Identification of chronological and photoageing-associated microRNAs in human skin

Micro RNA Dysregulation in Keratinocyte Carcinomas: Clinical Evidence, Functional Impact, and Future Directions

The keratinocyte carcinomas, basal cell carcinoma (BCC), and cutaneous squamous cell carcinoma (cSCC), are the most common cancers in humans. Recently, an increasing body of literature has investigated the role of miRNAs in keratinocyte carcinoma pathogenesis, progression and their use as therapeutic agents and targets, or biomarkers. However, there is very little consistency in the literature regarding the identity of and/or role of individual miRNAs in cSCC (and to a lesser extent BCC) biology. miRNA analyses that combine clinical evidence with experimental elucidation of targets and functional impact provide far more compelling evidence than studies purely based on clinical findings or bioinformatic analyses. In this study, we review the clinical evidence associated with miRNA dysregulation in KCs, assessing the quality of validation evidence provided, identify gaps, and provide recommendations for future studies based on relevant studies that investigated miRNA levels in human cSCC and BCC. Furthermore, we demonstrate how miRNAs contribute to the regulation of a diverse network of cellular functions, and that large-scale changes in tumor cell biology can be attributed to miRNA dysregulation. We highlight the need for further studies investigating the role of miRNAs as communicators between different cell types in the tumor microenvironment. Finally, we explore the clinical benefits of miRNAs as biomarkers of keratinocyte carcinoma prognosis and treatment.

Recent advances in exosomal non-coding RNA-based therapeutic approaches for photoaging

BACKGROUND

Photoaging is a degenerative biological process that affects the quality of life. It is caused by environmental factors including ultraviolet radiation (UVR), deep skin burns, smoking, active oxygen, chemical substances, and trauma. Among them, UVR plays a vital role in the aging process.

AIM

With the continuous development of modern medicine, clinical researchers have investigated novel approaches to treat aging. In particular, mesenchymal stem cells (MSCs), non-coding RNAs are involved in various physiological processes have broad clinical application as they have the advantages of convenient samples, abundant sources, and avoidable ethical issues.

METHODS

This article reviews research progress on five types of stem cell, exosomes, non-coding RNA in the context of photoaging treatment: adipose-derived stem cell, human umbilical cord MSCs, epidermal progenitor cells, keratinocyte stem cells, and hair follicle stem cells (HFSCs). It also includes stem cell related exosomes and their non-coding RNA research.

RESULTS

The results have clinical guiding significance for prevention and control of the onset and development of photoaging. It is found that stem cells secrete cytokines, cell growth factors, non-coding RNA, exosomes and proteins to repair aging skin tissues and achieve skin rejuvenation. In particular, stem cell exosomes and non-coding RNA are found to have significant research potential, as they possess the benefits of their source cells without the disadvantages which include immune rejection and granuloma formation.

Q-Switched 1064 nm Nd:YAG Laser Rejuvenates Photoaging Skin of Rats by Downregulating miR-196b-5p

Background: Q-switched 1064 nm Nd:YAG laser (1064-QSNYL) is efficient in rejuvenating photoaging skin, and microRNAs (miRNAs) participate in this process. Objective: In this study, we aimed to explore the effects of 1064-QSNYL on miR-196b-5p, TGF-beta receptor II (TGFBR2), and SMAD7 in the photoaging skin of rats. Methods: The relationship between miR-196b-5p and TGFBR2 in HaCaT cells was detected by real-time PCR and western blotting. A skin photoaging model was established in Wistar rats using ultraviolet (UV) radiation (UVR). Dermoscopy, hematoxylin-eosin (HE) staining, Sirius red staining, and hydroxyproline content were used to observe the effect of UVR on rat skin. The 1064-QSNYL was used for skin rejuvenation. The expression of COL3A1, TGFB1, TGFBR2, SMAD2, SMAD3, and SMAD7 was detected by real-time PCR and/or western blotting. Results: TGFBR2 was a specific target of miR-196b-5p in the skin. In HaCaT cells and the photoaging skin of rats, 1064-QSNYL treatment upregulated COL3A1 and TGFBR2 and downregulated SMAD7 and miR-196b-5p. Conclusions: We showed for the first time that 1064-QSNYL treatment rejuvenates photoaging rat skin by regulating TGFBR2 and SMAD7. Downregulation of miR-196b-5p assists in this process by targeting and upregulating TGFBR2.

