Changes of the basement membrane and type IV collagen in human skin during aging

The life cycle of type IV collagen

Type IV collagen is a large triple helical molecule that forms a covalently cross-linked network within basement membranes (BMs). Type IV collagen networks play key roles in mechanically supporting tissues, shaping organs, filtering blood, and cell signaling. To ensure tissue health and function, all aspects of the type IV collagen life cycle must be carried out accurately. However, the large triple helical structure and complex life-cycle of type IV collagen, poses many challenges to cells and tissues. Type IV collagen predominantly forms heterotrimers and to ensure proper construction, expression of the distinct α-chains that comprise a heterotrimer needs tight regulation. The α-chains must also be accurately modified by several enzymes, some of which are specific to collagens, to build and stabilize the triple helical trimer. In addition, type IV collagen is exceptionally long (400nm) and thus the packaging and trafficking of the triple helical trimer from the ER to the Golgi must be modified to accommodate the large type IV collagen molecule. During ER-to-Golgi trafficking, as well as during secretion and transport in the extracellular space type IV collagen also associates with specific chaperone molecules that maintain the structure and solubility of collagen IV. Type IV collagen trimers are then delivered to BMs from local and distant sources where they are integrated into BMs by interactions with cell surface receptors and many diverse BM resident proteins. Within BMs type IV collagen self-associates into a network and is crosslinked by BM resident enzymes. Finally, homeostatic type IV collagen levels in BMs are maintained by poorly understood mechanisms involving proteolysis and endocytosis. Here, we provide an overview of the life cycle of collagen IV, highlighting unique mechanisms and poorly understood aspects of type IV collagen regulation.

CD4+ T Cells Occupy Perivascular and Perifollicular Niches in Healthy Human Skin

Regulatory T cells (Tregs) are specialised T lymphocytes that sit at the nexus of immune regulation and tissue repair. While it is appreciated that a substantial number of Tregs are present in healthy human skin, less is known about their microanatomic spatial localisation. Knowledge about the specialised niches that Tregs occupy may aid in rational drug development to treat dermatologic diseases. Thus, we performed multiplexed immunohistochemistry for CD4 and FOXP3 (the lineage-defining transcription factor of Tregs) on healthy skin sections obtained from eight different cutaneous sites, and quantified Tregs and Tcon in distinct regions. We found that Tregs (CD4+ FOXP3+) comprised roughly 20% of CD4+ T cells in skin and that Tregs and T-conventional cells (Tcon; CD4+ Foxp3-) are enriched in follicularly dense skin and show preferential accumulation in perivascular and perifollicular niches in the upper dermis. Additionally, male skin shows a significant increase in the numbers of Tregs and Tcon, while female skin shows a higher Tcon:Treg ratio. We also find that the frequency of skin Tregs declines over time. Overall, we conclude that the upper dermal perivascular region is a niche that supports the accumulation of CD4+ T cells in steady-state human skin.

Radiofrequency Treatment Attenuates Age-Related Changes in Dermal-Epidermal Junctions of Animal Skin

The dermal-epidermal junction (DEJ) is essential for maintaining skin structural integrity and regulating cell survival and proliferation. Thus, DEJ rejuvenation is key for skin revitalization, particularly in age-related DEJ deterioration. Radiofrequency (RF) treatment, known for its ability to enhance collagen fiber production through thermal mechanisms and increase heat shock protein (HSP) expression, has emerged as a promising method for skin rejuvenation. Additionally, RF activates Piezo1, an ion channel implicated in macrophage polarization toward an M2 phenotype and enhanced TGF-β production. This study investigated the impact of RF treatment on HSP47 and HSP90 expression, known stimulators of DEJ protein expression. Furthermore, using in vitro and aged animal skin models, we assessed whether RF-induced Piezo1 activation and the subsequent M2 polarization could counter age-related DEJ changes. The RF treatment of H2O2-induced senescent keratinocytes upregulated the expression of HSP47, HSP90, TGF-β, and DEJ proteins, including collagen XVII. Similarly, the RF treatment of senescent macrophages increased Piezo1 and CD206 (M2 marker) expression. Conditioned media from RF-treated senescent macrophages enhanced the expression of TGF-β and DEJ proteins, such as nidogen and collagen IV, in senescent fibroblasts. In aged animal skin, RF treatment increased the expression of HSP47, HSP90, Piezo1, markers associated with M2 polarization, IL-10, and TGF-β. Additionally, RF treatment enhanced DEJ protein expression. Moreover, RF reduced lamina densa replication, disrupted lesions, promoted hemidesmosome formation, and increased epidermal thickness. Overall, RF treatment effectively enhanced DEJ protein expression and mitigated age-related DEJ structural changes by increasing HSP levels and activating Piezo1.

The combination of cigarette smoke and solar rays causes effects similar to skin aging in a bilayer skin model

Skin aging is a multifactorial process influenced by internal and external factors. The contribution of different environmental factors has been well established individually in the last few years. On the one hand, man is rarely exposed to a single factor, and on the other hand, there is very little knowledge about how these extrinsic factors may interact with each other or even how the skin may react to chronic exposure. This study aimed to evaluate the effect on skin aging of a chronic co-exposure of tissue-engineered skin substitutes to cigarette smoke extract (CSE) and solar simulator light (SSL). Skin substitutes were reconstructed according to the self-assembly method and then exposed to CSE followed by irradiation with SSL simultaneously transmitting UVA1, visible light and infrared. When skin substitutes were chronically exposed to CSE and SSL, a significant decrease in procollagen I synthesis and the inhibition of Smad2 phosphorylation of the TGF-β signaling pathway were observed. A 6.7-fold increase in MMP-1 activity was also observed when CSE was combined with SSL, resulting in a decrease in collagen III and collagen IV protein expression. The secretory profile resulting from the toxic synergy was investigated and several alterations were observed, notably an increase in the quantities of pro-inflammatory cytokines. The results also revealed the activation of the ERK1/2 (3.4-fold) and JNK (3.3-fold) pathways. Taken together, the results showed that a synergy between the two environmental factors could provoke premature skin aging.

Matricellular Proteins in the Homeostasis, Regeneration, and Aging of Skin

Matricellular proteins are secreted extracellular proteins that bear no primary structural functions but play crucial roles in tissue remodeling during development, homeostasis, and aging. Despite their low expression after birth, matricellular proteins within skin compartments support the structural function of many extracellular matrix proteins, such as collagens. In this review, we summarize the function of matricellular proteins in skin stem cell niches that influence stem cells' fate and self-renewal ability. In the epidermal stem cell niche, fibulin 7 promotes epidermal stem cells' heterogeneity and fitness into old age, and the transforming growth factor-β-induced protein ig-h3 (TGFBI)-enhances epidermal stem cell growth and wound healing. In the hair follicle stem cell niche, matricellular proteins such as periostin, tenascin C, SPARC, fibulin 1, CCN2, and R-Spondin 2 and 3 modulate stem cell activity during the hair cycle and may stabilize arrector pili muscle attachment to the hair follicle during piloerections (goosebumps). In skin wound healing, matricellular proteins are upregulated, and their functions have been examined in various gain-and-loss-of-function studies. However, much remains unknown concerning whether these proteins modulate skin stem cell behavior, plasticity, or cell-cell communications during wound healing and aging, leaving a new avenue for future studies.

