A mechanistic view on the aging human skin through ex vivo layer-by-layer analysis of mechanics and microstructure of facial and mammary dermis.
Ontology highlight
ABSTRACT:
SUBMITTER: Lynch B
PROVIDER: S-EPMC8764052 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description: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.
| S-EPMC5383004 | biostudies-literature
Project description:Gene electrotransfer (GET) is a proven and valuable tool for in vivo gene delivery to a variety of tissues such as skin, cardiac muscle, skeletal muscle, and tumors, with controllable gene delivery and expression levels. Optimizing gene expression is a challenging hurdle in preclinical studies, particularly for skin indications, due to differences in electrical conductivity of animal compared to human dermis. Therefore, the goal of this study was to develop an ex vivo model for GET using recellularized human dermis to more closely mimic human skin. Decellularized human dermis (DermACELL(®)) was cultured with human dermal fibroblasts and keratinocytes for 4 weeks. After one week of fibroblast culture, fibroblasts infiltrated and dispersed throughout the dermis. Air-liquid interface culture led to epithelial cell proliferation, stratification and terminal differentiation with distinct basal, spinous, granular and cornified strata. Firefly luciferase expression kinetics were evaluated after GET of recellularized constructs for testing gene delivery parameters to skin in vitro. Elevated luciferase expression persisted up to a week following GET compared to controls without electrotransfer. In summary, recellularized dermis structurally and functionally resembled native human skin in tissue histological organization and homeostasis, proving an effective 3D human skin model for preclinical gene delivery studies.
| S-EPMC6457670 | biostudies-literature
Project description:Vascular diseases such as diabetes and hypertension cause changes to the vasculature that can lead to vessel stiffening and the loss of vasoactivity. The microstructural bases of these changes are not presently fully understood. We present a new methodology for stain-free visualization, at a microscopic scale, of the morphology of the main passive components of the walls of unfixed resistance arteries and their response to changes in transmural pressure. Human resistance arteries were dissected from subcutaneous fat biopsies, mounted on a perfusion myograph, and imaged at varying transmural pressures using a multimodal nonlinear microscope. High-resolution three-dimensional images of elastic fibers, collagen, and cell nuclei were constructed. The honeycomb structure of the elastic fibers comprising the internal elastic layer became visible at a transmural pressure of 30 mmHg. The adventitia, comprising wavy collagen fibers punctuated by straight elastic fibers, thinned under pressure as the collagen network straightened and pulled taut. Quantitative measurements of fiber orientation were made as a function of pressure. A multilayer analytical model was used to calculate the stiffness and stress in each layer. The adventitia was calculated to be up to 10 times as stiff as the media and experienced up to 8 times the stress, depending on lumen diameter. This work reveals that pressure-induced reorganization of fibrous proteins gives rise to very high local strain fields and highlights the unique mechanical roles of both fibrous networks. It thereby provides a basis for understanding the micromechanical significance of structural changes that occur with age and disease.
| S-EPMC5206342 | biostudies-literature
Project description:New enzyme functions often evolve through the recruitment and optimization of latent promiscuous activities. How do mutations alter the molecular architecture of enzymes to enhance their activities? Can we infer general mechanisms that are common to most enzymes, or does each enzyme require a unique optimization process? The ability to predict the location and type of mutations necessary to enhance an enzyme's activity is critical to protein engineering and rational design. In this review, via the detailed examination of recent studies that have shed new light on the molecular changes underlying the optimization of enzyme function, we provide a mechanistic perspective of enzyme evolution. We first present a global survey of the prevalence of activity-enhancing mutations and their distribution within protein structures. We then delve into the molecular solutions that mediate functional optimization, specifically highlighting several common mechanisms that have been observed across multiple examples. As distinct protein sequences encounter different evolutionary bottlenecks, different mechanisms are likely to emerge along evolutionary trajectories toward improved function. Identifying the specific mechanism(s) that need to be improved upon, and tailoring our engineering efforts to each sequence, may considerably improve our chances to succeed in generating highly efficient catalysts in the future.
