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Jan 3, 2015 | By Alec

If you're into sports, whether you are active yourself or passionately follow a professional team, you've undoubtedly come across career-threatening injuries incurred on the field. Perhaps your own ambitions were cut short by injury. If so, you might have noticed that many of these time of injuries affect the knees, ankles or elbows of athletes. One of the most commonly occurring problem is an osteochondral injury; an injury to the smooth surface on the end of bones, where cartilage and bone come together.

These type of injuries commonly involve damage to the cartilage due to extreme levels of stress, and could result in bones fracturing or becoming unstable inside the joints. Often, patients suffer from pain and loss of function, while their chances of developing steoarthritis increases dramatically. While these type of injuries can be treated in a number of different ways, many are problematic, expensive and have 'suboptimal long term outcomes.' The body itself also has a very limited capacity of healing cartilage damage, so this could be a career killer for many athletes.

We were therefore very intrigued to learn of a new study by a team of scientists from the University of Melbourne, Australia. Spearheaded by PhD candidate Ken Ye, they have explored combinations of 3D bioprinted cell structures and 'Infrapatellar fat pad adipose stem cells' (or IPFP-ASCs). This interesting study revealed that these bioengineered structures could be used to develop osteochondral grafts, which can be used to treat those problematic cartilage injuries. While not as life-saving as 3D printed organ tissue or blood vessels, this particular 3D printing application could therefore be used to treat a common affliction affecting thousands of people all over the world.

The 3D printed scaffold housing the cartilage stem cells.

While still a long way away from practical implementation, Ken Ye expressed his hope in a recent paper published in the PLOS ONE journal that this new way of engineering tissue through 3D printing could offer 'treatment options that could overcome the limitations of current management options. The combination of cells, [3D printed] scaffold and biochemical factors may provide the possibility of true cartilage regeneration.'

These tissues for cartilage repair were seeded on custom-made, 3D printed structures made of Chitosan, on which they grew into potentially transplantable grafts over a period of four weeks. Chitosan is not a typical material we'd associate with 3D printing, but it is a biopolymer more widely used in biomedical engineering, in part for its antibacterial properties. Remarkably, it can be made from the shells of crustaceans and similar creatures.

Schematical function of the 3D printed scaffolding.

For this particular study, it's proven very useful as it shares 'It shares some structural characteristics with various glycosaminoglycans and hyaluronic acid found in native cartilage.' It is therefore commonly used in studies on cartilage, as printed structures of this material can be designed to mimic human cartilage. 'thus, in theory, should provide greater chance for cartilage regeneration.'

To 3D print his structures, Ken Ye designed a 3D structure resembling knee cartilage using AutoCAD modeling software, which was then 3D printed in a custom-set up on a microscopic scale; to do so, he relied on a disposable syringe (Nordson EFD), fitted with a remarkable nozzle with a diameter of a mere 200 µm. 'The chitosan solution was extrusion printed onto a glass slide immersed in a precipitating bath of isopropyl alcohol using a custom modified computer numerical control (CNC) milling machine (Sherline Products, CA).'

The whole printing set-up was powered with EMC2 (Linux) software, and extrusion printed a total of 24 scaffolds for the experiment at a rate of '150 mm/min, strand spacing of 0.25 mm, to a final size of 10 mm×10 mm×5 mm with a porosity of 250 µm. […] The extruded 3D scaffolds were then neutralised in a dilution series of ethanol and PBS over a period of two days.' While very different from our own desktop experimentations, the printing technology is thus FDM at its core.

The scaffolding and cell structure after four weeks of incubation.

While a whole lot of complex histological and genetical work was also needed, Ken Ye was eventually successful in cultivating three samples of cartilage replicates on his 3D printing structures over a period of four weeks (many of the other scaffold structures were used for control groups). These cell structures grew into 'pearlescent, white and shiny cartilage-like tissue 'caps'' that are theoretical transplantable onto damaged cartilage structures.

Theoretically, this approach could even be used to develop structures for treating 'quite substantial areas of cartilage damage'. The Chitosan scaffold structures, that were 3D printed, could function as a type of delivery mechanism for the cells, and would therefore also be transplanted onto injuries. 'Our results demonstrate the combination of TGFβ3 and BMP6 strongly promotes chondrogenesis with these cells in a 3D chitosan scaffold. This cell-scaffold construct may provide the basis of a viable chondral graft suitable for in vivo implantation.'

As Ken Ye's study is still ongoing, it will doubtlessly take years before we'll see anything like this being practically used in hospitals. But it is nonetless very intriguing to see that this manufacturing technology could even become a treatment method for common, non-life threatening afflictions. How long will it take before 3D printers become common in hospitals everywhere?

 

Posted in 3D Printing Applications

 

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