After receiving injections of neural stem cells, two of the three patients with broken spines have recovered feeling in previously paralysed areas.
The cells, acquired from donated fetal brain tissue, were injected directly into the injured region of their spinal cord between four and eight months after the injuries happened.
The patients also received a temporary course of immunosuppressive drugs to limit rejection of the cells.
StemCells, the company in Newark, California, that developed the treatment also conducted the testing.
"The fact we've seen responses to light touch, heat and electrical impulses so far down in two of the patients is very unexpected," New Scientist quoted Stephen Huhn of StemCells.
"They're really close to normal in those areas now in their sensitivity," he added.
Armin Curt of Balgrist University Hospital in Zurich, Switzerland, where the patients were treated, and principal investigator in the trial, added "We are very intrigued to see that patients have gained considerable sensory function."
The data are preliminary, but "these sensory changes suggest that the cells may be positively impacting recovery", said Curt.
Huhn noted that the company has "compelling data" from animal studies that the donated cells can repair nerves within broken spines.
He pointed out several reasons why the stem cells improve sensitivity.
They might help to restore myelin insulation to damaged nerves, improving the communication of signals to and from the brain. Or they could be enhancing the function of existing nerves, replacing them entirely or reducing the inflammation that hampers repair, he said.
Curt presented the results in London at the annual meeting of the International Spinal Cord Society.