Mechanical and geometrical cues influence cell behaviour. At the tissue level, almost all organs exhibit immediate mechanical responsiveness, in particular by increasing their stiffness in direct proportion to an applied mechanical stress. It was recently shown in cultured-cell models, in particular with fibroblasts, that the frequency of the applied stress is a fundamental stimulating parameter. However, the influence of the stimulus frequency at the tissue level has remained elusive. Using a device to deliver an oscillating torque that generates cyclic strain at different frequencies, we studied the effect(s) of mild skin massage in an ex vivo model and in vivo. Skin explants were maintained ex vivo for 10 days and massaged twice daily for one minute at various frequencies within the range of 65–85 Hz. Biopsies were analysed at D0, D5 and D10 and processed for immuno-histological staining specific to various dermal proteins. As compared to untreated skin explants, the massaging procedure clearly led to higher rates of expression, in particular for decorin, fibrillin, tropoelastin, and procollagen-1. The mechanical stimulus thus evoked an anti-aging response. Strikingly, the expression was found to depend on the stimulus frequency with maximum expression at 75Hz. We then tested whether this mechanical stimulus had an anti-aging effect in vivo. Twenty Caucasian women (aged 65-75y) applied a commercial anti-aging cream to the face and neck, followed by daily treatments using the anti-aging massage device for 8 weeks. A control group of twenty-two women, with similar ages to the first group, applied the cream alone. At W0, W4 and W8, a blinded evaluator assessed the global facial wrinkles, skin texture, lip area, cheek wrinkles, neck sagging and neck texture using a clinical grading scale. We found that combining the massaging device with a skin anti-aging formulation amplified the beneficial effects of the cream.
IntroductionIt is now recognized that to adequately protect skin from sun damage, sunscreens require a photostable combination of ultraviolet (UV) filters with a suitable level of UVA protection. The total amount of UV filters should be as low as possible to avoid adverse skin reactions, potential environmental impact, and to ensure acceptable texture for better application and usage.MethodsA synergistic combination of UV filters was selected to obtain a high sun protection factor (SPF) and UVA protection factor (UVA-PF). An oily vehicle was then added to the formula to improve the solubility and the photostability of the lipophilic UV filters.ResultsThe combination of filters, i.e., terephthalylidene dicamphor sulfonic acid (TDSA), bis-ethylhexyloxyphenol methoxyphenyl triazin (BEMT), and butyl methoxy dibenzoyl methane (BMDM), obtained an elevated SPF as well as a high UVA-PF. Isopropyl lauroyl sarcosinate (ILS), a derivative of a natural amino acid (sarcosine, also known as N-methylglycine) was introduced in this formulation in order to dissolve the oil-soluble UV absorbers and to photostabilize BMDM. The new sunscreen formulation obtained with this combination is photostable and contains a reduced amount of UV filters compared to other sunscreens with the same level of efficacy.ConclusionThis report described the steps resulting in the formulation of a new combination of UV filters in an oily emollient, which presents a high UVA-PF (UVA-PF = 38) and a SPF 50+, is photostable, and offers good protection against UV-induced biological damage.
Mechanical and geometrical cues influence cell behavior, playing a central role in embryogenesis, tissue physiology, and a wide variety of diseases. [1][2][3] Mechanobiology is a branch of biology that focuses on the mechanisms by which physical stresses induce changes in cells or tissues through mechanotransduction. It examines how the applied forces influence cell or tissue development, impact physiology, or even play a role in pathological processes. 4 At a cellular level, Cui Y et al observed in a recent work that those fibroblasts that normally require a rigid surface to grow and spread do not grow and do not spread when plated on soft nanopillar arrays, even after a static stretch. However, with cyclic stretching of the substrate, the cells spread and grow as if they were on a rigid substrate.Thus, a dynamic mechanical stimulus can compensate for a change in the mechanical environment of the cells. 5 At the tissue level, skin has sophisticated capabilities to sense and react to the environment. That contributes to the maintenance of peripheral homeostasis. Specifically, epidermal and dermal cells produce and respond to stress neurotransmitters, neuropeptides, and hormones. 6 Mechanical stimulation generates a biological response in the tissue of healthy skin, particularly from fibroblasts, 7 the most abundant cells in dermis. These cells play a major role in synthesizing collagen and elastic fibers in the extracellular matrix. AbstractBackground and objective: Different biological models have shown how mechanical stimulation may induce physiological responses from solicited cells, tissues, or organs. In models of cultured skin cells, the frequency of the mechanical stress appears to be a paramount parameter, generating a biological response in some cells, particularly from dermal fibroblasts. Our objective was to explore in ex vivo human skin explants the effects of mechanical stimulation. Materials and methods:Mechanical stimulations were provided by a torque test device, with different end effectors, able to generate cyclic strains at different frequencies (from 40 to 120 Hz). Skin explant samples were stimulated twice daily by the device for one minute, over 10 days.Results: At days 0, 5, and 10, samples were processed by immunohistological procedures, allowing some structural dermal proteins to be quantified (fluorescence).As compared to untreated skin explant samples, the stimulation procedure clearly led some proteins of the dermal-epidermal and some dermal proteins to be overexpressed. This stimulation was found to be frequency-dependent, with the greatest overall increases occurring at 60 and 90 Hz. Conclusion: For the first time, ultrafast ultrasound imaging in vitro (phantom mimicking skin mechanical properties) was used to analyze mechanical waves transmitted to the skin layers as a function of end effector shape. K E Y W O R D S controlled vibrations, shear waves, skin biomechanics, ultrafast ultrasound How to cite this article: Caberlotto E, Bernal M, Miller Z, et al. Controlled mechanical vibr...
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