The Johns Hopkins University researchers say human nerve stem cells they transplanted into damaged spinal cords of rats have survived, grown and in some cases connected with the rats' own spinal cord cells.

The accomplishment "establishes a new doctrine for regenerative neuroscience," said Dr. Vassilis Koliatsos, an associate professor of neuropathology.

"We don't yet know whether the connections we've seen can transmit nerve signals to the degree that a rat could be made to walk again," he added. "We're still in the proof-of-concept stage, but we're making progress and we're encouraged."

The research, conducted by Jun Yan, Leyan Xu, Annie Welsh, Glen Hatfield and Koliatsos, appears online in the journal PLoS Medicine.