Anti-aging Treatments Research Articles

Energy-Based Skin Rejuvenation: A Review of Mechanisms and Thermal Effects.

Energy-based photoelectric and ultrasonic devices are essential for skin rejuvenation and resurfacing in the field of plastic surgery and dermatology. Both functionality and appearance are impacted by factors that cause skin to age, and various energy types have variable skin penetration depths and modes of transmission. The objective is to advise safe and efficient antiaging treatment while precisely and sensitively controlling and assessing the extent of thermal damage to tissues caused by different kinds of energy-based devices. A literature search was conducted on PubMed to review the mechanisms of action and thermal effects of photoelectric and ultrasonic devices in skin remodeling applications. This paper reviews the thermal effects of energy-based devices in skin resurfacing applications, including the tissue level and molecular biochemical level. It seeks to summarize the distribution form, depth of action, and influencing factors of thermal effects in combination with the mechanisms of action of various types of devices. Accurate control of thermal damage is crucial for safe and effective skin remodeling treatments. Thorough investigation of molecular biochemical indicators and signaling pathways is needed for real-time monitoring and prevention of severe thermal injury. Ongoing research and technological advancements will improve the accuracy and control of thermal damage during treatments.

Queen Bee Larva, an Edible By-Product of Royal Jelly, Alleviate D-Galactose-Induced Aging in Mouse by Regulating Gut Microbiota Structure and Amino Acid Metabolism

Queen bee larva (QBL), as a by-product of royal jelly, is a kind of protein-rich edible insect. However, the development and utilization of QBL have been very limited for an extended period, resulting in considerable economic waste. Notably, QBL has substantial potential for anti-aging treatments; however, systematic studies have been scarce. The present study aimed to analyze the effects of freeze-dried QBL powder (QBLP) treatment in a D-galactose (D-gal)-induced-aging mouse and to explore the mechanisms. A behavioral test indicated that QBLP-treated mice had improved cognitive function and memory decline caused by aging compared to untreated aged mice. Furthermore, QBLP treatment improved organ index in aged mice and prevented pathological damage to the brain tissue. Concomitantly, treatment of D-gal-induced-aging mice with QBLP significantly reduced the oxidative damage of serum and increased the skin moisture content of aging mice. Finally, integrated analyses of the gut microbiota and the serum metabolome showed that QBLP supplementation altered the composition of the gut microbiota, enriched biochemical pathways associated with amino acid metabolism, and adjusted serum concentrations of beneficial free amino acids. Overall, QBLP can improve symptoms related to D-gal-induced aging in mice by regulating gut microbiota structure and amino acid metabolism.

Clinical Validation of Face-Fit Surface-Lighting Micro Light-Emitting Diode Mask for Skin Anti-Aging Treatment.

Photobiomodulation therapy based on micro light-emitting diodes (µLEDs) holds remarkable potential for the beauty industry. Here, a cosmetically effective face-fit surface-lighting µLED mask for skin anti-aging is introduced. The face-conformable mask enables deep tissue treatment through proximal light irradiation, with a 3D origami structure capable of adapting to complex facial contours with closed adherence. A blister-assisted laser transfer achieves rapid and accurate µLEDs transfer at a high throughput of 50 chips per second, facilitating a mass-producible and large-area process. Finally, clinical trials demonstrate significant improvements in elasticity, sagging, and wrinkles across six facial areas, with a maximum enhancement of 340% in deep skin elasticity of the perioral area compared to the conventional LED mask group.

Caenorhabditis elegans as in vivo model for the screening of natural plants-derived novel anti-aging compounds: a short introduction.

The global aging population highlights the need for effective anti-aging treatments. Natural products show promise, but thorough evaluation requires in vivo models due to the complexity of aging. Ethical concerns are driving a shift from traditional models like rabbits and mice to alternatives such as Caenorhabditis elegans. This microscopic nematode, with its short life cycle, genetic similarities to humans, and cost-effectiveness, is ideal for testing anti-aging compounds. We review studies using C. elegans to assess natural products, suggesting it could serve as a primary model for -evaluating the safety and efficacy of plant-derived anti-aging compounds.