| S-EPMC7380680 | biostudies-literature
Project description:Facial aging is the most visible manifestation of aging. People desire to look younger than others of the same chronological age. Hence, perceived age is often used as a visible marker of aging, while biological age, often estimated by methylation markers, is used as an objective measure of age. Multiple epigenetics-based clocks have been developed for accurate estimation of general biological age and the age of specific organs, including the skin. However, it is not clear whether the epigenetic biomarkers (CpGs) used in these clocks are drivers of aging processes or consequences of aging. In this proof-of-concept study, we integrate data from GWAS on perceived facial aging and EWAS on CpGs measured in blood. By running EW Mendelian randomization, we identify hundreds of putative CpGs that are potentially causal to perceived facial aging with similar numbers of damaging markers that causally drive or accelerate facial aging and protective methylation markers that causally slow down or protect from aging. We further demonstrate that while candidate causal CpGs have little overlap with known epigenetics-based clocks, they affect genes or proteins with known functions in skin aging, such as skin pigmentation, elastin, and collagen levels. Overall, our results suggest that blood methylation markers reflect facial aging processes, and thus can be used to quantify skin aging and develop anti-aging solutions that target the root causes of aging.
| S-EPMC10623707 | biostudies-literature
Project description:BackgroundHyaluronic acid (HA) is a key contributor to skin moisture (hydration), and MicroBotox demonstrates improvements for fine wrinkles of the face.ObjectivesThe author sought to evaluate the safety and efficacy of intradermal injection of hydrotoxin (combined mixture of MicroHA and MicroBotox) for the treatment of skin roughness and dryness on facial dermis.MethodsFifty women who had thin, dry skin with fine wrinkles throughout the whole face, especially in the crow's feet and forehead areas, were enrolled in the study. Two cc stabilized-HA filler and 1 cc (40 U) of botulinumtoxinA were mixed in the novel combined hydrotoxin mixture. Intended to hydrate the dermis and treat fine wrinkles of the face, the mixture was injected into the real dermal layer of the face. The volume of HA per site was 0.002 cc and toxin was 0.04 U. Skin roughness and stratum corneum hydration were measured at 1, 2, 3, and 6 months.ResultsOne month post-treatment, skin roughness was reduced to 50.19% in topographic computer analysis utilizing 10× dermascope photos. Stratum corneum hydration on crow's feet improved to 81.34% at 1 month and 56.12% at 2 months from pre-treatment baseline (P < 0.0001). Global Aesthetic improvement scale of Skin hydration and fine wrinkle improved.ConclusionsThe combination injection method of MicroHA and MicroBotox is not associated with side effects and showed significant synergic effect in improvement of skin roughness and moisturizing. Neuramix-hydrotoxin injection method is an easy and reproducible procedure to make constant injection depth and amount.Level of evidence: 4
| S-EPMC8240748 | biostudies-literature
Project description:ImportanceResearch in facial aging has focused on soft-tissue changes rather than bony changes despite evidence of the importance of underlying bony structural changes. Research has also been limited by comparing different patients in separate age groups rather than the same patients over time.ObjectiveTo longitudinally document patterns of change in the facial skeleton and determine a consistent methodology for measuring these changes.Design, setting, and participantsCase series study of university hospital system records using facial computed tomographic (CT) images timed at least 8 years apart in adults initially aged 40 to 55 years with no history of facial surgery who required repeated facial imaging that included the entire midface and cranium.Main outcomes and measuresFace CTs were analyzed for 3-dimensional constructions and 2-dimensional measurements to document changes in glabellar, piriform, and maxillary angles and piriform height and width.ResultsFourteen patients (5 men, 9 women; mean [SD] age, 51.1 [5.8] years) with mean (SD) follow-up of 9.7 (1.4) years were eligible for 2-dimensional analysis, which revealed statistically significant decreases in mean (SD) glabellar angles (from 68.8° [7.6°] to 66.5° [8.6°]) and maxillary angles on both the right (from 82.5° [6.3°] to 