Integrated analysis of bulk RNA and single-cell RNA sequencing data reveals potential biomarkers and immune infiltrates associated with N7-methylguanosine in osteoarthritis.

OBJECTIVE: The N7-methylguanosine (m7G) modification is known as a common post-transcriptional modification of RNA that has been found to be involved in the pathogenesis of various diseases. However, its role in osteoarthritis (OA) remains largely unknown. This study aimed to identify the genes associated with m7G modification in OA and further investigate their diagnostic value and immune infiltrates. METHODS: We constructed an OA risk model based on key m6A regulators using LASSO regression. Unsupervised clustering analysis was used to detect diverse m7G modification phenotypes and m7G gene clusters based on key m7G regulators in the 106 OA samples. We evaluated the features of the immune microenvironment between distinct risk groups, m7G modification phenotypes, and m7G gene clusters, using immune infiltration analysis. Single-cell analysis was performed to determine the relationship between the key m7G regulators and cartilage degeneration. Finally, in vitro and in vivo experiments were conducted to explore the potential roles of key m7G regulators in OA. RESULTS: Four key m7G regulators, including EIF1, JUND, NUDT16L1 , and NCBP1 , and two risk groups, m7G modification phenotypes, and m7G gene clusters were identified. A nomogram model constructed based on the key m7G regulators demonstrated its predictive role in the occurrence of OA. Moreover, the risk score of the patients in the high-risk group was higher than that of the patients in the low-risk group. Different immune infiltration characteristics were found among the risk groups, m7G modification phenotypes, and m7G gene clusters. Additionally, single-cell analysis confirmed ubiquitous expression of EIF1 and JUND across all chondrocyte subtypes. Furthermore, both genes were downregulated in OA cartilage, and ROC analysis demonstrated that EIF1 and JUND exhibited excellent performance in OA diagnosis. Finally, it was confirmed that inhibiting the expression of EIF1 and JUND induced upregulation of MMP13 and downregulation of collagen II. Further in vivo experiments indicated that suppression of EIF1 and JUND contributed to the progression of OA. CONCLUSION: Our study revealed four m7G regulators, including EIF1, JUND, NUDT16L1 , and NCBP1 , as novel biomarkers that may be associated with the immune infiltration during the progression of OA. Moreover, EIF1 and JUND may serve as potential therapeutic targets for preventing cartilage degeneration. However, further experiments are required to elucidate the molecular mechanisms underlying OA.