Printing body parts

The old saw that truth is stranger than fiction seemed particularly apposite when I read an article in the Feb 18th 2010 issue of The Economist (http://www.economist.com) entitled “Printing body parts: making a bit of me”. It what seems to me to be one of the most exciting recent developments in regenerative medicine, a machine that can print biological tissues is coming to market.

As is so often the case, this breakthrough has resulted from many years of painstaking research by several pioneers working at the interface of technologies that are conventionally regarded as unrelated, in this case regenerative medicine, printer technology and rapid-prototyping.

The first commercial 3D bio-printer for manufacturing human tissues has been developed by Organovo (http://organovo.com/), a company in San Diego that specialises in regenerative medicine, and Invetech (http://www.invetech.com.au/), an engineering and automation firm in Melbourne, Australia. One of Organovo’s founders, Gabor Forgacs of the University of Missouri (http://organprint.missouri.edu/www/), developed a prototype to study ways to produce human tissue for clinical uses.

The 3D bio-printer works in a similar way to some rapid-prototyping machines used in industry to make parts and mechanically functioning models. These are essentially inkjet printers, but working in three rather than in two dimensions. Such printers deposit droplets of polymer which fuse together to form a structure. With each pass of the printing heads, the base on which the object is being made moves down a notch. In this way, little by little, the object takes shape. Voids in the structure and complex shapes are supported by printing a scaffold of water-soluble material. Once the object is complete, the scaffold is washed away. Something similar can be done with biological materials.

Though printing tissues is new, growing them from scratch on scaffolds has already been done successfully. Anthony Atala and his colleagues at the Wake Forest Institute for Regenerative Medicine in North Carolina (http://www.wfubmc.edu/wfirm/) have made new bladders by utilising a combination of cell culture and a biodegradable bladder-shaped scaffold. In 2006, they transplanted bladders into seven patients, all of whom still have functioning bladders today.

The advantage of using a bioprinter is that it eliminates the need for a scaffold, so Dr Atala, too, is experimenting with inkjet technology. To see the technology in action you should view his video at
http://www.ted.com/talks/lang/eng/anthony_atala_growing_organs_engineering_tissue.html

The technology potentially is awesome. However, at the moment it is only possible to produce relatively simple tissues (like skin, blood vessels and muscle) and simple structures like bladders where you have only one or two cell types. It is going to be much more difficult and complex to generate solid, vascularised organ systems with the right functionality. Also, the current products from Organovo are for research purposes only.

However, the company expects that within five years, once clinical trials are complete, the printers will produce blood vessels for use as grafts in bypass surgery. With more research it should be possible to produce bigger, more complex body parts. Because the machines have the ability to make branched tubes, the technology could, for example, be used to create the networks of blood vessels needed to sustain larger printed organs, like kidneys, livers and hearts.