There are three main ways of doing this in lab now 1) letting live cells recolonize a structure that mimics a whole tissue 2) with 'many hundred cell' resolution printing cells in 'close to the right structure' and letting them use their own systems to resort themselves out (what was done here), and 3) single-cell resolution of very fine structures that make up the individual units of an organ. Each have their own difficulties. And once they converge (single cell->rapid->entire organ) you will see some pretty cool stuff.<p>One major impediment is similar to the 3D printing world - we need and rapid access at single micron levels. Right now most 3D printers get down to about 100microns. We need better.<p>We also need creative ways to mix cell types - your organs use many (but a finite number) of cell types dispersed in an organized way. Coming up with a clever way to use different 'inks' of cells in an organized way would be extraordinarily useful. As others have said - a primary reason is vascularization, but there are a number of cell types you'd need to worry about.<p>Definitely moving quickly though - we've seen pretty fast progress in lab keeping cells alive and starting to use different cell types for small structures. We can do any given manipulation. We now need to combine them to make the entire process fast, micron resolution, high viability, natural scaffoldings, with many cell types.<p>Futher - as this article points out, there's a LOT we can learn simply from being able to recreate and experiment on small portions of tissues and organs properly. The first results won't need to come from 'make a new liver' - but 'what does this thing in the liver do', or 'can we fix a liver just by doing this to it?'.
Interesting coverage in Popular Science as well [1]. They point out (as does the newscientist article) that the key to organ printing is vascularization (creating a blood supply for the organ). Once you have that conquered you should be good to go on Kidney's, Liver's, Spleen's, Heart Tissue, Etc.<p>[1] <a href="http://www.popsci.com/science/article/2013-07/how-3-d-printing-body-parts-will-revolutionize-medicine" rel="nofollow">http://www.popsci.com/science/article/2013-07/how-3-d-printi...</a>
I didn't have associated the idea of "printing" to a "human organ" yet. Very interesting. I wonder if, in the future, printing an organ would be easier than making it grow somehow until it gets functional for transplant.