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.

Stem cell-derived neurons

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.

They found that progenitor cells in a region known as the subventricular zone, which is critical for human cortical growth, were affected. Progenitor cells are “stem cell-like” cells that give rise to mature brain cells such as neurons. They also found that the progenitor cells transitioned from “growth” mode to “survival” mode, causing them to turn into neurons sooner than normal, which leads to fewer neurons in the brain and underdevelopment.

In a press release, Dr. Anca Pasca is quoted as saying,

“In the past 20 years, we’ve made a lot of progress in keeping extremely premature babies alive, but 70% to 80% of them have poor neurodevelopmental outcomes.”

The team then tested a small molecule to see if it could potentially reverse this response to low oxygen levels by keeping the progenitor cells in “growth” mode. The results of this are promising, and Dr. Sergiu Pasca is quoted as saying,

“It’s exciting because our findings tell us that pharmacologically manipulating this pathway could interfere with hypoxic injury to the brain, and potentially help with preventing damage.”

The complete findings of this study were published in Nature.