The recovery of breathing control in rats with long-term (up to one and a half years) spinal cord injuries has been achieved via a treatment strategy involving the injection of an enzyme. The findings are reported in Nature Communications this week.

Breathing impairments are the leading cause of death and disability following spinal cord injury. Nerve fibres that control breathing muscles are frequently disconnected after spinal cord injury and scar tissue gradually forms around these severed nerves, blocking regenerative attempts to reconnect. These fibres were previously thought to rapidly die if not reconnected soon after injury.

Philippa Warren and colleagues show that injecting the enzyme chondroitinase ABC into an area of the spine of rats in which neurons involved in breathing are found efficiently breaks down scar tissue that has built up long after spinal cord injury. They observed robust nerve sprouting after the removal of scar tissue, and animals with near lifelong (up to one and a half years) respiratory paralysis eventually regained almost complete breathing control. Additionally, they found that this recovery was enhanced when combined with intermittent hypoxia conditioning (exposure to periods of decreased oxygen levels), and was maintained up to six months after treatment.

The authors note that further research to determine the precise mechanism through which the recovery process occurred is ongoing.