Severe wounds from disasters like car wrecks, wartime battles, and even domestic disputes often leave blood vessels and nerves severed and damaged, bones broken, and cellular wreckage throughout the body. Neurosurgeons like Jason Huang, M.D., confront these issues daily.
Nerve damage is one of the most challenging wounds to treat. It’s suffered by over 350,000 victims of gunshots, stabbings, car accidents, and other unfortunate, violent events each year in the U.S. alone. But now, a step forward has been taken by Huang and colleagues toward the goal of repairing nerves in patients more effectively.
Published in PLoS ONE, Huang et al at the University of Rochester Medical Center report that a surprising set of cells may hold potential for nerve transplants.
In a study of rats, Huang’s research group identified that dorsal root ganglion neurons, or DRG cells, aid in creating thick, healthy nerves without provoking unwanted attention from the immune system.
“These are very serious injuries, and patients really suffer, many for a very long time,” said Huang, associate professor of Neurosurgery and Chief of Neurosurgery at Highland Hospital, an affiliate of the University of Rochester Medical Center.
“There are a variety of options, but none of them are ideal. Our long-term goal is to grow living nerves in the laboratory, then transplant them into patients and cut down the amount of time it takes for those nerves to work,” added Huang, whose project was funded by the National Institute of Neurological Disorders and Stroke and by the University of Rochester Medical Center.
In order for a damaged nerve to repair itself, the two disconnected but healthy portions of the nerve must somehow find each other through a maze of tissue and reconnect. For small wounds, this may happen naturally, much in the way skin grows back over small cuts. But for some nerve injuries, the gap is simply too large and the nerve can’t grow back without intervention.
Surgeons like Huang prefer the option of transplanting nerve tissue from elsewhere in the patient’s body. Say, for instance, a section of a nerve from the leg, back into the wounded area. This transplanted nerve acts as a scaffolding, a guide for a new nerve to grow and bridge the gap. And since the tissue comes from the patient, the body accepts the new nerve and doesn’t attack it.
But what about the patients who might have severe wounds in other areas of the body, making extra nerve tissue unavailable? An alternative might be a nerve transplant from a cadaver or an animal, but those bring other challenges, such as the lifelong need for powerful immunosuppressant drugs. One technology Huang and other neurosurgeons use is the NeuraGen Nerve Guide, a hollow, absorbable collagen tube through which nerve fibers can grow and find each other. This is often used to repair nerve damage over short distances less than half an inch long.
In the PLoS ONE study, Huang’s team compared several methods to attempt to bridge a nerve gap of about half an inch in rats. Nerve cells were transplanted from a different type of rat into the wound site. Results were compared with the NeuraGen’s technology alone and when paired with DRG cells or with other cells known as Schwann cells.
Four months passed and the team found that the tubes equipped with either DRG or Schwann cells helped bring about healthier nerves. Also the DRG cells provoked less, shall we say, unwanted attention from the immune system than the Schwann cells. It attracted twice as many macrophages and more of the immune compound interferon gamma.
“The conventional wisdom has been that Schwann cells play a critical role in the regenerative process,” said Huang, who is also a scientist in the Center for Neural Development and Disease. “While we know this is true, we have shown that DRG calls can play an important role also. We think DRG cells could be a rich resource for nerve regeneration.”
While we’d like to playfully say “May the Schwann be with you” for peripheral nerve damage sufferers, it looks like there’s great potential in these dorsal root ganglion (DRG) cells. We’re always excited for the potential of regenerative technologies applied to a variety of fields for the benefit of humanity– nerve regeneration being but one of these applications!
Weimin Liu, Yi Ren, Adam Bossert, Xiaowei Wang, Samantha Dayawansa, Jing Tong, Xiaoshen He, Douglas H. Smith, Harris A. Gelbard, Jason H. Huang. Allotransplanted Neurons Used to Repair Peripheral Nerve Injury Do Not Elicit Overt Immunogenicity. PLoS ONE, 2012; 7 (2): e31675 DOI: 10.1371/journal.pone.0031675
Image courtesy of University of Rochester Medical Center