It’s been a great week for spinal cord injury-related stem cell research – and it’s only Tuesday. In case you missed it, Asterias Biotherapeutics announced yesterday that it treated its first clinical trial participant with an embryonic stem cell-based therapy for complete spinal cord injury. “Complete” refers to injuries that cause a total loss of feeling and movement below the injury site.

Another study reported in Nature’s Scientific Reports showed progress in treating avulsion injuries, which damage nerve signals entering or leaving the spinal cord. These injuries often follow traffic, especially motorcycle, accidents and can cause paralysis, loss of sensation, and chronic pain. Although ruptured nerve fibers can grow back toward the spinal cord, inflammation blocks their return and prevents recovery.

To address this barrier, researchers transplanted human embryonic stem‑cell‑derived neurons into mice with an avulsion injury model. Five months later, nerve fibers had grown into the spinal cord. These reconnecting fibers came from the host mice, not the transplanted human neurons. The human neurons acted as a physical bridge and released proteins that reduced scarring and promoted nerve growth.

The mice with transplanted neurons showed functional improvement. They had greater sensitivity to touch and stronger grip than untreated mice.

Because stem cells can grow indefinitely, any future therapy must show that transplanted cells do not grow excessively. Encouragingly, the researchers saw no tumor formation or abnormal growth of human neurons.