Comparative effects of various absorbable threads in a rat model

Background: Conventional procedures including botulinum toxin and filler injections have their limitations in improving deep wrinkles and decreasing tissue laxity, and possess the propensity for vascular accidents. Absorbable thread is a recently commercialized field, but there is little evidence on comparative superiority. Objectives: We observed the effects of polydiaxanone (PDO) threads with different number of strands in relation to collagen production and histopathology in a rat model. Materials and methods: Dorsal skin of rat was divided into five different compartments and four different PDO threads and monofilament poly-lactic acid (PLA) thread were inserted. Tissue samples were obtained at week 1, 2, and 12 after the procedure for histopathologic review and real-time PCR for quantification of collagen. Results: Multiple PDO filaments produced more collagen at 2 weeks. Single-stranded PLA thread insertion resulted in more Col1α1 levels than the double PDO thread and also showed the most Col1α3 production at week 2. The amount of collagen showed a sharp decline at week 12. Histologic evaluation showed retained threads surrounded by fibrous capsule-like structure at week 12. Conclusion: We were able to observe more collagen production in multiple stranded PDO threads compared to a single strand and that increasing number of threads leads to more collagen synthesis.     

Multi-polydioxanone (PDO) scaffold for forehead wrinkle correction: A pilot study

Background: Forehead wrinkles are the result of contracture of the frontalis muscle and the skin aging process. Currently, hyaluronic acid filler and botulinum toxin are the main materials used for correction of these wrinkles. In addition, polydioxanone (PDO) thread has also been applied for this treatment. Objective: In order to evaluate the efficacy and safety of multi-PDO scaffold in animal and human skin, we tested PDO insertion in rat and mini-pig models and human volunteers with forehead wrinkles. Methods: A stent-shaped multi-PDO scaffold was inserted under the panniculus carnosus of rat dorsal skin and the subcutaneous layer of mini-pig dorsal skin and forehead wrinkles in three human volunteers. Results: Histological analysis at 12 weeks revealed evidence of de novo collagen synthesis, which was consistent with clinical results on photo evaluation. Conclusion: Stent-shaped multi-PDO scaffolds may be another effective and safe treatment modality for reduction of forehead wrinkles.     

Two years’ outcome of thread lifting with absorbable barbed PDO threads: Innovative score for objective and subjective assessment

Background: Thread-lifting rejuvenation procedures have evolved again, with the development of absorbable threads. Although they have gained popularity among plastic surgeons and dermatologists, very few articles have been written in literature about absorbable threads. This study aims to evaluate two years’ outcome of thread lifting using absorbable barbed threads for facial rejuvenation. Methods: Prospective comparative stud both objectively and subjectively and follow-up assessment for 24 months. Results: Thread lifting for face rejuvenation has significant long-lasting effects that include skin lifting from 3–10 mm and high degree of patients’ satisfaction with less incidence rate of complications, about 4.8%. Augmented results are obtained when thread lifting is combined with other lifting and rejuvenation modalities. Conclusion: Significant facial rejuvenation is achieved by thread lifting and highly augmented results are observed when they are combined with Botox, fillers, and/or platelet rich plasma (PRP) rejuvenations.     

Effect of pdo facelift threads on facial skin tissues: An ultrasonographic analysis

Background

Recent studies demonstrate that PDO threads, after being introduced into the facial skin, provide benefits due to collagen formation around the thread and improved vascularization.

Aims

This work aims to report the ultrasound and photographic follow-up after the execution of the facelift thread technique, thus evaluating the anti-aging treatment that PDO threads will provide for human facial skin.

Methods

The facelift will be performed using PDO thread 18G cannulated Sculpt i- Thread FML 100 × 185 mm, and 29G PDO thread Needled Flat i-Thread 38 × 50 mm. A total of 10 patients were selected for the study; all of them had medium-grade facial ptosis and aged 40–50 years old. In order to control tissue changes after thread, insertion ultrasound measurements will be made with Philips ultrasound 12 MHz linear probe at maximum resolution, initial evaluations and control of 30, 60, 90, and 120 days, measuring the skin layers: epidermis\dermis and hypodermis. Photographic control was performed before and after 120 days of intrusion of the PDO threads.

Results

The formation of collagen around the PDO thread was evidenced through ultrasound images in all patients in this study, as well as improvement in the appearance of the skin and sagging, evaluated by photographic control.

