Reflectance confocal microscopy (RCM) is a non-invasive imaging technology that allows real-time examination of the skin at nearly histologic resolution. It has been proved to be valuable in the clinics, but its application in animal models is limited. The main objectives were to identify characteristic confocal features in healthy murine skin, and evaluate the cutaneous alterations in the mouse model of oxazolone-induced dermatitis.
A VivaScope® microscope was used to take horizontal optical sections of the skin from the stratum corneum to the dermis, up to the maximum optical depth of 250 µm. Imaging was performed on healthy or lesional skin of male C57BL/6 mice. The dermatitis was induced in the depilated nape of sensitized mice by repeated topical challenges with oxazolone, and imaged 24 hours after each challenge.
The major architectural and cellular features of each stratum of the epidermis and dermis were identified in healthy skin. However, the patterns were not as pronounced as those described in humans, and the dermo-epidermal junction was indistinct.
Features of spongiotic dermatitis were visualized in the model. In the acute stage, there were areas of increased intercellular brightness (spongiosis), circumscribed oval hyporefractive areas (vesicles), and single or clusters of refractile round cells at the level of the stratum spinosum (exocytosis) and dermis. With chronicity, the honeycomb pattern was increased in thickness (acanthosis), and inflammatory cells were often observed with haphazardly arranged, highly refractile fibrilar fibers (fibrosis).
RCM represents a powerful tool to analyze skin changes in animal models, and complements histopathology when studying dynamic processes (blood flow), or structures and lesions usually altered by histological processing. Additionally, its non-invasive nature enables the monitoring of skin lesions in the same animal, which is particularly useful in models intended to mimic a chronic disease.

Application of reflectance confocal microscopy in the evaluation of murine healthy and lesional skin