By George Taniwaki
As often mentioned in this blog, there is a severe shortage of transplantable organs available for patients who need them. In the short-term, the only solution is to increase the number of donors, both living and deceased. But a possible long-term solution is to create artificial organs, also called regenerative medicine.
In a Mar 2011 blog post and an Aug 2010 blog post, I discussed various processes for making the substrates for artificial organs. These include using existing scaffolds from human or animal organs, printing the scaffold using 3D printers, or building the scaffolds from microbeads.
However, a kidney (and any other organ) is more than just a scaffold. The scaffold has to be filled with cells. The cells have to be the right kinds and have to be arranged in the correct order. And the cells have to be connected to a network of blood vessels that transports blood, tubules that carry away the urine, nerves that monitor and control the organ, and other systems that connect the organ to the rest of the body.
Blood vessels and tubules
One advance described in Los Angeles Times Jul 2012 is a novel technique for creating the blood vessels and tubules. The work was led by Jordan Miller and Christopher Chen, both of University of Pennsylvania’s Tissue Microfabrication Lab. A network of filaments is printed using a 3D printer. Instead of plastic that is commonly used in these printers use, the filaments are made from a special combination of glass-like sugars. The filaments are then coated with a polymer that acts as the scaffold for the endothelial cells that will become the blood vessels and tubules. After the cells are added, the sugar is washed away with water leaving a hollow tube. A great video explaining the process is available on YouTube.
Still image of Rep Rap 3D printer producing sugar filaments. Courtesy of Univ. of Pennsylvania
Creating organs without stem cells
So far, in these discussions of the use of 3D printers, the structures created have been in the order of 100 micron to 1 millimeter in scale. A recent advance in 3D printing of organic materials appears in Science Apr 2013 (subscription required). Gabriel Villar and Hagan Bayley of University of Oxford have created self-organizing shapes using droplets of aqueous material surrounded in a lipid film. Currently, each droplet is 50 microns in diameter. This is about 5 times larger than living cells, but the researchers believe there is no reason why future printers could not make smaller drops. Thus, entire “organs” could be made from these drops. A press release describes the process. Additional pictures showing layered droplets are available in the Los Angeles Times Apr 2013.
Two videos in the press release show how a network of drops with different electrical properties could be self-organizing. One is a computer animation, the other is an actual stop motion of a flat sheet of droplets curling into a sphere over a span of 348 minutes (just under 6 hours).
Still image of droplet network forming a sphere. Courtesy of University of Oxford