鈥淢ICROLUNGS鈥� grown from human tissue might one day help to replace the vast numbers of rats used to check the safety of drugs, cosmetics and other chemicals. The work is part of a growing drive to develop toxicology tests based on human cells as a replacement for animal testing.
Such efforts are made partly for ethical concerns, and partly because animal testing is so time-consuming and expensive. For example, the European Union鈥檚 require about 30,000 chemicals to be tested for toxicity over the next decade. Yet testing the effects of inhaling a single dose of a particular chemical typically requires more than 200 rats, while testing the chronic effects of breathing it in over time can take more than 3000. Meanwhile the 鈥� which covers items from deodorants and perfume to air-fresheners 鈥� seeks to ban all tests of cosmetics on animals by 2013.
Advertisement
The obvious alternative is to test chemicals on human cells grown in the lab. The difficulty, however, lies in enticing those cells to form complex tissue that responds as our organs do.
Cell biologist at the University of Cardiff, UK, has managed to grow human lung cells into flat differentiated layers that resemble the inner lining of the lungs. Her method is already being used for drug testing by companies such as Unilever and AstraZeneca. But when allowed to grow in three dimensions, as in the body, cells arrange themselves very differently, and this can change how they respond to chemical stimuli. 鈥淲e need to move from something flat to 3D structures,鈥� says B茅ruB茅.
A popular approach is to seed plastic scaffolds with stem cells to grow artificial 鈥渙rgans鈥�, but B茅ruB茅 and her colleagues have found an alternative which could allow thousands of drugs to be screened at once.
Instead of large scaffolds, B茅ruB茅 has grown lung cells on the surface of plastic spheres half a millimetre in diameter (see image), essentially producing a tiny inside-out lung around each bead (see image). The ultimate aim is to develop a chip on which thousands of microlungs can be grown then tested simultaneously, she told the in the UK last week (see image).
鈥淐ells grow on little plastic spheres, essentially producing a tiny inside-out lung around each bead鈥�
The big challenges will be getting the technique accepted by regulatory authorities and convincing academia that tiny globs of lab-grown tissue can tell us as much in tests as whole animals. But B茅ruB茅 points out that rat models are less relevant to humans than most people realise. Chocolate, for example, is lethal to rats and their anatomy is such that they can only breathe through their noses.
