2.2. Hindlimb Immobilization Model

All animal experiments were conducted in the animal facilities at Barcelona Biomedical Research Park (PRBB). This study was designed in accordance with the ethical standards on animal experimentation (EU 2010/63 CEE, Real Decreto 53/2013 BOE 34, Madrid, Spain). Ethical approval was obtained by the animal research committee (Animal welfare department in Catalonia, Spain, EBP-13-1485, 2015/04/20). Female C57BL/6J mice (10 weeks old and weight approximately 20 g) were obtained from Harlan Interfauna Ibérica SL (Barcelona, Spain). Mice were exposed to unilateral hindlimb immobilization as previously described to reproduce a model of disuse-induced muscle atrophy [7,8,9]. Briefly, the left hindlimb was shaved with clippers and was enveloped using surgical tape. The hindlimb was introduced in a 1.5 mL microcentrifuge tube with a cover and the bottom lids were removed, while maintaining the foot in a plantar-flexed position to induce the maximal atrophy of the target limb muscle. As the weight of the tube was approximately 0.6 g, it did not interfere with the usual mobility of the mice. The left hindlimb of the mice was immobilized for 7 consecutive days, with the time at which the splint was removed to let the animals move freely in their cages to evaluate muscle recovery being 7 days later.