Tendon healing in vitro: genetic modification of tenocytes with exogenous PDGF gene and promotion of collagen gene expression.

PURPOSE: Promotion of collagen production can increase tendon healing strength and reduce repair ruptures. Transfer of an exogenous growth factor gene to tenocytes of intrasynovial tendons may enhance the capacity of cells to produce collagen. We transferred the platelet-derived growth factor B (PDGF-B) gene to tenocytes and investigated its effects on the expression of the PDGF gene and the type I collagen gene in an in vitro tenocyte culture model.

METHODS: Tenocytes obtained from explant cultures of rat intrasynovial tendons were treated for 12 hours with the plasmid containing the PDGF complementary deoxyribonucleic acid (cDNA) with liposome and were then cultured for 6 additional days. The control tenocytes did not receive the exogenous gene and liposome. Efficiency of the gene transfer was evaluated by using reverse transcription polymerase chain reactions (RT-PCR) to detect the presence of the transferred gene in the tenocytes. Enhancement of the expression of the target gene was assessed by RT-PCR with primers effective to amplify both internal and transferred genes. Expression of the type I collagen gene was determined by quantitative analysis of the products of RT-PCR.

RESULTS: Levels of expression of the type I collagen gene by tenocytes were increased significantly by transfer of the exogenous PDGF gene to the tenocytes. Efficiency of the gene transfer was confirmed by the presence of exogenous PDGF cDNA in the tenocytes receiving the transferred gene. Expression of the PDGF gene increased significantly in the cells treated with exogenous PDGF cDNA.

CONCLUSIONS: Exogenous PDGF genes can be transferred effectively into intrasynovial tenocytes and the transfer increases significantly the expression of genes for PDGF and type I collagen. Transfer of the PDGF gene may offer a novel way of effectively promoting healing of intrasynovial flexor tendons. The findings warrant future in vivo study to test the effectiveness of gene therapy to promote flexor tendon healing.