Darek Fidyka, who was paralysed from the chest down in a knife attack in 2010, can now walk using a frame.
The treatment, a world first, was carried out by surgeons in Poland in collaboration with scientists in London.
BBC One’s Panorama programme had unique access to the project and spent a year charting the patient’s rehabilitation.
Darek Fidyka, 40, from Poland, was paralysed after being stabbed repeatedly in the back in the 2010 attack.
He said walking again – with the support of a frame – was “an incredible feeling”, adding: “When you can’t feel almost half your body, you are helpless, but when it starts coming back it’s like you were born again.”
Prof Geoff Raisman, chair of neural regeneration at University College London’s Institute of Neurology, led the UK research team.
He said what had been achieved was “more impressive than man walking on the moon”.
The treatment used olfactory ensheathing cells (OECs) – specialist cells that form part of the sense of smell.
OECs act as pathway cells that enable nerve fibres in the olfactory system to be continually renewed.
In the first of two operations, surgeons removed one of the patient’s olfactory bulbs and grew the cells in culture.
Two weeks later they transplanted the OECs into the spinal cord, which had been cut through in the knife attack apart from a thin strip of scar tissue on the right. They had just a drop of material to work with – about 500,000 cells.