Bovine placental hyaluronidase

The mice used in these studies were males from the C57BL/6 strain, obtained from the National Cancer Institute (National Institutes of Health) at ages 6–8 weeks and used for experiments within 2 weeks of their arrival. Animals were housed in colony cages at 21 °C with 12-h light/12-h dark cycles and had ad libitum access to standard chow (Harlan Teklad formula 7013) and water throughout the study. Transfection of mouse skeletal muscle with plasmid DNA was performed as described previously (12 (link)); briefly, mice were anesthetized with ketamine/xylazine, hindlimbs were shaved, and the TA muscles were injected with 30 μl of 0.4 units/μl bovine placental hyaluronidase (Sigma) resuspended in sterile 0.9% saline. Two hours later, mice were re-anesthetized. The TA muscles were then injected with 30 μl of plasmid DNA in sterile saline, coated with ultrasound jelly, and subjected to 10 20-ms pulses of 175 V/cm using an ECM-830 electroporator (BTX Harvard Apparatus). Following transfection, mice were returned to their cages to resume normal activities for 3–10 days before muscle harvest, as noted in the figure legends. Unilateral TA muscle immobilization was performed as described previously (1 (link)). All animal procedures were approved by the Institutional Animal Care and Use Committee of the University of Iowa.