Acute TGFα drives OA-associated transcriptional and metabolic remodelling in primary chondrocytes

Articular cartilage degeneration is a hallmark of osteoarthritis (OA); however, underlying molecular mechanisms remain poorly understood. Transforming growth factor alpha (TGFα) and chondrocyte metabolism have been independently implicated in OA pathogenesis; in this study, we investigated whether TGFα affects chondrocyte metabolism.

Immature murine articular chondrocytes (iMACs) were isolated from 4-6-day-old CD1 mice and treated with TGFα or vehicle control (ddH2O) for 24-72 h. Global transcriptional changes were assessed at 48 h by bulk RNA sequencing (n = 4) followed by gene set enrichment analysis. Gene expression was validated by qPCR (n = 4). Mitochondrial mass and membrane potential were assessed using MitoTracker Green and JC-1 (n = 6), respectively. Seahorse XFe analysis assessed changes in cellular metabolism following TGFα treatment, in the presence and absence of OA synovial fluid (n = 4).

TGFα treatment led to differential expression of 1643 genes (1305 upregulated, 338 downregulated), with enrichment in processes related to Response to Reactive Oxygen Species, Glycolysis, and Inflammatory Response. TGFα increased the expression of genes involved in antioxidant defence/ROS production (Sod3, Prdx1, Ucp2, Nox4), mitochondrial quality control (Bnip3), metabolism (Ldha), and inflammation (Tlr4), while inducing depolarization of the mitochondrial membrane potential in chondrocytes. TGFα enhanced extracellular acidification rate (ECAR) in the presence of OA synovial fluid.

Acute TGFα exposure induces transcriptional changes associated with ROS, glycolysis, and inflammatory signalling. TGFα decreases mitochondrial membrane potential, while increasing glycolysis in the presence of OA synovial fluid, supporting a link between TGFα signalling and metabolic reprogramming.