Conclusions

We can define that the PDO threads used for the facelift are effective in the formation of collagen around the thread (observed through the increase in the dermal layer), and improvement of the condition of the anti-aging factor through sagging skin, vascularization and thinning of the superficial fat layer (observed through the reduction of the subcutaneous or hypodermis layer).     

Barbed sutures “lunch time” lifting: evidence‐based efficacy

There is a growing trend nowadays for patients to seek the least invasive treatments possible with less risk of complications and downtime to correct rhytides and ptosis characteristic of aging. Nonsurgical face and neck rejuvenation has been attempted with various types of interventions. Suture suspension of the face, although not a new idea, has gained prominence with the advent of the so called “lunch‐time” face‐lift. Although some have embraced this technique, many more express doubts about its safety and efficacy limiting its widespread adoption. The present review aims to evaluate several clinical parameters pertaining to thread suspensions such as longevity of results of various types of polypropylene barbed sutures, their clinical efficacy and safety, and the risk of serious adverse events associated with such sutures. Early results of barbed suture suspension remain inconclusive. Adverse events do occur though mostly minor, self‐limited, and of short duration. Less clear are the data on the extent of the peak correction and the longevity of effect, and the long‐term effects of the sutures themselves. The popularity of barbed suture lifting has waned for the time being. Certainly, it should not be presented as an alternative to a face‐lift.     

Morphometry and epidermal fas expression of unexposed aged versus young skin

Background:

Identifying the molecular mechanisms of intrinsic aging is critical in developing modalities for reversal of cutaneous aging.

Objective:

The objective was to evaluate the expression of epidermal Fas, epidermal thickness, collagen, and elastic fibers degeneration in unexposed skin of aged individuals compared with young ones.

Materials and Methods:

Skin biopsies were taken from normal skin of the back of 22 old subjects (age range: 48-75 years) and 15 young subjects (age range: 18-28 years). Skin sections were stained with hematoxylin and eosin, Masson trichrome, orcein. Epidermal thickness was measured with image analyzer and scoring was done for collagen and elastic fiber degeneration. Fas immunostaining was done. Quantitative and qualitative data were compared statistically between the old and young subjects.

Results:

A statistically significant decreased epidermal thickness was found in old compared with young skin (P<0.05). A statistically significant number of patients showed decreased epidermal thickness, density, and fragmentation of both collagen and elastic fibers in old compared with young skin (P<0.001). Epidermal Fas expression was detected in 19 of 22 old subjects (86.4%) compared with 2 of 15 young subjects (13.3%) (P<0.001). There was no statistically significant correlation between age of old subjects and each of epidermal thickness, collagen, and elastic fiber degeneration.

Conclusion:

The decreased epidermal thickness and morphological alteration of collagen and elastic fibers are not correlated with aging and Fas-mediated apoptosis could be involved in thinning of the epidermis in unexposed aged skin.     

The matricellular protein periostin contributes to proper collagen function and is downregulated during skin aging

Background Periostin is a secreted 90 kDa matricellular protein, which is predominantly expressed in collagen-rich tissues. Collagen is the most abundant protein in mammals and has great tensile strength. Recent investigations have shown that periostin influences collagen fibrillogenesis and biomechanical properties of murine connective tissues.ObjectiveWe investigated the function of periostin concerning collagen homeostasis during intrinsic and extrinsic skin aging. For this purpose, human skin samples of young and old donors as well as samples of photoaged and sun-protected skin areas were analyzed for periostin expression. Using in vitro models, we determined the cell types responsible for periostin expression and performed functional analyses with periostin knockdown cells.MethodsTaqMan Real-Time PCR, UV irradiation, knockdown experiments, immunostaining, electron microscopy, collagen degradation assay, collagen crosslink analysis.ResultsPeriostin expression is highest in the papillary dermis and downregulated during skin aging. Fibroblasts and non-follicular skin derived precursors were identified as main source for periostin expression in human skin. Periostin knockdown in fibroblasts has no effect on collagen expression, but results in an increased fibril diameter and aberrant collagen structure. This leads to an increased susceptibility of collagen toward proteases, whereas recombinant periostin protects collagen fibrils from degradation.ConclusionOur data show that periostin plays an important role for proper collagen assembly and homeostasis. During skin aging periostin expression decreases and contributes to the phenotype of aged skin.     

