Optical features for chronological aging and photoaging skin by optical coherence tomography

A novel optical coherence tomography-based in vitro method of anti-aging skin analysis using 3D skin wrinkle mimics

BACKGROUND

Wrinkles represent a characteristic symptom of skin aging. In recent years, various studies have focused on their prevention and/or cure. However, clinical tests are still the only method available to directly detect and evaluate the anti-wrinkle efficacy of various substances. Moreover, no in vitro strategy for such anti-aging skin analysis has been reported. Therefore, in this study, we aimed to develop a novel technology to overcome these limitations.

MATERIALS AND METHODS

Full-thickness (FT) skin wrinkle mimics with various widths and depths were fabricated using a collagen stamping method. These were analyzed and compared using 2D and 3D Swept Source-Optical Coherence Tomography (SS-OCT) imaging technologies.

RESULTS

SS-OCT demonstrated superficial and cross-sectional images of the wrinkle mimics, and the size of the wrinkles was validated using image analysis. Retinoic acid treatment significantly decreased both the depth and width of wrinkles formed in the FT skin wrinkle mimics.

CONCLUSIONS

Using 3D tissue engineering and SS-OCT imaging technologies, we developed a novel in vitro technique that can directly detect skin wrinkles. This significantly efficient method could lead to an alternative strategy for animal experiments and preclinical anti-aging research on the skin.

Multiparametric Quantitative Analysis of Photodamage to Skin Using Optical Coherence Tomography

Ultraviolet (UV) irradiation causes 90% of photodamage to skin and long-term exposure to UV irradiation is the largest threat to skin health. To study the mechanism of UV-induced photodamage and the repair of sunburnt skin, the key problem to solve is how to non-destructively and continuously evaluate UV-induced photodamage to skin. In this study, a method to quantitatively analyze the structural and tissue optical parameters of artificial skin (AS) using optical coherence tomography (OCT) was proposed as a way to non-destructively and continuously evaluate the effect of photodamage. AS surface roughness was achieved based on the characteristic peaks of the intensity signal of the OCT images, and this was the basis for quantifying AS cuticle thickness using Dijkstra's algorithm. Local texture features within the AS were obtained through the gray-level co-occurrence matrix method. A modified depth-resolved algorithm was used to quantify the 3D scattering coefficient distribution within AS based on a single-scattering model. A multiparameter assessment of AS photodamage was carried out, and the results were compared with the MTT experiment results and H&E staining. The results of the UV photodamage experiments showed that the cuticle of the photodamaged model was thicker (56.5%) and had greater surface roughness (14.4%) compared with the normal cultured AS. The angular second moment was greater and the correlation was smaller, which was in agreement with the results of the H&E staining microscopy. The angular second moment and correlation showed a good linear relationship with the UV irradiation dose, illustrating the potential of OCT in measuring internal structural damage. The tissue scattering coefficient of AS correlated well with the MTT results, which can be used to quantify the damage to the bioactivity. The experimental results also demonstrate the anti-photodamage efficacy of the vitamin C factor. Quantitative analysis of structural and tissue optical parameters of AS by OCT enables the non-destructive and continuous detection of AS photodamage in multiple dimensions.

Assessing changes in facial skin quality using noninvasive in vivo clinical skin imaging techniques after use of a topical retinoid product in subjects with moderate-to-severe photodamage

BACKGROUND

Studies utilizing reflectance confocal microscopy (RCM) and dynamic optical coherence tomography (D-OCT) to assess cosmetic skin changes are limited.

METHODS

A 12-week, open-label study was conducted using RCM and D-OCT to evaluate the effects of a topical cosmetic retinol (RET05) on subjects with facial photodamage. Study endpoints included investigator grading, standardized (VISIA-CR) and 3D photography (Antera 3D), independent RCM (VivaScope1500) and D-OCT (VivoSight) image analysis, validated FACE-Q scales, and subject questionnaires.

RESULTS

Twenty-three subjects, 45- to 68-year old, with Fitzpatrick skin types II-IV completed the study. After 12 weeks of repeated application, RET05 demonstrated significant corresponding cosmetic improvements for overall photodamage, skin tone unevenness, tactile roughness, fine lines/wrinkles (forehead, periocular, and perioral), and coarse lines/wrinkles (forehead, periocular, and cheeks), and Allergan Skin Roughness Scale. FACE-Q assessments also demonstrated significant improvements from baseline at week 12. RCM analysis showed decreases in all epidermis, less compact stratum corneum (SC), more non-compact SC, decreases in coarse/huddled dermal fibers, and increases in fibrillar dermal fibers, as compared to baseline. D-OCT analysis showed significant decreases in epidermal thickness (ET), reduction of moderate/many collagen fragments and collagen bundles, and significant increases in the stroma attenuation coefficient and collagen density. Moreover, the dermal-epidermal junction was more pronounced, and vascular abundance at 300 and 500 μm depth increased. Independent evaluation of RCM and D-OCT images showed similar decreases in ET and improvements in dermal fibers.