Mechanotransduction through hemidesmosomes during aging and longevity

Hemidesmosomes are structural protein complexes localized at the interface of tissues with high mechanical demand and shear forces. Beyond tissue anchoring, hemidesmosomes have emerged as force-modulating structures important for translating mechanical cues into biochemical and transcriptional adaptation (i.e. mechanotransduction) across tissues. Here, we discuss the recent insights into the roles of hemidesmosomes in age-related tissue regeneration and aging in C. elegans, mice and humans. We highlight the emerging concept of preserved dynamic mechanoregulation of hemidesmosomes in tissue maintenance and healthy aging.

Using injectable fillers for chin and jawline rejuvenation

Objective

As the population ages, facial plastic providers must remain aware of the treatments to prevent and reverse the external signs of aging. In the mandibular region, skin laxity and soft tissue sagging in the jawline may lead to jowling and chin ptosis along with reduced chin projection. While surgical procedures, including chin implantation, may be performed, nonsurgical procedures are becoming increasingly popular due to their temporary, noninvasive, yet effective methods. This review covers the use of hyaluronic acid, calcium hydroxylapatite, poly-l-lactic acid, and polymethyl methacrylate in the jawline.

Methods

PubMed was searched for data on the mechanism of action, pertinent anatomy, indications, contraindications, technique, and evidence supporting the safety and efficacy of the fillers.

Results

There are a wide variety of fillers available for use in the lower face with unique characteristics and application methods. While the advantages of injectable fillers include relatively affordable cost, minimal patient discomfort, and limited recovery times, taking measures to prevent short- and long-term complications is necessary for optimal results.

Conclusions

Understanding the benefits and limitations of injectable fillers in the jawline can help providers appropriately counsel and treat patients.

Mesoscopic Monitoring of Human Skin Explants Viscoelastic Properties

The investigation of the mechanical properties of skin is of great interest for monitoring physiological and pathological changes in the cutaneous barrier function for dermatological and cosmetic issues. Skin constitutes a complex tissue because of its multi-layered organisation. From a rheological point of view, it can be considered to be a soft tissue with viscoelastic properties. In order to characterise ex vivo mechanical properties of skin on the mesoscopic scale, a biosensor including a thickness shear mode transducer (TSM) in contact with a skin explant was used. A specific experimental set-up was developed to monitor continuously and in real-time human skin explants, including the dermis and the epidermis. These were kept alive for up to 8 days. Skin viscoelastic evolutions can be quantified with a multi-frequency impedance measurement (from 5 MHz to 45 MHz) combined with a dedicated fractional calculus model. Two relevant parameters for the non-destructive mesoscopic characterisation of skin explants were extracted: the structural parameter αapp and the apparent viscosity ηapp. In this study, the validity of the biosensor, including repeatability and viability, was controlled. A typical signature of the viscoelastic evolutions of the different cutaneous layers was identified. Finally, monitoring was carried out on stripped explants mimicking a weakened barrier function.

Proteomic analysis reveals that aging rabbit vocal folds are more vulnerable to changes caused by systemic dehydration

BACKGROUND

Older adults are more prone to develop systemic dehydration. Systemic dehydration has implications for vocal fold biology by affecting gene and protein expression. The objective of this study was to quantify vocal fold protein changes between two age groups and hydration status, and to investigate the interaction of age and hydration status on protein expression, which has not been investigated in the context of vocal folds before. Comparative proteomics was used to analyze the vocal fold proteome of 6.5-month-old and > 3-year-old rabbits subjected to water ad libitum or water volume restriction protocol.

RESULTS

Young and older adult rabbits (n = 22) were either euhydrated (water ad libitum) or dehydrated by water volume restriction. Dehydration was confirmed by body weight loss of - 5.4% and - 4.6% in young and older groups, respectively, and a 1.7-fold increase of kidney renin gene expression in the young rabbits. LC-MS/MS identified 2286 proteins in the rabbit vocal folds of young and older adult rabbits combined. Of these, 177, 169, and 81 proteins were significantly (p ≤ 0.05) affected by age, hydration status, or the interaction of both factors, respectively. Analysis of the interaction effect revealed 32 proteins with opposite change patterns after dehydration between older and young rabbit vocal folds, while 31 proteins were differentially regulated only in the older adult rabbits and ten only in the young rabbits in response to systemic dehydration. The magnitude of changes for either up or downregulated proteins was higher in the older rabbits. These proteins are predominantly related to structural components of the extracellular matrix and muscle layer, suggesting a disturbance in the viscoelastic properties of aging vocal fold tissue, especially when subjected to systemic dehydration.

CONCLUSIONS

Water restriction is a laboratory protocol to assess systemic dehydration-related changes in the vocal fold tissue that is translatable to human subjects. Our findings showed a higher number of proteins differentially regulated with a greater magnitude of change in the vocal folds of older adult rabbits in the presence of systemic dehydration compared to younger rabbits. The association of these proteins with vocal fold structure and biomechanical properties suggests that older human subjects may be more vulnerable to the effects of systemic dehydration on vocal function. The clinical implications of these protein changes warrant more investigation, but age should be taken into consideration when evaluating vocal treatment recommendations that interfere with body fluid balance.

Palmitoyl‑RGD promotes the expression of dermal‑epidermal junction components in HaCaT cells

With age, the dermal‑epidermal junction (DEJ) becomes thinner and production of its protein components decreases; this may be associated with increased fragility and wrinkling of skin. Topical treatment with palmitoyl‑Arg‑Gly‑Asp (PAL‑RGD) improves facial wrinkles, skin elasticity and dermal density in humans. In the present study, the effect of PAL‑RGD on expression of DEJ components, such as laminin and collagen, was assessed. Human HaCaT keratinocytes were treated with PAL‑RGD. The protein expression levels of laminin‑332, collagen IV and collagen XVII were examined by western blotting. Reverse transcription-quantitative PCR was used to analyze laminin subunit (LAM)A3, LAMB3, LAMC2, collagen type IV α 1 chain (COL4A1) and COL17A1 mRNA expression levels. Western blot analysis showed that the expression levels of proteins comprising the DEJ, including laminin α3, β3 and γ2 and collagen IV and XVII demonstrated a significant dose‑dependent increase following PAL‑RGD treatment. Furthermore, PAL‑RGD treatment significantly enhanced LAMA3, LAMB3, LAMC2, COL4A1 and COL17A1 mRNA expression levels. PAL‑RGD may enhance the DEJ by inducing the expression of laminin‑332, collagen IV and collagen XVII.

