A Bulgarian man who was paralyzed from the chest down after a knife attack is miraculously able to walk again after undergoing a pioneering stem cell transplant surgery, in what scientists are hailing as “a breakthrough.”

Scientists in Poland were able to grow stem cells and inject them into Darek Fidyka’s completely severed spinal cord.

“This is more impressive than a man walking on the moon,” said Dr. Geoffrey Raisman, a professor at London’s Institute of Neurology’s University College and one of the study’s authors.

“Four years ago, (Fidyka) was stabbed in the back, an injury that severed his spine,” Raisman said of the 2010 knife attack.

The transplanted stem cells – called olfactory ensheathing cells (OEC) and olfactory nerve fibroblasts (ONF) – were taken from cells in the brain which control the sense of smell.

These OEC and ONF cells were injected and transplanted into the spinal cord; once there, doctors were able to repair the ends of the severed nerve fibres and reconnect the severed spinal cord back together. To help in the repair process, strips of nerve fibres were taken from Fidyka’s ankle to construct a “nerve bridge,” allowing these stem cells to grow along and unite the two severed stumps of the damaged spinal column together.

Dr. Charles Tator, a neurosurgeon at Toronto Western Hospital, told CTV News Channel what is so remarkable about OEC and ONF cells is that they have the ability to regenerate fast.

In the study, the OEC and ONF cells were able to join the severed spine in less than five weeks. It took another 19 months of physiotherapy rehabilitation before Fidyka began to feel sensation in his leg, and another six months to walk (with the help of a walker).

Raisman and his colleagues were responsible for discovering the procedure.

“It’s like a eureka moment. It’s actually many, many, many small steps, over many years, beginning with animals and ending with people,” Raisman told Britain’s SkyNews.

However, other scientists around the world are exercising caution before calling this a breakthrough and giving false hope to people.

“What we see in the report is almost an anecdotal report of one person who received a type of cell … It in itself may be promising, but it’s too early to say whether this is a breakthrough or not,” said Dr. Wolfram Tetzlaff, a professor at University of British Columbia.

Tator said OEC and ONF cells have been studied for spinal-cord injury over the past 15 years. What is new, he said, is “mixing those cells with the graph of the peripheral leg with the same person, so they’re not being rejected is a novel combination.

“I would like to see this strategy pursued because they have only tried it in one patient and the results look promising,” Tator cautioned. “But you can’t jump to conclusions on only one patient. There hasn’t been enough experience to promote this as a major breakthrough.”

The next step for the Polish scientists is to treat up to 10 more patients.

The research is being funded with $2 million raised from the father of famous Michelin-starred British chef David Nicholls, whose 19-year-old son, Daniel, was paralyzed in a diving accident last year. Nicholls raised the money for the spinal charity by creating a cookbook containing secret recipes from the world’s leading Michelin-star chefs.

“I made a promise to Dan, I would get him on his feet again or get him walking,” Nicholls said.

The findings were published in the journal Cell Transplantation.

With files from CTV medical specialist Avis Favaro and producer Elizabeth St. Philip