Chemical Peeling by SA-PEG Remodels Photo-damaged Skin: Suppressing p53 Expression and Normalizing Keratinocyte Differentiation

Update on Chemical Peels

Chemical peeling is a procedure used for cosmetic improvement of the skin or treatment of some medical skin disorders, by the application of chemical exfoliant. In spite of a long history of clinical use of chemical peels, understanding of the science behind the procedure is still evolving. In this article, we review new concepts, understandings, and publications in the field of chemical peels.

0.5-5% Supramolecular Salicylic Acid Hydrogel is Safe for Long-Term Topical Application and Improves the Expression of Genes Related to Skin Barrier Homeostasis in Mice Models

Background

As a keratolytic, salicylic acid (SA) can be topically applied in various formulations and doses in dermatology. Supramolecular SA hydrogel, a new SA formulation with higher bioavailability, is developed and commercially available nowadays. However, there still remain concerns that the long-term and continual application of SA at low concentrations may jeopardize the cutaneous barrier properties.

Aim of the Study

To reveal the long-term effects of 0.5-5% supramolecular SA hydrogel on the skin barrier in normal mice models.

Materials and Methods

The 0.5%, 1%, 2%, and 5% supramolecular SA hydrogel or hydrogel vehicle without SA was applied to mice's shaved dorsal skin once per day respectively. Tissue samples of the dorsal skin were harvested on day 14 and 28 of the serial application of SA for histopathological observation and transcriptomic analysis.

Results

Following topical supramolecular SA hydrogel therapy with various concentrations of SA (0.5%, 1%, 2%, and 5%) for 14 days and 28 days, there were no obvious macroscopic signs of impaired cutaneous health and no inflammatory or degenerative abnormalities were observed in histological results. Additionally, the transcriptomic analysis revealed that on day 14, SA dramatically altered the expression of genes related to the extracellular matrix structural constituent. And on day 28, SA regulated gene expression profiles of keratinization, cornified envelope, and lipid metabolism remarkably. Furthermore, the expression of skin barrier related genes was significantly elevated after the application of SA based on RNA-seq results, and this is likely to be associated with the PPAR signaling pathway according to the enrichment analysis.

Conclusion

Our findings demonstrated that the sustained topical administration of the 0.5-5% supramolecular SA hydrogel for up to 28 days did no harm to normal murine skin and upregulated the expression of genes related to the epidermal barrier.

Cultivation of human skin cells under physiological oxygen concentration modulates expression of skin significant genes and response to hydroxy acids

Physiological oxygen concentration (physioxia) ranges from 1 to 8% in human tissues while many researchers cultivate mammalian cells under an atmospheric concentration of 21% (hyperoxia). Oxygen is one of the significant gases which functions in human cells including energy production in mitochondria, metabolism in peroxidase, and transcription of various genes in company with HIF (Hypoxia-inducible factors) in the nucleus. Thus, mammalian cell culture should be deliberated on the oxygen concentration to mimic in vivo physiology. Here, we studied if the cultivation of human skin cells under physiological conditions could affect skin significant genes in barrier functions and dermal matrix formation. We further examined that some representative active ingredients in dermatology such as glycolic acid, gluconolactone, and salicylic acid work in different ways depending on the oxygen concentration. Taken together, we present the importance of oxygen concentration in skin cell culture for proper screening of novel ingredients as well as the mechanistic study of skin cell regulation.

The rise of Chemical Peeling in 19th-century European Dermatology: emergence of agents, formulations and treatments

BACKGROUND

Considering the increasing number of chemical peeling applications, also the interest in the history of chemical peelings and agents, has grown in dermatology. Research ascribes the first use of phenol as a chemical peeling agent to William Tilbury Fox (1836-1879) in 1871. Furthermore, Ferdinand von Hebra (1847-1902) is said to describe the properties of various peeling agents in 1874, and Paul Gerson Unna (1850-1929) adds resorcinol and trichloroacetic acid in 1882.

OBJECTIVE

To identify the first mentions of chemical peeling applications and agents in 19th-century dermatology.

METHODS

Nineteenth-century dermatologists were identified by an examination of literature of the last 30 years on the history of chemical peeling. Systematic examination of the medical textbooks of Hebra, Fox and Unna was conducted. It was proved whether the mentioned agents were used for chemical peeling applications.

RESULTS

The skin peeling property of phenol was already discovered by its first describer, the chemist Friedlieb Ferdinand Runge (1795-1867) in 1834. The Viennese dermatologist Hebra described phenol as a chemical peeling agent in 1860. Hebra and his associate Moriz Kaposi (1837-1902) stated that 'Lotio carbolica' was already used in London. Fox used phenol mostly as a disinfectant and not for chemical peelings since 1869. Unna described the chemical peeling property of salicylic acid in 1882 and gave the most comprehensive account of chemical peels of the 19th century in 1899. Unna also introduced the Gutta-percha plaster with salicylic acid and phenol. Around 1900, Unna was famous for his peeling paste with resorcinol in Germany.

CONCLUSIONS

A new chronology of the introduction of chemical peeling in dermatology can be drawn from the results. The German-speaking dermatology pioneered the treatment of skin diseases with chemical peelings as well as for aesthetical purposes 21 years earlier than hitherto known.

[Chemical peel treatments in dermatology]

Chemical peel treatments, which utilize a number of chemical peeling solutions subject to patient indication, are an easy to learn therapeutic technique suited for, in particular, various types of acne, acne scars, actinic keratosis and "sun-damaged skin". Especially the positive and long-lasting results of deep peels in the area of skin rejuvenation are deemed the gold standard against which other techniques, including lasers, must compare themselves. Other benefits of chemical peels include the flexibility to mix and match chemical solutions to custom design the treatment best suited for the desired degree of skin penetration, as well as the relatively low cost.

Tracking cells in their native habitat: lineage tracing in epithelial neoplasia

For tumours to develop, mutations must disrupt tissue homeostasis in favour of deregulated proliferation. Genetic lineage tracing has uncovered the behaviour of proliferating cells that underpins the maintenance of epithelial tissues and the barriers that are broken in neoplastic transformation. In this Review, we focus on new insights revealed by quantifying the behaviour of normal, preneoplastic and tumour cells in epithelia in transgenic mice and consider their potential importance in humans.

Le gènehairlessde la souris

The hairless gene in mammals encodes a nuclear factor that is highly expressed in skin and appears to control hair follicle integrity and cycling. In the absence of a normal and functional Hairless (Hr) protein, the hair bulb undergoes premature apoptosis during the first catagen stage of the hair cycle. The most striking effects of the mutation are loss of hair follicles and formation of epidermal utricles and dermal cysts. The hairless gene expression appears to be widespread and temporally regulated. The gene is strongly expressed in different compartments of the brain. Hairless mRNAs were detected in cartilage, gonads, thymus and colon. In addition to alopecia, hairless mice strains show subtle defects in the development and differentiation of various tissues and organs. The Hr protein is localised in cell nuclei and functions as a transcriptional regulator. Although its role has not been resolved in molecular terms, it was demonstrated that Hr is able to interact with multiple nuclear hormone receptors. Hr seems to be a part of a large multiprotein complex capable to repress transcription by its association to chromatin remodelling factors such as histone deacetylases. Recent experimental data suggest that Hr might be involved in Hox gene regulation, cell adhesion modulation and progenitor cells identity. At least in the skin, but probably in other organs, the Hr repressor seems to be responsible for the timing of epithelial cells differentiation.