CONCLUSION

This study was the first to utilize RCM and D-OCT to evaluate the cosmetic effects of a topical retinoid and further substantiate improvements in skin quality.

Methods of Non-Invasive In Vivo Optical Diagnostics in the Assessment of Structural Changes in the Skin Induced by Ultraviolet Exposure in an Experimental Model

Background: This paper demonstrates the use of optical diagnostic methods to assess the dynamic skin changes observed in acute and chronic exposure to ultraviolet (UV) radiation in vivo. Methods: Firstly, in order to initiate photoaging (chronic UV exposure), animals (n = 40) were divided into two groups: chronic UV exposure (n = 30), and control (n = 10; without irradiation). Photoaging in animals was induced by chronic repeated exposure to UVA radiation three times per week, for 12 weeks continuously, while the UV dose increased stepwise over the course of the experiment (55 minimal erythema doses (MED) in total). Laser fluorescence spectroscopy (LFS), optical tissue oximetry (OTO), laser Doppler flowmetry (LDF), and optical coherence tomography (OCT) of the shaved dorsum skin were performed regularly, once per week until the conclusion of the study. At 0, 5, and 12 weeks of the experiment, histological examination of animal tissues using hematoxylin/eosin and Masson’s trichrome staining was performed. At the second stage, erythema was induced in mice (n = 15) by acute UV exposure at high doses. The colorimetric assay of the image from a digital RGB camera was used to evaluate the erythema index. Results: The tissue content index η_collagen of collagen was appropriate for the characterization of skin photoaging. Significant differences (p < 0.05) in η_collagen were found between the control and photoaging groups from the 5th to the 9th week of the experiment. In addition, the rate of collagen degradation in the control group was about half that of the photoaging group. This marker allows the differentiation of photo- and chronoaging. OCT revealed the main optical layers of the skin in compliance with the histological pattern. The analysis of the RGB camera images provided visualization of the acute skin reaction to UV radiation. Conclusions: This study demonstrates the applicability of optical methods for the quantitative assessment of acute and chronic skin effects of UV exposure in vivo.

Optical coherence tomography-based non-invasive evaluation of premalignant lesions in SKH-1 mice

Non-invasively diagnosis of actinic keratoses (AK) is important for preventing cutaneous squamous cell carcinoma (cSCC). Optical coherence tomography (OCT) can be used to detect the cross-sectional skin micromorphology with sufficient resolution and imaging depth. It has the capability to reveal the changes in skin microstructure during the development of AK. Therefore, OCT can serve as a tool for diagnosing AK. This study explores the feasibility of OCT in evaluating the structural changes in mouse skin at the different stages following exposure to ultraviolet radiation. The performance of OCT is compared with histology, the gold standard in this context. The imaging results demonstrate that a wave-shaped irregular dermo-epidermal junction (DEJ), as well as the continuous thickening of the epidermis, are useful diagnostic parameters for diagnosing AK. Histological examinations confirm these observations. These findings emphasize the need for effective skin protection or medical treatment once changes in the DEJ and epidermis are detected. OCT shows strong potential for non-invasive evaluation of such changes and AK development, and can be used for the prevention of cSCC without the necessity of taking biopsies.

Andrographolide sodium bisulfate attenuates UV‑induced photo‑damage by activating the keap1/Nrf2 pathway and downregulating the NF‑κB pathway in HaCaT keratinocytes