Analysis of drug efficacy for inflammatory skin on an organ-chip system

Bacterial skin infections cause a variety of common skin diseases that require drugs that are safer than antibiotics and have fewer side effects. However, for evaluating skin disease drugs, human skin tissue in vitro constructed traditionally on Transwell has inefficient screening ability because of its fragile barrier function. With mechanical forces and dynamic flow, the organ-on-a-chip system became an innovative, automatic, and modular way to construct pathological models and analyze effective pharmaceutical ingredients in vitro. In this research, we integrated skin extracellular matrix and skin cells into a microfluidic chip to construct a biomimetic “interface-controlled-skin-on-chip” system (IC-SoC), which constructed a stable air–liquid interface (ALI) and necessary mechanical signals for the development of human skin equivalents. The results demonstrated that in the microfluidic system with a flowing microenvironment and ALI, the skin tissue formed in vitro could differentiate into more mature tissue morphological structures and improve barrier function. Then, following exposing the skin surface on the IC-SoC to the stimulation of Propionibacterium acnes (P.acnes) and SLS (sodium lauryl sulfate), the barrier function decreased, as well as inflammatory factors such as IL-1α, IL-8, and PEG2 increased in the medium channel of the IC-SoC. After this pathological skin model was treated with dexamethasone and polyphyllin H, the results showed that polyphyllin H had a significant repair effect on the skin barrier and a significant inhibition effect on the release of inflammation-related cytokines, and the effects were more prominent than dexamethasone. This automated microfluidic system delivers an efficient tissue model for toxicological applications and drug evaluation for bacterial-infected damaged skin instead of animals.

Vasculature atrophy causes a stiffened microenvironment that augments epidermal stem cell differentiation in aged skin

Stem cell loss causes tissue deterioration associated with aging. The accumulation of genomic and oxidative stress-induced DNA damage is an intrinsic cue for stem cell loss^1,2; however, whether there is an external microenvironmental cue that triggers stem cell loss remains unclear. Here we report that the involution of skin vasculature causes dermal stiffening that augments the differentiation and hemidesmosome fragility of interfollicular epidermal stem cells (IFESCs) in aged mouse skin. Aging-related IFESC dysregulation occurs in plantar and tail skin, and is correlated with prolonged calcium influx, which is contributed by the mechanoresponsive ion channel Piezo1 (ref. ³). Epidermal deletion of Piezo1 ameliorated IFESC dysregulation in aged skin, whereas Piezo1 activation augmented IFESC differentiation and hemidesmosome fragility in young mice. The dermis stiffened with age, which was accompanied by dermal vasculature atrophy. Conversely, induction of the dermal vasculature softened the dermis and ameliorated IFESC dysregulation in aged skin. Single-cell RNA sequencing of dermal fibroblasts identified an aging-associated anti-angiogenetic secretory molecule, pentraxin 3 (ref. ⁴), which caused dermal sclerotization and IFESC dysregulation in aged skin. Our findings show that the vasculature softens the microenvironment for stem cell maintenance and provide a potential mechanobiology-based therapeutic strategy against skin disorders in aging.

Molecular Mechanisms of Changes in Homeostasis of the Dermal Extracellular Matrix: Both Involutional and Mediated by Ultraviolet Radiation

Skin aging is a multi-factorial process that affects nearly every aspect of skin biology and function. With age, an impairment of structures, quality characteristics, and functions of the dermal extracellular matrix (ECM) occurs in the skin, which leads to disrupted functioning of dermal fibroblasts (DFs), the main cells supporting morphofunctional organization of the skin. The DF functioning directly depends on the state of the surrounding collagen matrix (CM). The intact collagen matrix ensures proper adhesion and mechanical tension in DFs, which allows these cells to maintain collagen homeostasis while ECM correctly regulates cellular processes. When the integrity of CM is destroyed, mechanotransduction is disrupted, which is accompanied by impairment of DF functioning and destruction of collagen homeostasis, thereby contributing to the progression of aging processes in skin tissues. This article considers in detail the processes of skin aging and associated changes in the skin layers, as well as the mechanisms of these processes at the molecular level.

Encapsulated Activated Grape Seed Extract: A Novel Formulation with Anti-Aging, Skin-Brightening, and Hydration Properties

Protein phosphatase 2A (PP2A) is a master regulatory protein that plays a critical role in oxidative stress signaling. A novel, proprietary grape seed extract called Activated Grape Seed Extract (AGSE), enriched for PP2A-activating flavonoids, was recently developed and demonstrated to have antioxidant and anti-inflammatory activities. AGSE is a purple-colored powder, with limited solubility restricting its use in a broad range of formulations. Our aim was to develop a formulation that reduced the color and increased the solubility of AGSE, allowing its skin-health-enhancing properties to be utilized in a wider array of products, and to test it clinically. Encapsulation was performed utilizing a liposome and hydroxypropyl-β-cyclodextrin, (HPCD)-based approach to produce Encapsulated AGSE (E-AGSE). Human dermal fibroblasts and epidermal keratinocytes were used to determine expression levels of aging and dermal–epidermal junction (DEJ) markers. EpiDerm™ was UVB-irradiated to measure the effects against cytokine release, DNA damage, apoptosis, and skin barrier. Human melanocytes were used to determine melanin production and mushroom tyrosinase was used for inhibitory activity. A 4-week, 31-subject sensitive-skin clinical was performed with 2% E-AGSE Essence to assess its activity on human skin. We demonstrated that E-AGSE inhibits PP2A demethylation, increases key anti-aging (collagen I, III, elastin) and DEJ markers, protects against UVB-induced DNA damage, reduces inflammation, and promotes filaggrin in vitro. Moreover, E-AGSE reduces melanin production via tyrosinase inhibition. Clinical assessment of E-AGSE showed that it reduces the appearance of wrinkles, brightens the skin, and boosts hydration. E-AGSE is a novel grape seed extract formulation enriched for PP2A-activating flavonoids that is clinically effective in sensitive skin, providing several benefits.

Collagen Biosynthesis, Processing, and Maturation in Lung Ageing

In addition to providing a macromolecular scaffold, the extracellular matrix (ECM) is a critical regulator of cell function by virtue of specific physical, biochemical, and mechanical properties. Collagen is the main ECM component and hence plays an essential role in the pathogenesis and progression of chronic lung disease. It is well-established that many chronic lung diseases, e.g., chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF) primarily manifest in the elderly, suggesting increased susceptibility of the aged lung or accumulated alterations in lung structure over time that favour disease. Here, we review the main steps of collagen biosynthesis, processing, and turnover and summarise what is currently known about alterations upon lung ageing, including changes in collagen composition, modification, and crosslinking. Recent proteomic data on mouse lung ageing indicates that, while the ER-resident machinery of collagen biosynthesis, modification and triple helix formation appears largely unchanged, there are specific changes in levels of type IV and type VI as well as the two fibril-associated collagens with interrupted triple helices (FACIT), namely type XIV and type XVI collagens. In addition, levels of the extracellular collagen crosslinking enzyme lysyl oxidase are decreased, indicating less enzymatically mediated collagen crosslinking upon ageing. The latter contrasts with the ageing-associated increase in collagen crosslinking by advanced glycation endproducts (AGEs), a result of spontaneous reactions of protein amino groups with reactive carbonyls, e.g., from monosaccharides or reactive dicarbonyls like methylglyoxal. Given the slow turnover of extracellular collagen such modifications accumulate even more in ageing tissues. In summary, the collective evidence points mainly toward age-induced alterations in collagen composition and drastic changes in the molecular nature of collagen crosslinks. Future work addressing the consequences of these changes may provide important clues for prevention of lung disease and for lung bioengineering and ultimately pave the way to novel targeted approaches in lung regenerative medicine.

