Lab-grown cartilage could be next big thing in knee replacements

Six hundred thousand Americans undergo knee replacement therapy every year in the United States to rid themselves of the pain of worn-out joints.

But instead of metal or plastic, imagine doctors inserting a strand of lab-grown cartilage to rejuvenate and cushion the joint. It could be medicine’s next big thing.

Sometimes the knees aren’t what they used to be.

It could be from years of pounding, or climbing or just advancing age.

“People can’t really even walk and then they have a hard time doing activities in their daily lives,” said Ibrahim Ozbolat, a tissue engineer at Penn State University.

Inside a Penn State University lab, Professor Ozbolat and his team are engineering a solution.

“We want to make cartilage made of patients’ own cells,” he said.

Ozbolat is an expert in three-dimensional bioprinting -- the technique of printing layers of living cells to create a 3D object. Like a nose, constructed from silicone, and printed in the lab.

Now the team is moving down the human body to the knee; producing cartilage patches to repair defects.

“Many of the strategies that we look at for repairing osteochondral defects involve stem cells,” said Daniel Hyes, a biomedical engineer working in the Penn State lab.

There are no blood vessels in cartilage tissue, so researchers say it’s a good type of tissue for bioprinting. Using cow cells as a test, Professor Ozbolat’s team grows the cartilage into strands that can be used as an ink substitute.

“So the bio-ink is the biological version of the ink that is used in paper printers,” he said.

In the future, Ozbolat says stem cells would be removed from a patient, cultured in a lab, the cartilage printed, and then transplanted back into a patient -- someday allowing scientists to print new and compatible, human parts.

If this process is eventually applied to humans, each individual would probably need to supply his or her own cells to avoid tissue rejection.

MEDICAL BREAKTHROUGHS

RESEARCH SUMMARY

TOPIC: PRINT YOUR OWN 3D CARTILAGE: MEDICINE’S NEXT BIG THING?

REPORT: MB #4302

BACKGROUND: When a patient’s knee is severely damaged as a result of injury or arthritis, it may result in limited mobility or ability to perform simple activities like climbing stairs or walking in general. It can even escalate to pain while sitting or lying down. Once medications and walking support are no longer helpful, a patient may consider total knee replacement surgery. Most knee pain is caused by three types of arthritis; osteoarthritis, rheumatoid arthritis, or post-traumatic arthritis. A knee replacement or knee arthroplasty might also be called a knee resurfacing because only the surface of the bones are actually replaced.

PROCEDURE: There are four steps to a total knee replacement procedure: preparing the bone by removing the damaged cartilage surfaces, positioning the implant with a metal component that recreates the surface of the joint; these metal parts may be press-fit or cemented into the bone. Then, the patella or knee cap is cut and resurfaced with a plastic button (depending on the case this step may be skipped.) Finally a medical-grade plastic spacer is inserted between the metal components to create a smooth gliding surface.

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NEW TECHNOLOGY: Bioengineers are now beginning to print replacement parts for nose and knee cartilage. Instead of metal or plastic, they are testing strands of lab-grown cartilage using 3D bioprinting; the technique of printing layers of living cells to create a 3D object. The team is now producing cartilage patches to repair knee defects as well as nose cartilage. Cartilage is avascular, it is made up of only one cell type and has no blood vessels within the tissue, so the researchers say it’s a good type of tissue for bioprinting. The team uses cow cells as a test to grow the cartilage into strands that can be used as a 3D substitute. The future holds the potential for stem cells to be removed from a patient, cultured in a lab for the 3D print, then transplanted back into the patient, someday allowing scientists to print human body parts! Previous attempts at growing cartilage began with cells embedded in a hydrogel, a substance composed of polymer chains and about 90 percent water that is used as a scaffold to grow the tissue;however, hydrogels don’t allow cells to grow as normal. It confines the cells and doesn’t allow them to communicate as they would in native tissue.

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