Non-coding RNAs in photoaging-related mechanisms: a new paradigm in skin health

The aging of skin is a biological process affected by environmental or genetic factors. Exposure to ultraviolet (UV) radiation is the main environmental factor causing skin aging. Cumulative UV-induced photodamage of the skin tissue is associated with premature cellular senescence, extracellular degradation, and inflammatory responses in photoaging processes. Non-coding RNAs (ncRNAs) are untranslated transcripts and master regulators of protein-coding genes. ncRNAs have a critical regulatory role in maintaining skin structure, skin barrier function, morphogenesis, and development. Altered ncRNA expression has been reported in various skin disorders such as photoaging and skin cancers. ncRNAs contribute to the suppression and promotion of photoaging by modulating signaling pathways such as mitogen-activated protein kinase (MAPK) pathway and regulating inflammatory cytokines, matrix metalloproteinases (MMPs), and senescence-associated genes. Elucidation of the functions of ncRNAs will improve the identification of molecular mechanisms underlying photoaging, and can be used in the development of therapeutic approaches in skin health and prevention of sun-induced aging. This review summarized the currently described ncRNAs and their functions in photoaging.

Exosomal lncRNA KLF3-AS1 derived from bone marrow mesenchymal stem cells stimulates angiogenesis to promote diabetic cutaneous wound healing

AIMS

We focused on BMSC-derived exosomal lncRNA KLF3-AS1 and its significance in diabetic cutaneous wound healing.

METHODS

Potential interaction between KLF3-AS1 and miR-383, miR-383 and VEGFA were predicted using bioinformatic analysis and validated by luciferase reporter, RIP, and FISH assays. The proliferation, apoptosis, migration and tube formation of HUVECs were evaluated by CCK-8, flow cytometry, wound healing, and tube formation assays, respectively. A murine diabetic cutaneous wound model was used to investigate therapeutic effects of exosomal KLF3-AS1 in vivo. Histological alterations in skin tissues were examined using HE, Masson staining, and immunostaining of CD31.

RESULTS

BMSC-derived exosomal KLF3-AS1 sufficiently promoted proliferation, migration, and tube formation, while inhibited apoptosis of HUVECs challenged by high glucose. The protective effects of exosomal KLF3-AS1 were achieved at least partially by down-regulating miR-383, and boosting the expression of its target, VEGFA. In vivo, exosomes from KLF3-AS1-expressing BMSCs demonstrated the best effects in promoting cutaneous wound healing in diabetic mice, which were associated with minimal weight loss, increased blood vessel formation, reduced inflammation, decreased miR-383 expression, and up-regulated VEGFA.

CONCLUSIONS

Exosomal lncRNA KLF3-AS1 derived from BMSCs induces angiogenesis to promote diabetic cutaneous wound healing.

Targeting microRNA for improved skin health

BACKGROUND

In human skin, miRNAs have important regulatory roles and are involved in the development, morphogenesis, and maintenance by influencing cell proliferation, differentiation, immune regulation, and wound healing. MiRNAs have been investigated for many years in various skin disorders such as atopic dermatitis, psoriasis, as well as malignant tumors. Only during recent times, cosmeceutical use of molecules/natural active ingredients to regulate miRNA expression for significant advances in skin health/care product development was recognized.

AIM

To review miRNAs with the potential to maintain and boost skin health and avoid premature aging by improving barrier function, preventing photoaging, hyperpigmentation, and chronological aging/senescence.

METHODS

Most of the cited articles were found through literature search on PubMed. The main search criteria was a keyword "skin" in combination with the following words: miRNA, photoaging, UV, barrier, aging, exposome, acne, wound healing, pigmentation, pollution, and senescence. Most of the articles reviewed for relevancy were published during the past 10 years.

RESULTS

All results are summarized in Figure 1, and they are based on cited references.

CONCLUSIONS

Thus, regulating miRNAs expression is a promising approach for novel therapy not only for targeting skin diseases but also for cosmeceutical interventions aiming to boost skin health.

Enhanced Platelet-Rich Plasma (ePRP) Stimulates Wound Healing through Effects on Metabolic Reprogramming in Fibroblasts

