Yangming Zhu, Yingjia Zhu, Peijian Tong, Feng Cheng
This study identified the key cell populations driving OA progression in the synovium and IFP, and screened four novel diagnostic biomarkers and three potential drug targets for OA, with their expression verified in an in vitro OA model. Lumacaftor and naldemedine were found to have multi-target binding activity to OA core drug targets. These findings deepen the understanding of OA's molecular mechanisms mediated by the synovium and IFP, and provide valuable experimental evidence for OA's early diagnosis and the development of targeted therapeutic drugs, including old drug repurposing.
OBJECTIVES: Osteoarthritis (OA) is a chronic degenerative joint disease with great challenges in early diagnosis and treatment, and the synovium and infrapatellar fat pad (IFP) play a synergistic role in its pathological progression. This study aimed to identify OA's key pathogenic cell populations, causal genes, diagnostic biomarkers and potential drug targets from the synovium and IFP via multi-omics analysis and experimental validation, and to evaluate the binding affinity between candidate drug targets and small-molecule compounds by molecular docking, so as to provide new molecular basis and therapeutic strategies for OA.
METHODS: Single-cell RNA sequencing (scRNA-seq) data of the synovial and IFP tissues (GSE216651) were obtained from the GEO database, and single-cell bioinformatics analyses (clustering, annotation, trajectory and cell-cell interaction analysis) were performed to screen OA-related key cell populations. Two-sample Mendelian randomization (MR) analysis was conducted by integrating OA-GWAS and eQTLGen data to identify OA-causal differentially expressed genes (DEGs), with sensitivity analyses verifying result robustness. PPI network, GO and KEGG analyses were used to elucidate the biological functions of core DEGs. The CeRNA network and DSigDB database were applied to screen diagnostic genes and drug target genes, respectively. An in vitro OA model was established by IL-1α-induced C28/i2 chondrocytes, and qRT-PCR validated the expression of core genes. Virtual screening from FDA database and molecular docking by AutoDock Vina were performed to evaluate the binding affinity of target proteins and candidate compounds. All statistical analyses were conducted with R 4.3, and P < 0.05 was statistically significant.
RESULTS: Four key OA-associated cell populations (fibroblasts, monocytes, stromal cells, macrophages) were identified, with macrophages specific to the OA group. MR analysis identified 18 OA-causal core DEGs, among which LRRN3 and PTGDS were expressed in the three major cell types. These DEGs were significantly enriched in OA-related processes/pathways such as lipid metabolism and Ras signaling pathway. Four diagnostic genes (GRAMD4, IL15, PITPNM1, SAMD12) and three core drug target genes (SAMD12, PTGDS, INSR) were screened out. qRT-PCR showed INSR was downregulated in the OA model, while the other five core genes were upregulated, consistent with MR results. Molecular docking revealed favorable binding affinity between the three target proteins and FDA-approved compounds; notably, lumacaftor and naldemedine exhibited high binding affinity to two of the three core drug targets, showing multi-target potential for OA treatment.
CONCLUSION: This study identified the key cell populations driving OA progression in the synovium and IFP, and screened four novel diagnostic biomarkers and three potential drug targets for OA, with their expression verified in an in vitro OA model. Lumacaftor and naldemedine were found to have multi-target binding activity to OA core drug targets. These findings deepen the understanding of OA's molecular mechanisms mediated by the synovium and IFP, and provide valuable experimental evidence for OA's early diagnosis and the development of targeted therapeutic drugs, including old drug repurposing.