Naturewatch briefing on the Three Rs
How biotechnology can lead to big gains for the 3Rs
Smart uses of biotechnology may lead to both fewer animals being used and better science. When win-win situations occur, they should be developed. The prime example of this is bioluminescence, where parts of an animal are induced to glow via fluorescent genes being added to its genome. This allows the interior of an animal to be observed in real-time non-invasively. This is not to downplay the ethical questions that surround biotechnology, but where unambiguous gains occur they should be recognised for that.
The possibility of a win-win situation occurring with bioluminescence is nicely expressed in a paper called ‘The neuronal naturalist: watching neurons in their native habitat”, by Jeff Lichtman and Scott Fraser [Nature Neuroscience Supplement, vol. 4, 1215-1220; available on-line here]. It is worth wading through the somewhat heavy technical language. In it, they say:
When faced with the challenge of studying developmental events in their natural settings, there are two relatively distinct strategies that could be adopted, which we will term 'static' and 'dynamic', respectively. The 'static' approach is to collect data from a timed series of animals (for example, animals of different ages), with each individual animal providing one piece of data. Changes must then be deduced by comparing the static images. The alternative, more technically daunting 'dynamic' approach is to follow the same structure over time, obtaining many data points from one animal and, potentially, capturing the key events directly.
Their analogy is that the static approach – which results in a high sacrifice of animals – is like trying to deduce the rules of American football by taking "one high-resolution snapshot at each of hundreds of different games, each collected at a different time point after the kickoff – but no two from the same game".
 |
The animal welfare benefits of bioluminescence is illustrated by this promotional graphic from the American company Xenogen. |
Early approaches suffered from two major drawbacks: the fluorescent dyes used had toxic side-effects, and observing techniques were too invasive – both of which detracted from the validity of the results obtained. As the technology has developed, the procedure has become substantially less invasive.
The advent of genetic modification has enabled fluorescent genes to be inserted into the mouse genome. Use of the GFP (green fluorescent protein) gene enables mice to be imaged not only non-invasively but also without restraints on the animals themselves. Obviously a mouse’s welfare is severely compromised if it is being bred to grow tumours, but such imaging techniques could be used to substantially reduce the numbers of mice being used. While this cannot win the approval of hard-line anti-vivisectionists, developing this technology would be a major application of the 3Rs.
It is also possible for the brain to be imaged non-invasively. Quoting again from Lichtman and Fraser,
The advent of positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) made it possible to monitor the workings of the brain innocuously and remotely, but similar access to the brain's microscopic structure—hidden inside the thick, opaque skull and meninges—seemed to lie far in the future. Remarkably, however, just as living animals with fluorescent neurons have come into existence, a separate technical advance has become widely available that offers the possibility of viewing them through non-invasive means. Two-photon laser-scanning microscopy (TPLSM, sometimes called mutiphoton microscopy) has recently progressed from a long-standing theoretical proposition to a practical tool.
Such techniques are attractive because they promise substantial benefits for animal welfare while also having the potential for better science – both because of the time-resolution offered and because they are carried out non-invasively. When such win-win situations occur, they must be exploited to the full. Part of the role of a Centre for the 3Rs must be to identify such opportunities and to enable funds to be channeled to researchers to develop them. This cannot happen if it is to be shackled by having a toxicology-only remit.