In vivo quantification of epidermis pigmentation and dermis papilla density with reflectance confocal microscopy: variations with age and skin phototype

Identifying characteristics of dermal fibroblasts in skin homeostasis and disease

Heterogeneous dermal fibroblasts are the main components that constitute the dermis. Distinct fibroblast subgroups show specific characteristics and functional plasticity that determine dermal structure during skin development and wound healing. Although researchers have described the roles of fibroblast subsets, this is not completely understood. We review recent evidence supporting understanding about the heterogeneity of fibroblasts. We summarize the origins and the identified profiles of fibroblast subpopulations. The characteristics of fibroblast subpopulations in both healthy and diseased states are highlighted, and the potential of subpopulations to be involved in wound healing in different ways was discussed. Additionally, we review the plasticity of subpopulations and the underlying signalling mechanisms. This review may provide greater insights into potential novel therapeutic targets and tissue regeneration strategies for the future.

Recent omics advances in hair aging biology and hair biomarkers analysis

Aging is a complex natural process that leads to a decline in physiological functions, which is visible in signs such as hair graying, thinning, and loss. Although hair graying is characterized by a loss of pigment in the hair shaft, the underlying mechanism of age-associated hair graying is not fully understood. Hair graying and loss can have a significant impact on an individual's self-esteem and self-confidence, potentially leading to mental health problems such as depression and anxiety. Omics technologies, which have applications beyond clinical medicine, have led to the discovery of candidate hair biomarkers and may provide insight into the complex biology of hair aging and identify targets for effective therapies. This review provides an up-to-date overview of recent omics discoveries, including age-associated alterations of proteins and metabolites in the hair shaft and follicle, and highlights the significance of hair aging and graying biomarker discoveries. The decline in hair follicle stem cell activity with aging decreased the regeneration capacity of hair follicles. Cellular senescence, oxidative damage and altered extracellular matrix of hair follicle constituents characterized hair follicle and hair shaft aging and graying. The review attempts to correlate the impact of endogenous and exogenous factors on hair aging. We close by discussing the main challenges and limitations of the field, defining major open questions and offering an outlook for future research.

Rete ridges: Morphogenesis, function, regulation, and reconstruction

Rete ridges (RRs) are distinct undulating microstructures at the junction of the dermis and epidermis in the skin of humans and certain animals. This structure is essential for enhancing the mechanical characteristics of skin and preserving homeostasis. With the development of tissue engineering and regenerative medicine, artificial skin grafts have made great progress in the field of skin healing. However, the restoration of RRs has been often disregarded or absent in artificial skin grafts, which potentially compromise the efficacy of tissue repair and regeneration. Therefore, this review collates recent research advances in understanding the structural features, function, morphogenesis, influencing factors, and reconstruction strategies pertaining to RRs. In addition, the preparation methods and limitations of tissue-engineered skin with RRs are discussed. STATEMENT OF SIGNIFICANCE: The technology for the development of tissue-engineered skin (TES) is widely studied and reported; however, the preparation of TES containing rete ridges (RRs) is often ignored, with no literature reviews on the structural reconstruction of RRs. This review focuses on the progress pertaining to RRs and focuses on the reconstruction methods for RRs. In addition, it discusses the limitations of existing reconstruction methods. Therefore, this review could be a valuable reference for transferring TES with RR structure from the laboratory to clinical applications in skin repair.

Automating reflectance confocal microscopy image analysis for dermatological research: a review

SIGNIFICANCE

Reflectance confocal microscopy (RCM) is a noninvasive, in vivo technology that offers near histopathological resolution at the cellular level. It is useful in the study of phenomena for which obtaining a biopsy is impractical or would cause unnecessary tissue damage and trauma to the patient.

AIM

This review covers the use of RCM in the study of skin and the use of machine learning to automate information extraction. It has two goals: (1) an overview of information provided by RCM on skin structure and how it changes over time in response to stimuli and in disease and (2) an overview of machine learning approaches developed to automate the extraction of key morphological features from RCM images.

APPROACH

A PubMed search was conducted with additional literature obtained from references lists.

RESULTS

The application of RCM as an in vivo tool in dermatological research and the biologically relevant information derived from it are presented. Algorithms for image classification to epidermal layers, delineation of the dermal-epidermal junction, classification of skin lesions, and demarcation of individual cells within an image, all important factors in the makeup of the skin barrier, were reviewed. Application of image analysis methods in RCM is hindered by low image quality due to noise and/or poor contrast. Use of supervised machine learning is limited by time-consuming manual labeling of RCM images.

