A Bulgarian man who was paralyzed from the chest down in a knife attack can now walk with the aid of a frame after receiving pioneering transplant treatment using cells from his nose.

The technique, described as a breakthrough by a study in the journal Cell Transplantation, involved transplanting what are known as olfactory ensheathing cells into the patient's spinal cord and constructing a "nerve bridge" between two stumps of the damaged spinal column.

"We believe... this procedure is the breakthrough which, as it is further developed, will result in a historic change in the currently hopeless outlook for people disabled by spinal cord injury," said Geoffrey Raisman, a professor at University College London's (UCL) institute of neurology, who led the research.

The 38-year-old patient, Darek Fidyka, was paralyzed after suffering stab wounds to his back in 2010. Following 19 months of treatment, he has recovered some voluntary movement and some sensation in his legs, his medics said.

The Nicholls Spinal Injury Foundation, a British-based charity which part-funded the research, said in statement that Fidyka was continuing to improve more than predicted, and was now able to drive and live more independently.

Raisman, a UCL spinal injury specialist, worked with surgeons at Wroclaw University Hospital in Poland to remove one of Fidyka's olfactory bulbs, which give people their sense of smell, and transplant his olfactory ensheathing cells (OECs) and olfactory nerve fibroblasts (ONFs) into the damaged area.

They used a nerve bridge constructed between the two stumps of the damage spinal column, they said in the study.

OECs are a type of cell found in both the peripheral and central nervous system. Together with ONFs, they make bundles of nerve fibers that run from the nasal mucosa to the olfactory bulb, where the sense of smell is located.

When the nerve fibers that carry smell become damaged, they are replaced by new nerve fibers which re-enter the olfactory bulbs, the researchers explained in their study.

OECs help this process by re-opening the surface of the bulbs for the new nerve fibers to enter -- leading Raisman and his team to believe transplanting OECs into the damaged spinal cord could enable severed nerve fibers to re-grow.

Raisman added that the technique of bridging the spinal cord with nerve grafts from the patient had been used in animal studies for years, but never before in combination with OECs.

"The OECs and the ONFs appeared to work together, but the mechanism between their interaction is still unclear," he said in a statement about the work.

Experts not directly involved in the work said its results offered some new hope, but said more work needed to be done to figure out what had led to this success, and more patients treated, before its potential could be properly assessed.

"While this study is only in one patient, it provides hope of a possible treatment for restoration of some function in individuals with complete spinal cord injury," said John Sladek, a professor of neurology and pediatrics at the University of Colorado School of Medicine in the United States.

Raisman and his team now plan to repeat the treatment technique in between three and five patients over the next three to five years. "This will enable a gradual optimization of the procedures," he told Reuters.