Lineage plasticity and signal dysregulation define the cellular trajectory of osteoarthritis progression.

This study aims to explore the plastic changes in cell lineages during the progression of osteoarthritis (OA) and their relationship with dysregulation of signaling pathways and provide new molecular targets for precise treatment. Single-cell RNA sequencing (scRNA-seq) technology was utilized to perform high-resolution cell lineage analysis of OA patients. The mappings of distinct cell subpopulations were systematically constructed and revealed the changes in key cell types and their transformation trajectories throughout the progression of OA. Furthermore, KEGG and GO enrichment and pseudotime trajectory analysis were applied to elucidate the functional reprogramming of different cell types and the dynamic imbalance of their signaling networks in OA. Additionally, in vitro experiments were conducted to validate the biological functions of candidate genes in OA. Articular cartilage showed a transcriptional cellular heterogeneity in OA by scRNA-seq analysis; the annotated PreFC, FC, and PreHTC subsets accounted for the main part of OA samples. PreFC cells revealed transcription, signaling, and metabolic reprogramming in OA; pseudotime trajectory found that PreFC transformed to FC cells under the condition of hypoxia and metabolic reprogramming, while fibrosis and ECM degradation pathways showed intense upregulation in preHTC evolved from PreFC cells. HIF1A and ANGPTL4 were identified as key molecular regulators of OA progression, contributing to ECM degradation, inflammation, and apoptosis in chondrocytes, as confirmed through functional validation. The cellular trajectories of OA show significant plasticity changes which are influenced by the dysregulation of multiple signaling pathways. This research provides new insights into the pathological process of OA and offers potential targets for therapeutic strategies targeting these abnormal mechanisms.