C. elegans

Even the early worm gets old: study unlocks a key to aging

/ Kevin McCormack / 1 Comment

A new study poses the question, ‘When does aging really begin?’ One glance in the mirror every morning is enough for me to know that regardless of where it begins I know where it’s going. And it’s not pretty.

But enough about me. Getting back to the question about aging, two researchers at Northwestern University have uncovered some clues that may give us a deeper understanding of aging and longevity, and even lead to new ways of improving quality of life as we get older.

The researchers were focused on C. elegans, a transparent roundworm. They initially thought that aging was a gradual process: that it began slowly and then picked up pace as the animal got older. Instead they found that in C. elegans aging begins just as soon as the animal reaches reproductive maturity. It hits its peak of fertility, and it is all downhill from there.

The researchers say that once C. elegans has finished producing eggs and sperm – ensuring its line will continue – a genetic switch is thrown by germline stem cells. This flipped switch begins the aging process by turning off the ‘heat shock response’; that’s a mechanism the body uses to protect cells from conditions that would normally pose a threat or even be deadly.

In a news release Richard Morimoto, the senior author of the study, says that without that protective mechanism in place the aging process begins:

“C. elegans has told us that aging is not a continuum of various events, which a lot of people thought it was. In a system where we can actually do the experiments, we discover a switch that is very precise for aging. All these stress pathways that insure robustness of tissue function are essential for life, so it was unexpected that a genetic switch is literally thrown eight hours into adulthood, leading to the simultaneous repression of the heat shock response and other cell stress responses.”

You read that right. In the case of poor old C. elegans the aging process begins just eight hours into adulthood. Of course the lifespan of the worm is only about 3 weeks so it’s not surprising the aging process kicks in quite so quickly.

To further test their findings the researchers carried out an experiment where they blocked the genetic switch from flipping, and the worm’s protective mechanisms remained strong.

Now, taking findings from something as small as a worm and trying to extrapolate them to larger animals is never easy. Nonetheless understanding what triggers aging in C. elegans could help us figure out if a similar process was taking place at the cellular level in people.

Morimoto says that knowledge might help us develop ways to improve our cellular quality of life and delay the onset of many of the diseases of aging:

“Wouldn’t it be better for society if people could be healthy and productive for a longer period during their lifetime? I am very interested in keeping the quality control systems optimal as long as we can, and now we have a target. Our findings suggest there should be a way to turn this genetic switch back on and protect our aging cells by increasing their ability to resist stress.”

The study is published in the journal Molecular Cell.

Multitasking molecule repairs damaged nerve cells, scientists discover in ‘stunning’ research breakthrough

/ cirmweb / 4 Comments

Every molecule in the body has a job to do—everything from maintaining healthy cell functions to removing dead or decaying cells requires a coordinated series of molecular switches to complete. There’s a lot we know about what these molecules do, but even more that we are still discovering.

The PSR-1 molecule, which normally clears out dead or dying nerve cells, has also been observed trying to repair them.

The PSR-1 molecule, which normally clears out dead or dying nerve cells, has also been observed trying to repair them.

And as reported in a pair of studies published this week in Nature and Nature Communications, a molecule that has long been known to clear out dying or damaged nerve cells also—amazingly—tries to heal them.

The molecule at the heart of these studies is called phophatidylserine receptor, or PSR-1 for short. PSR-1’s main job had been to target and remove cells that were dead or dying—a sort of cellular ‘cleanup crew.’

Some cells die because they’ve reached the end of their life cycle and are scheduled for destruction, a programmed cell death known as apoptosis. Other cells die because they have been damaged by disease or injury. In this study, scientists at the University of Colorado, Boulder and the University of Queensland (UQ) in Brisbane, Australia, discovered that not only does PSR-1 clear out dead cells, it tries to save the ones that haven’t quite kicked the bucket.

Specifically, the team observed PSR-1 literally reconnecting nerve fibers, known as axons, which had broken due to injury.

“I would call this an unexpected and somewhat stunning finding,” said one of the study’s lead authors Ding Xue in a news release. “This is the first time a molecule involved in apoptosis has been found to have the ability to repair severed axons, and we believe it has great therapeutic potential.”

Professor Ding Xue of the University of Colorado Boulder. [Credit: Casey A. Cass, University of Colorado]

Professor Ding Xue of the University of Colorado Boulder. [Credit: Casey A. Cass, University of Colorado]

Injuries to nerve cells that reside in the brain or spinal cord are particularly distressing because once damaged, the cells can’t be repaired. As a result, many research groups have looked to innovative ways of coaxing the cells to repair themselves. Xue and Hilliard see the potential of PSR-1 to be involved in such a strategy.

“This will open new avenues to try and exploit this knowledge in other systems closer to human physiology and hopefully move toward solving injuries,” said Hilliard.

The discovery of PSR-1’s role in axon repair is based off a key difference between cells undergoing programmed cell death and those that are dying due to injury.

During apoptosis, cells release a beacon to alert PSR-1 that they’re ready for removal. But when a nerve cell is injured, it sends out a distress signal. Explained Xue:

“The moment there is a cut to the nerve cell we see…a signal to PSR-1 molecules in the other part of the nerve that essentially says ‘I am in danger, come and save me.’”

While these experiments were performed in the model organism C. elegans (a small worm often used in this sort of research), the researchers are optimistic that a similar process is taking place in human nerve cells.

“Whether human PSR has the capacity to repair injured axons is still unknown. But I think our new research findings will spur a number of research groups to chase this question.”