Gene therapy for meniscal injury: Enhanced synthesis of proteoglycan and collagen by meniscal cells transduced with a TGFβ₁ gene

Objective: To determine whether meniscal cells can express a TGFβ₁ transgene delivered by a retroviral vector, and respond to the gene product by increasing matrix synthesis. Methods: Monolayer cultures of human and canine meniscal cells were infected with retroviruses carrying either a human TGFβ₁ cDNA or marker genes. Conditioned media were assayed for the presence of TGFβ₁. Biosynthesis assays using radiolabeled precursors were employed to determine the effects of the transgenes on the synthesis of proteoglycan, collagen and noncollagenous proteins. Collagen phenotyping was performed by SDS-PAGE. Results: Media conditioned by canine and human meniscal cells transduced with the TGFβ₁ gene, accumulated several nanograms/10⁶ cells of TGFβ₁ during a 48 h incubation. Media conditioned by control cells contained very little TGFβ₁. Transduction with the TGFβ₁ gene, but not marker genes, increased the synthesis of collagen and proteoglycan by 8-15-fold. The synthesis of noncollagenous proteins was enhanced more modestly. Monolayers of meniscal cells synthesized types I, III, V and VI collagen. The TGFβ₁ gene increased the synthesis of all types of collagen without altering the ratios between them. Conclusions: Meniscal cells are readily transduced by retroviral vectors and respond to the transfer of a TGFβ₁ cDNA by greatly increasing matrix synthesis. These findings encourage the further development of genetic approaches to the healing of meniscal lesions. (C) 2000 OsteoArthritis Research Society International.