OBJECTIVETo reproduce a stable mouse model of deep partial-thickness scald and to determine the hypoxia status in the wound.

METHODS(1) A homemade scald-producing apparatus with constant steam (92 °C) emission was used to reproduce scald injury on the back (2 cm in diameter) in 80 male BALB/c mice for different duration (2, 4, 6, and 8 s), with 20 mice for each scald duration. The nozzle was aligned perpendicularly to the back of mice, 2 cm above the skin surface. The gross condition of wound was observed with naked eyes immediately after injury. Skin samples of 5 mice with different burn duration were harvested 0, 12, 24, and 48 h after scald for histopathological observation with hematoxylin and eosin staining, to screen the scalding time and time for biopsy of scalded skin to determine proper scalding time for the experiment. (2) Model of deep partial-thickness scald was reproduced with the desired scalding time as shown in the preliminary experiment in another 5 BALB/c mice. The hypoxia status in subcutaneous tissue was observed with immunohistochemical staining 72 h after scald. Another 20 BALB/c mice were divided into normal control group (n = 5, without scald) and deep partial-thickness scald group (n = 15, scalded for a suitable duration as determined in the preliminary experiment) according to the random number table. The subcutaneous oxygen content in wound center, the margin of the wound, and the normal skin adjacent to the wound was detected with laser Doppler transcutaneous oxygen tension 72 h after scald, with 5 mice in each region. Data were processed with one-way analysis of variance.

RESULTS(1) The wound of mice with different scald durations was pale, clean, and no exudate was observed right after injury. (2) The burn depth developed gradually along with the scalding time and sample harvesting time, and it became stable 24 h after scalding. A deep partial-thickness injury was observed in the dermis of mice scalded for 4 s and harvested 24 h after scald, and it was shown that the external hair sheath was still present, and it was determined to be a deep partial-thickness scald. (3) Dense staining of pimonidazole (hypoxia) was found in deep partial-thickness scald wound 72 h after scald, especially in the marginal zones of the wounds. The partial oxygen pressure in the wound center, wound margin, and normal skin around the wound was respectively (36.2 ± 3.2), (37.0 ± 1.4), (37.4 ± 2.7) mm Hg (1 mm Hg = 0.133 kPa), showing no statistically significant difference among them (F = 74.705, P > 0.05), but they were significantly lower than that of the control group [(53.1 ± 2.4) mm Hg, with F values respectively 82.377, 91.375, 100.531, P values all below 0.05].

CONCLUSIONSDeep partial-thickness scald model can be reproduced in (20.0 ± 1.0) g male BALB/c mice by scalding with 92 °C hot steam for 4 s, and the depth of wound becomes stable 24 h after scalding. Hypoxia can be found in the scalded wounds, especially in the marginal zones of the wounds.