To form and function: on the role of basement membrane mechanics in tissue development, homeostasis and disease

The basement membrane (BM) is a special type of extracellular matrix that lines the basal side of epithelial and endothelial tissues. Functionally, the BM is important for providing physical and biochemical cues to the overlying cells, sculpting the tissue into its correct size and shape. In this review, we focus on recent studies that have unveiled the complex mechanical properties of the BM. We discuss how these properties can change during development, homeostasis and disease via different molecular mechanisms, and the subsequent impact on tissue form and function in a variety of organisms. We also explore how better characterization of BM mechanics can contribute to disease diagnosis and treatment, as well as development of better in silico and in vitro models that not only impact the fields of tissue engineering and regenerative medicine, but can also reduce the use of animals in research.

The Human Epidermal Basement Membrane: A Shaped and Cell Instructive Platform That Aging Slowly Alters

One of the most important functions of skin is to act as a protective barrier. To fulfill this role, the structural integrity of the skin depends on the dermal-epidermal junction-a complex network of extracellular matrix macromolecules that connect the outer epidermal layer to the underlying dermis. This junction provides both a structural support to keratinocytes and a specific niche that mediates signals influencing their behavior. It displays a distinctive microarchitecture characterized by an undulating pattern, strengthening dermal-epidermal connectivity and crosstalk. The optimal stiffness arising from the overall molecular organization, together with characteristic anchoring complexes, keeps the dermis and epidermis layers extremely well connected and capable of proper epidermal renewal and regeneration. Due to intrinsic and extrinsic factors, a large number of structural and biological changes accompany skin aging. These changes progressively weaken the dermal-epidermal junction substructure and affect its functions, contributing to the gradual decline in overall skin physiology. Most changes involve reduced turnover or altered enzymatic or non-enzymatic post-translational modifications, compromising the mechanical properties of matrix components and cells. This review combines recent and older data on organization of the dermal-epidermal junction, its mechanical properties and role in mechanotransduction, its involvement in regeneration, and its fate during the aging process.

Enzyme-digested Colla Corii Asini (E'jiao) accelerates wound healing and prevents ultraviolet A-induced collagen synthesis decline and wrinkle formation in three-dimensional skin equivalents

Cutaneous wound healing delay, collagen synthesis decline and wrinkle formation are the common features of skin aging. The aim of this study is to investigate repressive effects of Colla Corii Asini (CCA) (a traditional Chinese medicine which has been used for anti-aging) on hydrogen peroxide (300 µM, 2 h) and ultraviolet A (UVA) (3.2 mJ/cm²)-induced skin aging in vitro. To simulate the in vivo condition of CCA, CCA was digested by gastrointestinal enzymes and added to human gingival fibroblasts (HGF) and three dimensional (3D) skin equivalents at different concentrations. Cell viability assay showed that the enzyme-digested CCA (CCAD) exhibited significant preventive effects on hydrogen peroxide- and UVA-induced cell death. The in vitro scratch assay showed that CCAD was able to prevent hydrogen peroxide-induced wound healing delay in HGF cell sheets. Immunostaining and imaging analysis showed that CCAD could suppress UVA-reduced expression of type IV collagen and elastin in both HGF cells and the 3D skin equivalents. Using a tissue stretching system, wrinkles were formed on UVA-irradiated 3D skin equivalents. Without CCAD-treatment, the wrinkles on the skin were deep, whereas CCAD markedly reduced the depth of wrinkles. In conclusion, CCAD could protect skin cells from oxidative stress and UVA-induced harmful effects, accelerate wound healing, promote synthesis of collagen and elastin, and reduce wrinkles formation. CCAD might be developed as an anti-skin aging reagent in the cosmetic industry.

Alterations in extracellular matrix composition during aging and photoaging of the skin

Human skin is composed of the cell-rich epidermis, the extracellular matrix (ECM) rich dermis, and the hypodermis. Within the dermis, a dense network of ECM proteins provides structural support to the skin and regulates a wide variety of signaling pathways which govern cell proliferation and other critical processes. Both intrinsic aging, which occurs steadily over time, and extrinsic aging (photoaging), which occurs as a result of external insults such as solar radiation, cause alterations to the dermal ECM. In this study, we utilized both quantitative and global proteomics, alongside single harmonic generation (SHG) and two-photon autofluorescence (TPAF) imaging, to assess changes in dermal composition during intrinsic and extrinsic aging. We find that both intrinsic and extrinsic aging result in significant decreases in ECM-supporting proteoglycans and structural ECM integrity, evidenced by decreasing collagen abundance and increasing fibril fragmentation. Intrinsic aging also produces changes distinct from those produced by photoaging, including reductions in elastic fiber and crosslinking enzyme abundance. In contrast, photoaging is primarily defined by increases in elastic fiber-associated protein and pro-inflammatory proteases. Changes associated with photoaging are evident even in young (mid 20s) sun-exposed forearm skin, indicating that proteomic evidence of photoaging is present decades prior to clinical signs of photoaging. GO term enrichment revealed that both intrinsic aging and photoaging share common features of chronic inflammation. The proteomic data has been deposited to the ProteomeXchange Consortium via the PRIDE partner repository with the data set identifier PXD015982.

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Intrinsic aging and photoaging both decrease ECM-supporting proteoglycans and structural ECM.

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Intrinsic aging produces reductions in elastic fiber and crosslinking enzyme abundance.

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Photoaging results in increases in pro-inflammatory proteases and elastic fiber abundance.

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Intrinsic aging and photoaging share common features associated with chronic inflammation.

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Proteomic changes associated with photoaging are evident decades prior to clinical aging signs.

Impaired Neovascularization in Aging

Significance: The skin undergoes an inevitable degeneration as an individual ages. As intrinsic and extrinsic factors degrade the structural integrity of the skin, it experiences a critical loss of function and homeostatic stability. Thus, aged skin becomes increasingly susceptible to injury and displays a prolonged healing process. Recent Advances: Several studies have found significant differences during wound healing between younger and older individuals. The hypoxia-inducible factor 1-alpha (HIF-1α) signaling pathway has recently been identified as a major player in wound healing. Hypoxia-inducible factors (HIFs) are pleiotropic key regulators of oxygen homeostasis. HIF-1α is essential to neovascularization through its regulation of cytokines, such as SDF-1α (stromal cell-derived factor 1-alpha) and has been shown to upregulate the expression of genes important for a hypoxic response. Prolyl hydroxylase domain proteins (PHDs) and factor inhibiting HIF effectively block HIF-1α signaling in normoxia through hydroxylation, preventing the signaling cascade from activating, leading to impaired tissue survival. Critical Issues: Aged wounds are a major clinical burden, resisting modern treatment and costing millions in health care each year. At the molecular level, aging has been shown to interfere with PHD regulation, which in turn prevents HIF-1α from activating gene expression, ultimately leading to impaired healing. Other studies have identified loss of function in cells during aging, impeding processes such as angiogenesis. Future Directions: An improved understanding of the regulation of molecular mediators, such as HIF-1α and PHD, will allow for manipulation of the various factors underlying delayed wound healing in the aged. The findings highlighted in this may facilitate the development of potential therapeutic approaches involved in the alteration of cellular dynamics and aging.

