Neurones in the brain and spinal cord (the central nervous system) have very limited ability to regenerate after injury or disease. Damage is usually permanent, which is why stem cells are an attractive possibility.Conditions
• Spinal cord injury: axons are cut, so impulses cannot pass below the injury, causing paralysis.
• Multiple sclerosis: the immune system damages the myelin sheath around axons, slowing or blocking impulses.
• Parkinson's disease: loss of neurones that secrete dopamine.
• Stroke: neurones die when their blood supply is cut off.How stem cells could help
Stem cells could be differentiated into new neurones, or into glial cells, which support and insulate neurones. For example, oligodendrocytes made from stem cells could remyelinate axons, and dopamine-secreting neurones could be transplanted into the brains of Parkinson's patients. Early trials of such neurones are under way. Stem cells may also release growth factors that help surviving neurones recover.Challenges
Nervous tissue is especially hard to repair:
• new neurones must grow axons in the right direction and form synapses with the correct target cells to restore function
• after spinal cord injury, scar tissue at the injury site blocks new axons from growing across the gap
• transplanted cells must survive in the brain or spinal cord and must not form tumours.Because of this, treatments may partly restore function rather than fully cure the damage.
• Spinal cord injury: axons are cut, so impulses cannot pass below the injury, causing paralysis.
• Multiple sclerosis: the immune system damages the myelin sheath around axons, slowing or blocking impulses.
• Parkinson's disease: loss of neurones that secrete dopamine.
• Stroke: neurones die when their blood supply is cut off.How stem cells could help
Stem cells could be differentiated into new neurones, or into glial cells, which support and insulate neurones. For example, oligodendrocytes made from stem cells could remyelinate axons, and dopamine-secreting neurones could be transplanted into the brains of Parkinson's patients. Early trials of such neurones are under way. Stem cells may also release growth factors that help surviving neurones recover.Challenges
Nervous tissue is especially hard to repair:
• new neurones must grow axons in the right direction and form synapses with the correct target cells to restore function
• after spinal cord injury, scar tissue at the injury site blocks new axons from growing across the gap
• transplanted cells must survive in the brain or spinal cord and must not form tumours.Because of this, treatments may partly restore function rather than fully cure the damage.