Multifaceted amelioration of cutaneous photoageing by (0.3%) retinol.

BACKGROUND: Although retinol skin care products improve the appearance of photoaged skin, there is a need for an effective retinol concentration that provides skin benefits without irritation. OBJECTIVE: To compare the efficacy of topical 0.1%, 0.3% and 1% retinol in remodelling the cutaneous architecture in an in vivo experimental patch test study, and to determine tolerance of the most effective formulations when used in a daily in-use escalation study. METHODS: For the patch test study, retinol products were applied under occlusion, to the extensor forearm of photoaged volunteers (n = 5; age range 66-84 years), and 3 mm skin biopsies obtained after 12 days. Effects of different retinol concentrations, and a vehicle control, on key epidermal and dermal biomarkers of cellular proliferation and dermal remodelling were compared to untreated baseline. Separately, participants (n = 218) recorded their tolerance to 0.3% or 1% retinol over a six-week, approved regimen, which gradually increased the facial applications to once nightly. RESULTS: Retinol treatment induced a stepwise increase in epidermal thickness and induced the expression of stratum corneum proteins, filaggrin and KPRP. 0.3% retinol and 1% retinol were comparably effective at inducing keratinocyte proliferation in the epidermis, whilst reducing e-cadherin expression. Fibrillin-rich microfibril deposition was increased following treatment with 0.3% and 1% retinol (p < 0.01); other dermal components remained unaltered (e.g., fibronectin, collagen fibrils, elastin), and no evidence of local inflammation was detected. The in-use study found that 0.3% retinol was better tolerated than 1% retinol, with fewer and milder adverse events reported (χ2 (1) = 23.97; p < 0.001). CONCLUSIONS: This study suggests that 1% and 0.3% retinol concentrations were similarly effective at remodelling photodamaged skin in an in vivo model of long-term use. Use of 0.3% retinol in the escalation study was associated with fewer adverse reactions when applied daily. Hence, 0.3% retinol may be better tolerated than 1% retinol, thereby allowing longer-term topical application.

CONTEXTE: Même si les produits de soins pour la peau à base de rétinol améliorent l'apparence de la peau photovieillie, il est nécessaire d'obtenir une concentration efficace de rétinol procurant des bénéfices cutanés sans irritation. OBJECTIF: Comparer l'efficacité du rétinol à 0.1%, 0.3% et 1% en application locale dans le remodelage de l'architecture cutanée dans une étude d'irritation cutanée in vivo expérimental, et déterminer la tolérance des formulations les plus efficaces lorsqu'elles sont utilisées dans une étude à doses progressives quotidiennes en cours d'utilisation. MÉTHODES: Pour l'étude d'irritation cutanée, des produits à base de rétinol ont été appliqués sous occlusion, sur le muscle extenseur de l'avant-bras de volontaires présentant des signes de photovieillissement (n = 5; tranche d'âge: 66 à 84 ans), et des biopsies cutanées de 3 mm ont été obtenues après 12 jours. Les effets des différentes concentrations de rétinol, et d'un véhicule témoin sur les principaux biomarqueurs épidermiques et dermiques de la prolifération cellulaire et du remodelage dermique ont été comparés à ceux observés à une région non traitée. Séparément, les participants (n = 218) ont enregistré leur tolérance au rétinol à 0.3% ou 1% au cours d'un schéma posologique approuvé de six semaines, qui a progressivement augmenté les applications faciales à une fois par nuit. RÉSULTATS: Le traitement par rétinol a induit une augmentation progressive de l'épaisseur épidermique, et a induit l'expression des protéines de la couche cornée, la filaggrine et le KPRP. Le rétinol à 0.3% et le rétinol à 1% étaient aussi efficaces pour induire la prolifération des kératinocytes dans l'épiderme, tout en réduisant l'expression de la cadhérine E. Le dépôt de microfibrilles riches en fibrilline a augmenté après un traitement par rétinol à 0.3% et 1% (p < 0.001). CONCLUSIONS: Cette étude suggère que les concentrations de rétinol de 1% et 0.3% étaient aussi efficaces pour remodeler la peau photolésée dans un modèle in vivo lors d'une utilisation à long terme. L'utilisation de rétinol à 0.3% dans l'étude à doses progressives a été associée à moins d'effets indésirables lorsqu'il est appliqué quotidiennement. Par conséquent, le rétinol à 0.3% peut être mieux toléré que le rétinol à 1%, permettant ainsi une application topique à plus long terme.

