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Imagine going to the doctor for your aching knees

what if your doctor could actually listen to your body, monitoring the way your knees sound as they bend and flex

an instrument called a Surface Forces Apparatus (SFA), a device that measures the adhesion and friction forces between surfaces—in this case cartilage, the pad of tissue that covers the ends of bones at a joint.

degeneration of cartilage is the most common cause of osteoarthritis: The pads wear away, leaving bone grinding against bone

researchers found is that it isn't just any kind of friction that leads to the irreversible wear and tear on the material

currently believed that a high-friction force, or 'coefficient of friction,' is the primary factor in surface wear and damage

found is that this is not the case

The critical feature is not a high-friction force, but what is known as "stick-slip" friction, or, sometimes, "stiction."

Both are characterized by surfaces that initially stick together, and then accelerate away quickly once the static friction force is overcome

With stick-slip friction, the surfaces eventually pull slightly apart and slide across each other, stick again, and pull apart, causing jerky movements.

That's when things get damaged microscopically

Stick-slip is a common phenomenon. It is responsible for everything from computer hard drive crashes and automobile failures, to squeaking doors and music

same thing happens with a violin string

Even if you're pulling the bow steadily, it's moving in hundreds or thousands of little jerks per second, which determine the sound you hear

Each little jerk, no matter how submicroscopic, is an impact, and over time the accumulation of these impacts can deform surfaces, causing irreparable damage—first microscopically, then growing to macroscopic

it's not easy to tell the difference between types of friction at the microscopic level

Smooth-sliding joints might feel the same as those undergoing stiction, or the even more harmful stick-slip, especially in the early stages of arthritis

when measured with an ultra-sensitive and high-resolution instrument like the SFA, each type of friction revealed its own characteristic profile

Smooth-sliding joints yielded an almost smooth constant line (friction force or friction trace

with stiction showed up as a peak, as the "sticking" was being overcome, followed by a relatively smooth line

stick-slip shows the jagged saw-tooth profile of two surfaces repeatedly pulling apart, sticking, and pulling apart again

these measurements could be recorded by placing an acoustic or electric sensing device around joints, giving a signal similar to an EKG.

this could be a good way to measure and diagnose damage to the cartilage

to measure the progression, or even the early detection of symptoms related to arthritis

Early detection of conditions like arthritis has been a priority for many years

the functioning of joints is more complicated

scientists will continue their work by studying synovial fluid—the lubricating fluid between two cartilage surfaces in joints

plays a major role in whether or not the surfaces wear and tear, and the synergistic roles of the different molecules (proteins, lipids, and polymers

all involved in lubricating and preventing damage to our joints.

a number of directions to take, both fundamental and practical

it looks as if we need to focus our research on finding ways to prevent stick-slip motion, rather than lowering the friction force

8 metre long pliosaur was a

crocodile-like head, a short neck, whale-like body and four powerful flippers to propel it through water in pursuit of prey.

huge jaws and 20 cm long teeth

this particular individual was the unfortunate victim of an arthritis-like disease.

eroded its left jaw joint, displacing the lower jaw to one side

evidently lived with a crooked jaw for many years, because there are marks on the bone of the lower jaw where the teeth from the upper jaw impacted on the bone during feeding

the animal was still able to hunt in spite of its unfortunate condition.

signs on the skeleton to suggest that the animal could have been an old female who had developed the condition as part of the aging process

large size, and the fused skull bones

possibly female because its skull crest is quite low – presumed males had a higher crest.

In the same way that aging humans develop arthritic hips, this old lady developed an arthritic jaw, and survived with her disability for some time

unhealed fracture on the jaw indicates that at some time the jaw weakened and eventually broke

With a broken jaw, the pliosaur would not have been able to feed

They were at the top of their food chains, so there would not have been any predators to take advantage of an aging, disabled pliosaur – except for another pliosaur.

You can see these kinds of deformities in living animals, such as crocodiles or sperm whales and these animals can survive for years as long as they are still able to feed

is one of the leading causes of physical disability in the United States

some treatments can help relieve arthritis symptoms, there is no cure. Many patients with severe arthritis ultimately require a joint replacement

artificial cartilage built using a patient's own stem cells could offer enormous therapeutic potential

replacement cartilage could also be a game-changer for people with debilitating joint injuries, such as soldiers with battlefield injuries

Creating artificial cartilage requires three main elements: stem cells, biological factors to make the cells grow into cartilage, and a scaffold to give the tissue its shape

Tuan's 3-D printing approach achieves all three by extruding thin layers of stem cells embedded in a solution that retains its shape and provides growth factors

The ultimate vision is to give doctors a tool they can thread through a catheter to print new cartilage right where it's needed in the patient's body

other researchers have experimented with 3-D printing approaches for cartilage,

method represents a significant step forward because it uses visible light, while others have required UV light, which can be harmful to living cells.

In another significant step

used the 3-D printing method to produce the first "tissue-on-a-chip" replica of the bone-cartilage interface

the chip could serve as a test-bed for researchers to learn about how osteoarthritis develops and develop new drugs

Housing 96 blocks of living human tissue 4 millimeters across by 8 millimeters deep

As a next step, the team is working to combine their 3-D printing method with a nanofiber spinning technique they developed previously

They hope combining the two methods will provide a more robust scaffold and allow them to create artificial cartilage that even more closely resembles natural cartilage

halofuginone (HF) triggers a stress-response pathway that blocks the development of a harmful class of immune cells

prevents the autoimmune response without dampening immunity altogether

This compound could inspire novel therapeutic approaches to a variety of autoimmune disorders."

exciting example of how solving the molecular mechanism of traditional herbal medicine can lead both to new insights into physiological regulation and to novel approaches to the treatment of disease

Prior research had shown that HF reduced scarring in tissue, scleroderma (a tightening of the skin), multiple sclerosis, scar formation and even cancer progression.

Recognized only since 2006, Th17 cells are "bad actors," implicated in many autoimmune diseases such as inflammatory bowel disease, rheumatoid arthritis, multiple sclerosis and psoriasis

minute doses of HF reduced multiple sclerosis in a mouse model

Further analysis showed that HF was somehow turning on genes involved in a newly discovered pathway called the amino acid response pathway, or AAR

evidence that it extends lifespan and delays age-related inflammatory diseases in animal studies on caloric restriction

during a power outage we conserve what little juice we have left on our devices, foregoing chats in favor of emergency calls," said Whitman. "Cells use similar logic

Researchers do not yet fully understand the role that amino acid limitation plays in

researchers were able to home in on a single amino acid, called proline, and discovered that HF targeted and inhibited a particular enzyme (tRNA synthetase EPRS) responsible for incorporating proline into proteins that normally contain it.

proline also reversed other therapeutic effects of HF, inhibiting its effectiveness against the malaria parasite as well as certain cellular processes linked to tissue scarring