Distribution of Superficial Zone Protein (szp) in Osteoarthritic Cartilage

INTRODUCTION: Superficial zone protein (SZP) is a 345 kD glycoprotein, which contains glycosaminoglycan chains (1). Immunohistochemical and biochemical studies have demonstrated that this molecule displays a highly restricted distribution in normal articular cartilage (2,3). It is present at the very surface of the cartilage in the lamina splendens. The molecule is synthesized by chondrocytes in the superficial zone, but not by chondrocytes in the middle or deep zones of normal articular cartilage. Recent studies have shown SZP is homologous to megakaryocyte stimulating factor (MSF) (4) and lubricin (5), which is the major lubricating glycoprotein in synovial fluid. Human mutations in SZP cause the disorder camptodactyly-arthropathy-coxa vara-pericarditis (6). Monoclonal antibodies to human SZP have been generated (7). In this study the monoclonal antibodies have been used to analyze the distribution of SZP in human articular cartilage recovered from osteoarthritic patients at the time of joint replacement surgery.