New model for in vivo investigation after microvascular breakdown in burns: use of intravital fluorescent microscopy

Summary Background: The breakdown of skin microcirculation is assumed to play a key role in the pathophysiology after burn injury. The aim of the present study was to develop a burn model, which allows repetitive quantitative in vivo analysis of the microcirculation after a burn injury, focusing on the interaction between leukocytes and the endothelium. Materials and methods: Experiments were carried out on male hairless mice. Deep partial thickness burns were inflicted with a no-touch-technique to the ears. Intravital fluorescent microscopy in combination with FITC-dextran as a plasmamarker was used to assess microcirculatory parameters. Leukocytes were stained with rhodamine 6G. Preburn baseline data was obtained before as well as 1, 3, 7 and 14 days subsequent to the burn injury. Results: The non-perfused area decreased significantly over the observed period and perfusion was almost completely restored at day 14. The functional vessel density was characterized by reduction of perfused vessels immediately after burn and an increase after 24 h. Leukocyte endothelium interaction significantly increased immediately after injury; baseline values were reached 1 day later. The extravasation of the plasma marker into the surrounding tissue increased immediately after burn, decreased at day 1 and remained at this level during the following observation time. The venular as well as the arterial blood flow increased immediately subsequent to the burn injury, decreased after 1 day and reached baseline values at day 3. Conclusion: The presented burn model allows quantitative assessment of the dynamics of microcirculatory disturbances after thermal trauma by high quality visualization of both plasma stained microvessels and leukocyte–endothelium interaction.