Objective. To deliver and overexpress the hsp70 gene in cultured chondrocytes to investigate its effect on nitric oxide (NO)-induced apoptosis of chondrocytes.Methods. Primary chondrocyte cultures were established from rabbit joints. The cells were transduced with an empty adenovirus vector (Ax1w) or an adenovirus vector harboring the hsp70 E-tag fusion gene (AxSHEwt Degradation of articular cartilage, the major component of a joint, causes serious dysfunction of joints. Osteoarthritis (OA) is associated with degeneration of articular cartilage, but its pathogenesis has not yet been fully elucidated. Various biologic and chemical stress factors are thought to be involved in the occurrence and progression of OA, including mechanical stress, inflammatory cytokines such as interleukin-1 (IL-1) and tumor necrosis factor ␣, and reactive oxygen species (ROS) such as nitric oxide (NO). Chondrocytes are responsible for the maintenance of articular cartilage. Reduced cartilage cellularity has been postulated to play a role in the pathogenesis of OA (1,2), and the reduction in cellularity in human OA cartilage is partly attributable to apoptosis, i.e., programmed cell death. Recent studies have shown apoptosis of articular chondrocytes in OA in humans and in experimental animals (3,4), which implies the importance of apoptosis in the progression of the pathology of OA. Thus, apoptosis has attracted the attention of researchers as a potential etiologic factor in OA progression (5). If apoptosis of OA chondrocytes could be controlled, the implications of apoptosis in OA pathogenesis would become clearer, and the suppression method would suggest a novel therapeutic intervention against OA.One of the major cellular responses to stress involves synthesis of a set of highly conserved proteins, called heat-shock proteins (HSPs), during a process referred to as the stress response. In mammalian systems, HSPs include proteins with molecular weights of 110, 90, 70, 60, 40, and 27 kd. Some HSP members are constitutively expressed, and the expression levels increase in response to stress, while others are induced after exposure to stress. HSPs not only protect cells from stress-induced damage, but also facilitate the recovery of cells from the damage by binding to degraded or misfolded polypeptides (6-8). The inducible Hsp70 is a major HSP, and its expression is augmented in OA