Remodelling of fibrillin-rich microfibrils by solar-simulated radiation: impact of skin ethnicity.

Fibrillin-rich microfibrils (FRMs) constitute integral components of the dermal elastic fibre network with a distinctive ultrastructural 'beads-on-a-string' appearance that can be visualised using atomic force microscopy and characterised by measurement of their length and inter-bead periodicity. Their deposition within the dermis in photoprotected skin appears to be contingent on skin ethnicity, and influences the ultrastructure of papillary - but not reticular - dermal FRMs. Truncation and depletion of FRMs at the dermal-epidermal junction of skin occurs early in photoageing in people with lightly pigmented skin; a process of accelerated skin ageing that arises due to chronic sun exposure. Accumulation of ultraviolet radiation (UVR)-induced damage, either by the action of enzymes, oxidation or direct photon absorption, results in FRM remodelling and changes to ultrastructure. In the current study, the direct effect of UVR exposure on FRM ultrastructure was assayed by isolating FRMs from the papillary and reticular dermis of photoprotected buttock skin of individuals of either black African or white Northern European ancestry and exposing them to solar-simulated radiation (SSR). Exposure to SSR resulted in significant reduction in inter-bead periodicity for reticular dermis-derived FRMs across both cohorts. In contrast, papillary dermal FRMs exhibited significantly increased inter-bead periodicity, with the magnitude of damage greater for African FRMs, as compared to Northern European FRMs. Our data suggest that FRMs of the dermis should be considered as two distinct populations that differentially accrue damage in response to SSR. Furthermore, papillary dermal FRMs derived from black African subjects show greater change following UVR challenge, when extracted from skin. Future studies should focus on understanding the consequences of UVR exposure in vivo, regardless of skin ethnicity, on the molecular composition of FRMs and how this UVR-induced remodelling may affect the role FRMs play in skin homeostasis.

Heterogeneity of fibrillin-rich microfibrils extracted from human skin of diverse ethnicity.

The dermal elastic fibre network is the primary effector of skin elasticity, enabling it to extend and recoil many times over the lifetime of the individual. Fibrillin-rich microfibrils (FRMs) constitute integral components of the elastic fibre network, with their distribution showing differential deposition in the papillary dermis across individuals of diverse skin ethnicity. Despite these differential findings in histological presentation, it is not known if skin ethnicity influences FRM ultrastructure. FRMs are evolutionarily highly conserved from jellyfish to man and, regardless of tissue type or species, isolated FRMs have a characteristic 'beads-on-a-string' ultrastructural appearance, with an average inter-bead distance (or periodicity) of 56 nm. Here, skin biopsies were obtained from the photoprotected buttock of healthy volunteers (18-27 years; African: n = 5; European: n = 5), and FRMs were isolated from the superficial papillary dermis and deeper reticular dermis and imaged by atomic force microscopy. In the reticular dermis, there was no significant difference in FRM ultrastructure between European and African participants. In contrast, in the more superficial papillary dermis, inter-bead periodicity was significantly larger for FRMs extracted from European participants than from African participants by 2.20 nm (p < .001). We next assessed whether these differences in FRM ultrastructure were present during early postnatal development by characterizing FRMs from full-thickness neonatal foreskin. Analysis of FRM periodicity identified no significant difference between neonatal cohorts (p = .865). These data suggest that at birth, FRMs are developmentally invariant. However, in adults of diverse skin ethnicity, there is a deviation in ultrastructure for the papillary dermal FRMs that may be acquired during the passage of time from child to adulthood. Understanding the mechanism by which this difference in papillary dermal FRMs arises warrants further study.

