*2.1. Animal Model*

B6.129S7-Sod1tm1Leb/DnJ mice were purchased from the Jackson Laboratory (#003881, Bar Harbor, ME, USA). They were backcrossed with C57Bl/6NJ mice (#005304, Bar Harbor, ME, USA) and bred in-house at McGill University in the McIntyre Comparative Medicine and Animal Resources Centre. Mice were kept on a 12L:12D cycle; food and water were provided *ad libitum*, and the temperature was maintained at 22 ◦C. Young (3 to 4-month-old) and aged (18-month-old) wild-type (WT) and *Sod1* null (*Sod1*−/−) mutants mice were selected for this study. The number of mice in each group was from 3 to 6. Mice were euthanized by CO2 asphyxiation followed by cervical dislocation. Both epididymides were harvested. All animal studies were conducted in accordance with the principles and procedures outlined in the Guide to the Care and Use of Experimental Animals prepared by the Canadian Council on Animal Care (McGill Animal Care Committee protocol #4687).