Comparison of different thread products for facial rejuvenation: Materials and barb designs

Background

In recent years, the thread-lifting technique has become widely used in clinical settings. Several thread products are used in clinical practice, and there are many differences between products in terms of many aspects.

Methods

Six commercial thread products were collected and evaluated. The general structure, microstructure, elastic modulus, and strength were evaluated using microscopies and tensile testing in vitro. Seventy-two female rats were divided into six groups. Tissue samples were harvested and histologically evaluated at 1st, 4th, 8th, and 12th week using hematoxylin and eosin and Masson's trichrome staining.

Results

There were differences between products in terms of barb shape, microstructure, elasticity, and strength, and that could be attributed to the materials and barb structures. All threads showed good biological safety, and the density of collagen area in the dermis was increased compared to that in the control group.

Conclusions

This study provided an objective evaluation of barbed thread products, which indicated that all products can be used safely with certain effects in different indications.     

Outcome of facial rejuvenation with polydioxanone thread for Asians

Background: Techniques in rejuvenating the aging face have evolved, involving various types of threads. Facial rejuvenation with absorbable polydioxanone is popular in aesthetic clinics in Korea. Aim: The purpose of this study was to describe our polydioxanone thread method and to evaluate the outcomes of facial rejuvenation. Patients/Methods: A retrospective chart review was performed over a 12-month period. Thirty-five Asian patients were included. All participants underwent thread-lifting using polydioxanone. On each side, five 360° spiral cog threads were used in the procedure. The results were evaluated using photography and patient satisfaction. Results: Thirty-three patients (94.3%) were satisfied with the outcomes. Objective outcomes using photography were categorized as very much improved (68.6%), much improved (25.7%), and improved (5.7%). Subjective outcomes using patients’ satisfaction were categorized as excellent, very good, good, fair, and poor. The incidence of complications was low, and the complications resolved spontaneously without any surgical interventions. Asymmetry, however, was noted. Conclusions: Using our technique, we could achieve the desired facial rejuvenation. Our method demonstrated an excellent success rate in patients with moderate degree laxity. We believe that facial rejuvenation with polydioxanone thread for Asians is a safe and effective treatment method.     

Split-face histological and biochemical evaluation of tightening efficacy using temperature- and impedance-controlled continuous non-invasive radiofrequency energy

Background: Bipolar radiofrequency (RF) is capable of heating dermal collagen fibers and inducing skin tightening by collagen remodeling. Objective: To substantiate safety and improvement of skin laxity following skin heating with a novel temperature- and impedance-controlled non-invasive radiofrequency (RF) device by histological and biochemical evaluations. Methods: A split-face study was performed on 4 subjects who underwent 8 weekly RF sessions on one side of their face, leaving the other side an untreated control and then underwent facelift procedure. Clinical evaluation by photographs was done prior to the surgical procedure. Ex vivo fragments were harvested from both sides and compared. Morphometric analysis of dermal collagen fibers, collagen synthesis, and elastin synthesis evaluations were compared in triplicates. Results: Facial skin tightening was apparent in split-face photographs. A significant increase of 7.9% in dermal collagen content, and a significant increase of 34.7% in collagen synthesis were demonstrated in the treated samples. No statistically significant effect on elastin synthesis was detected. Conclusions: Skin tightening following treatment with non-invasive RF has proven histologically and biochemically to derive from increase in dermal collagen synthesis and content.     

Improving mandibular contour: A pilot study for indication of PPLA traction thread use

Background: The request for less-aggressive procedures to improve mandibular contour is increasing. Several kinds of threads have been used for this purpose. Nevertheless, PLLA (poly-L-Lactic acid) traction thread procedure has not been previously described. Aim: To investigate the role of PLLA traction threads in improving mandibular contour. Methods: Twenty women were enrolled in the study. They were differentially classified for skin laxity. Patients were treated in a single session with two PLLA traction threads per side. Specific post-procedure instructions were given to patients, and complications occurred after the procedures were estimated. A Fisher’s t-test was performed to identify criteria related to longevity of results. Results: We found longevity of results to be associated with younger age (p = 0.001), absence of severe skin laxity of jawline and neck (p = 0.001), and aesthetic satisfaction (p = 0.024). Edema, swelling, and temporary skin contour irregularities were found in most cases (N = 16; 80%), whereas paresthesia resolving without sequelae in 2–4 weeks was found in two cases (10%). Conclusions: Our results show that selected patients, younger than 51 and showing a mild-moderate degree of skin laxity of jawline and neck angle represent ideal candidates for PLLA traction thread treatment. Further studies will be performed to confirm our results.     

