Regulatory Effect and Mechanism of Tanshinone I on Cell Apoptosis in Steroid-Induced Osteonecrosis of the Femoral Head.

Steroid-induced osteonecrosis of the femoral head (SIONFH) is a debilitating orthopedic condition. This study investigated the mechanism of Tanshinone I (TsI) in SIONFH modulating apoptosis in SIONFH via the PI3K/AKT/mTOR pathway. A SIONFH rat model was treated with TsI and a PI3K activator. Bone mineral density (BMD), bone volume/total volume (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), and trabecular separation (Tb.Sp) were determined by microCT. Empty lacunae count, Osteopontin, and apoptosis of the femoral head tissues were assessed. Levels of Bax, cleaved-caspase-3, Bcl-2, and AKT, PI3K, and mTOR phosphorylation in femoral head tissues were determined by Western blot. SIONFH rats exhibited decreased BMD, BV/TV, Tb.N, and Tb.Th, increased Tb.Sp, reduced Osteopontin-positive cells, increased empty lacunae rate, and TUNEL and Osteopontin co-positive cells, elevated Bax and cleaved-caspase-3 protein levels, and diminished Bcl-2 protein expression. TsI promoted osteogenesis, attenuated SIONFH, and reduced apoptosis in SIONFH rats. TsI inhibited AKT, PI3K, and mTOR phosphorylation levels in the femoral head tissues of SIONFH rats, thereby repressing the PI3K/AKT/mTOR pathway activation. Activating the PI3K/AKT/mTOR pathway partially reversed TsI's effect in rats. Collectively, TsI limited the PI3K/AKT/mTOR pathway activation to reduce osteocyte apoptosis in SIONFH rats, which provided potential therapeutic insights for SIONFH treatment.