In vivo confocal laser scanning microscopy imaging of skin inflammation: Clinical applications and research directions

Abstract

In vivo confocal laser scanning microscopy (CLSM) is a novel imaging technique that provides noninvasive, morphological characterization of skin structures with a resolution that is very close to that of light microscopy. Moreover, as it allows repeated imaging of the same skin area at different time-points, it is an excellent method for monitoring disease course, response to treatment or specific stimuli and a path to study dynamic phenomena in real-time. To date, two different variants of in vivo CLSM have been authorized in dermatological field, namely the reflectance confocal microscopy predominantly for clinical diagnosis and the fluorescence confocal microscopy mainly for research purposes. This study describes the principles of in vivo CLSM technique, its role in the diagnosis and monitoring of inflammatory skin diseases, as well as some promising research directions to study the dynamics of skin inflammation using this method. In vivo CLSM evaluation of inflammatory dermatoses and of the skin inflammatory component in various diseases has an undoubted potential with broad applications ranging from clinical, morphological to experimental, functional studies involving the skin.

Keywords: in real-time; in vivo; reflectance confocal microscopy; skin inflammation.

Figure 1.

In vivo RCM features of psoriasis. (A) RCM image (0.5×0.5 mm) showing round to polygonal, nucleated bright cells (→) in the cornified layer corresponding to parakeratotic keratinocytes. (B) RCM image (0.5×0.5 mm) showing clustered refractile roundish structures (→) associated with dark areas (*) corresponding to accumulation of leukocytes in the cornified layer (Munro micro abscesses) or in the upper portion of the spinous layer (spongiform pustules of Kogoj). (C) RCM mosaic (1×1 mm) showing increased density of dermal papillae. (D) RCM image (0.5×0.5 mm) showing enlarged dermal papillae lacking bright ring of basal cells occupied by dilated blood vessels (▶) and surrounded by moderately refractile dendritic inflammatory cells (→).

Figure 2.

In vivo RCM features of lichen planus. (A) RCM image (0.5×0.5 mm) at the level of the granular-spinous layer showing increased intercellular spaces (spongiosis) (*), large, polygonal cells (hypergranulosis in a wedge-shaped pattern that corresponds to the Wickham's striae) (▶) and inflammatory cells that appear as roundish bright structures (→). (B) RCM image (0.5×0.5 mm) at the level of the epidermal-dermal junction showing non-edged and non-rimmed dermal papillae (▶) due to inflammatory cell infiltrate (→).

Figure 3.

In vivo RCM features of discoid lupus erythematosus. (A) RCM mosaic (1×1 mm) at the epidermal-dermal junction level showing disappearance of the papillary rings due to infiltrates of inflammatory cells (→). (B) RCM mosaic (1×1 mm) showing dillated follicle (*) with infundibular hyperkeratosis (▶) surrounded by inflammatory cells (→).

Figure 4.

Evaluation of skin wound healing in BALB/c mice by in vivo RCM. (A) Clinical aspect of the wound (→). (B) Corresponding dermoscopic image of lesional skin (→). (C) RCM of skin lesion showing a clear demarcation line between the scar and perilesional areas (→). (D) Lesional epidermis with polymorphic aspect (*) different as compared to the normal honeycombed pattern of the perilesional areas. (E) Superficial dermis with thin fibers creating a blurry aspect in the lesional area (*). (F and G) Tortuous blood vessels with increased blood flow (→) and bright inflammatory cells (▶) in perilesional dermis.

Figure 5.

In vivo RCM sequential images (0.25×0.25 mm) at the level of the epidermal-dermal junction, 0 min (A) and 25 min (B) after the administration of topical capsaicin. Dermal capillaries appear as black holes (→) inside dermal papillae, dark roundish areas (*) that are surrounded by bright circles (▶), corresponding to the epidermal basal layer. In real-time blood cells can be observed as moving bright elements inside the lumina of dermal capillaries. Dilation of dermal capillaries and flow of blood cells inside their lumina can be easily observed after 25 min of topical capsaicin.