High glucose-induced senescence contributes to tubular epithelial cell damage in diabetic nephropathy

Dysfunctional renal tubular epithelial cells, induced by high glucose, are commonly observed in the kidney tissues of diabetic nephropathy (DN) patients. The epithelial-mesenchymal transition (EMT) of these cells often leads to renal interstitial fibrosis and kidney damage in DN. High glucose also triggers mitochondrial damage and apoptosis, contributing further to the dysfunction of renal tubular epithelial cells. Cellular senescence, a recognized characteristic of DN, is primarily caused by high glucose. However, it remains unclear whether high glucose-induced cellular senescence in DN exacerbates the functional impairment of tubular epithelial cells. In this study, we examined the relationship between EMT and cellular senescence in kidney tissues from streptozotocin (STZ)-induced DN and HK-2 cells treated with high glucose (HG). We also investigated the impact of HG concentrations on tubular epithelial cells, specifically mitochondrial dysfunction, cellular senescence and apoptosis. These damages were primarily associated with the secretion of cytokines (such as IL-6, and TNF-α), production of reactive oxygen species (ROS), and an increase of intracellular Ca2+. Notably, resveratrol, an anti-aging agent, could effectively attenuate the occurrence of EMT, mitochondrial dysfunction, and apoptosis induced by HG. Mechanistically, anti-aging treatment leads to a reduction in cytokine secretion, ROS production, and intracellular Ca2+ levels.

Atractylodes macrocephala polysaccharides shield a D-galactose-induced aging model via gut microbiota modulation

This study explored the effect of a heteropolysaccharide (RAMP) on aging model mice and the importance of changes in the gut microbiota mediated by RAMP for the first time. The findings revealed that RAMP exerted protective effects on cognitive decline and oxidative stress in mice subjected to D-gal-induced aging, potentially by regulating the intestinal flora, according to the results of the Morris water maze test; brain and immune organ indices; hematoxylin and eosin-stained cerebral cortex images; transmission electron microscopy analysis of cortical neurons; and biochemical index measurements. In addition, 16S rRNA sequencing revealed notable changes in the abundance of Acidobacteriota, Anaerovoracaceae, and GCA-900066575 in the mouse model, all of which were abrogated by RAMP. These findings confirm that RAMP regulates the composition of mouse intestinal microorganisms. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) functional analyses linked these changes to 27 metabolic pathways, including those of the nervous system. Furthermore, metabolomics analysis revealed four RAMP-regulated metabolites related to lipid metabolism (2-dodecylbenzenesulfonic acid, N-undecylbenzenesulfonic acid, aspartyl-isoleucine, and 1-palmitoyl-2-(5-oxo-valeroyl)-sn-glycero-3-phosphate), suggesting that the mechanism potentially associated with lipid metabolism regulation. This study provides novel insights into the antiaging mechanisms of RAMP, suggesting its potential use in antiaging treatments.

Phytochemistry and Pharmacological Activity of Malva sylvestris L: A Detailed Insight.

Malva sylvestris L., is commonly referred to as Mallow and is found in Europe, Asia and Africa. This has been traditionally used for inflammation, gastrointestinal disturbances, skin disorders, menstrual pains, and urological disorders. This review covers phytoconstituents and Pharmacological activities of M. sylvestris. The plant contains a large number of phytochemical constituents having diverse pharmacological activities. The plant contains many phenolic compounds responsible for its strong antioxidant activity. Coumarins from Mallow have a potential anticancer activity. Malva sylvestris also contains essential as well as non-essential elements and minerals. Many researchers have provided evidence that Malva sylvestris is a good candidate for use as a medicinal herb and has good nutritional value. The leaves, in particular, offer properties like anticancer, skin whitening, and anti-aging. Furthermore, the aqueous extract was recently shown to have an anti-ulcerogenic effect. Malva sylvestris has a high potential for use in cosmetics such as skin whitening and anti-aging treatments. Methanolic extracts of Malva sylvestris leaves, and flowers showed strong antibacterial activity against a common plant pathogen bacterium. The plant also contains Malvone A, which is responsible for antibacterial action. The plant also possesses anti-inflammatory, analgesic, wound healing properties and various other activities.

Comparing Tretinoin to Other Topical Therapies in the Treatment of Skin Photoaging: A Systematic Review.

