Cool techbut they're exaggerating things a bit in the linked story.

From the news story:

This therapy took the form of a gel that was injected directly into the tissue wrapped around the spinal cords of several lab mice, 24 hours after researchers made a precise incision in the animals' spines

From the Science Article:

We injected saline solutions of 90:10 molar ratio of IKVAV PA2 coassembled with either FGF2 PA1 or with FGF2 PA2 into the spinal cord of mice 24 hours after a severe contusion in an established murine model of SCI (see supporting information for specific details of the animal model pro- tocol) (20).

So the news story calls it an incision (severed spinal cord) but it was actually a severe contusion (bruise). The article about how the injury is generated is here https://pubmed.ncbi.nlm.nih.gov/27517060/ but is rather unpleasant to read, not recommended.