Expression and Immunolocalisation of "cartilage" Superficial Zone Proteoglycan (szp) in Tendon

INTRODUCTION Superficial zone proteoglycan (SZP) is a ~345 kDa proteoglycan that is synthesised by the superficial zone chondrocytes (but not chondrocytes from midand deep zones) of bovine articular cartilage and some of the surface lining cells of the synovium [1]. SZP has been demonstrated to be a multifunctional protein that has potential growth promoting and matrix-binding properties associated with the N-terminal domain. Lubricating and cytoprotective properties (provided by mucin-like domains) and matrix binding and aggregating properties are associated with the C-terminal domain. In addition, SZP has been shown to be homologous to the precursor protein of megakaryocyte stimulating factor (MSF) [2]. Immunohistochemical localisation studies reveal that SZP accumulates at the articular surface of cartilage. However, to date, there have been few studies examining expression/localisation of SZP in other musculoskeletel tissues, therefore the present work investigates SZP in both young and mature tendon.