Creating whole organs in the lab is a distant dream. Some experts think it always will be. But as innovations in 3D bioprinting begin to filter out of research groups and into the commercial and clinical worlds, less headline-grabbing advances could nevertheless prove significant, as Margaret Harris reports

 

In biomedical science there are dreams and there are realities. Here is one of the realities: right now, more than 5000 people in the UK need a new kidney. Over the next year, after a median wait of about 30 months, slightly fewer than half of them will receive one. The rest will continue to wait, but they cannot hold on forever: in 2016, 457 Britons died while waiting for a new kidney, liver, heart or lung. Another 875 were taken off the waiting list, mostly because they had become too ill to receive a transplant.

 

Build your own

Now here is one of the dreams: what if, instead of relying on scarce donated organs, scientists could quickly and cheaply build healthy new ones in the laboratory, with cells taken from the patients themselves as the raw material? For the past 15 years this dream has helped drive investment and research in an interdisciplinary field known as 3D bioprinting. The basic idea is to take principles from additive manufacturing – where three-dimensional objects are “printed” layer by layer according to a pre-programmed design – and apply them to challenges in tissue engineering. So, in a typical bioprinting experiment, researchers might fill a specialized 3D printer with liquid or semi-liquid “bioinks” containing living cells, and input a blueprint for a desired final structure. The printer’s nozzles will then scoot back and forth, extruding mat­erial line by line until a three-dimensional chunk of tissue (such as the human ear shown above) takes shape. Depending on the type of cells being printed and the goal of the experiment, the cells may then spend days or weeks in a controlled environment, or bioreactor, that keeps cells supplied with nutrients and stimulates them to develop into mature tissue.

 

The list of tissues printed by this method is already impressively long, and includes tumours, blood vessels and organ tissues, as well as simpler structures such as cartilage, skin and bone. Given these achievements, it is easy to see why many have speculated that bioprinting could one day stretch to creating entire organs. At this point, though, another reality intrudes. “People are saying, ‘Oh, we will be printing organs, we will live forever’,” says Gabor Forgacs, a biophysicist who co-founded the first commercial 3D bioprinting firm, Organovo, in 2007. “And of course, that’s what we also thought at the very beginning. But that’s wishful thinking. This is a beautiful field. I think it has incredible promise. But one needs to be realistic.”