Identification and functional validation of <i>ACSL1</i> as a biomarker regulating ferroptosis in nucleus pulposus cell

Intervertebral disc degeneration (IVDD) is a prevalent musculoskeletal disorder characterized by the deterioration of nucleus pulposus (NP) cells, leading to significant impairments in patients' quality of life. Elucidating the molecular mechanisms underlying IVDD is essential for developing effective therapeutic strategies. In this study, we utilized weighted gene co-expression network analysis to identify key module eigengenes (MEs) from the GSE124272 dataset, combined with differential gene expression analysis to pinpoint differentially expressed genes (DEGs). Functional enrichment analysis revealed that MEs were primarily associated with lipid metabolism and immune response, while DEGs were enriched in immune response and cell proliferation pathways. By integrating MEs, DEGs, and ferroptosis-related genes, we identified six hub genes (acyl-CoA synthetase long-chain family member 1 [ACSL1], BACH1, CBS, CP, AKR1C1, and AKR1C3). Consensus clustering analysis classified samples into two immune-related subgroups, C1 and C2, with single-sample gene set enrichment analysis demonstrating distinct immune scores between the subgroups. Notably, ACSL1 showed the strongest correlation with immune cell infiltration and was significantly up-regulated in the C1 subgroup, which exhibited higher immune scores. In vitro experiments confirmed elevated ACSL1 expression in an IL-1β-induced degenerative NP cell model. Silencing ACSL1 improved cell viability, reduced apoptosis, and restored mitochondrial membrane potential, alongside significant changes in intracellular Fe2+, malondialdehyde, and glutathione levels. In vivo experiments further validated increased ACSL1 expression in intervertebral disc tissues of IVDD rats. Collectively, these findings highlight ACSL1 as a potential biomarker for the early diagnosis of IVDD and a promising therapeutic target.