The 2017 Australian of the Year award went to Professor Alan Mackay-Sim for his significant career in stem cell science.
The prize was linked to barbeque-stopping headlines equating his achievements to the scientific equivalent of “the moon landing” and “paving the road to recovery” for people with spinal cord injuries.
Such claims in the media imply that there is now a scientifically proven stem cell treatment for spinal cord injury. This is not the case.
For now, any clinic or headline claiming miracle cures should be viewed with caution, as they are likely to be trading on people’s hope.
Why stem cells for spinal cord injury?
Put simply, injury to the spinal cord causes damage to the nerve cells that transmit information between the brain and the rest of the body.
Depending on which part of the spine is involved, the injury can affect the nerves that control the muscles in our legs and arms; those that control bowel and bladder function and how we regulate body temperature and blood pressure; and those that carry the sensation of being touched. This occurs in part because injury and subsequent scarring affect not just the nerves but also the insulation that surrounds and protects them. The insulation – the myelin sheath – is damaged and the body cannot usually completely replace or regenerate this covering.
Stem cells can self-reproduce and grow into hundreds of different cell types, including nerves and the cells that make myelin. So the blue-sky vision is that stem cells could restore some nerve function by replacing missing or faulty cells, or prevent further damage caused by scarring.
Studies in animals have applied stem cells derived from sources including brain tissue, the lining of the nasal cavity, tooth pulp, and embryos (known as embryonic stem cells).
Dramatic improvements have been shown on some occasions, such as rats and mice regaining bladder control or the ability to walk after injury. While striking, such improvement often represents only a partial recovery. It holds significant promise, but is not direct evidence that such an approach will work in people, particularly those with more complex injuries.
What is happening now in clinical trials?
The translation of findings from basic laboratory stem cell research to effective and safe treatments in the clinic involves many steps and challenges. It needs a firm scientific basis from animal studies and then careful evaluation in humans.
Many clinical studies examining stem cells for spinal repair are currently underway. The approaches fit broadly into two categories:
using stem cells as a source of cells to replace those damaged as a result of injury
applying cells to act on the body’s own cells to accelerate repair or prevent further damage.
One study that has attracted significant interest involves the injection of myelin-producing cells made from human embryonic stem cells. Researchers hoped that these cells, once injected into the spinal cord, would mature and form a new coating on the nerve cells, restoring the ability of signals to cross the spinal cord injury site. Preliminary results seem to show that the cells are safe; studies are ongoing.
Other clinical trials use cells from patients’ own bone marrow or adipose tissue (fat), or from donated cord blood or nerves from fetal tissue. The scientific rationale is based on the possibility that when transplanted into the injured spinal cord, these cells may provide surrounding tissue with protective factors which help to re-establish some of the connections important for the network of nerves that carry information around the body.
The field as it stands combines years of research, and tens of millions of dollars of investment. However, the development of stem cell therapies for spinal cord injury remains a long way from translating laboratory promise into proven and effective bedside treatments.
The promise and uncertainty of ‘breakthroughs’
Each case is unique in people with spinal cord injury: the level of paralysis, and loss of sensation and function relate to the type of injury and its location. Injuries as a result of stab wounds or infection may result in different outcomes from those incurred as a result of trauma from a car accident or serious fall. The previous health of those injured, the care received at the time of injury, and the type of rehabilitation they access can all impact on subsequent health and mobility.
Such variability means caution needs to accompany claims of “man walking again” – particularly when reports relate to a single individual.
In the case that was linked to the Australian of the Year award, the actual 2013 study focused on whether it was safe to take the patient’s own nerves and other cells from the nose and place these into the damaged region of the spine. While the researchers themselves recommended caution in interpreting the results, accompanying media reports focused on the outcome from just one of the six participants.
While the outcome was significant for the gentleman involved, we simply do not know whether recovery may have occurred for this individual even without stem cells, given the type of injury (stab wounds), the level of injury, the accompanying rehabilitation that he received or a combination of these factors. It cannot be assumed a similar outcome would be the case for all people with spinal injury.
We are not there yet – but there is hope
Finding a way to alleviate the suffering of those with spinal cord injury, and many other conditions, drives the work of thousands of researchers and doctors around the globe. But stem cells are not a “silver bullet” and should not be immune from careful evaluation in clinical trials.
Failure to proceed with caution could actually cause harm. For example, a paraplegic woman who was also treated with nasal stem cells showed no clinical improvement, and developed a large mucus-secreting tumour in her spine. This case highlights the need for further refinement and assessment in properly conducted clinical trials before nasal stem cells can become part of mainstream medicine.
It’s also worth noting that for spinal cord injury, trials for recovery of function are not limited to the use of stem cells but include approaches focused on promoting health of surviving nerves (neuroprotection), surgery following injury, nerve transfers, electrical stimulation, external physical supports known as exoskeletons, nanotechnology and brain-machine interfaces.
Ultimately, determining which of these approaches will improve the lives of people with spinal injury can only be done through rigorous, ethical research.
Megan Munsie, Head of Education, Ethics, Law & Community Awareness Unit, Stem Cells Australia, University of Melbourne; Andrew Nunn, Adjunct Research Associate , Monash University, and Claire Tanner, Postdoctoral research fellow, University of Melbourne