Head transplants: Sergio Canavero Announces Successful Repair of Spinal Cords

mouse spinal cord
Mice after having their spinal cords severed then repaired with Canavero's technique. Ren et al/CNS Neuroscience and Therapeutics/Wiley

Updated | The scientific team planning to carry out the world's first human head transplant have announced the successful repair of severed spinal cords in rats, confirming their proof-of-principle study and helping show their technique "works across the board."

Sergio Canavero, the neuroscientist who first announced plans to carry out a head transplant in 2015, tells Newsweek the rats treated with the Gemini Protocol —his method of fusing spinal cords—regained movement and that there were no adverse side effects recorded.

Findings of the latest study are published in the Wiley journal CNS Neuroscience and Therapeutics. In it, a surgical team led by Xiaoping Ren from China's Harbin Medical University, severed the spinal cords of 15 rats. Nine of these were then treated with the technique, while the others served as controls.

The team used a polyethylene glycol (PEG), which seals and repairs damaged spinal cord nerve cells. They severed the spinal cords of the rats, then applied a cooled saline and adrenaline to reduce bleeding. The rats chosen to receive the PEG were then treated with it and the wounds were closed. They were given antibiotics for three days following the surgery.

All of the rats except one survived for a month after the operation. Rats treated with PEG were found to "steadily" recover motor function and, by day 28, had regained the ability to walk, with two of them returning to a state that was described as "basically normal."

"In this study, we thus confirmed that a severed thoracic spinal cord can be 're-fused' with behavioral recovery. Previous experiments in mice along with the current ones define a timeline of recovery between mice and rats: one week versus two weeks." The team said the key to spinal cord fusion is "sharp severance of the cords themselves," meaning minimal damage is done.

"Human application of the presently discussed technique would benefit from a method to assess progression of spinal fusion. This would allow a direct correlation with clinical recovery." Concluding, the scientists say paralysis after the spinal cord has been severed can be reversed to a "significant extent."

Canavero tells Newsweek: "[The] controlled study in rats proved that Gemini works. This confirms the small proof-of-principle studies... [and] is a fundamental advance.

"Critics said the transected spinal cord is unrecoverable and thus a human head transplant is impossible...The scans show the reconstructed cord. No pain syndrome emerged over the duration of the study, again rebutting a critic's 'worse than death' remark."

The team now plans to carry out experiments on dogs. This will help them show the technique works "across the board." This, Canavero says, will provide evidence of a strong effect and the results will be published over the coming months.

At present, the first human head transplant is scheduled to take place in China in December. The surgery will no longer be performed on Russian patient Valery Spiridonov, but instead will be a Chinese national.

Sergio Canavero
Sergio Canavero, who plans to carry out the world's first human head transplant in December this year. Russell Cheyne/Reuters

Canavero would not confirm whether the plan was still on track, and said forthcoming research papers would provide more details on other challenging aspects of the surgery. "Expect a global press conference where all details will be revealed."

Critics of the proposed human head transplant have been vocal since it was first announced. Commenting on it in 2015, Chad Gordon, professor neurological surgery at Johns Hopkins University, told BuzzFeed : "There's no way he's going to hook up somebody's brain to someone's spinal cord and have them be functional. On the conservative side, we're about 100 years away from being able to figure this out. If he's saying two, and he's promising a living, breathing, talking, moving human being? He's lying."

Jerry Silver, Professor of Neurosciences at Case Western Reserve University, Ohio, works on repairing spinal cords after injury. Commenting on the latest study, he tells Newsweek it is unclear whether to team had truly severed the cord completely. "I notice that in the last paragraph they state 'In conclusion, we have shown that the paralysis following full severance of the dorsal spinal cord can be reversed—to a significant extent—by immediate application of a fusogen.' Did they sever only the 'dorsal' cord?" he says.

He said the team also claims the axons—which form part of the spinal cord—had regenerated, but "they show no evidence for regeneration."

"There is no histology [the study of the microscopic structure of tissues] which is the only way to assess what is really going on here," Silver said, adding the BBB scores—the scoring system used to assess motor function in rats—were unrealistic.

"Two treated animals supposedly recover locomotor skills that are nearly normal (BBB scores of 19 and 20 out of a possible 21 total) and as a group they average a score of 12 which means that they can on average take multiple weight bearing steps. [This is] unbelievable. Too good to be true in my opinion, which mandates that these results will have be independently verified and properly analyzed before this work can be accepted as scientifically valid."

Responding to the criticism, Canavero said Silver was "unfamiliar" with the technique used. He says the claim that the BBB scores are "unrealistic" implies the team is "lying" and that it is time for experts who have been unable to repair damaged spinal cords "to stop criticizing those who do better."

"Gemini is revolutionary. We have been amazed ourselves," he says.

This story has been updated to include comments from Jerry Silver and Sergio Canavero's response.