Original article for free at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2768028/?tool=pubmed
Animal models have been a huge help in medical science. Almost everyone in the world today has benefited from medicines and surgical procedures all researched first in animal models. However, one of the main problems with animal models is that they’re not human, which means that some diseases don’t infect them in the same way (or at all), drugs don’t interact the same way as they would in humans (e.g. penicillin is very toxic to guinea pigs, but mostly harmless to us) and all the rest.
To combat one aspect of this problem, many groups from around the world have worked together to develop a strain of mice with human livers. Development of these mice was a ridiculously complex task and each step of development came from a different lab.