Osteochondrosis is an orthopedic developmental disease that affects subchondral bone and articular cartilage in humans and domestic animals, resulting in lameness and joint effusion. Here, we compared the molecular compositions of cartilage from healthy and osteochondrotic equine metacarpophalangeal joints to investigate the pathogenic processes of the disease. This comparison was carried out using an SP3-label-free proteomics workflow, analyzing the differences in protein abundance. Furthermore, mass spectrometry imaging (MSI) was employed for spatially resolved lipid analysis, providing a deeper understanding of osteochondrosis pathogenesis through molecular pathway analysis. Lipid readouts showed increased phosphatidylcholine (PC) lipid species and a downregulation of sphingomyelin (SM) lipids in osteochondrosis biopsies compared to healthy cartilage. Furthermore, spatial analysis of lipids revealed a higher presence of PC lipids in the superficial layer of the cartilage compared with the deep layer. Osteochondrosis-downregulated proteins were mainly involved in extracellular matrix (ECM) organization, protein folding, and hydroxylation, highlighting the importance of ECM imbalance in the osteochondrosis development. Protein-metabolite integration analysis reported a downregulation of glycolysis in the osteochondrosis group, which might lead to chondrocyte hypertrophy and ECM degradation. Our work provides novel insights into the underlying mechanisms associated with the development of osteochondrosis.
Kuik et al. (Sun,) studied this question.