Hope for paraplegic and quadriplegic patients to walk again

By Mark Waghorn via SWNS

Spinal cord injuries have been repaired in mice by reviving latent stem cells.

They turned into neurons called astrocytes that 'tile' the central nervous system.

The breakthrough offers hope for paraplegic and quadriplegic patients to walk again.

Corresponding author Professor Caetano Reis e Sousa said: "We hope studying these cells will help build a more complete picture of the role different types of stem cells play in repairing damage - which could have important implications for regenerative medicine."

Approximately 5.4 million people in the USA are living with paralysis, according to a study from the Christopher & Dana Reeve Foundation.

Sticky scar tissue prevents recovery by acting like glue - leading to loss of movement below the site.

Stem cells are the body's master cells - capable of becoming any type of tissue or organ.

In the skin and intestine, for example, stem cells are constantly active. But 'latent stem cells' lie waiting for harm to occur before being triggered.

Prof Sousa and his team identified a group that responds to injury in the central nervous system of mice.

They are part of the ependymal cells that line the walls of compartments in the brain and spinal cord that hold cerebrospinal fluid.

The team at the Francis Crick Institute in London, UK, hopes that a similar type exists in humans - opening the door to a potential cure for brain and spinal cord injuries.

Co-corresponding author Dr. Bruno Frederico said: "While we don't know if these cells exist in humans, if they do, it would be interesting to see if they also default to becoming astrocytes rather than neurons in response to damage.

"This might help explain why the mammalian central nervous system does not have a strong ability to repair itself after injury."

The cells were identified serendipitously during experiments on lab rodents. A fluorescence tool was looking for immune cells called dendritic cells in the brain.

They share a protein with the latter - and arise from embryonic progenitor cells. The study found they stay still and waft small hairs on their surface to help the flow of cerebrospinal fluid.

But in injured mouse spinal cords they respond by dividing - migrating towards the damaged area and differentiating into astrocytes, one of the major cell types of the nervous system.

The team also looked at these cells in detail in the lab and found they demonstrated key hallmarks of stem cell behavior.

They divided continuously over a long period of time and were also able to differentiate into all three main cell types of the central nervous system - neurons, astrocytes, and oligodendrocytes.

Dr. Frederico said: "If we could find a way to overcome the barriers that are stopping the differentiation into neurons and oligodendrocytes after spinal cord injury, it could present a new avenue of therapies to treat spinal cord injuries."

Unlocking the potential of these cells could help the body produce new neurons which are responsible for receiving and sending key signals for movement after spinal injury.

Prof Sousa said: "There was uncertainty over whether ependymal cells can have neural stem cell capabilities, but this study underscores their potential."

The study, published in the journal Developmental Cell, offers hope for the hundreds of thousands of people worldwide who suffer a spinal cord injury each year.

Cells in some tissues and organs proliferate after damage as part of the healing process. This does not apply to the spinal cord – a key roadblock to recovery.

The spinal cord is the key junction for the constant stream of electrical signals between the brain and the rest of the body.

Once harmed, injuries tend to be permanent because nerve cells cannot regenerate themselves.

Communication is then halted, leading to paralysis, loss of sensation and sometimes life-threatening consequences such as an inability to control breathing or heart rate.

Complete recovery from a spinal cord injury would have far-reaching social and economic benefits for millions of people.