TRIM21 silencing inhibits the apoptosis and expedites the osteogenic differentiation of dexamethasone‑induced MC3T3‑E1 cells by activating the Keap1/Nrf2 pathway

Steroid‑induced osteonecrosis of the femoral head (ONFH) is a serious complication caused by long‑term or excessive use of glucocorticoids. The present study aimed to ascertain the effects of tripartite motif‑containing protein 21 (TRIM21) on the process of steroid‑induced ONFH and its hidden action mechanism. TRIM21 expression in dexamethasone (Dex)‑treated mouse MC3T3‑E1 preosteoblast cells was examined using reverse transcription‑quantitative PCR and western blotting. The Cell Counting Kit‑8 (CCK‑8) method and lactate dehydrogenase release assay were used to respectively measure cell viability and injury. Flow cytometry analysis was used to assay cell apoptosis. Caspase 3 activity was evaluated using a specific assay, while alkaline phosphatase and Alizarin red S staining were used to evaluate osteogenesis. 2,7‑dichloro‑dihydrofluorescein diacetate fluorescence probe was used to estimate reactive oxygen species generation. Specific assay kits were used to appraise oxidative stress levels. In addition, the expression of apoptosis‑, osteogenic differentiation‑ and Kelch‑like ECH‑associated protein 1 (Keap1)/nuclear factor erythroid 2‑related factor 2 (Nrf2) signaling‑associated proteins was assessed using western blotting. In Nrf2 inhibitor (ML385)‑pretreated MC3T3‑E1 cells exposed to Dex, cell apoptosis, osteogenesis and oxidative stress were detected again as aforementioned. Results revealed that TRIM21 expression was raised in Dex‑induced MC3T3‑E1 cells and TRIM21 deletion improved the viability and osteogenic differentiation, whereas it hampered the oxidative stress and apoptosis in MC3T3‑E1 cells with Dex induction. In addition, silencing of TRIM21 activated Keap1/Nrf2 signaling. Moreover, ML385 partially abrogated the effects of TRIM21 depletion on the oxidative stress, apoptosis and osteogenic differentiation in MC3T3‑E1 cells exposed to Dex. In conclusion, TRIM21 silencing might activate Keap1/Nrf2 signaling to protect against steroid‑induced ONFH.