Low‐Intensity Pulsed Ultrasound Promotes Osteogenesis in Porous Titanium Alloys Through <scp>miR</scp> ‐1187/ <scp>BMP4</scp> Pathway

The repair of critical-sized bone defects remains a significant clinical challenge. Low-intensity pulsed ultrasound (LIPUS), in combination with porous titanium alloy (PTi) scaffolds, has emerged as a promising therapeutic strategy. However, its molecular mechanism remains unclear. This study aimed to investigate the role of bone morphogenetic protein 4 (BMP4) and microRNA-1187 (miR-1187) in LIPUS-mediated osteogenesis in PTi scaffolds. In vitro, the expression of BMP4 and miR-1187 in MC3T3-E1 cells following LIPUS stimulation was assessed using quantitative real-time PCR (RT-qPCR), western blotting, ELISA, alkaline phosphatase (ALP) activity assay, and staining techniques. A luciferase reporter assay confirmed BMP4 as a direct target of miR-1187. Functional studies demonstrated that BMP4 overexpression and miR-1187 inhibition promoted osteoblast differentiation, whereas BMP4 knockdown and miR-1187 overexpression suppressed osteogenesis. In vivo, a BMP4 knockdown rat model was established by si-BMP4 injection into mandibular defects and evaluated new bone formation using micro-CT and histological analyses. LIPUS stimulation significantly upregulated BMP4 expression, promoted new bone formation in PTi scaffolds, and partially rescued the inhibitory effects of BMP4 silencing. These findings establish BMP4 as a key regulator in LIPUS-enhanced osteogenesis via miR-1187 suppression. This mechanistic insight supports the combined use of LIPUS and PTi scaffolds for bone defect repair and highlights BMP4 as a potential therapeutic target to further enhance bone regeneration in LIPUS-stimulated scaffold therapies.