To demonstrate and analyze quantitatively the expression of marker genes in the Achilles tendon of rats by direct DNA injection and electroporation.

Enhanced green fluorescent protein (EGFP) cDNA or luciferase cDNA were injected into the mid-substance of rat Achilles tendon followed by various conditions of electroporation. Adenovirus encoding firefly luciferase was used to compare the transfection efficiency. Tendons were examined by confocal microscopy when EGEP was used and with luciferase, and the luminescence was measured quantitatively.

Combined injection with electroporation increased the fluorescence intensity. The results of luciferase cDNA injection and electroporation with 25 volts/0.25 cm and 50 volts/0.25 cm showed a ten times and thirty-three times higher luminescence respectively than without using electroporation. After DNA injection and electroporation using 50 volts, the luciferase activity was slightly lower than with viral transduciton using 106 plaque forming units.

Direct administration of therapeutic genes by electroporation accelerates the repair processes in musculoskeletal tissues.