Changes in the chondrocyte and extracellular matrix proteome during post-natal mouse cartilage development
Wilson, R and Readhead, EL and Brachvogel, B and Angelucci, C and Zivkovic, S and Gordon, L and Bernardo, BC and Stermann, J and Sekiguchi, K and Gorman, JJ and Bateman, JF, Changes in the chondrocyte and extracellular matrix proteome during post-natal mouse cartilage development, Molecular and Cellular Proteomics, 11, (1) Article M111.014159. ISSN 1535-9476 (2011) [Refereed Article]
Skeletal growth by endochondral ossification involves tightly coordinated chondrocyte differentiation that creates reserve, proliferating, prehypertrophic and hypertrophic cartilage zones in the growth plate. Many human skeletal disorders result from mutations in cartilage extracellular matrix (ECM) components that compromise both ECM architecture and chondrocyte function. Understanding normal cartilage development, composition and structure is therefore vital to unravel these disease mechanisms. To study this intricate process in vivo by proteomics, we analyzed mouse femoral head cartilage at developmental stages enriched in either immature chondrocytes or maturing/hypertrophic chondrocytes (post-natal days P3 and P21, respectively). Using LTQ-Orbitrap tandem mass spectrometry we identified 703 cartilage proteins. Differentially abundant proteins (q < 0.01) included prototypic markers for both early and late chondrocyte differentiation (epiphycan and collagen X, respectively) and novel ECM and cell adhesion proteins with no previously-described roles in cartilage development (tenascin X, vitrin, Urb, emilin-1 and the sushi repeat-containing proteins SRPX and SRPX2). Meta-analysis of cartilage development in vivo and an in vitro chondrocyte culture model (Wilson et al (2010)
Mol. Cell. Proteomics 9:6 1296–1313) identified components involved in both systems, such as Urb, and components with specific roles in vivo, including vitrin and cartilage intermediate layer protein-2 (CILP-2). Immunolocalization of Urb, vitrin and CILP-2 indicated specific roles at different maturation stages. In addition to ECM-related changes, we provide the first biochemical evidence of changing endoplasmic reticulum function during cartilage development. While the multifunctional chaperone BiP was not differentially expressed, enzymes and chaperones required specifically for collagen biosynthesis, such as the prolyl 3-hydroxylase 1, cartilage associated protein and peptidyl prolyl cis-trans isomerase B complex, were down-regulated during maturation. Conversely, the lumenal proteins calumenin, reticulocalbin-1 and reticulocalbin-2 were significantly increased, signifying a shift towards calcium-binding functions. This first proteomic analysis of cartilage development in vivo reveals the breadth of protein expression changes during chondrocyte maturation and ECM remodeling in the mouse femoral head.