Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Hop, skip or jump? Study says no to all of the above

18.04.2013
MIT engineers find that in the earliest stages of arthritis, high-impact exercise may worsen cartilage damage.

Osteoarthritis, which affects at least 20 percent of adults in the United States, leads to deterioration of cartilage, the rubbery tissue that prevents bones from rubbing together. By studying the molecular properties of cartilage, MIT engineers have now discovered how the earliest stages of arthritis make the tissue more susceptible to damage from physical activities such as running or jumping.

The findings could help researchers develop tests to diagnose arthritis earlier in patients at high risk for the disease and also guide engineers in designing replacement cartilage. The results also suggest that athletes who suffer traumatic knee injuries, such as a torn anterior cruciate ligament (ACL) — which gives them a greater chance of developing arthritis later in life — should be cautious when returning to their sport following surgery.

“It’s a clear signal to be careful of going right back out,” says Alan Grodzinsky, an MIT professor of biological, electrical and mechanical engineering and senior author of a paper describing the findings in a recent issue of the Biophysical Journal. “Even though your knee may be stabilized, there’s the possibility that deformation of cartilage at a high loading rate is still going to put it at risk.”

Cartilage is packed with protein-sugar complexes known as aggrecans, each made of about 100 highly charged molecules called glycosaminoglycans (GAGs). Those molecules protect joints by absorbing water and causing the tissue to stiffen as pressure is applied.

“The cartilage is a stiff sponge, filled with fluid, and as we compress it, fluid has to percolate through these closely spaced GAG chains,” Grodzinsky says. “The GAG chains provide resistance to flow, so the water can’t get out of our cartilage instantly when we compress it. That pressurization at the nanoscale increases the stiffness of our cartilage to high-loading-rate activities.”

The MIT team set out to investigate how the molecular structure of GAG generates this stiffening over such a wide range of activity — from sitting and doing nothing to running or jumping at high speed. To do this, they developed a new, highly sensitive type of atomic force microscopy (AFM), allowing them to measure how aggrecan reacts at the nanoscale to very high loading rates (the speeds at which forces are applied).

Conventional AFM, which generates high-resolution images by “feeling” the surface of a sample with a tiny probe tip, can also be used to subject samples to cyclic loading to measure their nanomechanical properties. But conventional AFM can apply only up to about 300 hertz (cycles per second). Hadi Tavakoli Nia, the lead author of the paper, and Iman Soltani Bozchalooi, both graduate students in mechanical engineering, developed a modified system that can apply much higher frequencies — up to 10 kilohertz, frequencies relevant to impact loading of joints.

‘A very floppy sponge’

Using this system, the researchers compared normal cartilage and cartilage treated with an enzyme that destroys GAG chains, mimicking the initial stages of osteoarthritis. In this early phase, collagen, which gives cartilage its structure, is usually still intact.

The researchers found that when exposed to very high loading rates — similar to what would be seen during running or jumping — normal cartilage was able to absorb fluid and stiffen normally. However, in the GAG-depleted tissue, fluid leaked out rapidly.

“That’s what puts the collagen in trouble, because now this becomes a very floppy sponge, and if you load it at higher rates the collagen network can be damaged,” Grodzinsky says. “At that point you begin an irreversible series of activities that can result in damage to the collagen and eventually osteoarthritis.”

There is currently no good way to diagnose arthritis during those early stages, which are usually painfree. Many researchers are working to further improve magnetic resonance imaging (MRI) to test for loss of aggrecan, while others are looking for blood or urine markers. If such a test existed, it would be especially useful for monitoring patients who have experienced an acute knee injury. It is estimated that at least 12 percent of all osteoarthritis cases originated with a traumatic joint injury, Grodzinsky says.

Researchers in Grodzinsky’s lab are now working to identify possible drugs that might halt the loss of aggrecan, as well as designing tissue scaffolds that could be implanted into patients who need cartilage-replacement surgery. The new AFM system should be useful for testing these scaffolds, to see if cells grown on the scaffold can produce the necessary tissue stiffening at high loading rates.

“These two aspects are really important: preventing cartilage degradation after injury and, if the cartilage is already damaged beyond its ability to be repaired, replacing it,” Grodzinsky says.

Other authors of the paper are Yang Li, a graduate student in biological engineering; Lin Han, a former MIT postdoc; Han-Hwa Hung, a research specialist in biological engineering; Eliot Frank, a principal research engineer in biological engineering; Kamal Youcef-Toumi, a professor of mechanical engineering; and Christine Ortiz, a professor of materials science and engineering and MIT’s dean for graduate education.

The research was funded by a Whitaker Foundation Fellowship, the National Science Foundation and the National Institutes of Health.

Written by: Anne Trafton, MIT News Office

Sarah McDonnell | EurekAlert!
Further information:
http://www.mit.edu

More articles from Studies and Analyses:

nachricht Rutgers-led innovation could spur faster, cheaper, nano-based manufacturing
14.02.2018 | Rutgers University

nachricht New study from the University of Halle: How climate change alters plant growth
12.01.2018 | Martin-Luther-Universität Halle-Wittenberg

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

Im Focus: Hybrid optics bring color imaging using ultrathin metalenses into focus

For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.

But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...

Im Focus: Stem cell divisions in the adult brain seen for the first time

Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.

The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...

Im Focus: Interference as a new method for cooling quantum devices

Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters

Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...

Im Focus: Autonomous 3D scanner supports individual manufacturing processes

Let’s say the armrest is broken in your vintage car. As things stand, you would need a lot of luck and persistence to find the right spare part. But in the world of Industrie 4.0 and production with batch sizes of one, you can simply scan the armrest and print it out. This is made possible by the first ever 3D scanner capable of working autonomously and in real time. The autonomous scanning system will be on display at the Hannover Messe Preview on February 6 and at the Hannover Messe proper from April 23 to 27, 2018 (Hall 6, Booth A30).

Part of the charm of vintage cars is that they stopped making them long ago, so it is special when you do see one out on the roads. If something breaks or...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Fingerprints of quantum entanglement

16.02.2018 | Information Technology

'Living bandages': NUST MISIS scientists develop biocompatible anti-burn nanofibers

16.02.2018 | Health and Medicine

Hubble sees Neptune's mysterious shrinking storm

16.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>