CONCLUSIONS

RCM has great potential in the study of skin structures. The use of artificial intelligence could enable an easier, more reproducible, precise, and rigorous study of RCM images for the understanding of skin structures, skin barrier, and skin inflammation and lesions. Although several attempts have been made, further work is still needed to provide a definite gold standard and overcome issues related to image quality, limited labeled datasets, and lack of phenotype variability in available databases.

Mechanical stretching can modify the papillary dermis pattern and papillary fibroblast characteristics during skin regeneration

Clinical application of mechanical stretching is a reconstructive method for skin repair. Although studies have reported dermal fibroblast heterogeneity, whether stretching affects individual fibroblast subpopulations equally remains unclear. Here, we show the changes in dermal structure and papillary fibroblast (Fp) in regenerated human skin. Exhausted skin regeneration caused dermal-epidermal junction (DEJ) flattening, papillary dermis thinning, and an increase in the type III collagen (COL3)/type I collagen (COL1) ratio with upregulated hallmarks of aging. Well-regenerated skin displayed a notable increase in the Fp population. Consistent changes were observed in the rat expansion model. Moreover, we found that TGFβ1 expression was especially increased in skin showing good regeneration. Activation of the TGFβ1/Smad2/3 pathway improved exhausted skin regeneration and resulted in increased collagen content and Fp proliferation, while pharmacological inhibition of TGFβ1 action impacted well-regenerated skin. Short-term mechanical stretching that promoted skin regeneration enhanced Fp proliferation, extracellular matrix (ECM) synthesis, and increased TGFβ1 expression, leading to good regeneration. Conversely, long-term stretching induced premature Fp senescence, leading to poor regeneration. This work shows the mechanism of mechanical stretching in well skin regeneration that enhances Fp proliferation and ECM synthesis via the TGFβ1/Smad2/3 pathway, and highlights a crucial role of Fps in stretching-induced skin regeneration.

Line-field confocal optical coherence tomography as a tool for three-dimensional in vivo quantification of healthy epidermis: A pilot study

Epidermal three-dimensional (3D) topography/quantification has not been completely characterized yet. The recently developed line-field confocal optical coherence tomography (LC-OCT) provides real-time, high-resolution, in-vivo 3D imaging of the skin. This pilot study aimed at quantifying epidermal metrics (epidermal thicknesses, dermal-epidermal junction [DEJ] undulation and keratinocyte number/shape/size) using 3D LC-OCT. For each study participant (8 female, skin-type-II, younger/older volunteers), seven body sites were imaged with LC-OCT. Epidermal metrics were calculated by segmentations and measurements assisted by artificial intelligence (AI) when appropriate. Thicknesses of epidermis/SC, DEJ undulation and keratinocyte nuclei volume varied across body sites. Evidence of keratinocyte maturation was observed in vivo: keratinocyte nuclei being small/spherical near the DEJ and flatter/elliptical near the skin surface. Skin microanatomy can be quantified by combining LC-OCT and AI. This technology could be highly relevant to understand aging processes and conditions linked to epidermal disorders. Future clinical/research applications are to be expected in this scenario.

Reproduction of patterns in melanocytic proliferations by agent-based simulation and geometric modeling

Spatio-temporal patterns of melanocytic proliferations observed in vivo are important for diagnosis but the mechanisms that produce them are poorly understood. Here we present an agent-based model for simulating the emergence of the main biologic patterns found in melanocytic proliferations. Our model portrays the extracellular matrix of the dermo-epidermal junction as a two-dimensional manifold and we simulate cellular migration in terms of geometric translations driven by adhesive, repulsive and random forces. Abstracted cellular functions and melanocyte-matrix interactions are modeled as stochastic events. For identification and validation we use visual renderings of simulated cell populations in a horizontal perspective that reproduce growth patterns observed in vivo by sequential dermatoscopy and corresponding vertical views that reproduce the arrangement of melanocytes observed in histopathologic sections. Our results show that a balanced interplay of proliferation and migration produces the typical reticular pattern of nevi, whereas the globular pattern involves additional cellular mechanisms. We further demonstrate that slight variations in the three basic cellular properties proliferation, migration, and adhesion are sufficient to produce a large variety of morphological appearances of nevi. We anticipate our model to be a starting point for the reproduction of more complex scenarios that will help to establish functional connections between abstracted microscopic behavior and macroscopic patterns in all types of melanocytic proliferations including melanoma.

