Photoacoustic microscopy in detecting skin injuries in rats

Cui Hui; Peng Bibo; Yu Lihua; Zhou Xianjie; Song Huina; Li Shengnan; Ren Junxia

doi:10.3969/j.issn.1009-4237.2025.09.009

Abstract：Objective To evaluate the efficacy of photoacoustic microscopy(PAM)in assessing cutaneous damage progression in rat models of incised wound or scald.Methods Twelve male SD rats aged 8-10 weeks were randomly assigned to two groups(n=6 per group):an incised wound model group and a scald wound model group.The incised wounds were created on the depilated dorsal skin using a biopsy punch,while the scalds were induced u-sing a standardized scald device.Wound progression was monitored at 1,3,7,and 28 d post-modeling by both con-ventional measurement and PAM.The former assessed the wound area and healing rate using a digital caliper and a small-animal imaging system,with subsequent analysis performed using ImageJ software.The PAM employed the In-sight-RSPAM2 system to acquire high-resolution images,and the accompanying Insight Analysis 2.3.3 software was used to further quantify wound area,lesion depth,vascular density,blood flow velocity,and oxygen saturation.Results The incised wounds exhibited faster healing,achieving 80.3%±6.8%closure by Day 28.In contrast,the scald wounds showed initial expansion followed by delayed healing,reaching only 69.1%±14.8%closure at the same endpoint.The wound areas of the incised rats measured by the two methods showed a mean difference of 0.06 cm2,with the 95%limits of agreement being 0.0001-0.1236 cm2.The PAM testing demonstrated that in the rat incised wound model,the lesion depth decreased significantly from(1509.70±249.44)μm to(426.41±49.23)μm during the 28-day healing period,with evident neoangiogenesis observed at Day 28.On Day 1 post-injury,the incised and scalded rats showed blood flow velocities of(4.31±0.10)mm/s and(3.38±0.12)mm/s,oxygen satu-rations of 71.20%±2.73%and 71.83%±8.29%,respectively,which were increased to(4.70±0.69)mm/s and(4.48±0.32)mm/s for blood flow velocity,and 75.25%±2.30%and 80.00%±2.25%for oxygen saturation by Day 3.From Day 7 to Day 28 post-injury,the skin wound blood oxygen saturation of the incised rats showed an in-creased trend(76.48%±2.22%to 82.58%±3.07%),while the blood flow velocity(mm/s,4.57±0.22 to 4.74±0.23)and blood oxygen saturation(81.48%±2.02%to 81.19%±2.20%)in scalded rats showed a plateaued trend.Conclusion PAM enables non-invasive longitudinal monitoring of cutaneous wounds in rats,providing quan-titative assessments of the wound area,lesion depth,and structural/functional parameters in both the injured tissue and surrounding vasculature.