Potentially beneficial effects of rhamnose on skin ageing: an in vitro and in vivo study

OBJECTIVE

Recent findings showed that skin ageing preferentially affects human papillary dermal fibroblasts suggesting that the papillary dermis represents a critical zone altered by skin ageing. Based on these findings, we investigated the potential anti-ageing effect of rhamnose.

METHODS

We investigated the potential anti-ageing effect of rhamnose using in vitro reconstructed skin containing fibroblasts obtained either from young or old donors, and in vivo clinical investigation.

RESULTS

We detected positive effects of rhamnose in both epidermal and dermal compartments of in vitro reconstructed skin. Moreover, we were able to show that such in vitro findings were also obtained in vivo including an effect on collagen IV and procollagen I production.

CONCLUSION

We provide evidence that rhamnose has a potentially beneficial effect on papillary dermis and dermal-epidermal junction, both of the areas which are affected by skin ageing.

Electrospun Nanometer to Micrometer Scale Biomimetic Synthetic Membrane Scaffolds in Drug Delivery and Tissue Engineering: A Review

The scaffold technology research utilizes biomimicry to produce efficient scaffolds that mimic the natural cell growth environment including the basement membrane for tissue engineering. Because the natural basement membrane is composed of fibrillar protein networks of nanoscale diameter, the scaffold produced should efficiently mimic the nanoscale topography at a low production cost. Electrospinning is a technique that can achieve that. This review discusses the physical and chemical characteristics of the basement membrane and its significance on cell growth and overall focuses on nanoscale biomimetic synthetic membrane scaffolds primarily generated using electrospinning and their application in drug delivery and tissue engineering.

Non-invasive biomarkers derived from the extracellular matrix associate with response to immune checkpoint blockade (anti-CTLA-4) in metastatic melanoma patients

Background

Excessive extracellular matrix (ECM) remodeling and a reactive stroma can affect T-cell infiltration and T-cell activity in the tumor and hereby influence response to immune checkpoint inhibitors (ICI). In the pursuit of finding biomarkers that predict treatment response, we evaluated the association between serum biomarkers of collagen and vimentin turnover and outcomes in metastatic melanoma patients treated with the anti-CTLA-4 antibody ipilimumab (IPI).

Methods

Type III collagen formation (PRO-C3), MMP-degraded type I, type III and type IV collagens (C1M, C3M and C4M), and citrullinated and MMP-degraded vimentin (VICM) were measured with ELISAs in serum from metastatic melanoma patients before (n = 66) and 3 weeks after (n = 52) initiation of IPI treatment. Biomarker levels were associated with Disease Control Rate (DCR) and survival outcomes.

Results

We found that baseline levels of PRO-C3 (p = 0.011), C1M (p = 0.003), C3M (p = 0.013) and C4M (p = 0.027) were significantly elevated in patients with progressive disease (PD). Univariate Cox regression analysis identified high PRO-C3 (p = 0.021) and C4M (p = 0.008) as predictors of poor overall survival (OS) and the biomarkers remained significant when evaluated with other covariates (PRO-C3 (p = 0.049) and C4M (p = 0.046)). Multivariate analysis identified VICM as a predictor of longer OS (p = 0.026). Similarly, a high C3M/PRO-C3 ratio predicted for increased OS (p = 0.034). Only C3M (p = 0.003) and VICM (p < 0.0001) increased 3 weeks after treatment.

Conclusions

ECM and tissue remodeling quantified in pre-treatment serum were associated with response and survival outcomes in metastatic melanoma patients treated with IPI. This highlights the importance of addressing the ECM and stromal component non-invasively in future ICI studies.

Electronic supplementary material

The online version of this article (10.1186/s40425-018-0474-z) contains supplementary material, which is available to authorized users.

With Great Age Comes Great Metastatic Ability: Ovarian Cancer and the Appeal of the Aging Peritoneal Microenvironment

Age is one of the biggest risk factors for ovarian cancer. Older women have higher rates of diagnosis and death associated with the disease. In mouse models, it was shown that aged mice had greater tumor burden than their younger counterparts when intraperitoneally injected with ovarian tumor cells. While very few papers have been published looking at the direct link between ovarian cancer metastasis and age, there is a wealth of information on how age affects metastatic microenvironments. Mesothelial cells, the peritoneal extracellular matrix (ECM), fibroblasts, adipocytes and immune cells all exhibit distinct changes with age. The aged peritoneum hosts a higher number of senescent cells than its younger counterpart, in both the mesothelium and the stroma. These senescent cells promote an inflammatory profile and overexpress Matrix Metalloproteinases (MMPs), which remodel the ECM. The aged ECM is also modified by dysregulated collagen and laminin synthesis, increases in age-related crosslinking and increasing ovarian cancer invasion into the matrix. These changes contribute to a vastly different microenvironment in young and aged models for circulating ovarian cancer cells, creating a more welcoming “soil”.

Reliability of the skin blotting method when used on the elderly

The aim of this study was to compare protein secretion on intact skin of extremities and verify the relationship between the marker proteins on abdominal skin and systemic factors using skin blotting. A cross-sectional study was conducted among elderly patients aged 65 years and older (N = 73) at a long-term medical facility in Japan. Skin blotting was performed on the right and left forearms, right and left lower legs, and abdomen. Pearson's correlations and Bland-Altman plots were utilised for comparing the protein secretion from the skin between the right or left forearms or lower legs. Multiple regression analysis was applied to determine the relationship between intensity levels of 3 proteins on the abdominal skin and the systemic factors. Bland-Altman plots demonstrated that there was no significant difference between right and left secretion levels on the forearms and lower legs among 3 proteins. Multiple regression analysis showed that age and antiplatelet use was positively associated with decreased collagen type IV and increased matrix metalloproteinase 2 levels, respectively. Our findings suggested that collecting samples from either the right or the left skin would be sufficient if skin properties between arms and legs are evaluated using skin blotting.

Understanding angiogenesis during aging: opportunities for discoveries and new models

Microvascular network growth and remodeling are common denominators for most age-related pathologies. For multiple pathologies (myocardial infarction, stroke, hypertension), promoting microvascular growth, termed angiogenesis, would be beneficial. For others (cancer, retinopathies, rheumatoid arthritis), blocking angiogenesis would be desirable. Most therapeutic strategies, however, are motivated based on studies using adult animal models. This approach is problematic and does not account for the impaired angiogenesis or the inherent network structure changes that might result from age. Considering the common conception that angiogenesis is impaired with age, a need exists to identify the causes and mechanisms of angiogenesis in aged scenarios and for new tools to enable comparison of aged versus adult responses to therapy. The objective of this article is to introduce opportunities for advancing our understanding of angiogenesis in aging through the discovery of novel cell changes along aged microvascular networks and the development of novel ex vivo models.

