to be used for human spinal repair therapy, these sources of cells are not acceptable for transplantation. At the Centre for Molecular Neurobiology we have been working on a different approach based on our knowledge of the olfactory mucosa in the nose, the sense organ of smell.

At the Centre for Molecular Neurobiology, Griffith University, we are acknowledged leaders in the biology of the regeneration of the olfactory sensory neurones in the nose. With the knowledge gained from prior studies, we reasoned that a better source of ensheathing cells for therapy would be cells isolated from the nose. The olfactory mucosa is easily biopsied, and the lamina propria (containing the ensheathing cells) is easily separated from the overlying olfactory epithelium (containing the sensory neurones). The ensheathing cells can then be grown in culture. With our collaborators at the University of New South Wales, Department of Anatomy and Cell Biology (Dr Jike Lu and Professor Philomena Waite) we have been testing the ability of nasally-derived olfactory ensheathing cells to repair the transected spinal cord.

Our recent unpublished studies indicate:

  1. that olfactory nerve ensheathing glia from the olfactory mucosa can promote behavioural recovery after complete spinal transection in the rat (Lu et al, 2000).
  1. that when olfactory ensheathing cell transplants are delayed until one month after spinal transection the transplant-induced behavioural recovery is similar to that when the transplants are made at the time of spinal cord transection (Lu et al, 2002Brain, in press).
  1. that the olfactory mucosa is surgically accessible (Féron et al., 1998) and the lamina propria can be isolated from these biopsies and the ensheathing cells can be isolated and cultured (unpublished results). Biopsies were taken from patients undergoing nasal surgery. Different regions of the nasal cavity were examined for the volume of the olfactory nerve in the lamina propria and the density of ensheathing glia. This was assessed histologically and by culturing the glia in vitro. These experiments in humans suggest that several regions of the nasal cavity contain high numbers of ensheathing glia, which can be grown in vitro.

METHODOLOGY

Project outline.

Eight patients will participate in the trial: four in the surgical/transplant arm, and four controls. Patients will be chosen according to strict guidelines (please see attached “Selection Criteria” sheet). Both groups will undergo the same investigations and assessments at each stage of the trial. (Please see attached “Timetable of Investigations” Sheet).

The control patients will not undergo any type of surgical procedure. “Neutral” assessors, who will not know to which group each candidate belongs, will conduct assessments. To facilitate this, control patients will have a dressing in place to replicate that of the patients who have had cells implanted. After recovery from the surgery the patients are then monitored for return of behavioural function and side effects.

Submissions to the Ethics Committees of Griffith University and The Princess Alexandra Research Foundation have been approved. On this basis, funding has been granted from the Princess Alexandra Hospital Research Foundation for the project.

Harvest of olfactory glial cells.

Nasal biopsies will be made under general anaesthetic. This is a quick procedure (about 30 min). A piece of olfactory mucosa is removed about 5-10mm square located in the back of the upper nose on the medial septum or the lateral wall of the nasal cavity. The olfactory area is 5cm x 2cm in each side of the nose. The olfactory epithelium regenerates (Féron et al., 1998; Murrell et al., 1996) and the sense of smell is not affected after biopsy of the olfactory epithelium (Féron et al., 1999b; Lanza et al., 1994).

Olfactory ensheathing cell culture

The patients’ upper nasal tissues will be cultured at Griffith University Centre for Molecular Neurobiology. The tissue is treated in a complex process until only ensheathing cells remain. These cells will then be cultured to increase their number.

The cell culture facilities including refrigeration and incubation equipment at Griffith University meets the necessary TGA standards.

Cell transplantation

When there are enough cells for transplantation (about six weeks), the patients will have the transplantation operation under general anaesthesia. First a laminectomy is made at the site of the previous injury to remove the posterior face of one vertebra, exposing the dura at the site of lesion. The dura is opened and micro-injections of the suspension of cells are placed in a grid pattern in the spinal cord. It is envisaged that twenty four to thirty injections may be required over a 2-3cm segment of crushed damaged scar tissue. The size of injection is envisaged to be 1 mm3 – therefore 1000 such injections would make up the volume of 1cm3 (1ml).

As mentioned earlier, this is a phase one human trial, and as such, we are taking a fairly conservative approach. We are excited to have the opportunity to utilise the innovative research on olfactory glial cells by our colleagues at Griffith University, and are quietly optimistic of a positive outcome.

References

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Féron, F., Mackay-Sim, A., Andrieu, J., Matthaei, K., Holley, A. and Sicard, G. (1999a) Stress induces neurogenesis in non-neuronal cell cultures of adult olfactory epithelium. Neuroscience 88, 571-583.

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Féron, F., Vincent , A. and Mackay-Sim, A. (1999c) Dopamine promotes differentiation of olfactory neuron in vitro. Brain Research 845, 252-259.

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Lu J, Féron F, Mackay-Sim A and Waite PME (2002) Olfactory ensheathing cells promote locomotor recovery after delayed transplantation into transected spinal cord. Brain (in press).

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