Stories about: nerve regeneration

Novel therapeutic cocktail could restore fine motor skills after spinal cord injury and stroke

CST axons sprout from intact to injured side
Therapeutic mixture induces sprouting of axons from healthy (L) into the injured (R) side of the spinal cord.

Neuron cells have long finger-like structures, called axons, that extend outward to conduct impulses and transmit information to other neurons and muscle fibers. After spinal cord injury or stroke, axons originating in the brain’s cortex and along the spinal cord become damaged, disrupting motor skills. Now, reported today in Neuron, a team of scientists at Boston Children’s Hospital has developed a method to promote axon regrowth after injury.

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Fast-regenerating mice offer clues for stroke, spinal cord and optic nerve injury

axon regeneration CNS
The CAST mouse from Thailand–genetically distinct from most lab mice–may have the right ingredients for nerve regeneration. (Courtesy Jackson Laboratory)

Second in a two-part series on nerve regeneration. Read part 1.

The search for therapies to spur regeneration after spinal cord injury, stroke and other central nervous system injuries hasn’t been all that successful to date. Getting nerve fibers (axons) to regenerate in mammals, typically lab mice, has often involved manipulating oncogenes or tumor suppressor genes to encourage growth, a move that could greatly increase a person’s risk of cancer.

A study published online last week by Neuron, led by the F.M. Kirby Neurobiology Center at Boston Children’s Hospital, took a completely different tactic.

Seeing little success at first, the researchers wondered whether they were working with the wrong mice.

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Proteomics provides new leads into nerve regeneration

Nerve regeneration. From Santiago Ramón y Cajal’s “Estudios sobre la degeneración y regeneración del sistema nervioso” (1913-14). Via Scholarpedia.

nerve regeneration proteomicsFirst in a two-part series on nerve regeneration. Read part 2

Researchers have tried for a century to get injured nerves in the brain and spinal cord to regenerate. Various combinations of growth-promoting and growth-inhibiting molecules have been found helpful, but results have often been hard to replicate. There have been some notable glimmers of hope in recent years, but the goal of regenerating a nerve fiber enough to wire up properly in the brain and actually function again has been largely elusive.

“The majority of axons still cannot regenerate,” says Zhigang He, PhD, a member of the F.M. Kirby Neurobiology Center at Boston Children’s Hospital. “This suggests we need to find additional molecules, additional mechanisms.”

Microarray analyses—which show what genes are transcribed (turned on) in injured nerves—have helped to some extent, but the plentiful leads they turn up are hard to analyze and often don’t pan out. The problem, says Judith Steen, PhD, who runs a proteomics lab at the Kirby Center, is that even when the genes are transcribed, the cell may not actually build the proteins they encode.

That’s where proteomics comes in. “By measuring proteins, you get a more direct, downstream readout of the system,” Steen says.

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Questioning “wait and see” in motor nerve injuries

Untreated carpal tunnel syndrome causing atrophy of the muscles of the thumb (Harry Gouvas/Wikimedia Commons)

It’s common in medicine for physicians to “wait and see” before taking treatment to a more invasive (or expensive) level. But when it comes to motor nerve injuries, combined laboratory and clinical evidence suggests that approach may be fundamentally wrong.

That would go for injuries including carpal tunnel syndrome, cubital tunnel syndrome (a compression injury of the ulnar nerve in the elbow), nerve damage from surgery or chemotherapy, and brachial plexus avulsion injuries (these often happen when people fall off their bikes; the arm is bent backwards and nerves get ripped out of the spinal cord).

In serious cases, patients may recover sensory function, but rarely recover full muscle function and strength. Lab studies by neuroscientists at Children’s Hospital Boston provide a biological explanation, and therein may lie a solution.

It’s not that injured motor nerve fibers don’t regrow – they can. It’s that they don’t grow fast enough.

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The science of spinal cord repair: where we are

For more than a century, neuroscientists have been trying to figure out how to repair broken nerves in the spinal cord–and the rest of the central nervous system–after injury. They’ve produced a steady stream of promising discoveries–treatments that promote nerve growth in the laboratory dish and animals, even some reports of paralyzed rodents regaining motor function. So why are people with spinal cord injury (SCI) still without therapies that repair their nerve damage?

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