Many morphological and histological changes take place in aging skin. Topical tretinoin is the gold standard anti-aging agent used to reduce signs of aging through stimulation of epidermal growth and differentiation and inhibition of collagenase. The aim of this systematic review is to summarize studies evaluating the efficacy of tretinoin compared with other topical medications and cosmeceuticals in reducing the appearance of skin aging. A systematic review was conducted following the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) guidelines. The literature search was conducted using the PubMed and Embase databases from conception to December 2023. Studies were included if they compared anti-aging outcomes of topical medications with those of topical tretinoin (also called all-trans retinoic acid and retinoic acid). Studies were excluded if they compared non-topical anti-aging treatments with tretinoin or were conducted on animal models. The literature search resulted in 25 studies that met all inclusion and exclusion criteria. The most common study comparators to tretinoin included other forms of vitamin A. Outcomes were reported on the basis of visual reduction of aging signs, histological assessment of the epidermis and dermis, and protein expression. Although comparators to tretinoin had variable efficacy (greater in 7 studies, equivalent in 13 studies, and less in 3 studies), most studies found the comparator to be less irritating and better tolerated by patients than tretinoin. Tretinoin is currently the gold standard therapy for the treatment of photoaging, but its poor tolerability often limits its use. Unfortunately, given that most studies comparing topical therapies with tretinoin are of poor quality and/or demonstrate bias, there is a lack of substantial evidence to support an alternative first-line therapy. However, given there are some data to support the efficacy of retinoid precursors, namely retinaldehyde, pro-retinal nanoparticles, and conjugated alpha-hydroxy acid and retinoid (AHA-ret), these agents can be considered a second-line option for anti-aging treatment in patients who cannot tolerate tretinoin.

Teh Hitam Cammelia Sinensis Dan Manfaatnya Untuk Kesehatan Pendekatan Berbasis Sains Dan Nilai Islam

Black tea from Camellia sinensis has been a highly popular beverage in Indonesia since the 17th century. Various types of Camellia sinensis tea include white tea, green tea, oolong tea, and black tea. Each type of tea has a distinct antioxidant profile, with black tea containing the highest caffeine content. All types of tea are rich in antioxidants like polyphenols, which play a crucial role in protecting the body from free radicals and reducing the risk of various diseases such as Alzheimer's, diabetes, stroke, hypertension, obesity, cancer, and have antibacterial properties while also serving as an anti-aging treatment for the skin.From an Islamic perspective, the Quran contains numerous verses that command humans to observe and study Allah's creations. This underscores the belief that nothing Allah has created is without purpose, implying that every creation has significant benefits. The consumption of black tea aligns with the principle of maintaining physical health as a form of spiritual responsibility, as also instructed in the Quran. The integration of scientific approaches with religious values elevates black tea beyond merely a beverage enjoyed for its taste, tradition, and health benefits, making it a part of a holistic healthy lifestyle. Utilizing tea production technology and advancing research to uncover the benefits of black tea is a way of expressing gratitude and is considered an act of worship, as its development adheres to the principle of benefiting others.

Does Microbiome Contribute to Longevity? Compositional and Functional Differences in Gut Microbiota in Chinese Long-Living (>90 Years) and Elderly (65-74 Years) Adults.

The study of longevity and its determinants has been revitalized with the rise of microbiome scholarship. The gut microbiota have been established to play essential protective, metabolic, and physiological roles in human health and disease. The gut dysbiosis has been identified as an important factor contributing to the development of multiple diseases. Accordingly, it is reasonable to hypothesize that the gut microbiota of long-living individuals have healthy antiaging-associated gut microbes, which, by extension, might provide specific molecular targets for antiaging treatments and interventions. In the present study, we compared the gut microbiota of Chinese individuals in two different age groups, long-living adults (aged over 90 years) and elderly adults (aged 65-74 years) who were free of major diseases. We found significantly lower relative abundances of bacteria in the genera Sutterella and Megamonas in the long-living individuals. Furthermore, we established that while biological processes such as autophagy (GO:0006914) and telomere maintenance through semiconservative replication (GO:0032201) were enhanced in the long-living group, response to lipopolysaccharide (GO:0032496), nicotinamide adenine dinucleotide oxidation (GO:0006116), and S-adenosyl methionine metabolism (GO:0046500) were weakened. Moreover, the two groups were found to differ with respect to amino acid metabolism. We suggest that these compositional and functional differences in the gut microbiota may potentially be associated with mechanisms that contribute to determining longevity or aging.

