Copper-Sensitive Metabolic Stress in IL-1β-Induced Dysfunction of Tendon Progenitor Cells: An In Vitro and Transcriptomic Study

Tendinopathy is a complex disorder involving inflammation, oxidative stress, extracellular matrix damage, and changes in cellular metabolism. Cuproptosis is a type of regulated cell death that depends on copper and is associated with mitochondrial protein lipoylation and proteotoxic stress. This study investigated whether IL-1β-induced dysfunction of tendon progenitor cells (TPCs) is accompanied by changes in cuproptosis-associated genes and whether pharmacological modulation of copper availability alters this phenotype. Rat TPCs were stimulated with IL-1β, exposed to copper chloride (CuCl2) and the copper ionophore elesclomol (ES), and cotreated with the copper chelator tetrathiomolybdate (TTM). Cellular metabolic activity, gene expression, and reactive oxygen species (ROS) production were assessed. Bulk RNA-sequencing data from IL-1β-treated rat TPCs (GSE253913) and single-cell RNA-sequencing data from cultured human tendon-derived progenitor cells (GSE150482) were analyzed. In rats, transcriptomic analysis showed mainly an inflammatory response to IL-1β, with only slight changes in genes associated with copper and mitochondrial functions. IL-1β decreased TPC metabolic activity and the expression of tenogenic markers such as Scx, Col1a1, and Col3a1, while it increased inflammatory and catabolic markers, ROS production, and the expression of Dld and Lipt1. TTM attenuated these effects, restoring metabolic activity and some tenogenic markers, and reducing ROS, Dld, and Lipt1 levels. Exposure to ES + Cu triggered a TTM-sensitive phenotype characterized by reduced metabolic activity, decreased expression of tenogenic genes, increased ROS levels, and altered expression of cuproptosis-related genes. The human single-cell dataset analysis also revealed condition-dependent changes in mitochondrial lipoylation genes, including DLAT and DLST. Overall, these findings suggest that inflammatory TPC dysfunction is linked to copper-sensitive mitochondrial stress and gene changes related to cuproptosis pathways.