Healing a wound in a mouse is far easier than healing one in a human, and other scientists cautioned the research was a long way away from the clinic. But they agreed it took us a step closer to understanding – and hopefully controlling – stem cells’ magic.
“It is a really impressive piece of work,” said Mark Fear, a regenerative medicine expert based at the University of Western Australia. “Having said that, if you are looking at the translation of this into humans, this is really a long way off.”
The potential of stem cells, which can replicate infinitely and turn into any type of cell in the body, is most obvious when we cut the skin or shatter a bone: it is different types of stem cells that repair the damage.
Find a way to control the process and you gain the ability to rebuild or reshape flesh at will, or replace old tissue with new. But that has proved frustratingly elusive for decades.
Using multiphoton microscopy, Professor Currie’s team was able to film the movement of cells as they congregated around a wound on a zebrafish.
When the body detects an injury, it floods the area with immune cells to clean up the damage – that’s why rolled ankles swell.
Scientists thought that after immune cells had done their job, they left, allowing the wound to start healing.
But under the microscope, they saw the immune cells hanging around. Macrophages, the garbage-collecting cells of the immune system, clustered around stem cells in a sort of cellular embrace, “almost in a loving way, you could say, if you were not a scientist”, said Professor Currie.
Closer inspection revealed the macrophages were sending signals to the stem cells using a signalling hormone called NAMPT – presumably instructing them to begin repairing the damage.
“The macrophage is not the dump truck,” said Professor Currie, “it is the ringmaster. I think it’s the intelligent component.”
NAMPT is naturally secreted in animals including humans. The team suspects giving high doses of it may supercharge the process, or “kick the stem cells into hyperdrive”, as Professor Currie puts it.
When his team removed the immune cells, the wounds did not heal; when they applied an NAMPT paste to a wound on a mouse, it substantially increased healing speed. The team are now working to test the compound on a range of other conditions.
A decade ago, stem cells were set to revolutionise medicine. But despite 30 years of work, coaxing out their power has been frustrating. Only one stem cell treatment – for leukaemia – has been approved in Australia.
Scientists have tried implanting stem cells in wounds or damaged hearts, but for unclear reasons they simply sat there, stubbornly refusing to heal.
Many stem cell therapies offered by clinics today are, sadly, little more than pseudoscience and are the target of a crackdown by Australia’s medical regulator.
“Our team was the first team to try out allogeneic stem cell injection into the disc, to try to repair it. That did not work. We saw 90 per cent death of those stem cells in the disc,” said Ashish Diwan, director of the department of orthopaedic surgery at Sydney’s St George Hospital.
“The potential of figuring out that interaction, that small mechanism between macrophages and stem cells is something nice, a very nice story. And it opens up the door for more investigation and better quality treatment,” said Dr Diwan. “Is there potential there? Maybe there is.”
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Liam is The Age and Sydney Morning Herald’s science reporter