Effect of Osteoblast-Derived Extracellular Vesicles on Osteosarcoma Cells’ Transcriptional Profile: Role of Shuttled miRNAs

Background/Objectives: Osteosarcoma is the most common primary malignant bone tumour, affecting children and young adults. Recent evidence suggests that extracellular vesicles (EVs), small membrane-bound nanoparticles released by all cell types, play a key role in intercellular communication within the tumour microenvironment. Therefore, we aimed to investigate the effects of osteoblast-derived EVs (OB-EVs) on osteosarcoma cell behaviour and to characterise the transcriptional and miRNA-mediated mechanisms underlying these effects. Methods: Phenotypic assays were performed to assess metabolic activity, proliferation, apoptosis, and invasion ability of human osteosarcoma cell lines after treatment with OB-EVs. Illumina-based RNAseq was conducted on RNA isolated from OB-EVs-treated cells, and qRT-PCR was assessed using commercially available TaqMan miRNA cards on RNA isolated from OB-EVs. Results: In U2OS cells, OB-EVs reduced metabolic activity (1.30-fold decrease, p = 0.0137) and proliferation (1.70-fold decrease, p = 0.017) while increasing apoptosis (1.15-fold increase, p = 0.014). In MG63, OB-EVs increased proliferation (4.9-fold increase, p = 0.020) without affecting tumour cell aggressiveness, while normal osteoblast behaviour was not affected by OB-EVs. MNNG/HOS cells treated with OB-EVs for 48 h showed substantial transcriptomic changes, with 296 differentially expressed genes (97 up- and 199 down-regulated in OB-EVs treated cells versus untreated cells), indicating a direct impact of OB-EVs on gene expression. Intriguingly, Gene Set Enrichment Analysis (GSEA) showed trends consistent with modulation of signalling pathways, including Wnt/β-catenin and NOTCH. Conversely, miRNA profiling of OB-EVs identified 13 highly expressed miRNA. Integration of transcriptomic and miRNA target prediction data highlighted convergent pathway-level signals, suggesting that OB-EVs may modulate tumour-associated regulatory networks. Conclusions: Taken together, these findings indicate that OB-EVs modulate osteosarcoma cell phenotype, with miRNA shuttling representing a potentially relevant contributing mechanism. The integrative analysis suggests that pathways associated with proliferation and cellular homeostasis, including Wnt/β-catenin signalling, may be involved, although further functional validation is required to confirm these mechanisms.