The Human Epidermal Basement Membrane: A Shaped and Cell Instructive Platform That Aging Slowly Alters

One of the most important functions of skin is to act as a protective barrier. To fulfill this role, the structural integrity of the skin depends on the dermal-epidermal junction-a complex network of extracellular matrix macromolecules that connect the outer epidermal layer to the underlying dermis. This junction provides both a structural support to keratinocytes and a specific niche that mediates signals influencing their behavior. It displays a distinctive microarchitecture characterized by an undulating pattern, strengthening dermal-epidermal connectivity and crosstalk. The optimal stiffness arising from the overall molecular organization, together with characteristic anchoring complexes, keeps the dermis and epidermis layers extremely well connected and capable of proper epidermal renewal and regeneration. Due to intrinsic and extrinsic factors, a large number of structural and biological changes accompany skin aging. These changes progressively weaken the dermal-epidermal junction substructure and affect its functions, contributing to the gradual decline in overall skin physiology. Most changes involve reduced turnover or altered enzymatic or non-enzymatic post-translational modifications, compromising the mechanical properties of matrix components and cells. This review combines recent and older data on organization of the dermal-epidermal junction, its mechanical properties and role in mechanotransduction, its involvement in regeneration, and its fate during the aging process.

Structural skin changes in elderly people investigated by reflectance confocal microscopy

BACKGROUND

Reflectance confocal microscopy (RCM) is particularly suitable for the study of skin ageing because it provides nearly histological information in vivo and non-invasively. However, there are no studies that evaluated RCM skin features of a large population older than 70 years.

OBJECTIVES

The aim of our investigation was to study age-related skin changes in an elderly population by RCM and to evaluate their topographical and gender differences.

METHODS

We obtained RCM images of photoprotected (volar arm) and chronic (face) and intermittently photoexposed (dorsal forearm) body sites of 209 volunteers (105 women and 104 men, mean age: 77.5, range 74-81 years). 15 previously reported and new RCM parameters related to skin ageing were assessed.

RESULTS

Photoexposed sites had thicker suprapapillary epidermis, more linear, distant and thin furrows, higher presence of mottled pigmentation, polycyclic papillae and coarse and huddled collagen and lower presence of dermal papillae than the photoprotected site. Irregular honeycomb pattern was not higher in photoexposed sites, indicating that it is probably more dependent on intrinsic ageing. Two ageing scores defined for facial skin ageing (epidermal disarray score and epidermal hyperplasia score) were found useful for the identification of photoageing. Gender differences only concerned some RCM parameters (i.e. thickness of different layers of the epidermis, furrows and collagen score) and some body sites, in line with the fact that women and men of our cohort had no major differences in clinically visible skin ageing.

CONCLUSIONS

Our study confirmed that RCM is a powerful non-invasive technique to microscopically quantify ageing signs and our observations contribute to highlight the differences between intrinsic and extrinsic ageing.

Slide-free clinical imaging of melanin with absolute quantities using label-free third-harmonic-generation enhancement-ratio microscopy

The capability to image the 3D distribution of melanin in human skin in vivo with absolute quantities and microscopic details will not only enable noninvasive histopathological diagnosis of melanin-related cutaneous disorders, but also make long term treatment assessment possible. In this paper, we demonstrate clinical in vivo imaging of the melanin distribution in human skin with absolute quantities on mass density and with microscopic details by using label-free third-harmonic-generation (THG) enhancement-ratio microscopy. As the dominant absorber in skin, melanin provides the strongest THG nonlinearity in human skin due to resonance enhancement. We show that the THG-enhancement-ratio (erTHG) parameter can be calibrated in vivo and can indicate the melanin mass density. With an unprecedented clinical imaging resolution, our study revealed erTHG-microscopy's unique capability for long-term treatment assessment and direct clinical observation of melanin's micro-distribution to shed light into the unknown pathway and regulation mechanism of melanosome transfer and translocation.

