Abstract
Purpose :
Well-designed animal studies are critical for establishing the safety and efficacy of ocular gene therapies or drugs prior to clinical trial. Mice have been widely used as a mammalian model in preclinical studies due to their physiological and genetic similarities to humans, relative ease of breeding, and short generation time. Aniridia is a rare congenital blindness with unmet therapeutic needs, which is caused by mutations in the PAX6 gene. Here we will highlight the importance of breeding strategies for successful preclinical studies using cohorts of Pax6 mutant mice as an example.
Methods :
First generation hybrid mice are a good choice for therapy development as they are genetically identical, but carry genomic polymorphisms as does the human population. To generate a cohort of age-matched mice with significant statistical power, 8 129S1/SvImJ Pax6 mutant (MMRRC #050624-MU) male studs were chosen based on age (>6 weeks, <8 months) and experienced (5 days of mating with a surplus female followed by 5 days of rest). 8 C57BL/6J ROSA-stop-tdTomato (JAX #007914) females were crowded (group housed in a single cage for 8-10 days prior to mating to suppress estrus cycle). To increase the rate of pregnancy, mice were mated in pairs. After one week, females were removed and singly housed in a fresh cage. Cages were checked (by looking from outside the cage to minimize stress) for births daily 18-27 days after the mating. This breeding strategy was used monthly to generate cohorts. Investigator blinding was not possible during the breeding and treatment due to the phenotype of the Pax6 mutant mice, but it was practiced during assessment of outcome (histological analysis) to minimize bias and maximize result validity.
Results :
We have used this breeding strategy 9 times to succesfully generate 52 ± 8 (MEAN ± SD) age-matched (± 3.5 days) mice per cohort. The following breeding colony size will help investigators calculate financial costs for generating a single experimental cohort of mice. 8 singly housed studs, and 8 single breeding cages were required to generate the experimental cohorts. With a maximum of 5 adult mice per single cage, 10-12 cages were allocated to weans from each cohort.
Conclusions :
We demonstrated the practicality of the suggested breeding strategy by generating age-matched reporter mice in an efficient and timely manner. We have also offered investigators insight on space requirements to generate these mice.
This is a 2021 ARVO Annual Meeting abstract.