Advanced technology based on Poly(deep eutectic solvent) core–shell nanomaterials enriched with Fructus Choerospondias phenols for efficient defense against UVB-induced ferroptosis

Plant phenolic compounds serve as significant natural antioxidants. However, traditional preparation methods face sustainability challenges. In this study, we synthesized a novel deep eutectic solvent (DES) modified core–shell nanomaterial composed of betaine, ethylene glycol and dopamine hydrochloride based on the spatial arrangement formed by the abundant weak interaction forces in the poly(deep eutectic solvent) (PDES). Utilizing the PDES magnetic nanomaterial and combined with ultrasound-assisted matrix solid phase dispersion (UA-MSPD), it was able to efficiently enrich Fructus Choerospondias phenols (FCP) up to 61.468 ± 0.405 mg/g. Density functional theory (DFT) was used to analyze the adsorption mechanism between the material and the target compounds, which involved weak interactions of electrostatics, hydrogen bonds, and π-π stacking, while maintaining the activity of phenols without destroying the molecular structure. Remarkably, the adsorption efficiency of the material remained above 80 % after six repetitions, indicating excellent reusability. FCPs were identified and analyzed using ultra-performance liquid chromatography-tandem triple quadrupole mass spectrometry (UPLC-Q-TOF-MS). The FCP prepared by Fe3O4@SiO2@PDES exhibited superior in vitro antioxidant performance, achieving enrichment and purification in one step. Cell experiment results showed that FCP could scavenge ROS, regulate cytokines, and reduce ferroptosis caused by ultraviolet radiation, making FCP have therapeutic value in practical applications. The technology opens up a new way for the green and sustainable production and enrichment of plant phenolic compounds for anti-aging treatment.

Effects of Nicotinamide Mononucleotide Supplementation on Muscle and Liver Functions Among the Middle-Aged and Elderly: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

Nicotinamide Mononucleotide (NMN) has gained attention as a precursor to Nicotinamide Adenine Dinucleotide (NAD+) in recent years, commonly utilized in anti-aging therapies. The anti-aging effects of NMN on muscle and liver functions in middleaged and elderly people are still unclear. Based on available randomized controlled trials, we conducted a meta-analysis to evaluate the impact of NMN on muscle and liver functions in middle-aged and elderly individuals. We conducted searches on three electronic databases (PubMed, Embase, Web of Science) for randomized controlled trials involving NMN interventions in middle-aged and elderly populations. Through the Cochrane Handbook, we assessed the specific methodological quality. All statistical analyses were obtained by Stata15, and statistical significance was set as P<0.05. There were 412 participants from 9 studies in this meta-analysis. Based on changes in gait speed (SMD: 0.34 m/s, 95%CI [0.03, 0.66] p = 0.033), NMN had significant effects on muscle mass. Moreover, NMN had a better effect on ALT (SMD: -0.29 IU/L, 95%CI [-0.55, -0.03] p = 0.028). Subgroup analysis indicated that administering a small dose of NMN exerted the most prominent impact on Homeostasis Model Assessment-Insulin Resistance (HOMA-IR). NMN has positive efficacy in enhancing muscle function, reducing insulin resistance and lowering aminotransferase levels in middle-aged and elderly individuals. NMN is an encouraging and considerable drug for anti-aging treatment.

Sympathetic Motor Neuron Dysfunction is a Missing Link in Age-Associated Sympathetic Overactivity.

Overactivity of the sympathetic nervous system is a hallmark of aging. The cellular mechanisms behind this overactivity remain poorly understood, with most attention paid to likely central nervous system components. In this work, we hypothesized that aging also affects the function of motor neurons in the peripheral sympathetic ganglia. To test this hypothesis, we compared the electrophysiological responses and ion-channel activity of neurons isolated from the superior cervical ganglia of young (12 weeks), middle-aged (64 weeks), and old (115 weeks) mice. These approaches showed that aging does impact the intrinsic properties of sympathetic motor neurons, increasing spontaneous and evoked firing responses. A reduction of M current emerged as a major contributor to age-related hyperexcitability. Thus, it is essential to consider the effect of aging on motor components of the sympathetic reflex as a crucial part of the mechanism involved in sympathetic overactivity.

Wrinkle Reduction Using Tetrapeptide-68 Contained in an O/W Formulation: A Randomized Double-Blind Placebo-Controlled Study.

Peptides, composed of 2-50 amino acids, have gained attention in anti-aging treatments due to their high safety, low irritation, and cost-effective production. This study aimed to evaluate the anti-wrinkle efficacy of Tetrapeptide-68, derived from the skin structural protein Loricrin, on periorbital wrinkles in women aged 30-65 years. A 12-week, double-blind, randomized controlled trial was conducted with 25 participants who applied the Tetrapeptide-68 (100 ppm) O/W formulation around the eyes. Skin physiological parameters were assessed at baseline, 4, 8, and 12 weeks. Participants also completed efficacy and usability questionnaires. Significant improvements in wrinkle reduction were observed with Tetrapeptide-68 cream treatment, as measured by various skin roughness parameters and 3D imaging analysis. Participants reported positive changes in skin texture and moisture levels, with no adverse reactions noted. Tetrapeptide-68 cream demonstrates promising anti-wrinkle effects, highlighting its potential as an effective ingredient in anti-aging skincare formulations. Further studies are recommended to explore its long-term benefits and underlying mechanisms.