Efficacy of a wound-dressing biomaterial on prevention of postinflammatory hyperpigmentation after suction blister epidermal grafting in stable vitiligo patients: a controlled assessor-blinded clinical study with in vitro bioactivity investigation

Postinflammatory hyperpigmentation (PIH) is a common disfiguring complication following inflammatory dermatoses and cosmetic procedures in dark-skinned individuals. Anti-inflammatory and repairing agents targeting primary inflammation and injury are becoming promising choices for preventing PIH. The aim of this active-controlled, assessor-blinded, intra-individual monocentric study was to evaluate the preventive effect of a wound-dressing biomaterial, mussel adhesive protein (MAP) in the suction blister-induced PIH model. Twenty Chinese patients underwent suction blister epidermal grafting had defined wound areas to receive a topical MAP spray or a potent corticosteroid cream once daily for seven consecutive days after operation. In situ semi-quantitative evaluations of inflammation and pigmentation were achieved by Mexameter, reflectance confocal microscopy and dermoscopy on week 1, week 4, and week 12. Topical application of MAP exerted remarkably inhibitory effect on PIH comparable to fluticasone propionate, manifested as significantly lower melanin index and papillary contrast measured by Mexameter and confocal microscopy on week 12 compared to untreated sites. Although MAP exhibited moderate anti-inflammatory effect weaker than fluticasone propionate, MAP-treated sites healed faster than steroid-treated and untreated sites. The biological activity of MAP was further studied in UVB-irradiated HaCaT cell model, which revealed MAP decreased the expression of UVB-induced α-melanocyte stimulating hormone (α-MSH) and pro-inflammatory cytokines (IL-1α, IL-6, COX-2). It also protected HaCaT cells from UVB-induced cell death and apoptosis. In conclusion, MAP could be a novel postoperational wound dressing preventing PIH associated with skin inflammation and injury.

Study on melanin enhanced third harmonic generation in a live cell model

Melanin dominates the endogenous contrasts of in vivo third harmonic generation (THG) imaging of human skin. A recent study investigated the THG in melanin solution and a linear relationship between melanin concentration and THG intensity was reported, in contrast to the expected nonlinear relationship. Since melanin hydrocolloid solution is very different from the skin tissue, here we report our study on the origin of the melanin-enhanced THG by using a live cell model. Different from the previous conclusion, our live cell study has indicated an initial nonlinear process where the THG intensity was enhanced according to the 3.5th power of melanin mass density (MMD). When the MMD is higher than 11 mg/ml, a transition from the resonance-enhanced THG to the high-order hyper-Rayleigh scattering process occurs. This saturation phenomenon of the virtual-transition-based THG nonlinear process is attributed to the multi-melanosome-induced scattering within the sub-femtoliter focal volume.

Efficacy of D-pigment dermocosmetic lightening product for solar lentigo lesions of the hand: A randomized controlled trial

Solar lentigo, benign lesions which mostly appear on chronically, sun-exposed surfaces, are associated with ageing. Patients are increasingly requesting a more uniform skin texture, especially for hands. Treatment options include dermoabrasion, intense pulsed light, cryotherapy, peelings, and laser therapy. Topical compounds can be employed, in alternative or associated with dermatologic procedures. The current study was designed to evaluate solar lentigo hyperpigmentation, skin architecture and clinician and patient assessments comparing a dermocosmetic lightening product (active) with a moisturizing product (control) according to clinical, digital and subjective analyses in 72 lesions over 12-month follow up period. Statistically significant differences were observed between the lesions treated with the active compared to the control in terms of papillary brightness (p = 0.03) and contrast (p = 0.03), and in the limitation of dermal-epidermal junction destructuring (p = 0.03) according to dermal-epidermal junction destructuring score at Reflectance Confocal Microscopy. Luminance (p = 0.04) and redness (p = 0.03) were improved at color analysis, and physician and patient evaluations favored the active in efficacy and patient satisfaction investigations. The dermocosmetic lightening product utilized in the current study proved to be more effective, according to clinical, digital and subjective analyses in reducing lesion hyperpigmentation, stabilizing the lesion skin architecture and increasing patient satisfaction compared to the control in a cohort of 36 subjects, over a 12-month period. Beside demonstrating the efficacy of this topical lightening product, we propose a “destructuring score”, which improves the robustness of solar lentigo’s evaluation, and can be used in future studies to standardize the quantitative comparisons of different treatment options.

