3D-printed TCP-HA scaffolds delivering MicroRNA-302a-3p improve bone regeneration in a mouse calvarial model

OBJECTIVE: To demonstrate that hydroxyapatite nanoparticles modified with 3-aminopropyltriethoxysilane (HA-NPs-APTES) carrying microRNA-302a-3p (miR) within a 3D-printed tricalcium phosphate/hydroxyapatite (TCP/HA) scaffold can increase healing of a critical-sized bone defect. MATERIALS AND METHODS: 3D-printed TCP/HA scaffolds were modified with HA-NPs-APTES by two methods (M1, M2). Particle dispersion was visualized by fluorescence microscopy. Biocompatibility was tested by resazurin assay. Delivery of miR and osteogenic gene expression were evaluated by qPCR. After selecting the best method (M2), scaffolds and scaffolds+HA-NPs-APTES with or without miR were implanted in 4 mm mouse calvarial defects (n=4 per group). After 2, 4 and 6 weeks, bone regeneration was evaluated by microCT and histology. RESULTS: Both M1 and M2 were biocompatible with cell adhesion. M2 showed significantly higher miR delivery, resulting in COUP-TFII downregulation and RUNX2 upregulation. In vivo, M2 scaffolds increased BV/TV and reduced unfilled pore numbers at all time points; histomorphometry showed earlier central new bone formation with HA-NPs-APTES-miR scaffolds. CONCLUSION: TCP/HA scaffolds modified with HA-NPs-APTES facilitate miR delivery and enhance bone regeneration in a mouse calvarial model.