Spinal cords are precarious things; once contorted or broken, they cannot be regrown… unless you’re a lamprey. A lamprey, not to be confused with an eel, is a jawless fish that is characterized by a toothed, cylindrical mouth that it bores into its prey to suck out the blood. However, the fish, which appears to be a vicious alien from Men in Black, is not as primitive as one might believe. In fact, its biology is as eccentric as its appearance. Like an alien from Men in Black, it can regrow a transected spine!
Such an ability would work wonders for human beings, if only we could harness it. As it turns out, we don’t have to seek a lamprey’s help. Humans already possess the same genes that enable a lamprey to regrow its spine or revive it from paralysis.
“Scientists have known for many years that the lamprey achieves spontaneous recovery from spinal cord injury, but we have not known the molecular recipe that accompanies and supports this remarkable capacity,” says Ona Bloom of the Feinstein Institute for Medical Research and the Zucker School of Medicine at Hofstra/Northwell, a former Marine Biological Laboratory (MBL) Whitman Center Fellow.
Bloom was one of the collaborators on a project to determine “all the genes that change during the time course of recovery.” The collaborators at the MBL and other institutions found that the genes involved in the natural recovery of injured or paralyzed spines are also active in the repair of the peripheral nervous system in mammals. The peripheral nervous system is the counterpart of the central nervous system, it is the extensive branch of nerves aside from the brain and the spinal cord.
Lampreys shared a common ancestor with us about 550 million years ago and can fully regrow an injured spinal cord without any treatment or medication. “They can go from paralysis to full swimming behaviors in 10 to 12 weeks,” says Jennifer Morgan, director of the MBL’s Eugene Bell Center for Regenerative Biology and Tissue Engineering and one of the authors of the study published in Scientific Reports.
The knowledge of the pertinent genes, according to Bloom, can be used “to test if specific pathways are actually essential to the process.”
WnT Signaling Pathway
To determine the pathways essential to recovery, researchers had to injure the spinal cord first. To injure the lampreys, the researchers incised the subjects’ spinal cords. The researchers then wasted no time and immediately began to monitor the physiological processes involved in the recovery. They took samples from their subjects’ brains and spinal cords at regular intervals from the first hours after the incision until three months later, once the spinal cords had recovered.
The researchers discovered that many genes crucial to the recovery were part of what is called the WnT signaling pathway. The pathway is central to tissue development. In fact, it’s so important that when researchers inhibited its functioning with a drug, the animals never recovered their ability to swim. Currently, there is a dearth of research on the WnT pathway. Hopefully, further dedicated research will reveal why the pathway is seemingly indispensable to the healing process.
An unexpected finding was the injury’s effect on the lamprey’s brain. The injury and recovery induced multiple genetic changes in the brain. This corroborates the much-speculated notion that the brain changes considerably after a spinal cord injury. The results, no doubt, are startling.
The problem with genes is that a trait is not a function of a single gene: there is no single gene responsible for, say, our language. A trait is the result of a tremendously complex interplay of genes, some we are aware of and some we know nothing about. Even a trait as innocuous as the color of our eyes is determined by the simultaneous activation and deactivation of several genes.
The same is the case with the recovery of an injured or paralyzed spinal cord. The combinatorial play of genes that govern the recovery seems inscrutable, but studies like these give us hope, they edge us closer to success. In the near future, treating a broken back might prove to be as difficult as treating a broken finger.