Hepatocyte growth factor (HGF), which is produced by human mesenchymal stem cells (hMSCs), appeared to both repair existing damage and prevent future neurological harm in a mouse model of the disease.
hMSCs are already being tested in clinical trials as treatment for autoimmune and neurological conditions. These findings identify HGF as a means by which the cells might exert their protective and regenerative effects in the case of MS.
'The importance of this work is we think we've identified the driver of the recovery', confirmed Professor Robert Miller from Case Western Reserve University School of Medicine in the USA, who led the study.
MS is caused by the body's immune system attacking its own tissue, specifically the protective coating around nerve cells called myelin. Myelin sheaths protect nerve cells from damage and help them conduct electrical signals. Their destruction in MS leads to a progressive loss of motor function, coordination, vision and cognition.
Approximately 100,000 people in the UK have MS and no cure is available. Current treatments focus on suppressing the immune system to prevent further damage and slow disease progression.
Professor Miller's team had previously shown that hMSCs could reverse the symptoms of a mouse model of the disease. In the current study, published in Nature Neuroscience, similar effects were observed when MS mice were injected with only the liquid medium in which the hMSCs were grown.
This suggested recovery was caused by something the cells secreted, which upon further investigation was found to be HGF. Injecting HGF alone decreased levels of substances promoting inflammation and stimulated the re-growth of myelin around damaged nerves.
These findings highlight the potential for a therapy that both prevents further damage and promotes repair. Studies into how to identify HMSCs that produce higher levels of HGF are underway, with the aim of enhancing hMSC-based therapies.
Professor Miller now asks whether 'we could now take away the mesenchymal stem cells and treat only with hepatocyte growth factor. We've shown we can do that in an animal but it's not clear if we can do that in a patient'.
Professor Jacques Gallipeau, co-director of the Emory-Georgia Tech Centre for Regenerative Therapy in the USA, who was not involved in the study, told The Scientist that 'the best cell therapy [would be] done without a cell. Identifying these factors and testing them as single agents is an important short-term deliverable of stem cell science'.