Real-time, in vivo quantification of melanocytes by near-infrared reflectance confocal microscopy in the Guinea pig animal model

Skin healing and collagen changes of rats after fractional erbium:yttrium aluminum garnet laser: observation by reflectance confocal microscopy with confirmed histological evidence

The fractional erbium:yttrium aluminum garnet (Er:YAG) laser is widely applied. Microstructural changes after laser treatment have been observed with histopathology. Epidermal and dermal microstructures have also been analyzed using reflectance confocal microscopy (RCM). However, no studies have compared these two types of microstructural changes in the same subject at multiple time points after irradiation, and it is unclear if these two types of changes are consistent. We use RCM to observe the effect of different laser energies on skin healing and collagen changes in the skin of Sprague-Dawley rats that had been irradiated by fractional Er:YAG lasering at different energies. RCM was used to observe skin healing and detect collagen changes at different time points. Collagen changes were observed using hematoxylin and eosin (H&E) staining and quantitatively analyzed by western blot. RCM showed that, irrespective of laser energy, microscopic treatment zones (MTZs) were larger at 1 day after irradiation. The MTZs then reduced in size from 3 to 7 days after irradiation. The higher the energy, the larger the MTZ area. The amount of collagen also increased with time from 1 day to 8 weeks. However, the increase in the collagen amount on both RCM and H&E staining was not influenced by the laser energy. Western blotting confirmed that the amount of type I and type III collagens increased over time, but there were no significant differences between the different energy groups (p > 0.05). In conclusion, RCM is a reliable technique for observing and evaluating skin healing and collagen expression after laser irradiation.

Clinical nonlinear laser imaging of human skin: a review

Nonlinear optical microscopy has the potential of being used in vivo as a noninvasive imaging modality for both epidermal and dermal imaging. This paper reviews the capabilities of nonlinear microscopy as a noninvasive high-resolution tool for clinical skin inspection. In particular, we show that two-photon fluorescence microscopy can be used as a diagnostic tool for characterizing epidermal layers by means of a morphological examination. Additional functional information on the metabolic state of cells can be provided by measuring the fluorescence decay of NADH. This approach allows differentiating epidermal layers having different structural and cytological features and has the potential of diagnosing pathologies in a very early stage. Regarding therapy follow-up, we demonstrate that nonlinear microscopy could be successfully used for monitoring the effect of a treatment. In particular, combined two-photon fluorescence and second-harmonic generation microscopy were used in vivo for monitoring collagen remodeling after microablative fractional laser resurfacing and for quantitatively monitoring psoriasis on the basis of the morphology of epidermal cells and dermal papillae. We believe that the described microscopic modalities could find in the near future a stable place in a clinical dermatological setting for quantitative diagnostic purposes and as a monitoring method for various treatments.

Reflectance confocal microscopy for pigmentary disorders

In vivo reflectance confocal microscopy (RCM) is a non-invasive, repetitive imaging tool that provides real-time images at nearly cellular histological resolution. Application of this technology to skin imaging during the last decade has been a great advance in dermatology. As melanin is the strongest endogenous contrast in human skin, pigmentary disorders caused by abnormal amounts of melanin in the skin could be the most suitable candidates for RCM examination. This article reviewed the RCM applications in the characterization and management of pigmentary disorders. The application of RCM in pigmentary disorders has been expanded to describe hyper- and hypopigmentary disorders as well as pigmented skin tumors. The great advantages of non-invasive and repetitive examination of RCM may provide its usefulness not only in the diagnosis and management of pigmentary disorders, but also in researching pathogenesis of pigmentary disorders.

In vivo confocal scanning laser microscopy in dermatology

The need to improve the diagnostic accuracy and sensitivity for skin tumours has led to the development of new non-invasive, in vivo techniques including ultrasound, dermoscopy, digital photography, confocal scanning laser microscopy, magnetic resonance imaging and optical coherence tomography. Of all these in vivo techniques, only confocal scanning laser microscopy allows for the examination of the epidermis and papillary dermis at a resolution approaching histological detail. This review article looks at some of the most important applications of this new technology, highlighting its qualities and limitations.

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

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.

Detection of UV-Induced Pigmentary and Epidermal Changes Over Time Using In Vivo Reflectance Confocal Microscopy

In vivo reflectance confocal microscopy (RCM) provides high-resolution optical sections of the skin in its native state, without needing to fix or section the tissue. Melanin provides an excellent contrast for RCM, giving a bright signal in the confocal images. The pigmented guinea-pig is a common animal model to study human pigment induction and modulation, as its tanning response is comparable to human tanning after exposure to ultraviolet radiation (UVR). We investigated the applicability of RCM to detecting UVR-induced pigmentary changes in this model. Animals were exposed to solar simulator radiation for 7 days. RCM was performed during the irradiation and follow-up period. Compared to non-irradiated skin, an increase in melanocyte size, dendricity, and number, as well as increased pigment in keratinocytes, was seen in the irradiated epidermis. Interestingly, these changes could be detected even before a tanning response was clinically visible. UVR-induced epidermal hyperplasia could also be detected and quantified. In conclusion, in vivo RCM is a sensitive non-invasive imaging technique that can repeatedly measure epidermal pigmentation and thickness, as demonstrated in the guinea-pig model. This technique should greatly enhance our appreciation of dynamic pigmentary changes in human or animal skin over time and in response to specific stimuli.

Topical Application of a Protein Kinase C Inhibitor Reduces Skin and Hair Pigmentation

To determine whether inhibition of PKC-beta activity decreases pigmentation, paired cultures of primary human melanocytes were first pretreated with bisindolylmaleimide (Bis), a selective PKC inhibitor, or vehicle alone for 30 min, and then treated with TPA for an additional 90 min to activate PKC in the presence of Bis. Bis blocked the expected induction of tyrosinase activity by activation of PKC. Addition of a peptide corresponding to amino acids 501-511 of tyrosinase containing its PKC-beta phosphorylation site, a presumptive PKC-beta pseudosubstrate, gave similar results. To determine whether Bis reduces pigmentation in vivo, the backs of four shaved and depilated pigmented guinea pigs were UV irradiated with a solar simulator for 2 wk excluding weekends. Compared to vehicle alone, Bis (300 microM), applied twice daily to paired sites for various periods encompassing the irradiation period, decreased tanning. Bis also, although less strikingly, reduced basal epidermal melanin when topically applied twice daily, 5 d per wk, for 3 wk to shaved and depilated unirradiated skin. Moreover, topical application of Bis (100 microM) once daily for 9 d to the freshly depilated backs of 8-wk-old mice markedly lightened the color of regrowing hair. These results demonstrate that inhibiting PKC activity in vivo selectively blocks tanning and reduces basal pigmentation in the epidermis and in anagen hair shafts.