As a source of growth factors for expediting wound healing and tissue regeneration, plasma-rich plasma (PRP) has been extensively applied in diverse fields including orthopaedics, ophthalmology, oral and maxillofacial surgery, dentistry, and gynaecology. However, the function of PRP in metabolic regulations remains enigmatic. A standardized method was devised herein to enrich growth factors and to lyophilize it as enhanced PRP (ePRP) powder, which could become ubiquitously available without mechanical centrifugation in clinical practice. To identify metabolic reprogramming in human dermal fibroblasts under ePRP treatment, putative metabolic targets were identified by transcriptome profiling and validated for their metabolic effects and mechanism. ePRP does not only promote wound healing but re-aligns energy metabolism by shifting to glycolysis through stimulation of glycolytic enzyme activity in fibroblasts. On the contrary, oxygen consumption rates and several mitochondrial respiration activities were attenuated in ePRP-treated fibroblasts. Furthermore, ePRP treatment drives the mitochondrial resetting by hindering the mitochondrial biogenesis-related genes and results in a dampened mitochondrial mass. Antioxidant production was further increased by ePRP treatment to prevent reactive oxygen species formation. Besides, ePRP also halts the senescence progression of fibroblasts by activating SIRT1 expression. Importantly, the glycolytic inhibitor 2-DG can completely reverse the ePRP-enhanced wound healing capacity, whereas the mitochondrial inhibitor oligomycin cannot. This is the first study to utilize PRP for comprehensively investigating its effects on the metabolic reprogramming of fibroblasts. These findings indicate that PRP’s primary metabolic regulation is to promote metabolic reprogramming toward glycolytic energy metabolism in fibroblasts, preserving redox equilibrium and allowing anabolic pathways necessary for the healing and anti-ageing process.

Structural and Functional Changes and Possible Molecular Mechanisms in Aged Skin

Skin aging is a complex process influenced by intrinsic and extrinsic factors. Together, these factors affect the structure and function of the epidermis and dermis. Histologically, aging skin typically shows epidermal atrophy due to decreased cell numbers. The dermis of aged skin shows decreased numbers of mast cells and fibroblasts. Fibroblast senescence contributes to skin aging by secreting a senescence-associated secretory phenotype, which decreases proliferation by impairing the release of essential growth factors and enhancing degradation of the extracellular matrix through activation of matrix metalloproteinases (MMPs). Several molecular mechanisms affect skin aging including telomere shortening, oxidative stress and MMP, cytokines, autophagic control, microRNAs, and the microbiome. Accumulating evidence on the molecular mechanisms of skin aging has provided clinicians with a wide range of therapeutic targets for treating aging skin.

An update in toxicology of ageing

The field of ageing research has been rapidly advancing in recent decades and it had provided insight into the complexity of ageing phenomenon. However, as the organism-environment interaction appears to significantly affect the organismal pace of ageing, the systematic approach for gerontogenic risk assessment of environmental factors has yet to be established. This puts demand on development of effective biomarker of ageing, as a relevant tool to quantify effects of gerontogenic exposures, contingent on multidisciplinary research approach. Here we review the current knowledge regarding the main endogenous gerontogenic pathways involved in acceleration of ageing through environmental exposures. These include inflammatory and oxidative stress-triggered processes, dysregulation of maintenance of cellular anabolism and catabolism and loss of protein homeostasis. The most effective biomarkers showing specificity and relevancy to ageing phenotypes are summarized, as well. The crucial part of this review was dedicated to the comprehensive overview of environmental gerontogens including various types of radiation, certain types of pesticides, heavy metals, drugs and addictive substances, unhealthy dietary patterns, and sedentary life as well as psychosocial stress. The reported effects in vitro and in vivo of both recognized and potential gerontogens are described with respect to the up-to-date knowledge in geroscience. Finally, hormetic and ageing decelerating effects of environmental factors are briefly discussed, as well.

The dark side of daylight: photoaging and the tumor microenvironment in melanoma progression

Continued thinning of the atmospheric ozone, which protects the earth from damaging ultraviolet radiation (UVR), will result in elevated levels of UVR reaching the earth's surface, leading to a drastic increase in the incidence of skin cancer. In addition to promoting carcinogenesis in skin cells, UVR is a potent extrinsic driver of age-related changes in the skin known as "photoaging." We are in the preliminary stages of understanding of the role of intrinsic aging in melanoma, and the tumor-permissive effects of photoaging on the skin microenvironment remain largely unexplored. In this Review, we provide an overview of the impact of UVR on the skin microenvironment, addressing changes that converge or diverge with those observed in intrinsic aging. Intrinsic and extrinsic aging promote phenotypic changes to skin cell populations that alter fundamental processes such as melanogenesis, extracellular matrix deposition, inflammation, and immune response. Given the relevance of these processes in cancer, we discuss how photoaging might render the skin microenvironment permissive to melanoma progression.