Enhanced Neurogenic Biomarker Expression and Reinnervation in Human Acute Skin Wounds Treated by Electrical Stimulation.

Electrical stimulation (ES) is known to promote cutaneous healing; however, its ability to regulate reinnervation remains unclear. First, we show that ES treatment of human acute cutaneous wounds (n = 40) increased reinnervation. Next, to define neurophysiologic mechanisms through which ES affects repair, microarray analysis of wound biopsy samples was performed on days 3, 7, 10, and 14 after wounding. This identified neural differentiation biomarkers TUBB3 (melanocyte development and neuronal marker) and its upstream molecule FIG4 (phosphatidylinositol (3,5)-bisphosphate 5-phosphatase) as significantly up-regulated after ES treatment. To demonstrate a functional ES-TUBB3 axis in cutaneous healing, we showed increased TUBB3+ melanocytes and melanogenesis plus FIG4 and nerve growth factor expression, suggesting higher cellular differentiation. In support of this role of ES to regulate neural crest-derived cell fate and differentiation in vivo, knockdown of FIG4 in neuroblastoma cells resulted in vacuologenesis and cell degeneration, whereas ES treatment after FIG4-small interfering RNA transfection enhanced neural differentiation, survival, and integrity. Further characterization showed increased TUBB3+ and protein gene product 9.5+ Merkel cells during in vivo repair, after ES. We demonstrate that ES contributes to increased expression of neural differentiation biomarkers, reinnervation, and expansion of melanocyte and Merkel cell pool during repair. Targeted ES-assisted acceleration of healing has significant clinical implications.

The impact of intrinsic ageing on the protein composition of the dermal-epidermal junction.

The dermal-epidermal junction of human skin exhibits age-related remodelling, resulting in a flattened appearance and reduced surface area. Despite this, a paucity of information is available regarding which protein components change with advancing age. Here we report a significant reduction in the protein distribution of collagen IV (P<0.0001), collagen VII (P<0.001), collagen XVII (P<0.01), integrin ß4 (P<0.001) and laminin-332 (P<0.0001) in intrinsically aged skin. The functional implication of this altered protein composition appears to be loss of structural integrity and may, in part, explain the increased fragility of aged skin.

Abnormal chondrocyte apoptosis in the cartilage growth plate is influenced by genetic background and deletion of CHOP in a targeted mouse model of pseudoachondroplasia.

Pseudoachondroplasia (PSACH) is an autosomal dominant skeletal dysplasia caused by mutations in cartilage oligomeric matrix protein (COMP) and characterised by short limbed dwarfism and early onset osteoarthritis. Mouse models of PSACH show variable retention of mutant COMP in the ER of chondrocytes, however, in each case a different stress pathway is activated and the underlying disease mechanisms remain largely unknown. T585M COMP mutant mice are a model of moderate PSACH and demonstrate a mild ER stress response. Although mutant COMP is not retained in significant quantities within the ER of chondrocytes, both BiP and the pro-apoptotic ER stress-related transcription factor CHOP are mildly elevated, whilst bcl-2 levels are decreased, resulting in increased and spatially dysregulated chondrocyte apoptosis. To determine whether the abnormal chondrocyte apoptosis observed in the growth plate of mutant mice is CHOP-mediated, we bred T585M COMP mutant mice with CHOP-null mice to homozygosity, and analysed the resulting phenotype. Although abnormal apoptosis was alleviated in the resting zone following CHOP deletion, the mutant growth plates were generally more disorganised. Furthermore, the bone lengths of COMP mutant CHOP null mice were significantly shorter at 9 weeks of age when compared to the COMP mutant mice, including a significant difference in the skull length. Overall, these data demonstrate that CHOP-mediated apoptosis is an early event in the pathobiology of PSACH and suggest that the lack of CHOP, in conjunction with a COMP mutation, may lead to aggravation of the skeletal phenotype via a potentially synergistic effect on endochondral ossification.