81.0° [7.1°]) and left (from 83.0° [5.8°] to 81.0° [7.0°]), as well as increases in mean (SD) piriform width (from 24.5 [1.6] mm to 25.5 [1.3] mm). Nine patients (3 men, 6 women; mean [SD] age, 51.4 [6.3] years) with mean (SD) follow-up imaging at 9.6 (1.5) years were eligible for 3-dimensional analysis, which revealed statistically significant decreases in mean (SD) maxillary angles (from 56.5° [6.6°] to 51.6° [7.6°]) and piriform angles (from 50.8° [3.4°] to 49.1° [3.4°]). Statistically significant differences between the sexes were also noted: Initial mean (SD) glabellar angle for men was 61.7° (5.7°) vs 72.7° (5.4°) for women, with final values of 57.9° (4.9°) vs 71.2° (6.0°). Mean (SD) maxillary angle initial values were 87.8° (6.1°) (right) and 87.1° (4.9°) (left) for men, with 79.6° (4.3°) and 80.6° (5.0°) for women, respectively. Final values were 87.0° (4.4°) and 86.9° (4.1°) for men and 77.7° (6.1°) and 77.7° (6.2°) for women, respectively. Mean (SD) piriform height for men was 35.0 (2.0) mm initially and 35.5 (2.1) mm finally, vs 31.3 (2.8) and 31.6 (3.0) mm for women, respectively.Conclusions and relevanceOur pilot study of repeated CT images of patients over several years supports previous studies of bony facial aging and further characterizes these changes. This study is the first, to our knowledge, to document bony changes of the face in the same group of patients at different time points to better characterize facial aging. We also detail an improved methodology to study bony aging to contribute to additional research in the field.Level of evidenceNA.
| S-EPMC5710626 | biostudies-literature
Project description:Architecture and microstructure of type I collagen fibers constitute central regulators of tumor invasion with aligned fibers providing a route for migration of stromal and cancer cells. Several different aspects of fibrillar collagen, such as stiffness, density, thickness, and pore size, may regulate migration of cancer cells, but determining effects of any one parameter requires clear decoupling of physical properties of collagen networks. The objective of this work is to develop and apply an in vitro three-dimensional (3D) tumor-extra cellular matrix (ECM) model with tunable physical parameters to define how stromal fibroblasts modulate collagen microstructure to control migration of breast cancer cells. We incorporated two different types of polyhedral oligomeric silsesquioxane (POSS) nano-molecules into a collagen/alginate matrix to induce different mechanisms of gelling. The resultant biomimetic, nanocomposite hydrogels show different collagen fibrillar microstructures while maintaining constant overall matrix stiffness, density, and porosimetry. Spheroids of human mammary fibroblasts embedded in these 3D matrices remodel the collagen network to varying extents based on differences in underlying matrix microstructures. The remodeled collagen matrix shows oriented, thicker fibrillar tracks, facilitating invasion of tumor cells. By decoupling effects of matrix stiffness and architecture, our nanocomposite hydrogels serve as robust platforms to investigate how biophysical properties of tumor environments control key processes regulating tumor progression in breast cancer and other malignancies. STATEMENT OF SIGNIFICANCE: Our manuscript demonstrates a new type of nanocomposite hydrogel with two different gelling mechanisms, produced by incorporating two types of polyhedral oligomeric silsesquioxane (POSS) nano-molecules into a collagen/alginate matrix. The resultant biomimetic hydrogels show different fibrillar collagen microstructures while maintaining constant overall matrix stiffness, density, and porosimetry. These gels allow us to uncouple effects of matrix stiffness versus architecture on migration and invasion of breast cancer cells and stromal fibroblasts. Upon embedding spheroids of human mammary fibroblasts (HMFs) and dissociated 231 breast cancer cells, we showed that HMFs remodeled the collagen network to differing extents dependent on starting matrix microstructures in each hydrogel. The remodeled collagen matrix showed aligned collagen fibers perpendicular to the surface of a spheroid with migrating HMFs following these fibers as occurs in tumors in vivo. To our knowledge, this is the first study showing significant different fibrillar collagen microstructures with constant collagen density and gel stiffness. This study establishes a new type of nanocomposite 3D hydrogels for studies of biophysical and cellular interactions in engineered tumor environments.
