sdRNA-D43 derived from small nucleolar RNA snoRD43 improves chondrocyte senescence and osteoarthritis progression by negatively regulating PINK1/Parkin-mediated mitophagy pathway via dual-targeting NRF1 and WIPI2

Chondrocyte senescence play an essential role in osteoarthritis (OA) progression. Recent studies have shown that snoRNA-derived RNA fragments (sdRNAs) are novel regulators of post-transcriptional gene expression. However, the expression profiles and their role in post-transcriptional gene regulation in chondrocyte senescence and OA progression is unknown. Here, we determined sdRNAs expression profile and explored sdRNA-D43 role in OA and its mechanism. We used qPCR arrays to determine sdRNAs expression in the chondrocytes of areas undamaged and damaged of the three knee OA samples. SdRNA-D43 expression was determined using quantitative reverse transcription-polymerase chain reaction and in situ hybridization. Then, bioinformatics analysis was conducted on the target genes that might be silenced by sdRNA-D43. Primary chondrocytes of damaged regions of knee OA samples were transfected with a sdRNA-D43 inhibitor or mimic to determine their functions, including in relation to mitophagy and chondrocyte senescence. Argonaute2-RNA immunoprecipitation and luciferase reporter assays were conducted to determine the target gene of sdRNA-D43. In a rat OA model induced by monosodium iodoacetate, adeno-associated virus sh-rat-sdRNA-D43 was injected into the knee joint cavity to assess its in vivo effects. sdRNA-D43 expression were upregulated in damaged areas of knee OA cartilage with increased senescent chondrocytes. sdRNA-D43 inhibited mitophagy and promoted chondrocytes senescence during OA progression. Mechanistically, sdRNA-D43 silenced the expression of both NRF1 and WIPI2 by binding to their 3′-UTR in an Argonaute2‑dependent manner, which inhibited PINK1/Parkin-mediated pathway. Additionally, injection of AAV-sh-sdRNA-D43 alleviated the progression of OA in a monosodium iodoacetate-induced rat model. Our results reveal an important role for a novel sdRNA-D43 in OA progression. sdRNA-D43 improves chondrocyte senescence by negatively regulating PINK1/Parkin-mediated mitophagy pathway via dual-targeting NRF1 and WIPI2, which provide a potential therapeutic strategy for OA treatment.