Enzyme Development for Human Islet Isolation: Five Decades of Progress or Stagnation?

In comparison to procedures used for the separation of individual cell types from other organs, the process of human pancreatic islet isolation aims to digest the pancreatic exocrine matrix completely without dispersing the individual cells within the endocrine cell cluster. This objective is unique within the field of tissue separation, and outlines the challenge of islet isolation to balance two opposing priorities. Although significant progress has been made in the characterization and production of enzyme blends for islet isolation, there are still numerous areas which require improvement. The ultimate goal of enzyme production, namely the routine production of a consistent and standardized enzyme blend, has still not been realized. This seems to be mainly the result of a lack of detailed knowledge regarding the structure of the pancreatic extracellular matrix and the synergistic interplay between collagenase and different supplementary proteases during the degradation of the extracellular matrix. Furthermore, the activation of intrinsic proteolytic enzymes produced by the pancreatic acinar cells, also impacts on the chance of a successful outcome of human islet isolation. This overview discusses the challenges of pancreatic enzymatic digestion during human islet isolation, and outlines the developments in this field over the past 5 decades.

Postnatal changes and sexual dimorphism in collagen expression in mouse skin

To investigate sexual dimorphism and postnatal changes in skin collagen expression, mRNA levels of collagens and their regulatory factors in male and female skin were examined during the first 120 days of age by quantitative realtime PCR. Levels of mRNAs encoding extracellular matrices did not show any differences between male and female mice until day 15. Col1a1 and Col1a2 mRNAs noticeably increased at day 30 and remained at high levels until day 120 in male mice, while those in female mice remained at low levels during the period. Consistent with the mRNA expression, pepsin-soluble type I collagen contents in skin was very high in mature male as compared to female. Col3a1 mRNA in male mice also showed significantly high level at day 120 as compared to female. On the other hand, expression of mRNAs encoding TGF-ßs and their receptors did not show apparent sexual dimorphism although small significant differences were observed at some points. Castration at 60 days of age resulted in a significant decrease in type I collagen mRNA expression within 3 days, and noticeably decreased expression of all fibril collagen mRNAs examined within 14 days, while administration of testosterone tube maintained the mRNA expression at high levels. Despite the in vivo effect of testosterone, administration of physiological concentrations of testosterone did not affect fibril collagen mRNA expression in either human or mouse skin fibroblasts in vitro, suggesting that testosterone does not directly affect collagen expression in fibroblasts. In summary, present study demonstrated dynamic postnatal changes in expression of collagens and their regulatory factors, and suggest that testosterone and its effects on collagen expression are responsible for the skin sexual dimorphism but the effects of testosterone is not due to direct action on dermal fibroblasts.

Skin property can predict the development of skin tears among elderly patients: a prospective cohort study

The aim of this study was to identify skin properties that may be used to predict the development of a skin tear (ST) among elderly patients. A prospective cohort study was conducted among elderly patients aged 65 and older (N = 149) at a long-term medical facility in Japan over an 8-month period. Skin properties at baseline were measured on the forearm using a 20-MHz ultrasound scanner, which measured the thickness of the dermis layer and low-echogenic pixels, and skin blotting method, which evaluated the levels of collagen type IV, matrix metalloproteinase-2 and tumour necrosis factor-alpha. Adjusted hazard ratios (HRs) for the main confounders were obtained using the Cox proportional hazard model. A total of 52 STs were recorded among the 21 patients, resulting in an incidence rate of 1·13/1000 person-days. The predictor of STs was dermis thickness (HR = 0·52; 95% confidence interval = 0·33-0·81; P-value = 0·004). The cut-off point for dermis thickness was 0·80 mm (area under the curve = 0·77; 95% confidence interval = 0·66-0·88; P-value = 0·006). Our results suggest that measuring the dermis thickness at baseline is an easy and accurate way to identify a high-risk patient.

Morphometry of skeletal muscle capillaries: the relationship between capillary ultrastructure and ageing in humans

AIM

To determine whether the ultrastructure of the capillary system in human skeletal muscle changes during advancing senescence, we evaluated the compartmental and subcompartmental organization of capillaries from vastus lateralis muscle (VL) biopsies of 41 non-diseased persons aged 23-75 years.

METHODS

From each VL biopsy, 38-40 randomly selected capillaries were assessed by transmission electron microscopy and subsequent morphometry with a newly established tablet-based image analysis technique.

RESULTS

Quantification of the compartmental organization revealed most indicators of the capillary ultrastructure to be only non-significantly altered (P > 0.05) over age. However, the peri-capillary basement membrane (BM) was thicker in the older participants than in the younger ones (P ≤ 0.05). Regression analysis revealed a bipartite relationship between the two parameters: a homogenous slight increase in BM thickness up to the age of approximately 50 years was followed by a second phase with more scattered BM thickness values. In 44.5% of the capillary profiles, projections/filopodia of the pericytes (PCs) traversed the BM and invaded endothelial cells (ECs) visible as PC pegs in pale cytoplasm holes (EC sockets). Strikingly, PC pegs were often in proximity to the EC nucleus. In PC profiles, sockets were likewise detected in 14.2% of the capillaries. Within these PC sockets, cellular profiles were frequently seen, which could be assigned to EC filopodia, internal PC curling or PC-PC interactions. Quantification of the occurrence of peg-socket junctions revealed the proportions of empty EC sockets and empty PC sockets to increase (P ≤ 0.05) during ageing.

CONCLUSION

Our investigation demonstrates advancing senescence to be associated with increase in BM thickness and loss of EC and PC filopodia length in skeletal muscle capillaries.

Phlorizin, an Active Ingredient of Eleutherococcus senticosus, Increases Proliferative Potential of Keratinocytes with Inhibition of MiR135b and Increased Expression of Type IV Collagen

E. senticosus extract (ESE), known as antioxidant, has diverse pharmacologic effects. It is also used as an antiaging agent for the skin and phlorizin (PZ) is identified as a main ingredient. In this study, the effects of PZ on epidermal stem cells were investigated. Cultured normal human keratinocytes and skin equivalents are used to test whether PZ affects proliferative potential of keratinocytes and how it regulates these effects. Skin equivalents (SEs) were treated with ESE and the results showed that the epidermis became slightly thickened on addition of 0.002% ESE. The staining intensity of p63 as well as proliferating cell nuclear antigen (PCNA) is increased, and integrin α6 was upregulated. Analysis of ESE confirmed that PZ is the main ingredient. When SEs were treated with PZ, similar findings were observed. In particular, the expression of integrin α6, integrin β1, and type IV collagen was increased. Levels of mRNA for type IV collagen were increased and levels of miR135b were downregulated. All these findings suggested that PZ can affect the proliferative potential of epidermal cells in part by microenvironment changes via miR135b downregulation and following increased expression of type IV collagen.

