Intraarticular gene transfer of thrombospondin-1 suppresses the disease progression of experimental osteoarthritis

In osteoarthritis, angiogenesis, which occurs in the osteochondral junction and synovium, may accelerate inflammation and contribute to the severity of the disease. We used anterior cruciate ligament-transection (ACLT) to investigate the therapeutic effect of an angiogenesis inhibitor, thrombospondin-1 (TSP-1), in a rat model of osteoarthritis. Osteoarthritis was induced in Wistar rats in the knee of one hind leg. After ACLT, AdTSP-1 (adenoviral vector encoding mouse TSP-1) was intraarticularly injected into the knee joints. Transgene expression, angiogenesis, and inflammatory responses in the knee joints were examined. They were also assessed morphologically, radiographically, and histologically for manifestations of disease. The levels of TSP-1 peaked on day 3 and were substantially maintained for at least 9 days after AdTSP-1 infection. Adenovirus-mediated gene expression was detected in the synovial membrane and chondrocytes. TSP-1 gene transfer induced transforming growth factor-β (TGF-β) production, but it reduced microvessel density, macrophage infiltration, and interleukin-1β (IL-1β) levels. Gross morphological and histopathological examinations revealed that rats treated with AdTSP-1 had less severe osteoarthritis than controls. In vivo adenovirus-mediated TSP-1 gene transfer significantly reduced microvessel density, inflammation, and suppressed the progression of osteoarthritis. This study provides potential applications of TSP-1 gene delivery for treating osteoarthritis.