Combined treatment for skin laxity of the aging face with monopolar radiofrequency and intense focused ultrasound in Korean subjects

Background: Although various minimal invasive approaches are available for aging skin laxity, they alone may not lead to notably satisfactory results. Objective: To evaluate the effectiveness and safety of combination regimen with monopolar radiofrequency (MRF) and intense-focused ultrasound (IFUS) in facial lifting and tightening. Methods: Twenty-two Korean participants with aging face received a sequential single session of MRF and IFUS treatment. Objective and subjective assessments for improvement were performed at the 20-week post-treatment. Safety profiles were also recorded, and skin biopsies were taken at baseline and follow-up visit. Results: Based on the objective assessment for the overall facial skin tightening and laxity, 19 patients (90%) demonstrated “moderate” or better improvements (more than 25%) compared with baseline. Specifically, improvements of skin laxity and sagging, and droopy jaw line were more noticeable compared with that of superficial skin texture (P < 0.05). Subjective satisfactions were generally consistent with objective findings, and no serious adverse effect was observed. Histologic evaluation showed increased dermal collagen fibers throughout the dermis after treatments (P < 0.05). Conclusion: Combination treatment of MRF and IFUS has cumulative benefits for skin lifting and tightening with satisfactory safety profiles in Asian subjects.     

Neuropeptides Profile and Increased Innervation in Becker's Nevus

BackgroundMelanocytes are derived from neural crest, and various pigmentary disorders may accompany abnormalities in nerve system or develop following dermatome, suggesting that melanocyte and pigmentation may be closely related to neural factors. There are reports of Becker''s nevus (BN) showing linear and segmental configuration, suggesting the association of BN with nerve system. However, there are no studies regarding the expression of neuropeptides in BN.ObjectiveWe investigated the expression of neuropeptides and innervation in BN.MethodsPolymerase chain reaction (PCR) array of 84 genes related to neuronal process was done. Among the genes with 10-fold or more increase in lesional, real-time PCR was performed for neuropeptide Y (NPY), galanin, neurotensin (NTS) and their receptors skin compared to normal skin. IHC stain was done to look for the expression of NPY, galanin, NTS and their receptors and the distribution of protein gene products (PGP) 9.5 immunoreactive nerve fibers.ResultsPCR array revealed that 16 out of 84 genes related to neuronal process were increased by 10-fold or more in lesional skin. In real-time PCR of NPY, galanin, NTS and their receptors, statistically significant increase of NPY1R (p<0.05) and marginally significant increase of NPY2R, GAL2R, and NTS2R (p<0.1) was verified in lesional skin. In immunohistochemistry, NPY, NPY1R NPY2R, and NTS2R were highly expressed in lesional skin and increased PGP 9.5 immunoreactive linear nerve fibers were found in the epidermis of BN.ConclusionNPY, galanin, NTS and their receptors and increased innervation may play a role in the pathogenesis of BN.     

Effect of mesotherapy with nanochip in the treatment of facial rejuvenation

ABSTRACT

Objective: To observe the clinical effect of mesotherapy with nanochip for facial rejuvenation.

Methods: 24 volunteers with aging skin were treated with a polycomponent formulation – NCTF® BOOST 135 HA for 5 times (once weekly for 3 times and successively biweekly for 2 times). Photographs were taken by VISIA at baseline, and after 1, 4, 10 weeks, while global scores for photoaging (GSP), improvement scores, volunteers’ satisfaction, parameters describing the properties of the skin, and adverse effects were assessed during each follow-up period.

Results: Total 20 volunteers completed the treatment. Evaluation of the whole face showed that GSP, skin texture (ophthalmic wrinkles, dermal thickness, and intensity of collagen fibers of skin), and skin brightness (Lab value) significantly improved at 4 weeks compared to baseline, while the difference between 4 and 10 weeks was not statistically significant. No evident improvement was observed in pigmented spots, telangiectasia, skin tightening, trans-epidermal water loss (TEWL), and skin hydration. Slight erythema, pain was the most common side effect.

Conclusion: Mesotherapy with nanochip can improve skin texture and brightness, but the effect is not permanent. It is recommended that the treatment be used as a complementary method for patients with facial rejuvenation needs.     

