Hsa_circ_0101645 contributes to excessive autophagy and apoptosis in intervertebral disc degeneration by acting as a miR-1304-5p sponge modulating BNIP3 expression.

BACKGROUND: Intervertebral disc (IVD) degeneration (IVDD) is the pathological foundation and principal cause for degenerative spine related diseases. Currently, its molecular pathogenesis and reliable biomarkers remain poorly understood. This study intends to elucidate the potential molecular mechanisms of circular RNAs (circRNAs) in IVDD, and to identify novel targeted therapeutic strategies. METHODS: Differentially expressed circRNAs (DE-circRNAs) were obtained by a secondary analysis of the IVDD-related dataset GSE67566, followed by enrichment analysis of their host genes. Both in vitro mechanical loading-induced and in vivo tail suspension-induced models were applied to validate the functions of hsa_circ_0101645, miRNA-1304-05p, and BCL2 Interacting Protein 3 (BNIP3) in IVDD. The competing endogenous RNA (ceRNA) mechanism involving hsa_circ_0101645/miR-1304-5p/BNIP3 was authenticated using dual luciferase reporter genes, Argonaute2-RNA binding protein immunoprecipitation, and RNA-RNA pull down. RESULTS: In the bioinformatics, there were 354 significantly down-regulated and 282 up-regulated DE-circRNAs in IVDD. The host genes of these circRNAs were mainly enriched in cell morphogenesis, autophagy, and apoptosis. In clinical samples, hsa_circ_0101645 in DE-circRNAs was markedly overexpressed in endplate chondrocytes (EPC) derived from IVDD patients and was predominantly localized in the cytoplasm. In vitro, overexpression of hsa_circ_0101645 and BNIP3, or knockdown of miR-1304-5p, dramatically diminished EPC viability and enlarged apoptosis and autophagic flux. In vivo, sa_circ_0101645 knockdown alleviated structural collapse and tissue lesions in the cartilage endplates, nucleus pulposus and annulus fibrosus of the IVD. Mechanistically, Hsa_circ_0101645 upregulated BNIP3 expression by serving as miR-1304-5p sponge. CONCLUSIONS: Hsa_circ_0101645 service as ceRNA that facilitates IVDD process by mediating proliferation, apoptosis, and excessive autophagy of CEP via the miR-1304-5p/BNIP3 axis. These findings suggest that hsa_circ_0101645 represents a promising molecular target for IVDD therapy.