The Effect of Fluence on Macrophage Kinetics, Oxidative Stress, and Wound Closure Using Real-Time In Vivo Imaging

Abstract

Objective: The aim of our study was to quantify the effect of doses delivered by a He:Ne laser on individual macrophage kinetics, tissue oxidative stress, and wound closure using real-time in vivo imaging. Background: Photobiomodulation has been reported to reduce tissue inflammation and accelerate wound closure; however, precise parameters of laser settings to optimize macrophage behavior have not been established. We hypothesized that quantitative and real-time in vivo imaging could identify optimal fluence for macrophage migration, reduction of reactive oxygen species, and acceleration of wound closure. Methods: Larval zebrafish Tg(mpeg-dendra2) were loaded with dihydroethidium for oxidative stress detection. Fish were caudal fin injured, treated with 635 nm continuous 5 mW He:Ne laser irradiation at 3, 9, or 18 J/cm 2 and time-lapsed imaged within the first 120 min postinjury. Images taken 1 and 24-h postinjury were compared for percentage wound closure. Results: A fluence of 3 J/cm 2 demonstrated significant increases in macrophage migration speed, fewer stops along the way, and greatest directed migration toward the wound. These findings were associated with a significant reduction in wound content reactive oxygen species when compared with control wounded fins. Both 3 and 9 J/cm 2 significantly accelerated wound closure when compared with nonirradiated control fish. Conclusions: Wound macrophage activity could be manipulated by applied fluence, leading to reduced levels of wound reactive oxygen species and accelerated wound closure. The zebrafish model provides a means to quantitatively compare wound macrophage behavior in response to a variety of laser treatment parameters in real time.

Application of transgenic zebrafish for investigating inflammatory responses to nanomaterials: Recommendations for new users

“…A less severe, more moderate injury can be induced whereby the tip of the notochord is used as the marker for transection, avoiding damage to the notochord and blood vessels (Figure 3) (Barros-Becker et al, 2017, Hoodless et al, 2016, Li et al, 2012, Lucas et al, 2013. A minor injury can be inflicted through making a small tissue nick in the tail fin (Elks et al, 2011;Paredes et al, 2019;Tauzin et al, 2014). We suggest that a moderate injury is employed when investigating NM toxicity in injured zebrafish to ensure the inflammatory response initiated is robust (i.e., can be detected) but avoids damage to critical structures such as the blood vessels or the notochord, as the latter may make quantification of the response more variable and challenging.…”