The authors explained they have achieved a major breakthrough in the printing of 3D tissue. With their system, cartilage is "printed".
The printer was used to make cartilage constructs which could eventually be implanted into specific areas of injured patients, such as joints, to help regrow cartilage.
They created a printer hybrid which is a combination of two low-cost fabrication techniques:
- An electrospinning machine
- An ink jet printer
Their material is stronger and harder wearing than other kinds of artificial cartilageThe scientists said that by combining these two systems, they were able to build a structure made from synthetic and natural materials. While the natural gel materials provide an environment in which cells can grow, the synthetic material ensures the strength of the construct.
They managed to produce, in this hybrid system, cartilage constructs that were much more mechanically stable compared to those an ink jet printer could produce using just gel material.
They also found that the constructs maintained their functional characteristics in both the laboratory and a real-life system.
The electrospinning machine uses an electrical current to generate extremely fine fibers from a polymer solution. Electrospinning allows the polymers' composition to be controlled easily, producing porous structures that encourage cells to incorporate into surrounding tissue.
Co-author, James Yoo, M.D., Ph.D., said:
"This is a proof of concept study and illustrates that a combination of materials and fabrication methods generates durable implantable constructs. Other methods of fabrication, such as robotic systems, are currently being developed to further improve the production of implantable tissue constructs."
Flexible mats, made of electrospun synthetic polymer, were combined with a solution of cartilage cells from a rabbit ear. The mats were combined layer-by-layer with the cartilage cells which were deposited using a traditional ink jet printer. The mats were 0.4mm thick, with a diagonal of 10cm.
They measured their strength by loading them with different weights. One week later they tested to find out whether the cartilage cells were still alive.
Testing the constructs in a real life systemsThe scientists inserted the constructs into mice for two, four and eight weeks to determine how well they performed in a real life system. Within eight weeks of being implanted, the constructs had developed the structures and properties that are typically found in elastic cartilage, demonstrating their potential for use in injured humans.
The cartilage constructs could eventually be clinically applied using a blueprint from an MRI scan of a knee, for example, from which a matching construct could be created. "A careful selection of scaffold material for each patient's construct would allow the implant to withstand mechanical forces while encouraging new cartilage to organize and fill the defect," they added.
Engineering cartilage from pluripotent stem cellsResearchers from Duke Medicine managed to engineer cartilage from induced pluripotent stem cells, which were grown and sorted for use in the repair of tissue of patients with osteoarthritis or injuries.
They reported their findings on the Proceedings of the National Academy of Sciences. The scientists added that iPSCs (induved pluripotent stem cells) could eventually be used effectively for patients with specific cartilage tissue injuries or defects.
Co-author, Farshid Guilak, PhD., said:
"This technique of creating induced pluripotent stem cells - an achievement honored with this year's Nobel Prize in medicine for Shimya Yamanaka of Kyoto University - is a way to take adult stem cells and convert them so they have the properties of embryonic stem cells."
Written by Christian Nordqvist