Clinical purpura and elastosis and their correlation with skin tears in an aged population

The previous research reported the results of a prospect cohort study that used logistic regression analysis to construct a risk prediction model for skin tears in individuals aged over 65 years. The model identified three baseline individual characteristics (male gender, history of STs, and history of falls) and two baseline skin manifestations (purpura and elastosis) that predicted the risk of dorsal forearm skin tears. This paper outlines the relationships between baseline skin manifestations and the risk of skin tears. Univariable logistic regression analysis was conducted of all the baseline data collected from the same-study participants to identify variables that significantly predicted purpura and elastosis at baseline. Amongst the 173 participants, 71 (41%) developed one or more skin tears, and in these participants, 52 (73.2%) displayed purpura, 41 (57.8%) had elastosis, and 30 (42.3%) exhibited both manifestations of the dorsal forearm at baseline. Four individual characteristics (age, history of skin tears, history of falls, and antiplatelet therapy) and three skin properties (pH, subepidermal low echogenicity band of the forearms, and skin thickness) were found to predict the risk of purpura. Conversely, three individual variables (age, gender, and smoking), three clinical skin variables (uneven skin pigmentation, cutis rhomboidalis nuchae, and history of actinic keratosis) and one skin property variable (collagen type IV) predicted the risk of skin elastosis. Progressive changes to the skin's structural and mechanical properties from the underlying effects of chronological ageing, and environmental and lifestyle-related influences increased the risk of purpura and elastotic skin manifestations and concomitantly increased risk of skin tears amongst participants.

Diagnostic Accuracy of Reflectance Confocal Microscopy for Diagnosis of Skin Lesions: An Update

Context.—

Histopathology is the current standard to diagnose skin disease. However, biopsy may not always be feasible, such as in patients with multiple nevi, a patient with a lesion on an aesthetically significant site, or in children. Recently, noninvasive techniques, including reflectance confocal microscopy (RCM), optical coherence tomography, and Raman spectroscopy, have enabled dermatologists to manage skin lesions in real time without the need for biopsy.

Objective.—

To report the updated diagnostic accuracy of RCM for equivocal skin lesions.

Design.—

In this study, we retrospectively reviewed our data of clinically suspicious lesions from 2010 to 2017 that were evaluated by RCM.

Results.—

Our results showed an overall sensitivity of 98.2% and specificity of 99.8%.

Conclusions.—

In conclusion, RCM is a noninvasive real-time tool with the potential to diagnose skin lesions with high accuracy and without biopsy.

Beyond photoaging: additional factors involved in the process of skin aging

Studies assessing the impact of extrinsic factors on skin aging have increased during the last with the increase in life expectancy. Although most of the studies are about the sun radiation impact, many factors should be considered in elderly people, beyond environmental conditions. Lifestyle factors, like diet, sleeping, smoking, should be analyzed carefully, as common age-related conditions (menopause, diabetes, pulmonary diseases, etc.). All these factors could accelerate the natural decline of skin structure and functions, possibly affecting the responses to treatments and drugs. This review demonstrates that growing evidence regarding environmental factors that are associated with lifestyle and comorbidities deserve greater attention from researchers and dermatologists and may require new approaches in the management of skin aging.

Protection against summer solar lentigo over-pigmentation with a SPF30 daily cream

BACKGROUND/PURPOSE

The aim of this study was to measure lentigines' pigmentation over a long period of time and evaluate if summer over-pigmentation can be avoided by the use a SPF30 day skin cream.

METHODS

Seventeen healthy female volunteers aged 50 and over and presenting lentigines participated in the study from spring to summer. Throughout the study, all subjects applied a SPF30 daily skin cream to only one hand. Color measurements of the target lesions were performed with a chromameter and with a color-calibrated camera. Target lesions were also imaged with in vivo reflectance confocal microscopy (RCM). A specific procedure for re-registering the images was developed to ensure that the same papillae were measured over time.

RESULTS

Both color measurement methods, chromametry and color-calibrated camera, showed that lentigines treated over time with the SPF30 day skin cream were significantly lighter than the non-treated lentigines. The RCM images showed a decrease in the papillary contrast for the treated lentigines.

CONCLUSION

This study shows that this over-pigmentation can be avoided using a SPF30 day skin cream. Moreover, we have demonstrated that very fine re-registration of the RCM images is possible and ensures a more robust analysis.

Nanoethosomal formulation of gammaoryzanol for skin-aging protection and wrinkle improvement: a histopathological study

BACKGROUND

Free radical scavengers and antioxidants, with the main focus on enhanced targeting to the skin layers, can provide protection against skin ageing.

