AgEBB-MU CAFNR Extension

Robert E. Thomas
Information Specialist

Thursday, May 15, 2008

Scientists hope to mimic sea lampreys' ability
to recover from spinal cord injuries

COLUMBIA, Mo. - Researchers are studying the sea lamprey, an eel-like parasitic fish that rapidly recovers from severed spinal cords, hoping for insights into mechanisms for increasing regeneration following spinal cord injuries in humans.

The sea lamprey has unique and powerful advantages that make it ideally suited for studying neural regeneration following a spinal cord injury, said Andrew McClellan, University of Missouri professor of biological sciences and bioengineering.

"Specific conditions within its central nervous system lead to spontaneous repair of neural injuries and recovery of locomotor function," he said. "We would like to mimic these conditions in humans."

An estimated 250,000 Americans suffer debilitating spinal injuries each year. Most spinal injuries occur to males in their teens or early twenties, McClellan said, who will need costly long-term medical care.

Unlike higher vertebrates, lampreys do not form dense scar tissue at sites of neural injuries. In higher vertebrates, when a lesion occurs in the nervous system, non-neuronal cells called glial cells invade the injured area. Glial cells protect and nourish neurons but leave a thick scar. The scar is one of the factors that block the regeneration of nerve fibers, or axons, which conduct electrical impulses to other nerve cells.

Regeneration occurs when axons sprout to form growth cones and interact with myelin, a substance that forms an insulating layer around axons.

"That is a second factor that blocks regeneration," McClellan said. This interaction causes calcium inside injured neurons to enter the growth cone, making it retract or withdraw.

"We have good evidence that in injured lampreys, calcium channels-which are proteins in nerve cell membranes through which calcium enters the growth cone-are reduced. This keeps calcium levels inside injured nerve cells relatively low," McClellan said.

Calcium blockers could be used in higher vertebrates, but that would interfere with important calcium functions elsewhere in the organism.

"It may be possible to engineer injured nerve cells to down-regulate calcium channels. One possibility would be genetic or molecular manipulations that mimic what nerve cells in the lampreys normally do following injuries," he said.

Lampreys are jawless fish with a toothed, funnel-like mouth. Larval lampreys are filter feeders, while adult lampreys, which can grow up to 36 inches long, feed by attaching to fish and sucking out blood and tissue.

Source: Andrew McClellan, 573-882-1447

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