Laser scalpel opens way for nerve regeneration studies in worms

December 15, 2004

Using a precisely targeted laser, researchers have snipped apart a single neuron in the roundworm C. elegans -- an achievement that opens a new avenue for studying nerve regeneration in this genetically manipulable animal. Indeed, their initial studies have demonstrated that the severed nerves of worms are capable of regenerating and regaining full function. According to the researchers, studying nerve regeneration in the worm could provide answers to questions that are not accessible currently by doing experiments in more complex animals, including mice and zebrafish. A research team that included Yishi Jin, a Howard Hughes Medical Institute investigator at the University of California, Santa Cruz (UCSC), Andrew Chisholm, also of UCSC, and Adela Ben-Yakar, who was at Stanford University and is now at the University of Texas at Austin, reported its achievement in the December 16, 2004, issue of the journal Nature. Other co-authors are from Stanford University and UCSC.

The researchers used a laser that produces energy pulses of 200-quadrillionths of a second in a beam focused to less than one-hundredth the diameter of a human hair. The laser can vaporize tissue precisely without causing extensive heat or damage that would compromise the viability of the targeted cell or surrounding tissue, said the researchers.

"This new capability of cutting individual nerves offers the opportunity to use the well-characterized genetics of C. elegans to study the basic mechanisms of nerve regeneration," said Jin. "Until now there has been little study of nerve regeneration using genetic methodology, because most studies have been done on higher vertebrate organisms, where following the consequences of genetic manipulation is not yet readily accessible." Such studies, said Jin, would involve making mutations in genes believed to be involved in nerve regeneration and studying the effects on regeneration following laser severing of the nerves.

In the experiments reported in Nature, the researchers first introduced a gene that produced a green fluorescent protein in the target nerve, in this case, one that controls a particular muscle movement in the worm. When they directed the laser at the cable-like axon that snaked away from the nerve-cell body, they found they could precisely sever the axon. They observed that both ends of the severed nerve axon immediately retracted, but that in about half the cases, the nerve regrew in about a day. By doing dye-uptake experiments, the researchers could see that the laser had actually cut the axons, and had not simply bleached the region hit by the beam.

The researchers also noticed an intriguing and potentially important result: The worms that had been operated on showed evidence that the nerves had regrown and also regained the ability to move the muscle served by the neuron. This observation indicated that the regrowth of the nerve caused functional changes.

Among the immediate questions raised by the new experiments is how the nerves regrow after cutting, said Jin. "We see that the proximal end, nearest the cell body, appears to begin regrowth, and the distal end seems to hang around for a while. Depending on how fast the proximal end regrows, it might attach to the distal end. Otherwise, the distal end seems to deteriorate, and the nerve regeneration will proceed from the proximal end. However, we will need to do more detailed studies to determine whether regeneration is of the two cut axons, or due to a complete regrowth," she said.

According to Jin, the laser they used had a custom-built apparatus to permit the precise focus of laser on biological samples, but the laser itself is available commercially. Thus, the technique can be readily adopted by other laboratories, she said. And with its proven ability to cut individual nerves, Jin said she could envision the laser being used for other applications, such as selective ablation of subcellular structures, to explore their role in nerve regeneration.

Howard Hughes Medical Institute

Related Laser Articles from Brightsurf:

Laser technology: New trick for infrared laser pulses
For a long time, scientists have been looking for simple methods to produce infrared laser pulses.

Sensors get a laser shape up
Laser writing breathes life into high-performance sensing platforms.

Laser-powered nanomotors chart their own course
The University of Tokyo introduced a system of gold nanorods that acts like a tiny light-driven motor, with its direction of motion is determined by the orientation of the motors.

What laser color do you like?
Researchers at the National Institute of Standards and Technology (NIST) and the University of Maryland have developed a microchip technology that can convert invisible near-infrared laser light into any one of a panoply of visible laser colors, including red, orange, yellow and green.

Laser technology: The Turbulence and the Comb
While the light of an ordinary laser only has one single, well-defined wavelength, a so-called ''frequency comb'' consists of different light frequencies, which are precisely arranged at regular distances, much like the teeth of a comb.

A laser for penetrating waves
The 'Landau-level laser' is an exciting concept for an unusual radiation source.

Laser light detects tumors
A team of researchers from Jena presents a groundbreaking new method for the rapid, gentle and reliable detection of tumors with laser light.

The first laser radio transmitter
For the first time, researchers at Harvard School of Engineering have used a laser as a radio transmitter and receiver, paving the way for towards ultra-high-speed Wi-Fi and new types of hybrid electronic-photonic devices.

The random anti-laser
Scientists at TU Wien have found a way to build the 'opposite' of a laser -- a device that absorbs a specific light wave perfectly.

Laser 'drill' sets a new world record in laser-driven electron acceleration
Combining a first laser pulse to heat up and 'drill' through a plasma, and another to accelerate electrons to incredibly high energies in just tens of centimeters, scientists have nearly doubled the previous record for laser-driven particle acceleration at Berkeley Lab's BELLA Center.

Read More: Laser News and Laser Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to