Real-TimeReflectance Confocal Microscopy, a Noninvasive Tool for in vivo Quantitative Evaluation of Comedolysis in the Rhino Mouse Model

Abstract

Background: Near-infrared reflectance confocal microscopy (RCM) is a noninvasive tool that provides real-time images of thin virtual horizontal tissue sections. Aims/Methods: We have used a rhino mouse model in combination with topical application of all-trans-retinoic acid and all-trans-retinol to investigate the usefulness of RCM as a noninvasive imaging tool to evaluate comedolysis in vivo and over time. Optical images were correlated with routine histology. Results: Our results demonstrate that RCM in vivo can visualize the process of transformation of utriculi (pseudocomedones) towards a normal-appearing follicular structure during retinoid treatment. The retinoic acid intervention group showed a dose-related response, while the vehicle-treated group did not show utricular changes. Conclusions: RCM represents a useful tool for in vivo morphological and quantitative evaluation of skin utriculi over time and could be used as an adjunct tool to histopathological techniques for comedolysis studies.

Passive immunoprotection targeting a secreted CAMP factor of Propionibacterium acnes as a novel immunotherapeutic for acne vulgaris

“…Rhino mice, a genetic mutant mouse with utricles that create larger follicles, have been utilized to determine compound comedogenicity [61]. However, Rhino mice cannot produce antibodies against thymus-dependent antigens [62], and thus may not be an appropriate model for vaccination.…”

Computer-assisted alignment and tracking of acne lesions indicate that most inflammatory lesions arise from comedones and de novo

“…This can potentially be resolved in the future with novel devices that allow noninvasive evaluation of follicular structures in vivo such as real-time reflectance confocal microscopy, which has already been used to assess comedolysis in the rhino mouse model. 25 As our photographs were taken every 2 weeks, it is possible that comedones may have formed and subsequently progressed to inflammatory lesions in that time, but only the latter were captured on film. It has been shown that, like the hair follicles, comedones undergo cycling 26 with many closed comedones resolving within 12 days based on clinical observations, 6 whereas some open comedones persisted for months.…”

Animal models of skin disease for drug discovery

“…P. acnes are anaerobic Gram-positive bacteria and cause inflammation leading to scarring in severe cases. The list of animal models that have been used in the study of acne include the rabbit ear model, rhino mouse model [138], Mexican hairless dog model [138,139], Golden Hamster model, swine, and guinea pig [140]. …”