Is it possible to obtain long-lasting results with thread lift in the brow region? Introduction of a new suspension technique and evaluation of 50 patients

Background

Eyebrow region is a dynamic region, and it has a thinner skin prone to wrinkles and sagging. Descended brows could be repositioned immediately with fewer complications by the use of the threads. Despite all its advantages, the main drawback of absorbable thread lift is its short duration of lifting effect.

Aims

This report aims to describe our thread lift technique we have implemented to counteract the descent of the brows and evaluate our results in 50 patients.

Patients/Methods

A retrospective chart review was carried out over a period of 1 year from September 2019 to 2020 for the patients who underwent thread lifting for eyebrows in a private clinic in Ankara. Complications after the procedure, durability of the results, global esthetic improvement scale (GAIS) score, and patient satisfaction survey scores were recorded.

Results

The study group was composed of 50 female patients with a median age of 34 years. The median duration of the procedure is 15 months. Nine (18%) patients experienced complications related to the procedure including ecchymosis, edema, erythema, skin dimpling, and pain. Three weeks after the procedure, the position of the eyebrows of eight (16%) patients were improved, 18 (36%) patients were much improved, and 24 (48%) patients were very much improved according to GAIS.

Conclusions

So far, the most disappointing feature of the threads was the poor long-term sustainability of the outcomes. Our thread lift technique for brows offers a significant improvement in the position of the eyebrows in a short time with decreased downtime. More importantly, it can be possible to improve the longevity of the results with this approach.     

TREATMENT OF SKIN AGING WITH TOPICAL ESTROGENS

Background. The coincidence of climacteric symptoms and the beginning of skin aging suggests that estrogen deficiency may be a common and important factor in the perimenopausal woman. Often hormones have been considered important in endogenous aging of the skin, but their role has not been clearly defined. Therefore, we investigated, whether topical treatment of the skin with estrogen could reverse some of the changes in the aging skin. Materials and Methods. The effects of 0.01% estradiol and 0.3% estriol compounds were compared in 59 preclimacteric women with skin aging symptoms. Monthly determinations of estrodiol (E2), follicle-stimulating hormone (FSH), and prolactin (PRL) were done and the monthly clinical monitoring was supplemented by measurements of skin hydration by corneometry and profilometry. In 10 patients, skin biopsies were taken for immunohistochemical determination of collagen types I and III. Results. After treatment for 6 months, elasticity and firmness of the skin had markedly improved and the wrinkle depth and pore sizes had decreased by 61 to 100% in both groups. Furthermore, skin moisture had increased and the measurement of wrinkles using skin profilometry, revealed significant, or even highly significant, decreases of wrinkle depth in the estradiol and the estriol groups, respectively. On immunohistochemistry, significant increases of Type III collagen labeling were combined with increased numbers of collagen fibers at the end of the treatment period. As to hormone levels, only those of PRL had increased significantly and no systemic hormonal side effects were noted. Conclusion. Both estrogen compounds were found to be highly effective in preventing or treating skin aging in perimenopausal women, clinically, by measurement data, and by an increase in collagen Type III.     

Polydeoxyribonucleotides Improve Diabetic Wound Healing in Mouse Animal Model for Experimental Validation

BackgroundWound healing mechanisms is believed to have effects similar to wound healing disorders in diabetic patients, including abnormal inflammatory cells, angiogenesis disorders, and reduced collagen synthesis. Therefore, reestablishment of structural and promoted angiogenesis could be beneficial to promote wound healing process.ObjectiveTherefore, we investigated whether the polydeoxyribonucleotide (PDRN) that was self-production in Korea, could be useful as an intradermal injection for promoting wound healing. Also, we validate for wound healing effect of PDRN using healing-impaired (db/db) mice.MethodsIn this study, we confirmed the effects of PDRN by creating wound models in in vitro and in vivo model. Using an in vitro wound healing assay, we observed that PDRN stimulated closure of wounded monolayers of human fibroblast cells. PDRN (8.25 mg/ml) or phosphate-buffered saline (0.9% NaCl) was injected once daily into the dermis adjacent to the wound for 12 days after skin injury.ResultsTime course observations revealed that mice treated with PDRN showed accelerated wound closure and epidermal and dermal regeneration, enhanced angiogenesis. The wound area and depth decreased at 3, 6, 9, and 12 days after skin injury. Histological evaluation showed an increase of vascular endothelial growth factor, CD31, and collagen fibers in the PDRN group compared with the control group, indicating that PDRN was effective in the treatment of delayed wound healing caused by diabetes.ConclusionThis study suggests that our PDRN has a wound healing effect in transgenic animal models with cells and diabetes through angiogenesis.     

