Dynamic characterization of vascular response and treatment in oral traumatic ulcer in mice via photoacoustic imaging.

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Dynamic surveillance of vasculature is essential for evaluating the healing of oral ulcer. Existing techniques used in vascular imaging face limitations, such as inadequate spatial resolution, restricted diagnostic depth, and the necessity of exogenous contrast agents. Therefore, this study aimed to use robust photoacoustic imaging (PAI) for the dynamic monitoring of vascular response during healing and the associated treatment process of oral ulcer. Kunming mice (male, 8 weeks old, 31-41 g) were treated with 50% acetic acid for 90 s on the tongue mucosa for induction of oral traumatic ulcer. Mice were randomly divided into three groups (n=12): the control, compound chamomile and lidocaine hydrochloride gel (CCLH), and phycocyanin (PC) groups. PAI was then conducted on days 0, 2, 3, 5, and 7 to obtain vessel parameters of the ulcer area, including vessel intensity, density, mean diameter, maximum diameter, and curvature. Immunohistochemical and hematoxylin and eosin (HE) staining were performed on days 3 and 7 to assess microvessel density and inflammation score. The ulcer healing rate and body weight changes were evaluated for clinical observation. Beginning on the second day after ulcer induction, there was a progressive increase over time in blood intensity and vessel parameters, including vascular density and diameter. On day 7, the CCLH and PC groups demonstrated significantly higher measures than did the control group in terms of blood intensity (P<0.05 and P<0.01), vascular density (both P values <0.05), mean diameter (both P values <0.01), and maximum diameter (P<0.01 and P<0.05). Vessel curvature in the two treatment groups exhibited no significant differences compared to that in the control group (both P values >0.05). The effects of vascular morphological changes were further supported by the histological and clinical outcomes. On day 7, compared to that of the control group, the level of microvessel density was significantly higher in both the CCLH (P<0.01) and PC (P<0.05) groups. The histopathological score in PC group was significantly lower than that of the control group on day 7 (P<0.05). Additionally, compared to that of the control group, the healing rates of the CCLH (P<0.01) and PC groups (P<0.05) were superior on day 7. On day 3, the control group showed more weight loss than did the CCLH (P<0.05) and PC (P<0.01) groups. These findings indicate that PAI is a valuable strategy for the dynamic and quantitative analysis of vascular alterations in oral traumatic ulcers and support its prospective application in improving clinical treatment.