OBJECTIVE

The aim of the present study was to prepare nanoethosomal formulation of gammaoryzanol (GO), a water insoluble antioxidant, for its dermal delivery to prevent skin aging.

METHODS

Nanoethosomal formulation was prepared by a modified ethanol injection method and characterized by using laser light scattering, scanning electronic microscope (SEM) and X-ray diffraction (XRD) techniques. The effects of formulation parameters on nanoparticle size, encapsulation efficiency percent (EE%) and loading capacity percent (LC%) were investigated. Antioxidant activity of GO-loaded formulation was investigated in vitro using normal African green monkey kidney fibroblast cells (Vero). The effect of control and GO-loaded nanoethosomal formulation on superoxide dismutase (SOD) and malondialdehyde (MDA) content of rat skin was also probed. Furthermore, the effect of GO-loaded nanoethosomes on skin wrinkle improvement was studied by dermoscopic and histological examination on healthy humans and UV-irradiated rats, respectively.

RESULTS

The optimized nanoethosomal formulation showed promising characteristics including narrow size distribution 0.17 ± 0.02, mean diameter of 98.9 ± 0.05 nm, EE% of 97.12 ± 3.62%, LC% of 13.87 ± 1.36% and zeta potential value of -15.1 ± 0.9 mV. The XRD results confirmed uniform drug dispersion in the nanoethosomes structure. In vitro and in vivo antioxidant studies confirmed the superior antioxidant effect of GO-loaded nanoethosomal formulation compared with control groups (blank nanoethosomes and GO suspension).

CONCLUSIONS

Nanoethosomes was a promising carrier for dermal delivery of GO and consequently had superior anti-aging effect.

Assessment of skin pigmentation by confocal microscopy: Influence of solar exposure and protection habits on cutaneous hyperchromias

BACKGROUND

Cutaneous hyperchromias are disorders of skin pigmentation involving an increase of melanin production and its irregular accumulation in skin cells. It is known that the use of sunscreens helps to prevent changes in the skin pigmentation pattern, but the structural and morphological alterations that occur in the different types of hyperpigmentations need better elucidation.

OBJECTIVE

To assess the influence of solar exposure and protection habits on the pattern of skin pigmentation using reflectance confocal microscopy (RCM).

METHODS

Forty volunteers aged 18-39 years with skin hyperpigmentation participated in the study. Skin characterization was performed by imaging techniques and by assessing the habits of solar exposure and protection by applying questionnaires to the volunteers. RCM was used to record sequences of confocal sections at areas of interest and to examine cell shape and brightness in the basal cell layer of the lesion and in normal perilesional skin. Furthermore, high-resolution images were obtained for analysis of the spots.

RESULTS

Sunlight influences the number and location of spots as the face of volunteers with higher solar exposure was covered with spots, whereas volunteers with less exposure had fewer spots located in the nose and cheeks region due to greater exposure of these areas to the sun.

CONCLUSION

The data showed the importance of sun protection for preventing changes in the pattern of skin pigmentation, and RCM proved to be an important tool for skin characterization.

A Marked Poisson Process Driven Latent Shape Model for 3D Segmentation of Reflectance Confocal Microscopy Image Stacks of Human Skin

Segmenting objects of interest from 3D data sets is a common problem encountered in biological data. Small field of view and intrinsic biological variability combined with optically subtle changes of intensity, resolution, and low contrast in images make the task of segmentation difficult, especially for microscopy of unstained living or freshly excised thick tissues. Incorporating shape information in addition to the appearance of the object of interest can often help improve segmentation performance. However, the shapes of objects in tissue can be highly variable and design of a flexible shape model that encompasses these variations is challenging. To address such complex segmentation problems, we propose a unified probabilistic framework that can incorporate the uncertainty associated with complex shapes, variable appearance, and unknown locations. The driving application that inspired the development of this framework is a biologically important segmentation problem: the task of automatically detecting and segmenting the dermal-epidermal junction (DEJ) in 3D reflectance confocal microscopy (RCM) images of human skin. RCM imaging allows noninvasive observation of cellular, nuclear, and morphological detail. The DEJ is an important morphological feature as it is where disorder, disease, and cancer usually start. Detecting the DEJ is challenging, because it is a 2D surface in a 3D volume which has strong but highly variable number of irregularly spaced and variably shaped "peaks and valleys." In addition, RCM imaging resolution, contrast, and intensity vary with depth. Thus, a prior model needs to incorporate the intrinsic structure while allowing variability in essentially all its parameters. We propose a model which can incorporate objects of interest with complex shapes and variable appearance in an unsupervised setting by utilizing domain knowledge to build appropriate priors of the model. Our novel strategy to model this structure combines a spatial Poisson process with shape priors and performs inference using Gibbs sampling. Experimental results show that the proposed unsupervised model is able to automatically detect the DEJ with physiologically relevant accuracy in the range 10- 20 μm .