Karakteristik Durian Lokal Sinapeul di Dusun Sinapeul Kecamatan Ujungberung, Majalengka

Durian (Durio spp.) is a tropical fruit with high economic and cultural value in Indonesia. As a member of the genus Durio, there are nine consumable species of durian, with D. zibethinus being the most widely cultivated. Indonesia boasts various types of durian, differing in taste, aroma, and flesh color, which are crucial assets for increasing the number of superior parent plants. Durian is renowned for its unique taste and offers numerous benefits, including consumption as fresh or processed fruit, use in anti-aging treatments, and blood pressure improvement. Morphological identification of durian is essential for determining fruit quality, which is vital in plant breeding. The Sinapeul durian, a local variety from Majalengka, has unique characteristics and significant economic value, but knowledge about its distribution remains limited. This research aims to analyze the distribution and characteristics of the Sinapeul durian around the area of PT. Indocement Tunggal Prakarsa Tbk Unit Palimanan Cirebon, to support conservation and sustainable utilization efforts, and to provide a basis for the propagation of the increasingly rare Sinapeul durian

Prevention of UVB-Induced Photoaging by an Ethyl Acetate Fraction from Allomyrina dichotoma Larvae and Its Potential Mechanisms in Human Dermal Fibroblasts.

Allomyrina dichotoma larvae (ADL) is an insect type that is used ethnopharmacologically to treat various diseases; however, its use as an antiaging treatment has not been widely studied. Previously, we found that an ethyl acetate (EA) fraction derived from an ADL extract (ADLE) has a high polyphenol content and antioxidant properties. In this study, we identified the underlying molecular mechanism for the protective effect of the EA fraction against UVB-induced photodamage in vitro and ex vivo. UVB treatment increased intracellular reactive oxygen species levels and DNA damage; the latter of which was significantly decreased following cotreatment with the EA fraction. Biological markers of aging, such as p16INK4a, p21WAF1, and senescence-associated β-gal levels, were induced by UVB treatment but significantly suppressed following EA-fraction treatment. UVB-induced upregulation of matrix metalloproteinase (MMP)-1 and downregulation of COL1A1 were also reversed by EA-fraction treatment in both cells and a 3D skin model, which resulted in increased keratin and collagen deposition. Moreover, EA-fraction treatment inhibited the phosphorylation of MAPKs (p38, ERK, and JNK) and nuclear factor (NF-)-kB and decreased the levels of inflammatory cytokines in UVB-treated cells. The results indicate that an EA fraction from ADLE ameliorates UVB-induced degradation of COL1A1 by inhibiting MMP expression and inactivating the MAPK/NF-κB p65/AP-1 signaling pathway involved in this process.

Sexual dimorphism association of combined exposure to volatile organic compounds (VOC) with kidney damage

BackgroundEpidemiological evidence emphasizes air pollutants' role in chronic kidney disease (CKD). Volatile organic compounds (VOCs) contribute to air pollution, yet research on VOCs and kidney damage, especially gender disparities, is limited. MethodsThis study analyzed NHANES data to explore associations between urinary VOC metabolite mixtures (VOCMs) and key kidney-related parameters: estimated glomerular filtration rate (eGFR), albumin-to-creatinine ratio (ACR), chronic kidney disease (CKD), and albuminuria. Mediation analyses assessed the potential mediating roles of biological aging (BA) and serum albumin in VOCM mixtures' effects on kidney damage. Sensitivity analyses were also conducted. ResultsThe mixture analysis unveiled a noteworthy positive association between VOCM mixtures and the risk of developing CKD, coupled with a significant negative correlation with eGFR within the overall participant cohort. These findings remained consistent when examining the female subgroup. However, among male participants, no significant link emerged between VOCM mixtures and CKD or eGFR. Furthermore, in both the overall and female participant groups, there was an absence of a significant correlation between VOCM mixtures and either ACR or albuminuria. On the other hand, in male participants, while no significant correlation was detected with albuminuria, a significant positive correlation was observed with ACR. Pollutant analysis identified potential links between kidney damage and 1,3-butadiene, toluene, ethylbenzene, styrene, xylene, acrolein, crotonaldehyde and propylene oxide. Mediation analyses suggested that BA might partially mediate the relationship between VOCM mixtures and kidney damage. ConclusionThe current findings highlight the widespread exposure to VOCs among the general U.S. adult population and indicate a potential correlation between exposure to VOC mixtures and compromised renal function parameters, with notable gender disparities. Females appear to exhibit greater sensitivity to impaired renal function resulting from VOCs exposure. Anti-aging treatments may offer some mitigation against kidney damage due to VOCs exposure.

