Nayan Yi, Muyun Wu, Xiaojie Ma, Yuhan Xie, Heng Sun, Yuxi Zhang, Xing Cui
Myeloma-derived exosomal circ_0002724 promotes osteoclast activation and bone resorption and is associated with regulation of the miR-4753-3p/IFIT1/RANK network. These findings provide new insights into exosome-mediated tumor-bone microenvironment communication and suggest circ_0002724 as a potential biomarker and candidate therapeutic target for MBD.
BACKGROUND: Myeloma bone disease (MBD) is driven by excessive osteoclast activation and progressive bone destruction, but the role of exosomal circular RNAs (circRNAs) from myeloma cells remains unclear.
METHODS: Exosomes from U266 and MM1S cells were isolated and used to treat THP-1 cells. Osteoclast differentiation was assessed by TRAP staining and bone resorption assay. circRNA sequencing of U266 exosomes and MBD patient blood was performed to identify overlapping circRNAs. A ceRNA network was constructed using circBank and miRTarBase, combined with single-cell RNA-seq (GSE271107) to prioritize candidate target genes. Functional experiments included circ_0002724 knockdown/overexpression in U266 cells, exosomal transfer, TRAP, bone resorption, qRT-PCR, RNA-FISH/IF, dual-luciferase reporter assay, and immunohistochemistry of patient bone marrow biopsies.
RESULTS: U266-derived exosomes exhibited stronger osteoclast-inducing activity than MM1S-derived exosomes. Intersection analysis identified 14 common circRNAs, among which circ_0002724 showed the highest predicted miRNA-binding capacity and was significantly upregulated in THP-1 cells after exosome treatment. A circ_0002724-associated regulatory network identified miR-4753-3p, IFIT1, and RANK as potential downstream components. Single-cell analysis revealed that IFIT1 was highly expressed in MM osteoclast precursor cells and increased during osteoclast differentiation. Exosomal circ_0002724 was internalized by THP-1 cells; circ_0002724 knockdown reduced, whereas overexpression enhanced, TRAP-positive osteoclast formation and bone resorption activity, accompanied by altered RANK and IFIT1 expression. Dual-luciferase reporter assays supported the interactions between circ_0002724, miR-4753-3p, RANK, and IFIT1. Immunohistochemical analysis of patient biopsies demonstrated positive associations of circ_0002724, RANK, and IFIT1 with MBD severity.
CONCLUSIONS: Myeloma-derived exosomal circ_0002724 promotes osteoclast activation and bone resorption and is associated with regulation of the miR-4753-3p/IFIT1/RANK network. These findings provide new insights into exosome-mediated tumor-bone microenvironment communication and suggest circ_0002724 as a potential biomarker and candidate therapeutic target for MBD.