Lipidomics unravels lipid changes in osteoarthritis articular cartilage

Osteoarthritis (OA) is linked to disrupted lipid metabolism. We aimed to profile the lipid composition of human articular cartilage, investigate OA-associated lipidome changes, and explore biological effects. Lipidomic profiling and computational analyses were performed on human articular chondrocytes (hACs) from non-OA (n = 13) and OA (n = 14) hips. Lipid changes were confirmed in the destabilisation of the medial meniscus (DMM) mouse model. The effect of specific lipids was evaluated by in vitro supplementation and gene silencing. We identified 573 lipid species covering 11 lipid classes in hACs. OA and non-OA hACs showed distinct lipid profiles. Most ceramides and dihydroceramides were increased, while cholesteryl esters, diacylglycerols, triacylglycerols, sphingomyelins, hexosylceramides, and lactosylceramides were predominantly decreased in OA chondrocytes. Most upregulated lipids in OA contained C18:1, C20:4, or C22:4 side chains. Many downregulated lipids contained C18:2 or odd-chain C17:0. Lipid profiling of articular cartilage from the DMM mouse model paralleled changes in OA hACs, including odd-chain C17:0 reduction. Further analysis showed that deficiency in enzyme 2-hydroxyacyl-CoA lyase 1 (HACL1), responsible for odd-chain fatty acid synthesis, leads to accumulation of 2-hydroxy C18:0, precursor of C17:0, which results in a shift in hACs from an anabolic to a catabolic state. Our study maps the hAC lipid composition and highlights changes in lipid profiles associated with OA. Dysregulation of certain lipids, especially odd-chain fatty acids, linked to a deficiency in the enzyme HACL1, leads to pathological changes. This understanding opens potential avenues for therapies aimed at targeting lipid imbalances to slow down or treat OA.