Eli5 why we test on mice?

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They aren’t biologically compatible with us and so often seems like treatments that work with mice stumble at human testing stage.
So why do we keep using mice? Why not a different animal more closely related to us?

In: Biology

They are cheap, reproduce like wild fire, easy to manipulate and people don’t really care too much about the lives of mice.

Mice are not that different from us. They are cheap to maintain and reproduce very quickly. They also are pretty stupid, and it feels a lot more humane to experiment on them instead of let’s say monkeys.

We also now have these very inbred lines of mice where the genetic diversity in the mice is very low. This makes experimental results more consistent across different labs. It would be very difficult to switch to another animal and get similar results without lots of world wide changes where all labs would work on a new strain of animal to use for tests.

Lab mice/rats are:

– Well-understood (if slightly inaccurate). We know where mice are and aren’t correlated to people, and we know how to take good care of mice so that they aren’t living in any more stress than is necessary for the study (to prevent side effects). We can even induce specific illness or predispositions to illnesses so that we can test against the actual condition, genetic or otherwise.

– Cheap. You can get a whole ton of lab mice/rats cheaply and quickly. They are low maintenance, low upkeep, and easy to deal with. When you’re doing a screening study, you’re interested in trying multiple conditions/drugs quickly, so you want fast turnaround time and fast procurement.

Other animals, like monkeys, will be used at other stages of the development process. But for first-pass trials, lab mice/rats are the most efficient candidate. Since those are the first time any given drug will be run in a live organism, that’s what you hear about the most. But that just obscures that other animal models do get used, just later on.

We do use pigs for some testing. Pigs are pretty closely related to us, with a lot of similar organs and biology. But pigs are big and expensive, and mice are biologically pretty close to us too. They respond to a lot of things the same or similar ways humans do. Plus, they have real short (relatively short) generational gaps, so you can see how something might affect reproduction or generations down the line without needing to wait actual human generations.