Comparison of differential protein expression of the marginal transitional zone in neonatal and weanling-aged foals

The marginal transitional zone (MTZ) is peripherally located within the diarthrodial joint, and represents the junction of synovium, fibrous joint capsule, articular cartilage, periosteum, and bone. The purpose of this study is to characterize age-related differences in protein expression of matrix and molecular regulators in the marginal transitional zone of neonatal and weanling foals. Several families of proteins with known roles in cartilage and bone development are investigated, including matrix molecules, members of the Wnt signaling family, apoptotic factors and paracrine cell signaling molecules. Our results demonstrate differential protein expression in the marginal transitional zone from the lateral femoral trochlear ridge of neonatal and weanling foals. Protein expression of several paracrine signaling molecules (Ihh, PTHrP, PDGF, VEGF, β-catenin, cytochrome C) within MTZ cartilage is higher in weanling-aged foals. Collagen type II and lubricin expression is similarly greater in weanling-aged foals, while matrix metalloproteinases are lower, likely reflecting the remodeling that occurs during cartilage development as increasing forces are placed on cartilage.