Oxidative and inflammatory damage has been suggested to play important roles in the pathogenesis of skin photoaging. Andrographolide sodium bisulfate (ASB) is a soluble derivative of andrographolide and has known antioxidant and anti‑inflammatory properties. In the present study, cellular experiments were designed to investigate the molecular mechanisms underlying the effect of ASB in relieving ultraviolet (UV)‑induced photo‑damage. Following ASB pretreatment and UV irradiation, the apoptosis and necrosis of HaCaT cells were investigated by Hoechst 33342/propidium iodide staining. Reactive oxygen species (ROS) production was investigated using a DCFH‑DA fluorescence probe. Furthermore, the protein expression levels of p65, NF‑κB inhibitor‑α, nuclear factor E2‑related factor 2 (Nrf2) and kelch‑like ECH‑associated protein 1 (keap1) were measured via western blotting and immunofluorescence analyses. Furthermore, NF‑κB‑mediated cytokines were assessed by ELISA, and Nrf2‑mediated genes were detected by reverse transcription‑quantitative PCR. Pretreatment with ASB markedly increased cell viability, decreased cell apoptosis and decreased UV‑induced excess ROS levels. In addition, ASB activated the production of Nrf2 and increased the mRNA expression levels of glutamate‑cysteine ligase catalytic subunit and NAD(P)H quinone oxidoreductase 1, while ASB downregulated the protein expression of p65 and decreased the production of interleukin (IL)‑1β, IL‑6 and tumor necrosis factor‑α. These results suggested that ASB attenuates UV‑induced photo‑damage by activating the keap1/Nrf2 pathway and downregulating the NF‑κB pathway in HaCaT keratinocytes.

Optical Coherence Tomography Imaging of Normal, Chronologically Aged, Photoaged and Photodamaged Skin: A Systematic Review

BACKGROUND

Optical coherence tomography (OCT) is capable of providing a noninvasive real-time cross-sectional image of the skin through light-based interferometry, a method sometimes described as "light-based ultrasound." One key application of OCT in dermatology is the visualization of dermal collagen during chronological aging, photoaging, or photodamage. These skin conditions are typically managed by the practitioner's subjective assessment of severity and response to therapy.

OBJECTIVE

The purpose of this review is to present available evidence on the ability of OCT to image normal, chronologically aged, photoaged and photodamaged skin in human subjects.

METHODS AND MATERIALS

The authors have searched Medline, PubMed, EMBASE, Web of Science, Google Scholar, and Cochrane Library databases for published literature on the imaging of skin collagen by OCT using the following search terms: "optical coherence tomography," "OCT," "skin," "collagen," "photoaging," "wrinkles," and "photodamage."

RESULTS

The search resulted in 23 articles investigating OCT-based skin collagen imaging, which met their search criteria.

CONCLUSION

The authors anticipate tremendous growth in the field of OCT-based skin imaging that will parallel the development ultrasound technology has experienced over the past 30 years. They foresee that the use of OCT imaging to evaluate skin aging will not only help identify pathological changes earlier, but will also assist in the evaluation of the response to therapy longitudinally without biopsy.

In vitro 3-D model based on extending time of culture for studying chronological epidermis aging

Skin aging is a complex phenomenon in which several mechanisms operate simultaneously. Among them, intrinsic aging is a time-dependent process, which leads to gradual skin changes affecting its structure and function such as thinning down of both epidermal and dermal compartments and a flattening and fragility of the dermo-epidermal junction. Today, several approaches have been proposed for the generation of aged skin in vitro, including skin explants from aged donors and three-dimensional skin equivalent treated by aging-inducing chemical compounds or engineered with human cells isolated from aged donors. The aim of this study was to develop and validate a new in vitro model of aging based on skin equivalent demonstrating the same phenotypic changes that were observed in chronological aging. By using prolonged culture as a proxy for cellular aging, we extended to 120 days the culture time of a skin equivalent model based on collagen-glycosaminoglycan-chitosan porous polymer and engineered with human skin cells from photo-protected sites of young donors. Morphological, immunohistological and ultrastructural analysis at different time points of the culture allowed characterizing the phenotypic changes observed in our model in comparison to samples of non photo-exposed normal human skin from different ages. We firstly confirmed that long-term cultured skin equivalents are still morphologically consistent and functionally active even after 120 days of culture. However, similar to in vivo chronological skin aging a significant decrease of the epidermis thickness as well as the number of keratinocyte expressing proliferation marker Ki67 are observed in extended culture time skin equivalent. Epidermal differentiation markers loricrin, filaggrin, involucrin and transglutaminase, also strongly decreased. Ultrastructural analysis of basement membrane showed typical features of aged skin such as duplication of lamina densa and alterations of hemidesmosomes. Moreover, the expression of hyaluronan and its surface receptor CD44 drastically decreased as observed during chronological skin aging. Finally, we found that the level of p16INK4A expression significantly increased supporting cellular senescence process associated to our model. To conclude, the major morphological and ultrastructural epidermal modifications observed in both our extended culture skin equivalent model and skin biopsies from old donors validate the relevance of our model for studying chronological aging, understanding and elucidating age-related modifications of basic skin biological processes. In addition, our model provides a unique tool for identifying new targeted molecules intended at improving the appearance of aging skin.