Soybean-fragmented proteoglycans against skin aging

Objective: The majority of age-dependent skin changes happen in the dermis layer inducing changes in skin collagen and in the proteoglycans. The main aim of this work is to study the efficacy of a Proteum serum, containing soybean-fragmented proteoglycans, against skin aging. Materials and methods: In vitro tests were performed to evaluate the Proteum serum ability on activating the production of collagen and proteoglycans. An in vivo long-term study was performed to determine the efficacy of the Proteum serum when applied on skin. Protection of healthy skin against detergent-induced dermatitis and the antioxidant properties of the applied Proteum serum were also studied. Results and discussion: The in vitro tests demonstrated that the Proteum serum was able to elevate the production of molecules which are essential for supporting the dermal extracellular matrix organization. These results were correlated by the in vivo measurements where a clear trend on improving the measured skin parameters due to the Proteum serum application was found. Conclusions: A beneficial effect of the Proteum serum was demonstrated with an improvement in the skin roughness and a reinforcement of the skin barrier function. Moreover, a significant protector effect on human stratum corneum against lipids peroxides (LPO) was demonstrated.     

Heat Shock Protein-70 Expression in Vitiligo and its Relation to the Disease Activity

Background:Vitiligo is a progressive depigmenting disorder characterized by the loss of functional melanocytes from the epidermis. The etiopathogenesis of vitiligo is still unclear. Heat shock proteins (HSPs) are prime candidates to connect stress to the skin. HSPs were found to be implicated in autoimmune diseases such as rheumatoid arthritis and other skin disorders as psoriasis.Results:Our analysis revealed a significantly higher expression of HSP-70 mRNA in lesional skin biopsies from vitiligo patients compared to nonlesional skin biopsies from vitiligo patients (P < 0.001) and compared to skin biopsies from healthy controls (P < 0.001). The level of HSP-70 was not found to be correlated with age, sex, or disease duration. The expression of HSP-70 was correlated with the disease activity and patients with active vitiligo showed higher mean HSP-70 level compared to those with inactive disease.Conclusions:HSP-70 plays a role in the pathogenesis of vitiligo and may enhance the immune response in active disease.     

Exploratory Study of Epidermis,Basement Membrane Zone,Upper Dermis Alterations and Wnt Pathway Activation in Melasma Compared to Adjacent and Retroauricular Skin

BackgroundMelasma is a chronic acquired focal hypermelanosis which pathogenesis has not been fully elucidated. Classical pathophysiologic studies have analysed the affected and perilesional areas, but little is known about the status of sun-protected skin, which is subjected to the same endogenous and genetic factors.ObjectiveTo assess the histological characteristics of melasma compared to adjacent and retroauricular skin.MethodsSkin samples were collected from 10 female from: melasma, perilesional area and retroauricular. The samples were stained (haematoxylin-eosin, periodic acid-Schiff, Fontana-Masson, picrosirius red, toluidine blue and Verhoeff), immunolabelled for CD34 and Wnt1. The data from the skin sites were analysed simultaneously by a multivariate model.ResultsMelasma skin exhibited noteworthy stratum corneum compaction, greater collagen heterogeneity, solar elastosis, higher number of mast cells, basement membrane zone (BMZ) damage, Wnt1 expression, pendulum melanocytes, higher cellularity and vascular proliferation at the superficial dermis. Stratum corneum compaction, collagen heterogeneity and BMZ abnormalities were variables associated to melasma that not follow a continuum through retroauricular to adjacent skin. Mast cell count was the variable that disclosed correlation with the most other abnormalities as well as had the greater contribution in the multivariate model.ConclusionIn addition to melanocyte hyperactivity, melasma skin exhibits alterations in the epidermal barrier, upper dermis and BMZ, which differ from the adjacent sun-exposed skin and retroauricular skin, indicating a distinct phenotype, rather than a mere extension of photoageing or intrinsic ageing. Mast cells appear to play a central role in the physiopathology of melasma.