A research team of engineers has developed a method to create artificial cartilage using 3D printing that may one day allow us to grow replacement patches for worn out joints.
“Our goal is to create tissue that can be used to replace large amounts of worn out tissue or design patches,” said Ibrahim T Ozbolat, associate professor of engineering science and mechanics. “Those who have osteoarthritis in their joints suffer a lot. We need a new alternative treatment for this.”
Cartilage represents a good target for bioprinting due to its simple structure, consisting of only one cell type and with no blood cells in the tissue. Additionally, its inability to repair itself means that the prospect of artificial patches represents an important medical opportunity.
Previous attempts to create cartilage did so by embedding cells in a hydrogel, a substance comprising of polymer chains and water that acts as a scaffold for the tissue’s growth. This method didn’t allow cells to grow as normal, however, meaning that the created tissues lacked sufficient mechanical integrity. Ozbolat’s team’s new method allows them to produce larger scale tissues without the need for a scaffold.
The method consists initially of creating a tiny tube from algae extract. Cartilage cells taken from cows are then injected into the tube and allowed to grow for about a week and adhere to each other. Because cells do not stick to alginate, the tube can be removed to leave a strand of printable cartilage.
This strand substitutes for ink in the 3D printing process. Using a specially designed prototype nozzle, the 3D printer lays down rows of cartilage strands in a pattern chosen by the researchers. After about half an hour, the cartilage patch self-adheres enough to move to a petri dish containing nutrient media. The nutrient media allows the patch to further integrate into a single piece of tissue.
“We can manufacture the strands in any length we want,” said Ozbolat. “Because there is no scaffolding, the process of printing the cartilage is scalable, so the patches can be made bigger as well. We can mimic real articular cartilage by printing strands vertically and then horizontally to mimic the natural architecture.”
The cartilage produced by the team is currently inferior to natural cartilage, but better than the cartilage made using hydrogel scaffolding. However, Ozbolat believes mechanical pressure on the artificial cartilage will improve its mechanical properties, mimicking the way in which natural cartilage forms with pressure from the joints.
Applying the process to human cartilage will likely involve each individual treated providing their own source material to avoid tissue rejection.
However, once successful, we will have proven the possibility of artificially repairing tissues, as opposed to our current limitation to replacement or support.
Other tissues are far more complex than cartilage but if we consider it a starting point, this developing method could potentially lead to the ability to create “patches” for a variety of tissues, enabling us to combat the degradation of cells that leads to a variety of medical problems.