LIPUS promotes osteogenesis via the mcirc_9393-miR-217/326-SIRT1 axis in porous Ti6Al4V scaffolds

The repair of critical-sized bone defects remains a significant clinical challenge. Low-intensity pulsed ultrasound (LIPUS) in conjunction with scaffolds has emerged as a promising therapeutic approach. However, the osteogenic mechanisms of LIPUS combined with porous scaffolds remain incompletely understood, and the osteogenic efficacy requires further enhancement. Here, we investigate the molecular mechanisms underlying mcirc_9393-mediated osteoblastic differentiation and osteogenesis promoted by LIPUS in Ti64 scaffolds. We demonstrate that LIPUS significantly upregulates mcirc_9393 expression, which is critical for LIPUS-induced osteoblast differentiation within Ti64 scaffolds. Mechanistically, mcirc_9393 and miR-217/326, as well as miR-217/326 and sirtuin1 (SIRT1), competitively bind to overlapping miRNA response elements (MREs). Functionally, LIPUS-driven mcirc_9393 upregulation acts as a sponge for miR-217 and miR-326, relieving their inhibitory effects on SIRT1 and promoting osteoblast differentiation. In vivo, mcirc_9393 overexpression enhances scaffold-mediated bone formation under LIPUS stimulation. These findings reveal that LIPUS augments osteogenesis in Ti64 scaffolds via the mcirc_9393/miR-217-326/SIRT1 axis and highlight mcirc_9393 as a potential therapeutic target for improving bone regeneration in LIPUS-scaffold combinatorial therapies.