BACKGROUND: Recent advancements in gene therapy have provided new methodology for treating ischemia in lower extremities. Gene transfer of angiogenic factors to ischemic tissues may promote local proliferation of new vessels and form collateral circulation. OBJECTIVE: To observe histopathological changes in the femoral and intramuscular nerve three months after intramuscular injection of hepatocyte growth factor (HGF) into the peripheral skeletal muscle in a canine model of lower limb ischemia. DESIGN: Randomized occlusion modelled and verification animal study. SETTING: Experimental Center, Lanzhou General Hospital of Lanzhou Military Area Command of Chinese PLA. MATERIALS: This study was performed at Animal Experimental Center, Lanzhou General Hospital of Lanzhou Military Area Command of Chinese PLA from September to November 2006. A total of eight male mongrel dogs, weighing 12-15 kg and 1.5-3 years of age, were selected for this study. This experimental study was in accordance with local ethics standards. Recombinant plasmid carrying HGF (pUDKH) and occlusion model plasmid (pUDK) were provided by the Third Laboratory of Radiation Medical Institute, Academy of Military Medical Sciences of PLA. METHODS: Grouping and model establishment: under anesthesia, complete vascular occlusion models were established on the left lower extremities. The experimental dogs were randomly divided into a model group and a pUDKH treatment group, with four dogs in each group. Dogs in the pUDKH group were injected with 0.15 mg/kg pUDKH. Ten minutes later, intramuscular injections were performed at three spots into the peripheral skeletal muscle of the left hind limb, as well as lateral injections at two spots. The injection volume at each spot was 0.2 mL. Dogs in the model group were injected with pUDK, and dosage and injection method were identical to the treatment group.MAIN OUTCOME MEASURES: Histopathological changes in the femoral nerve, as well as intal and extal intramuscular nerve tissues in the hind limb of dogs three months after plasmid injection under optic microscope. RESULTS: (1) Histopathological changes in the femoral nerve: tiny nerves from the femoral nerve to the intramuscular nerve exhibited marked degeneration in the model group. The degenerating features included neurites, myelin sheaths, and Schwann cell nuclei. Neuropathy in the pUDKH treatment group was not detected. (2) Histopathological changes of the intramuscular nerve: large and irregular vacuoles were present on several longitudinal sections of intramuscular nerve fibers in the model group, as well as annular-shaped blank regions on transverse sections of peripheral neurites. In the pUDKH treatment group, large, blank regions were present in several segments of partial nerve fibers of the longitudinal intramuscular nerve region, but only a few nerve fibers exhibited annular-shaped blank regions on the transverse section of peripheral neurites. CONCLUSION: Local pUDKH injection may relieve or block femoral and intramuscular nerve tissue injury in a canine mocel of lower limb ischemia.