A rapid, valid and inexpensive assay for measuring epiphyseal plates in mouse tibia.

One of the most accurate indices of changes in somatic tissue growth rate in rodents is the width of tibial epiphyseal plates as unlike most mammals, rodent growth plates never ossify. Unfortunately, the original procedure to measure tibial epiphyseal plate width (TEPW) was developed for rats and yields poor results with mice. This paper demonstrates a simple method for silver staining growth plates that can be used to inexpensively and quickly measure the TEPW of mice. Poor visualization due to overstaining and the shattering of growth plates necessitated several revisions to the original protocol. These include exposing the growth plate prior to acetone dehydration, reducing the silver nitrate concentration from 2% to 1.5% and staining time from 2 min to 10 s and finally, the use of reflective light rather than transmissive light when imaging. The optimized protocol was then validated by generating an age-dependent TEPW growth curve that matched changes in tibia length. A total of 120 tibias were processed in a combined time of less than one day and for less than $30. By contrast, histological processing in the university's core facility would have cost $1440 and taken approximately three weeks. Thus, the revised protocol is vastly more cost effective, reliable and can be performed considerably quicker with minimal training.