| S-EPMC6291359 | biostudies-literature
Project description:Numerous clinical cohorts are exposed to reduced skeletal loading and associated bone loss, including surgical patients, stroke and spinal cord injury victims, and women on bed rest during pregnancy. In this context, understanding disuse-related bone loss is critical to developing interventions to prevent fractures and the associated morbidity, mortality, and cost to the health care system. The aim of this pilot study was to use high-resolution peripheral QCT (HR-pQCT) to examine changes in trabecular and cortical microstructure and biomechanics during a period of non weight bearing (WB) and during recovery following return to normal WB. Surgical patients requiring a 6-week non WB period (n=12, 34.8±7.7 yrs) were scanned at the affected and contralateral tibia prior to surgery, after the 6-week non WB period, and 6 and 13 weeks after returning to full WB. At the affected ultradistal tibia, integral vBMD (including both trabecular and cortical compartments) decreased with respect to baseline (-1.2%), trabecular number increased (+5.6%), while trabecular thickness (-5.4%), separation (-4.6%), and heterogeneity (-7.2%) decreased (all p<0.05). Six weeks after return to full WB, trabecular structure measures reverted to baseline levels. In contrast, integral vBMD continued to decrease after 6 (-2.0%, p<0.05) and 13 weeks (-2.5%, p=0.07) of full WB. At the affected distal site, the disuse period resulted in increased porosity (+16.1%, p<0.005), which remained elevated after 6 weeks (+16.8%, p<0.01) and after 13 weeks (+16.2%, p<0.05). A novel topological analysis applied to the distal tibia cortex demonstrated increased number of canals with surface topology ("slabs" +21.7%, p<0.01) and curve topology ("tubes" +15.0%, p<0.05) as well as increased number of canal junctions (+21.4%, p<0.05) following the disuse period. Porosity increased uniformly through increases in both pore size and number. Finite element analysis at the ultradistal tibia showed decreased stiffness and failure load (-2.8% and -2.4%, p<0.01) following non WB. These biomechanical predictions remained depressed following 6 and 13 weeks of full WB. Finite element analysis at the distal site followed similar trends. Our results suggest that detectable microstructural and biomechanical degradation occurs--particularly within the cortical compartment--as a result of non WB and persists following return to normal loading. A better understanding of these microstructural changes and their short- and long-term influence on biomechanics may have clinical relevance in the context of disuse-related fracture prevention.
| S-EPMC4041600 | biostudies-literature
Project description:The ability to measure dynamic structural changes within a cell under applied load is essential for developing more accurate models of cell mechanics and mechanotransduction. Atomic force microscopy is a powerful tool for evaluating cell mechanics, but the dominant applied forces and sample strains are in the vertical direction, perpendicular to the imaging plane of standard fluorescence imaging. Here we report on a combined sideways imaging and vertical light sheet illumination system integrated with AFM. Our system enables high frame rate, low background imaging of subcellular structural dynamics in the vertical plane synchronized with AFM force data. Using our system for cell compression measurements, we correlated stiffening features in the force indentation data with onset of nuclear deformation revealed in the imaging data. In adhesion studies we were able to correlate detailed features in the force data during adhesive release events with strain at the membrane and within the nucleus.
| S-EPMC5784156 | biostudies-literature