Continuous Transforming Growth Factor β1 Secretion by Cell-Mediated Gene Therapy Maintains Chondrocyte Redifferentiation

One of the most important factors in the production of cartilage is transforming growth factor β1 (TGF-β1). To obtain sustained release of TGF-β1, a cell-mediated gene therapy technique was introduced. We infected chondrocytes with a retroviral vector carrying the TGF-β1 gene. The single clone derivative showed sustained TGF-β1 secretion. It also showed constitutive type II collagen expression. Whereas the TGF-β1 protein itself is unable to induce formation of cartilage in vivo, human chondrocytes engineered to express a retroviral vector encoding TGF-β1 showed cartilage formation in vivo when cells were injected into nude mice intradermally. These data suggest that cell-mediated gene therapy using TGF-β1 as a transgene would be a promising treatment for osteoarthritis.