Quantitative analysis of intrinsic skin aging in dermal papillae by in vivo harmonic generation microscopy

Chronological skin aging is associated with flattening of the dermal-epidermal junction (DEJ), but to date no quantitative analysis focusing on the aging changes in the dermal papillae (DP) has been performed. The aim of the study is to determine the architectural changes and the collagen density related to chronological aging in the dermal papilla zone (DPZ) by in vivo harmonic generation microscopy (HGM) with a sub-femtoliter spatial resolution. We recruited 48 Asian subjects and obtained in vivo images on the sun-protected volar forearm. Six parameters were defined to quantify 3D morphological changes of the DPZ, which we analyzed both manually and computationally to study their correlation with age. The depth of DPZ, the average height of isolated DP, and the 3D interdigitation index decreased with age, while DP number density, DP volume, and the collagen density in DP remained constant over time. In vivo high-resolution HGM technology has uncovered chronological aging-related variations in DP, and sheds light on real-time quantitative skin fragility assessment and disease diagnostics based on collagen density and morphology.

Changes in dermal papilla structures due to aging in the facial cheek region

BACKGROUND/PURPOSE

In the past, it has been possible to measure the dermal papilla structures which are undulations between the epidermis and dermis by noninvasive method. However, almost all of previous studies were not intended to measure facial skin but another site of body. Here, we investigated age-dependent alterations for dermal papilla structures in the facial cheek region after elucidating the difference of characteristics between the body site.

METHODS

The surface of the dermis was observed under scanning electron microscope (SEM) using face and abdominal skin biopsy samples. A total of 90 Japanese women were investigated by in vivo confocal laser microscope (CLSM). The number and the shape in the horizontal cross-sectional images of the dermal papilla were analyzed.

RESULTS

The facial skin had different characteristics in comparison to the abdominal skin by SEM observation. Under CLSM observation, we found abnormal dermal papilla structures which were accompanied by spots or enlarged pore areas and eliminated these structures from our analysis. We revealed a decrease in the number of normal dermal papilla structures with age and large individual differences at younger ages.

CONCLUSION

We found abnormal dermal papilla structures and differences in the dermal papilla structures between face and other body site. With these taken into consideration, we could precisely investigate the aging alteration of normal dermal papilla structures in the face.

Relation between skin micro-topography, roughness, and skin age

BACKGROUND

The topography of the skin surface consists of lines, wrinkles, and scales. Primary and secondary lines form a network like structure that may be identified as polygons. Skin surface roughness measurements are widely applied in dermatological research and practice but the relation between roughness parameters and their anatomical equivalents are unclear. This study aimed to investigate whether the number of closed polygons (NCP) per measurement field can be used as a reliable parameter to measure skin surface topography. For this purpose, we analysed the relation between skin surface roughness parameters and NCP in different age groups.

METHODS

Images of the volar forearm skin of 38 subjects (14 children, 12 younger, and 12 older adults) were obtained with the VisioScan VC98. The NCP was counted by three independent researchers and selected roughness parameters were measured. Interrater reliability of counting the number of closed polygons and correlations between NCP, roughness parameters, and age were calculated.

RESULTS

The mean NCP/mm² in children was 3.1 (SD 1.1), in younger adults 1.0 (SD 0.7), and in older adults 1.0 (SD 0.9). The interrater reliability was 0.9. A negative correlation of NCP/mm² with age was observed, whereas measured roughness parameters were positively associated with age. NCP/mm² was weakly related to skin roughness.

CONCLUSION

The NCP/mm² is a reproducible parameter for characterizing the skin surface topography. It is proposed as an additional parameter in dermatological research and practice because it represents distinct aspects of the cutaneous profile not covered by established roughness parameters.