New concepts in basement membrane biology

Basement membranes (BMs) are thin sheets of extracellular matrix that outline epithelia, muscle fibers, blood vessels and peripheral nerves. The current view of BM structure and functions is based mainly on transmission electron microscopy imaging, in vitro protein binding assays, and phenotype analysis of human patients, mutant mice and invertebrata. Recently, MS-based protein analysis, biomechanical testing and cell adhesion assays with in vivo derived BMs have led to new and unexpected insights. Proteomic analysis combined with ultrastructural studies showed that many BMs undergo compositional and structural changes with advancing age. Atomic force microscopy measurements in combination with phenotype analysis have revealed an altered mechanical stiffness that correlates with specific BM pathologies in mutant mice and human patients. Atomic force microscopy-based height measurements strongly suggest that BMs are more than two-fold thicker than previously estimated, providing greater freedom for modelling the large protein polymers within BMs. In addition, data gathered using BMs extracted from mutant mice showed that laminin has a crucial role in BM stability. Finally, recent evidence demonstrate that BMs are bi-functionally organized, leading to the proposition that BM-sidedness contributes to the alternating epithelial and stromal tissue arrangements that are found in all metazoan species. We propose that BMs are ancient structures with tissue-organizing functions and were essential in the evolution of metazoan species.

"Skin facts" to optimize aesthetic outcomes

Aesthetic providers need to be well versed in the anatomy and intricacies of the skin. This foundational skin knowledge is critical in assessing clients' aged skin during the aesthetic consultation. A sound understanding of the skin is also a prerequisite to any facial rejuvenation procedure. This article provides the aesthetic provider with the basics of skin anatomy and how the skin changes over time.

Differential expression of cathepsins K, S and V between young and aged Caucasian women skin epidermis

Cutaneous aging translates drastic structural and functional alterations in the extracellular matrix (ECM). Multiple mechanisms are involved, including changes in protease levels. We investigated the age-related protein expression and activity of cysteine cathepsins and the expression of two endogenous protein inhibitors in young and aged Caucasian women skin epidermis. Immunofluorescence studies indicate that the expression of cathepsins K, S and V, as well as cystatins A and M/E within keratinocytes is reduced in photoprotected skin of aged women. Furthermore, the overall endopeptidase activity of cysteine cathepsins in epidermis lysates decreased with age. Albeit dermal elastic fiber and laminin expression is reduced in aged skin, staining of nidogen-1, a key protein in BM assembly that is sensitive to proteolysis by cysteine, metallo- and serine proteases, has a similar pattern in both young and aged skin. Since cathepsins contribute to the hydrolysis and turnover of ECM/basement membrane components, the abnormal protein degradation and deposition during aging process may be related in part to a decline of lysosomal/endosomal cathepsin K, S and V activity.

Diabetes-induced morphological, biomechanical, and compositional changes in ocular basement membranes

The current study investigates the structural and compositional changes of ocular basement membranes (BMs) during long-term diabetes. By comparing retinal vascular BMs and the inner limiting membrane (ILM) from diabetic and non-diabetic human eyes by light and transmission electron microscopy (TEM), a massive, diabetes-related increase in the thickness of these BMs was detected. The increase in ILM thickness was confirmed by atomic force microscopy (AFM) on native ILM flat-mount preparations. AFM also detected a diabetes-induced increase in ILM stiffness. The changes in BM morphology and biophysical properties were accompanied by partial changes in the biochemical composition as shown by immunocytochemistry and western blots: agrin, fibronectin and tenascin underwent relative increases in concentration in diabetic BMs as compared to non-diabetic BMs. Fibronectin and tenascin were particularly high in the BMs of outlining microvascular aneurisms. The present data showed that retinal vascular BMs and the ILM undergo morphological, biomechanical and compositional changes during long-term diabetes. The increase in BM thickness not only resulted from an up-regulation of the standard BM proteins, but also from the expression of diabetes-specific extracellular matrix proteins that are not normally found in retinal BMs.

The bi-functional organization of human basement membranes

The current basement membrane (BM) model proposes a single-layered extracellular matrix (ECM) sheet that is predominantly composed of laminins, collagen IVs and proteoglycans. The present data show that BM proteins and their domains are asymmetrically organized providing human BMs with side-specific properties: A) isolated human BMs roll up in a side-specific pattern, with the epithelial side facing outward and the stromal side inward. The rolling is independent of the curvature of the tissue from which the BMs were isolated. B) The epithelial side of BMs is twice as stiff as the stromal side, and C) epithelial cells adhere to the epithelial side of BMs only. Side-selective cell adhesion was also confirmed for BMs from mice and from chick embryos. We propose that the bi-functional organization of BMs is an inherent property of BMs and helps build the basic tissue architecture of metazoans with alternating epithelial and connective tissue layers.

Effects of serially passaged fibroblasts on dermal and epidermal morphogenesis in human skin equivalents

Serial passaging has a profound effect on primary cells. Since serially passaged cells show signs of cellular aging, serial passaging is used as an in vitro model of aging. To relate the effect of in vitro aging more to in vivo aging, we generated human skin equivalents (HSEs). We investigated if HSEs generated with late passage fibroblasts show characteristics of aged skin when compared with HSEs generated with early passage fibroblasts. Late passage fibroblasts had enlarged cell bodies and were more often positive for myofibroblast marker α-smooth muscle actin, senescence associated β-galactosidase and p16 compared with early passage fibroblasts. Skin equivalents generated with late passage fibroblasts had a thinner dermis, which could partly be explained by increased matrix metalloproteinase-1 secretion. In equivalents generated with late passage fibroblasts epidermal expression of keratin 6 was increased, and of keratin 10 slightly decreased. However, epidermal proliferation, epidermal thickness and basement membrane formation were not affected. In conclusion, compared with HSEs generated with early passage fibroblasts, HSEs generated with late passage fibroblasts showed changes in the dermis, but no or minimal changes in the basement membrane and the epidermis.

Protein composition and biomechanical properties of in vivo-derived basement membranes

Basement membranes (BMs) evolved together with the first metazoan species approximately 500 million years ago. Main functions of BMs are stabilizing epithelial cell layers and connecting different types of tissues to functional, multicellular organisms. Mutations of BM proteins from worms to humans are either embryonic lethal or result in severe diseases, including muscular dystrophy, blindness, deafness, kidney defects, cardio-vascular abnormalities or retinal and cortical malformations. In vivo-derived BMs are difficult to come by; they are very thin and sticky and, therefore, difficult to handle and probe. In addition, BMs are difficult to solubilize complicating their biochemical analysis. For these reasons, most of our knowledge of BM biology is based on studies of the BM-like extracellular matrix (ECM) of mouse yolk sac tumors or from studies of the lens capsule, an unusually thick BM. Recently, isolation procedures for a variety of BMs have been described, and new techniques have been developed to directly analyze the protein compositions, the biomechanical properties and the biological functions of BMs. New findings show that native BMs consist of approximately 20 proteins. BMs are four times thicker than previously recorded, and proteoglycans are mainly responsible to determine the thickness of BMs by binding large quantities of water to the matrix. The mechanical stiffness of BMs is similar to that of articular cartilage. In mice with mutation of BM proteins, the stiffness of BMs is often reduced. As a consequence, these BMs rupture due to mechanical instability explaining many of the pathological phenotypes. Finally, the morphology and protein composition of human BMs changes with age, thus BMs are dynamic in their structure, composition and biomechanical properties.

