062 Application of gene therapy to tendon healing: modification of tenocytes with exogeneous pdgf and vegf genes to promote collagen production

Abstract

Purpose: Gene therapy provides a useful method to enhance wound healing, but it has not been attempted in healing of wounds in flexor tendons in the hands, which inherently lack sufficient intrinsic healing capacity. To explore the potential of application of gene therapy to tendon wound healing, we genetically modified tenocytes with the platelet-derived growth factor-B (PDGF-B) and the vascular endothelial growth factor (VEGF) gene and investigated the expression of the genes for collagen production in an in vitro model of the proliferating tenocytes. Method: Tenocytes were obtained from cultures of rat intrasynovial tendons and randomly distributed to 34 dishes. The tenocytes in dishes in two experimental groups (n = 9, each group) were treated for 12 hours with the plasmid containing the PDGF-B cDNA or the VEGF cDNA and were then cultured for 5 days; tenocytes in the other eight dished received sham vector and the tenocytes in the control dishes (n = 8) did not receive the exogenous gene. Efficiency of the gene transfer was evaluated by detection of the presence of the transgene in the tenocytes by reverse transcription polymerase chain reactions (RT-PCR). Levels of expression of type I and III collagen, and TGF-β genes were determined by quantitative analysis of the products of RT-PCR. Results: Expression of the type I collagen gene was significantly increased by transfer of the exogenous PFDGF gene to the tenocytes (p < 0.001). Transfer of the PDGF-B gene did not affect the expression of TGF-β and the type III collagen genes significantly. Expression of TGF-β gene increased significantly in the cells treated with exogenous VEGF cDNA (p = 0.039). Expression of type I and III collagen genes by tenocytes was minimally affected by transfer of the VEGF gene to the tenocytes and was significantly weaker than that stimulated by PDGF-B gene therapy (p = 0.001). Efficient gene transfer was confirmed by the presence of the PDGF-B gene or the VEGF gene in the tenocytes receiving the transferred genes. Conclusions: Transfer of exogenous PDGF-B gene significantly enhances expression of the type I collagen gene of the tenocytes. Transfer of exogenous VEGF gene has very limited effects on promotion of collagen production in the proliferating tenocytes. In contrast, transfer of the VEGF gene significantly increases expression of the TGF-β gene. This study suggests that transfer of the PDGF-B gene may offer a novel way of effectively promoting healing of intrasynovial flexor tendons. VEGF gene therapy is not as beneficial as PDGF-B gene therapy to tendon healing and may increase activities of TGF-β that are associated with adhesion formations.