In vivo model of graded soft tissue ischemia. (A) Schematic diagram of a novel ischemia model consisting of paired skin incisions (black lines) along the dorsal surface of mice. (B) (C) (D) Parallel incisions penetrating the skin were made, and a silicone sheet was placed beneath the undermined tissue. The tissue was then reinserted to its original position (panel C), and gross evidence of necrosis (arrow) was evident in the central portion at 1 week following surgery (panel D). (E) Oxygen levels were measured by means of an oxygen probe, and a corresponding gradient of hypoxia was noted within the incised tissue at day 4 following surgery. (F) Color laser Doppler analysis of the incised skin also confirmed the presence of an ischemic gradient, with blood flow diminishing toward the central portion; the color scale illustrates variations in blood flow from maximum perfusion (red) to minimal perfusion (dark blue).