Facial Rejuvenation: A Global Trend of Dermatological Procedures in the Last Decade.

We aimed to track the global trend of cosmetic treatment outcomes for facial rejuvenation and the differences in modalities used in East Asian and Western populations. Articles reporting on facial rejuvenation procedures (invasive/noninvasive) were identified in PubMed from 2013 to March 2023 and bibliometrically analyzed for type of published document, citation frequency, authors with most articles, author's affiliation, and frequency distribution of keywords. From 553 articles, most were published in 2021 (n = 86, 15.6%). Western countries (n = 323, 58.4%) contributed more than East Asian (n = 230, 41.6%), with more invasive interventions (n = 355, 64.2%) than noninvasive techniques (n = 198, 35.8%). Numbers of invasive techniques in West versus East Asian countries were 225 (40.7%) versus 135 (24.4%). Main indications were the reduction of facial wrinkles and antiageing treatments. Hyaluronic acid, fillers, and botulinum toxin were the main hotspots for invasive treatments, whereas laser, platelet-rich plasma, and radiofrequency were for noninvasive treatments. Nasolabial folds (13.4%) and glabellar lines (12.4%) were the top research hotspots in the East Asian and Western regions. Common adverse events were pain, erythema, swelling, and bruising. Approximately, 89.3% of publications were from single countries, whereas 10.7% of publications were from international collaborations. Most articles (n = 387; 69.95%) presented their findings using level II evidence. Dermatological surgery (IF = 2.914) had the greatest number of publications (n = 109; 19.71%). The main hotspots were antiaging and youthfulness. This study provides a trend and a new perspective on the future research directions in the field of facial rejuvenation.

Translatability of life-extending pharmacological treatments between different species.

Anti-aging research has made significant strides in identifying treatments capable of extending lifespan across a range of organisms, from simple invertebrates to mammals. This review showcases the current state of anti-aging interventions, highlighting the lifespan extensions observed in animal models through various treatments and the challenges encountered in translating these findings to humans. Despite promising results in lower organisms, the translation of anti-aging treatments to human applications presents a considerable challenge. This discrepancy can be attributed to the increasing complexity of biological systems, species-specific metabolic and genetic differences, and the redundancy of metabolic pathways linked to longevity. Our review focuses on analyzing these challenges, offering insights into the efficacy of anti-aging mechanisms across species and identifying key barriers to their translation into human treatments. By synthesizing current knowledge and identifying gaps in translatability, this review aims to underscore the importance of advancing these therapies for human benefit. Bridging this gap is essential to assess the potential of such treatments in extending the human healthspan.

Quantification of age-related changes in the structure and mechanical function of skin with multiscale imaging

The mechanical properties of skin change during aging but the relationships between structure and mechanical function remain poorly understood. Previous work has shown that young skin exhibits a substantial decrease in tissue volume, a large macro-scale Poisson’s ratio, and an increase in micro-scale collagen fiber alignment during mechanical stretch. In this study, label-free multiphoton microscopy was used to quantify how the microstructure and fiber kinematics of aged mouse skin affect its mechanical function. In an unloaded state, aged skin was found to have less collagen alignment and more non-enzymatic collagen fiber crosslinks. Skin samples were then loaded in uniaxial tension and aged skin exhibited a lower mechanical stiffness compared to young skin. Aged tissue also demonstrated less volume reduction and a lower macro-scale Poisson’s ratio at 10% uniaxial strain, but not at 20% strain. The magnitude of 3D fiber realignment in the direction of loading was not different between age groups, and the amount of realignment in young and aged skin was less than expected based on theoretical fiber kinematics affine to the local deformation. These findings provide key insights on how the collagen fiber microstructure changes with age, and how those changes affect the mechanical function of skin, findings which may help guide wound healing or anti-aging treatments.