Heads Up: Nanoribbon Scaffold Helps Cord Splicing

Posted by Sam Maddox in Research News on September 27, 2016

This story caught my eye, it got a lot of coverage, so maybe your eye too. Spinal cords of lab animals were sliced with a sharp scalpel; the cut ends were then sort of fused back together with a secret sauce added to tiny graphene nanoribbon scaffolds, developed at Rice University in Houston. The surgeons who did the slicing, at Konkuk University in South Korea, called this combo “Texas PEG,” PEG being polyethylene glycol, a substance well-studied in spinal cord nerve repair but never developed clinically.

How about they call it “Cowboy PEG,” on account of the wild-west nature of the man who inspired this collaboration, Sergio Canavero. He may be familiar to you – he’s the Italian neurosurgeon planning the human head transplant, which I wrote about in February 2015 (Old Head, New Body); Canavero calls this HEAVEN, the Head Anastomosis Venture, and he has a volunteer lined up, along with the makings of a surgical team. Canavero thinks it could happen next year.

Don’t count on it; the head transplant may or may not ever happen. Besides the technical issues, there are huge ethical concerns, and no source of money to pull it off. It’s of interest here because it is indeed a story about restoring spinal cord function.

Tour and SikkermaPh.D. student William Sikkema at Rice’s Faculty of Chemistry and Nano Center contacted Canavero after hearing about the challenge to splice a head to another body – especially the alignment of the spinal cord stumps. Canavero said send me some of y’all’s cool nanoribbons. Sikkema did just that.

The sequence as it unfolded for me: Rice’s public relations office put out a story last week, Graphene nanoribbons show promise for healing spinal injuries. The story describes the efforts of James Tour, a synthetic organic chemist at Rice. From the release:

The Tour lab has spent a decade working with graphene nanoribbons, starting with the discovery of a chemical process to “unzip” them from multiwalled carbon nanotubes, as revealed in a Nature paper in 2009. Since then, the researchers have used them to enhance materials for the likes of deicers for airplane wings, better batteries and less-permeable containers for natural gas storage.

When the biocompatible nanoribbons have their edges functionalized with PEG chains and are then further mixed with PEG, they form an electrically active network that helps the severed ends of a spinal cord reconnect.

“Neurons grow nicely on graphene because it’s a conductive surface and it stimulates neuronal growth,” Tour said.

Here’s more from Tour:

“My motivation is spinal cord repair. If this works, it’s going to have huge ramifications for spinal injuries. But we thought, if you’re going to be working towards a head transplant, you’re going to need this, so let us help you.”

The Rice release was triggered by publication of a paper, a collaboration of the Tour lab and the Koreans. It appeared in the journal Surgical Neurology International.

Concluded the paper:

Four of the PEG-GNR treated rats died accidentally (drowning during a storm that filled the underground lab) subsequently to the SSEP study. The surviving rat is reported here versus controls treated with saline.

In this preliminary report, we show how the conductive GNR additive to PEG[ 8 10 ] appears to afford a quick recovery of neurophysiologic sensory transmission in the spinal cord versus none in controls. The behavioral recovery in the surviving rat was remarkable, versus none in the controls.

Wait a second. The study began with ten animals, five got the cowboy combo -- the scaffold and the sauce -- and five got a spinal slice and no treatment. Four of the treated animals drowned. This is not a long, drawn out study, so why wouldn’t the group just start over, treat another batch of five, and have a more reasonable baseline of data that might reveal an important pattern? But no, they went to press with one treated animal.

From Rice: more work to do.

Tour said Texas-PEG’s potential to help patients with spinal cord injuries is too promising to be minimized. “Our goal is to develop this as a way to address spinal cord injury. We think we’re on the right path,” he said.

“This is an exciting neurophysiological analysis following complete severance of a spinal cord,” Tour said. “It is not a behavioral or locomotive study of the subsequent repair. The tangential singular locomotive analysis here is an intriguing marker, but it is not in a statistically significant set of animals. The next phases of the study will highlight the locomotive and behavioral skills with statistical relevance to assess whether these qualities follow the favorable neurophysiology that we recorded here.”

Last week, in a separate commentary about the Rice/Korea study, Canavaro enthused about its significance toward his head swap goal.

The initial results are indeed nothing short of miraculous. Somatosensory evoked potentials recovered to a good extent within 24 hours! Unfortunately, an accidental mishap led to the death of four of the five study animals. However, the sole survivor re-acquired almost normal motor behaviors. To put these results into perspective, rats treated with normal PEG recovered to a BBB score of 8 within 4 weeks, versus a BBB score of 19–20 within 2 weeks with TexasPEG!

Say, is he allowed to use exclamation points in a science journal? Canavero went on:

While of course these results are in need of duplication, there can be no doubt that this new batch of data confirm that a spinal cord, once severed, can be refused with useful behavioral recovery.

Footnote: The September issue of Atlantic Monthly has a full feature on Canavero and his project, “The Audacious Plan to Save This Man’s Life by Transplanting His Head.” The subhead: “What would happen if it actually works?” It’s a good read, including detail on Valery Spiridonov, the 31-year old Russian who is willing to have his head stitched to a new body. He has Werdnig-Hoffmann’s, a fatal motor neuron disease. Here’s a bit from the piece, written by Sam Kean:

Perhaps the biggest obstacle is repairing the spinal cord so that the patient’s brain can control the new body. Nerves outside the spinal cord can regrow, which explains why hand and face transplantees can learn to chew and smile and twiddle their thumbs again. Cells within the spinal cord don’t grow back, but chemicals such as peg can fuse cells, breaking open their membranes and forcing them to glom together into a larger, hybrid cell. When applied to the severed spinal-cord stumps of rodents and dogs, the amber fluid can fuse nerve cells above and below the injury and thereby reestablish communication, however imperfect, between the brain and the lower body.