*4.4. Animals*

As the experimental animals, forty-five male Japanese White rabbits weighing about 3.5 kg each were used. As the glucocorticoid-induced rabbit osteonecrosis model [1], methylprednisolone (MP) 20 mg/kg was injected into a gluteus muscle only once in 15 rabbits of MP+/TAU− group. In 15 animals of MP+/TAU+ group, after MP injection into a gluteus muscle, taurine 100 mg/kg was injected via an auricular vein for 5 continuous days. A control group was also prepared in which physiological saline 3 mL was injected into a gluteus muscle in 15 rabbits (MP−/TAU− group). The animals in all of

the groups were sacrificed 2 weeks later with thiopental sodium (NIPRO ES Pharma, Osaka, Japan) delivered by rapid injection via an auricular vein. The bilateral femora were then quickly resected. After fixation of the resected femurs in 10% neutral buffered formalin, decalcification was done with formic acid, and paraffin embedded specimens were cut into 4 μm thick sections with a microtome. This study was conducted in accordance with all guidelines of the Animal Research Committee of Kanazawa Medical University (#2018-13; approval date: 1 April 2020).
