At sacrifice day, mice were euthanized using CO2. Hind paws were dissected, fixed in 4% paraformaldehyde (PFA) for 24 h, and decalcified in 10% EDTA and 100 mM Tris, pH 7.5, for 2 weeks under constant shaking (22). Decalcified paws were stored in 70% ethanol until further processing. Front paws were dissected, snap frozen in liquid N2, and stored at −80°C until further processing.