Skin Immunomodulation during Regeneration: Emerging New Targets

Adipose-Derived Stem Cells (ADSC) are present within the hypodermis and are also expected to play a pivotal role in wound healing, immunomodulation, and rejuvenation activities. They orchestrate, through their exosome, the mechanisms associated to cell differentiation, proliferation, and cell migration by upregulating genes implicated in different functions including skin barrier, immunomodulation, cell proliferation, and epidermal regeneration. ADSCs directly interact with their microenvironment and specifically the immune cells, including macrophages and T and B cells, resulting in differential inflammatory and anti-inflammatory mechanisms impacting, in return, ADSCs microenvironment and thus skin function. These useful features of ADSCs are involved in tissue repair, where the required cell proliferation, angiogenesis, and anti-inflammatory responses should occur rapidly in damaged sites. Different pathways involved have been reported such as Growth Differentiation Factor-11 (GDF11), Tumor Growth Factor (TGF)-β, Metalloproteinase (MMP), microRNA, and inflammatory cytokines that might serve as specific biomarkers of their immunomodulating capacity. In this review, we try to highlight ADSCs’ network and explore the potential indicators of their immunomodulatory effect in skin regeneration and aging. Assessment of these biomarkers might be useful and should be considered when designing new clinical therapies using ADSCs or their specific exosomes focusing on their immunomodulation activity.

Epigenetic Regulation of Epidermal Differentiation

The epidermis is the outer part of the skin that protects the organism from dehydration and shields from external insults. Epidermal cells, called keratinocytes, undergo a series of morphological and metabolic changes that allow them to establish the biochemical and structural elements of an effective epidermal barrier. This process, known as epidermal differentiation, is critical for the maintenance of the epidermis under physiological conditions and also under stress or in various skin pathologies. Epidermal differentiation relies on a highly coordinated program of gene expression. Epigenetic mechanisms, which commonly include DNA methylation, covalent histone modifications, and microRNA (miRNA) activity, modulate various stages of gene expression by altering chromatin accessibility and mRNA stability. Their involvement in epidermal differentiation is a matter of intensive studies, and the results obtained thus far show a complex network of epigenetic factors, acting together with transcriptional regulators, to maintain epidermal homeostasis and counteract adverse effects of environmental stressors.

The Role of microRNAs in Organismal and Skin Aging

The aging process starts directly after birth and lasts for the entire lifespan; it manifests itself with a decline in an organism’s ability to adapt and is linked to the development of age-related diseases that eventually lead to premature death. This review aims to explore how microRNAs (miRNAs) are involved in skin functioning and aging. Recent evidence has suggested that miRNAs regulate all aspects of cutaneous biogenesis, functionality, and aging. It has been noted that some miRNAs were down-regulated in long-lived individuals, such as let-7, miR-17, and miR-34 (known as longevity-related miRNAs). They are conserved in humans and presumably promote lifespan prolongation; conversely, they are up-regulated in age-related diseases, like cancers. The analysis of the age-associated cutaneous miRNAs revealed the increased expression of miR-130, miR-138, and miR-181a/b in keratinocytes during replicative senescence. These miRNAs affected cell proliferation pathways via targeting the p63 and Sirtuin 1 mRNAs. Notably, miR-181a was also implicated in skin immunosenescence, represented by the Langerhans cells. Dermal fibroblasts also expressed increased the levels of the biomarkers of aging that affect telomere maintenance and all phases of the cellular life cycle, such as let-7, miR-23a-3p, 34a-5p, miR-125a, miR-181a-5p, and miR-221/222-3p. Among them, the miR-34 family, stimulated by ultraviolet B irradiation, deteriorates collagen in the extracellular matrix due to the activation of the matrix metalloproteinases and thereby potentiates wrinkle formation. In addition to the pro-aging effects of miRNAs, the plausible antiaging activity of miR-146a that antagonized the UVA-induced inhibition of proliferation and suppressed aging-related genes (e.g., p21WAF-1, p16, and p53) through targeting Smad4 has also been noticed. Nevertheless, the role of miRNAs in skin aging is still not fully elucidated and needs to be further discovered and explained.

Expression of miR-135b in Psoriatic Skin and Its Association with Disease Improvement

miRNAs have been associated with psoriasis since just over a decade. However, we are far from a complete understanding of their role during the development of this disease. Our objective was to characterize the cutaneous expression of miRNAs not previously described in psoriasis, the changes induced following the treatment with biologicals and their association with disease improvement. Next generation sequencing was performed from five skin samples from psoriasis patients (lesional and non-lesional skin) and five controls, and from this cohort, 12 microRNAs were selected to be analyzed in skin samples from 44 patients with plaque psoriasis. In 15 patients, an additional sample was obtained after three months of biological treatment. MiR-9-5p, miR-133a-3p and miR-375 were downregulated in the lesional skin of psoriasis patients. After treatment, expression of miR-133a-3p, miR-375, miR-378a and miR-135b in residual lesions returned towards the levels observed in non-lesional skin. The decrease in miR-135b levels after treatment with biologics was associated with both the improvement of patients evaluated through Psoriasis Area and Severity Index score and the decrease in local inflammatory response. Moreover, basal expression of miR-135b along with age was associated with the improvement of psoriasis, suggesting its possible usefulness as a prognostic biomarker.