Photoaging and Sequential Function Reversal with Cellular-Resolution Optical Coherence Tomography in a Nude Mice Model

Research on Circular RNA Expression Profiles in the Photoaging Mouse Model

Background

Nude mouse has been widely used to study photoaging induced by long-term chronic UV exposure. Circular RNAs (circRNAs) have been previously identified in several diseases. However, the roles of circRNAs in photoaging and potential regulatory mechanisms remain unclear.

Objectives

To identify specific circRNAs differentially expressed in photoaged skin and investigate their potential role in aging.

Materials and Methods

In this study, we screened out the microarray data to profile the expression of circRNAs. The circRNAs were analyzed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) biological pathway.

Results

36 circRNAs were identified to be differentially expressed between the UV group and control group (fold change > 1.5; P < 0.05), including 6 upregulated and 30 downregulated circRNAs. GO and KEGG biological pathway analyses indicated that the changes in circRNAs were associated with cancer, inflammation, oxidative stress, and metabolism.

Conclusions

This present study revealed a circRNAs expression profiling in vivo. These findings not only provide a new possibility to prevent the occurrence of photoaging but also have therapeutic values for photoaging and associated skin diseases.

Adaptability of melanocytes post ultraviolet stimulation in patients with melasma

BACKGROUND

Dynamic in vivo changes in melanin in melasma lesions after exposure to ultraviolet (UV) irradiation have not been described.

OBJECTIVES

To determine whether melasma lesions and nearby perilesions demonstrated different adaptive responses to UV irradiation and whether the tanning responses were different among different locations on face.

METHODS

We collected sequential images from real-time cellular resolution full-field optical coherence tomography (CRFF-OCT) at melasma lesions and perilesions among 20 Asian patients. Quantitative and layer distribution analyses for melanin were performed using a computer-aided detection (CADe) system that utilizes spatial compounding-based denoising convolutional neural networks.

RESULTS

The detected melanin (D) is melanin with a diameter >0.5 µm, among which confetti melanin (C) has a diameter of >3.3 µm and corresponds to a melanosome-rich package. The calculated C/D ratio is proportional to active melanin transportation. Before UV exposure, melasma lesions had more detected melanin (p = 0.0271), confetti melanin (p = 0.0163), and increased C/D ratio (p = 0.0152) in the basal layer compared to those of perilesions. After exposure to UV irradiation, perilesions have both increased confetti melanin (p = 0.0452) and the C/D ratio (p = 0.0369) in basal layer, and this effect was most prominent in right cheek (p = 0.030). There were however no significant differences in the detected, confetti, or granular melanin areas before and after exposure to UV irradiation in melasma lesions in all the skin layers.

CONCLUSIONS

Hyperactive melanocytes with a higher baseline C/D ratio were noted in the melasma lesions. They were "fixed" on the plateau and were not responsive to UV irradiation regardless of the location on face. Perilesions retained adaptability with a dynamic response to UV irradiation, in which more confetti melanin was shed, mainly in the basal layer. Therefore, aggravating effect of UV on melasma was mainly due to UV-responsive perilesions rather than lesions.

Repeated exposure to fractional CO2 laser delays squamous cell carcinoma formation and prevents clinical and subclinical photodamage visualized by line-field confocal optical coherence tomography and histology

OBJECTIVES

Ablative fractional laser (AFL) is a well-established modality for treating ultraviolet radiation (UVR)-induced skin photodamage. We aimed to investigate the potential of AFL to delay squamous cell carcinoma (SCC) formation and prevent photodamage in a preclinical UVR-induced SCC model.

MATERIALS AND METHODS

Hairless C3.Cg-Hrhr /TifBomTac mice (n = 50) were exposed to UVR three times weekly throughout the study. UV-exposed mice were randomized to two groups that received dorsal CO2 AFL (10 mJ/mb, 10% density) or no treatment. AFL was performed every other week for a total of 16 weeks (nine treatments in total). The primary outcome was time to tumor occurrence. In a subset of mice on Day 150, prevention of clinical photodamage was assessed by examination of skin tightness and dyspigmentation. Concomitantly, assessment of subclinical photoprevention based on normalization of keratinocyte dysplasia, dermo-fiber morphology (collagen and elastin fibers), and skin thickness, was performed using line-field confocal optical coherence tomography (LC-OCT) and histology.

RESULTS

Repeated AFL treatments delayed SCC tumor development compared to UVR control mice by 12, 19, and 30 days for first, second, and third tumors, respectively (p ≤ 0.0017). Compared to UVR controls, AFL prevented photodamage both clinically and subclinically, based on LC-OCT and histology. In the epidermal layer, AFL imparted photopreventative effects including reduced dyspigmentation and keratinocyte dysplasia (1 vs. 2.5, p = 0.0079) and partial normalization of the epidermal thickness (p < 0.0001). In the dermis, AFL led to twofold greater skin tightness (p = 0.0079), improved dermo-fiber structure, and dermal thickness (p = 0.0011).

CONCLUSION

In conclusion, repeated AFL treatments of UVR-exposed skin significantly delayed SCC tumor formation and prevented clinical and imaging-assessed subclinical signs of photodamage, indicating a potential for AFL in prevention strategies for SCC and photodamage in high-risk populations.