Review on Labisia pumila (Kacip Fatimah): bioactive phytochemicals and skin collagen synthesis promoting herb

Labisia pumila is a traditional herb widely used as post-partum medication for centuries. Recently, extensive researches have been carried out on the phytochemical identification, biological and toxicological studies for the herb. Phytochemicals found in the herbal extract showed high antioxidant properties, which were essential for various pharmacological activities. The significant findings are anti-estrogenic deficiency and -immunodeficiency diseases. Another finding that has considerable impact on natural product research is the contribution of L. pumila in promoting skin collagen synthesis. The performance of the herb as anti-aging agent due to natural aging process and accelerated by UV radiation was reviewed critically.

Evolution of the clonogenic potential of human epidermal stem/progenitor cells with age

A number of clinical observations have indicated that the regenerative potential and overall function of the epidermis is modified with age. The epidermis becomes thinner, repairs itself less efficiently after wounding, and presents modified barrier function recovery. In addition, the dermal papillae flatten out with increasing age, suggesting a modification in the interaction between epidermal and dermal compartments. As the epidermal regenerative capacity is dependent upon stem and progenitor cell function, it is naturally of interest to identify and understand age-related changes in these particular keratinocyte populations. Previous studies have indicated that the number of stem cells does not decrease with age in mouse models but little solid evidence is currently available concerning human skin. The objective of this study was to evaluate the clonogenic potential of keratinocyte populations isolated from the epidermis of over 50 human donors ranging from 18 to 71 years old. The data indicate that the number of epidermal cells presenting high regenerative potential does not dramatically decline with age in human skin. The authors believe that changes in the microenvironment controlling epidermal basal cell activity are more likely to explain the differences in epidermal function observed with increasing age.

Characterization of Type I and IV Collagens by Raman Microspectroscopy: Identification of Spectral Markers of the Dermo-Epidermal Junction

Type I and IV collagens are important constituents of the skin. Type I collagen is found in all dermal layers in high proportion, while type IV collagen is localized in the basement membrane of the dermo-epidermal junction (DEJ). These proteins are strongly altered during aging or cancer progression. Although they possess amino acid compositions which, are close, they present also important structural differences inducing specific physicochemical properties. Raman spectroscopy is based on a nondestructive interaction of the light with the matter. This technique permits to probe the intrinsic molecular composition of the samples without staining or particular preparation. The aim of our research is to study the correlation between the molecular conformations of type I and IV collagens and their Raman features. We showed that signals specific of each protein can be revealed and that they translate structural differences between the two collagens. From this collagens spectral characterization, the analysis of skin sections also permitted to identify spectral markers of dermis, epidermis, and epidermis/dermis interface. These preliminary results represent basic data for further studies, particularly to probe skin molecular alterations induced by chronologic aging.

Aging alters functionally human dermal papillary fibroblasts but not reticular fibroblasts: a new view of skin morphogenesis and aging

Understanding the contribution of the dermis in skin aging is a key question, since this tissue is particularly important for skin integrity, and because its properties can affect the epidermis. Characteristics of matched pairs of dermal papillary and reticular fibroblasts (Fp and Fr) were investigated throughout aging, comparing morphology, secretion of cytokines, MMPs/TIMPs, growth potential, and interaction with epidermal keratinocytes. We observed that Fp populations were characterized by a higher proportion of small cells with low granularity and a higher growth potential than Fr populations. However, these differences became less marked with increasing age of donors. Aging was also associated with changes in the secretion activity of both Fp and Fr. Using a reconstructed skin model, we evidenced that Fp and Fr cells do not possess equivalent capacities to sustain keratinopoiesis. Comparing Fp and Fr from young donors, we noticed that dermal equivalents containing Fp were more potent to promote epidermal morphogenesis than those containing Fr. These data emphasize the complexity of dermal fibroblast biology and document the specific functional properties of Fp and Fr. Our results suggest a new model of skin aging in which marked alterations of Fp may affect the histological characteristics of skin.

Expression and functional analysis of beta-adrenoceptor subtypes in rabbit submandibular gland

beta-Adrenoceptors (beta-ARs) mediate important physiological functions in salivary glands. Here we investigated the expression and function of beta-AR subtypes in rabbit submandibular gland (SMG). Both beta(1)- and beta(2)-ARs, but not beta(3)-AR, were strongly expressed in rabbit SMG. beta(1)-AR proteins were widely expressed in acinar and ductal cells whereas beta(2)-AR proteins were mainly detected in ductal cells. A [(3)H]-dihydroalprenolol binding assay revealed that beta-AR B(max) was 186+/-11.9 fmol/mg protein and K(d) was 2.71+/-0.23 nM. A competitive binding assay with CGP 20712A, a beta(1)-AR antagonist, indicated that the proportion of beta(1)-AR and beta(2)-AR was 71.9% and 28.1%, respectively. Gland perfusion with the beta-AR agonist isoproterenol induced a significant increase in saliva secretion which was abolished by pretreatment with the non-selective beta-AR antagonist propranolol. Pretreatment with beta(1)- or beta(2)-AR selective antagonists, CGP 20712A or ICI 118551, diminished isoproterenol-induced increase in saliva secretion by 71.2% and 28.8%, respectively. The expression of alpha-amylase mRNA was significantly stimulated by isoproterenol, which was eliminated by propranolol and CGP 20712A. Perfusion with isoproterenol decreased alpha-amylase protein storage in SMG and increased alpha-amylase activity in saliva. These alterations became less significant after pretreatment with propranolol and CGP 20712A. Our results suggest that both beta(1)- and beta(2)-ARs are expressed in rabbit SMG. beta(1)-AR is the predominant subtype and may play an important role in regulating saliva and alpha-amylase secretion.

Effects of methyl paraben on skin keratinocytes

Some ingredients of dermatological formulations result in skin irritation and allergy. In particular, preservatives have been reported extensively as a cause of allergic contact dermatitis. The study focused on parabens which have been used extensively as antimicrobial preservatives in foods, drugs and cosmetics. The aim of this study was to clarify the effects of the daily use of methyl paraben (MP) on human skin. The concentrations of MP in the stratum corneum (SC) of the human forearm were measured using the cup method and GC-MS after daily applications of MP containing formulations. The study also investigated the effects of long-term exposure to MP on keratinocytes in vitro. Normal human keratinocytes and the skin equivalents were cultured in the medium containing MP. The following changes were analysed: proliferating ability, apoptotic cells, morphological changes, mRNA and protein expressions. After 1 month of daily applications of MP containing formulations, MP remained unmetabolized and persisted slightly in the SC. MP decreased the proliferating ability of keratinocytes and changed the cell morphology. MP also decreased the expressions of hyaluronan synthase 1 and 2 mRNAs and type IV collagen. In contrast, it increased the expressions of involucrin and HSP27. Furthermore, MP influenced the epidermal differentiation of the skin equivalent. These results suggest that MP exposure through application of dermatological formulations results in MP persistence and accumulation in the SC, and that MP might influence the aging and differentiation of keratinocytes.