What Are Aged Mice

Aged mice, the "grown up citizens" of the rodent world, can tell us a lot about diseases, particularly diseases of aging

Mice have been used since the 1600s as living scientific models. In modern traditional experiments, most mice used are six to eight weeks old. However, there are many experiments that require older mice, from mature through the mouse equivalent of old age.

What Are Aged Mice?

There is no exact definition of "aged mouse", but it could be considered as any mouse that has at least made it to maturity. This is typically around 3-6 months, or roughly the equivalent of 20-30 years old in humans.

Any strain of mouse can be aged, from typical Black 6 mice to genetically modified mice. They are simply mice that have been housed, fed, and taken care of without any other research intervention until they reach maturity.

For companies that provide them, it can be as simple as setting some cages aside for the mice to age naturally.

What Kinds of Studies Are Aged Mice Used For?

Most drugs for human use would be considered intervention, as opposed to prevention. These are drugs or treatments that are taken after symptoms develop. In order to test some of these treatments in mice for pre-clinical drug trials, the mouse itself has to develop symptoms before a treatment can be tried.

"With genetically modified mice, sometimes the disease takes a long time to show up," said Chris Dowdy, Associate Director of Scientific Development for Charles River's Research Models and Services. "You need to have time for the phenotype to start to have symptoms, and then you intervene."

A genetically modified mouse that is intended to be used after it has aged might be used for researching neurological decline, tumor growth, or more specific diseases like muscular dystrophy or Alzheimer's.

But even normal lab mice can be used for age-related research. Most mice lose vision or hearing in old age, or become obese, or lose muscle function. A range of ages can be used for researching these common ailments shared by mice and humans.

Why Not Just Buy Mice and Wait?

"The advantage of buying aged mice is outsourcing anything you don't want to do yourself," Dowdy said. "And if the other person doing it happens to be a commercial entity who's done it at scale for over 70 years, you can take advantage of those economies of scale."

The advantage of buying a mouse already aged from a reputable supplier is the logistics and infrastructure that you wouldn't want to create yourself. It also minimizes the risk of not ending up with the right number of mice, since you can't predict what might happen to mice over a longer time span. If you know you need 10 aged mice, how many would you need to start with if breeding yourself from scratch?

Colony Management Over Time

The most important consideration for caring for aging mice is constant health monitoring. For the experiment to succeed, you have to control as many variables as possible. It is relatively easy to care for mice for a week or so before they are needed, but over time this effort and cost adds up. For academic researchers in particular, who entrust their mice to students still in training, this can add variables based on the inexperience of those caring for the animals.

Internet Colony Management,a proprietary management tool used by our contract breeding group, is one method for ensuring mice are properly cared for as they age. A system like this not only keeps tabs on the mice at all times, with real-time data updates from technicians, but it also stores generations of lineage date for each mouse. You can know the mouse's entire family health history while also making sure they are kept safe and heathy until they are needed.

As interest in aging research grows, aged mice are proving their worth.

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