It is not yet known whether it is possible to generate extensive neuroplasticity in a system that has been injured for a long time and now contains many more complications such as abundant scar tissue, large holes in the spinal cord and where many spinal nerve cells and long range nerve fibres have died or degenerated.

BBC: 'Hope' for the paralysed?

Scientists have discovered that, contrary to long-standing dogma, nerve cells in the spinal cord do retain an intrinsic ability to regenerate despite their normal failure to do so.

FORBES: Magazine Article

In 1952 Jonas Salk (1914-1995) and Albert Sabin (1906-1993) raced to come up with a vaccine for poliomyelitis--a virus that causes inflammation of nerve cells in the spinal cord, which can cause paralysis, atrophy of the skeletal muscles and death.

FORBES: 85 Innovations 1939-1955

For example, fresh nerve cells could alleviate spinal-cord injuries, or newly made heart cells could repair a site scarred by a heart attack.

WSJ: Experiment Brings Human Cloning One Step Closer

Ephrins are believed to control the growth of nerve cells necessary to help form proper circuits within the spinal cord.

BBC: Discovery prompts spinal cord hope

The researchers say the transplanted cells regenerated nerve fibres across the damaged region of the spinal cord.

BBC: Nose cell transplant enables paralysed dogs to walk