Epidermal Regeneration in Lampreys

Adult lampreys (Lethenteron reissneri, body length: 15 cm ± 1 cm) were obtained from Huanren Manchu Autonomous County, Benxi, Liaoning Province, China. The lampreys were then maintained in an aquarium at 4 °C. All lamprey handling and experimental procedures were approved by the Animal Welfare and Research Ethics Committee of the Institute of Dalian Medical University. For the epidermal regeneration challenge, adult lampreys (N = 30) were divided randomly into five groups: no wound (CTL), 0 days after damage (Dam 0 d), 2 days after damage (Dam 2 d), 7 days after damage (Dam 7 d), 14 days after damage (Dam 14 d), and 21 days after damage (Dam 21 d). After anesthetization with 0.05% MS-222 (tricaine methanesulfonate, Sigma–Aldrich, E10521, St. Louis, MO, USA), the body surface was scraped using a sterilized scalpel to create a wound bed (1.5 cm × 0.5 cm) until no more mucoid tissue could be scraped. The whole process was performed gently to minimize damage to the dermis. For full-thickness damage, a scalpel with only a 5-mm blade exposed was used to make a 0.5-cm-long wound on the side of the lamprey parallel to the body. Images were captured with a zoom stereo microscope (SMZ1500, Nikon, Japan).