Expression of anchorin CII (cartilage annexin V) in human young, normal adult, and osteoarthritic cartilage

In its tissue-specific function as a collagen receptor of chondrocytes, car tilage annexin V (anchorin CII) occupies a key position in the organization of the cell-extracellular matrix (ECM) junction for the tissue. The genera l role of annexin V (Anx V) in other tissues suggests involvement in cellul ar secretory processes and in regulation of apoptosis. Immunohistochemical analysis of Anx V in growth plate cartilage, confirmed by in situ hybridiza tion, suggests that Anx V is prominently expressed and forms a major consti tuent of growth plate chondrocytes. Anx V epitopes are also located in the pericellular matrix of hypertrophic cartilage. In adult articular cartilage the expression is downregulated, with the highest levels of immunostaining found in the upper third of the articular cartilage layers and almost no a ntigen found in the deep layers. Osteoarthritic (OA) cartilage is character ized by a significant upregulation of message and protein throughout the en tire depth of the tissue, an accumulation of cytoplasmic annexin V epitopes , and a release of epitopes into the pericellular and interterritorial matr ix, in part co-localized with granular structures. Therefore, Anx V express ion and tissue distribution may serve as a histological marker for metaboli c alterations and for changes in the cellular phenotype associated with OA.