Several studies have demonstrated that exosomes (Exos) are involved in the regulation of macrophage polarization and osteoclast differentiation. However, the characteristics as well as roles of exosomes from human periodontal ligament cells (hPDLCs-Exos) in M1/M2 macrophage polarization and osteoclast differentiation remain unclear. Here, periodontal ligament cells were successfully extracted by method of improved Type-I collagen enzyme digestion. hPDLCs-Exos were extracted by ultracentrifugation. hPDLCs-Exos were identified by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA) and western blotting (WB). Osteoclast differentiation was evaluated by real-time quantitative polymerase chain reaction (RT-qPCR), WB and tartrate-resistant acid phosphatase (TRAP) staining. M1/M2 macrophage polarization were evaluated by RT-qPCR and WB. The results showed hPDLCs-Exos promoted osteoclast differentiation and M2 macrophage polarization, but inhibited M1 macrophage polarization. Moreover, M1 macrophages inhibited osteoclast differentiation, whereas M2 macrophages promoted osteoclast differentiation. It has shown that hPDLCs-Exos promoted osteoclast differentiation by inhibiting M1 and promoting M2 macrophage polarization.

Purpose: MicroRNA-34c-5p (miR-34c-5p) plays a pivotal role in bone remodeling, yet its therapeutic potential is hindered by challenges such as instability, limited cellular internalization, and immune responses. This study was aimed at developing innovative scaffolds capable of efficiently delivering microRNAs (miRNAs), specifically miR-34c-5p. Methods: Chitosan (CS)/sodium tripolyphosphate (STPP)/sodium alginate (SA) scaffolds, referred to as CTS scaffolds, were synthesized at a specific ratio and characterized using dynamic light scattering and scanning electron microscopy (SEM). Cytotoxicity assessments were conducted through cell activity staining. The loading capacity and releasing performance of miRNAs were quantified using spectrophotometry. Subsequently, the in vivo efficacy of miR-34c-5p Agomir/Antagomir in regulating bone repair was evaluated in the rabbit cranial bone defect model, with micro-CT scanning and histological analysis conducted at 4, 8, and 12 weeks. Results: CTS scaffolds with a composition ratio of 1:0.2:0.1 were successfully synthesized, exhibiting a mean particle size of 360.1 nm. SEM revealed scaffolds had the porous spongy structure. Cell activity staining confirmed the excellent biocompatibility of the CTS scaffolds. Spectrophotometry demonstrated miR-34c-5p Antagomir were continually released, reaching 91.41% within 30 days. Differential new bone formation was observed between the miR-34c-5p Agomir and Antagomir groups. Micro-CT imaging and histological staining revealed varying degrees of bone regeneration, with notable improvements in the miR-34c-5p Antagomir group. Conclusion: CTS scaffolds with a composition ratio of 1:0.2:0.1 demonstrate favorable biocompatibility and enable efficient loading and sustained release of miR-34c-5p Antagomir. The study suggests potential applications of miR-34c-5p Antagomir in promoting bone repair and highlights the promise of innovative scaffolds for therapeutic miRNAs administration in bone regeneration.