Isolation of an "Early" Transit Amplifying Keratinocyte Population in Human Epidermis: A Role for the Low Affinity Neurotrophin Receptor CD271.

In the interfollicular epidermis (IFE), stem cells (KSC) generate transit amplifying (TA) cells that, after symmetric divisions, produce differentiating daughters. Here, we isolated and characterized the highly proliferative interfollicular epidermal basal cell population "early" TA (ETA) cells, based on their capacity to adhere to type IV collagen. Proliferation and colony-forming efficiency in ETA cells are lower than in KSC but higher than in "late" TA (LTA).

Hyaluronic acid detection and relative quantification by mass spectrometry imaging in human skin tissues.

Hyaluronic acid (HA) is a major component of the skin, contributing to tissue hydration and biomechanical properties. As HA content in the skin decreases with age, formulas containing HA are widely used in cosmetics and HA injections in aesthetic procedures to reduce the signs of aging. To prove the beneficial effects of these treatments, efficient quantification of HA levels in the skin is necessary, but remains difficult.

"You look sleepy…" The impact of sleep restriction on skin parameters and facial appearance of 24 women.

Background: Total sleep deprivation has a visible impact on subjective facial appearance. However, there is a lack of knowledge on how moderate sleep restriction objectively impairs skin quality and facial aspect.

Methods: Twenty-four healthy good-sleeping women, aged 30-55, volunteered for this study on the impact of sleep restriction (SR) on their facial skin.

Oxidative damage and impairment of protein quality control systems in keratinocytes exposed to a volatile organic compounds cocktail.

Compelling evidence suggests that volatile organic compounds (VOCs) have potentially harmful effects to the skin. However, knowledge about cellular signaling events and toxicity subsequent to VOC exposure to human skin cells is still poorly documented. The aim of this study was to focus on the interaction between 5 different VOCs (hexane, toluene, acetaldehyde, formaldehyde and acetone) at doses mimicking chronic low level environmental exposure and the effect on human keratinocytes to get better insight into VOC-cell interactions.

E-cadherin mediates ultraviolet radiation- and calcium-induced melanin transfer in human skin cells.

Skin pigmentation is directed by epidermal melanin units, characterized by long-lived and dendritic epidermal melanocytes (MC) that interact with viable keratinocytes (KC) to contribute melanin to the epidermis. Previously, we reported that MC:KC contact is required for melanosome transfer that can be enhanced by filopodi, and by UVR/UVA irradiation, which can upregulate melanosome transfer via Myosin X-mediated control of MC filopodia. Both MC and KC express Ca -dependent E-cadherins.

Skin tumours and skin aging in 209 French elderly people: the PROOF study.

Few studies have evaluated the prevalence of skin tumours in the geriatric population and none have analysed different skin aging parameters for whole-body skin in this population. To evaluate the prevalence of skin tumours and global skin aging in a French cohort of elderly people. In total, 209 subjects, 105 women and 104 men (mean age: 77.

Skin protection against dicarbonyl stress by the glyoxalase system.

Skin ageing is the result of intrinsic and photo-ageing, due to UV exposure, that both share important molecular features including alterations of proteins. Indeed, proteins can be modified by many molecular processes such as glycation. Glycation occurs when glucose or its derivates the dicarbonyl compounds glyoxal (GO) and methylglyoxal (MG) react with amines of proteins leading to the formation of advanced glycation endproducts (AGE).

Modelling epidermis homoeostasis and psoriasis pathogenesis.

We present a computational model to study the spatio-temporal dynamics of epidermis homoeostasis under normal and pathological conditions. The model consists of a population kinetics model of the central transition pathway of keratinocyte proliferation, differentiation and loss and an agent-based model that propagates cell movements and generates the stratified epidermis. The model recapitulates observed homoeostatic cell density distribution, the epidermal turnover time and the multilayered tissue structure.

Binding of chondroitin 4-sulfate to cathepsin S regulates its enzymatic activity.

Human cysteine cathepsin S (catS) participates in distinct physiological and pathophysiological cellular processes and is considered as a valuable therapeutic target in autoimmune diseases, cancer, atherosclerosis, and asthma. We evaluated the capacity of negatively charged glycosaminoglycans (heparin, heparan sulfate, chondroitin 4/6-sulfates, dermatan sulfate, and hyaluronic acid) to modulate the activity of catS. Chondroitin 4-sulfate (C4-S) impaired the collagenolytic activity (type IV collagen) and inhibited the peptidase activity (Z-Phe-Arg-AMC) of catS at pH 5.

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.

Hormesis-based anti-aging products: a case study of a novel cosmetic.

Application of hormesis in aging research and interventions is becoming increasingly attractive and successful. The reason for this is the realization that mild stress-induced activation of one or more stress response (SR) pathways, and its consequent stimulation of repair mechanisms, is effective in reducing the age-related accumulation of molecular damage. For example, repeated heat stress-induced synthesis of heat shock proteins has been shown to have a variety of anti-aging effects on growth and other cellular and biochemical characteristics of normal human skin fibroblasts, keratinocytes and endothelial cells undergoing aging in vitro.

Cleavage of nidogen-1 by cathepsin S impairs its binding to basement membrane partners.

Cathepsin S (catS), which is expressed in normal human keratinocytes and localized close to the dermal-epidermal junction (DEJ) degrades some of major basement membrane (BM) constituents. Among them, catS readily hydrolyzed in a time and dose dependent manner human nidogen-1 (nid-1) and nidogen-2, which are key proteins in the BM structure. CatS preferentially cleaved nid-1 at both acid and neutral pH.

Human skin keratinocytes, melanocytes, and fibroblasts contain distinct circadian clock machineries.

Skin acts as a barrier between the environment and internal organs and performs functions that are critical for the preservation of body homeostasis. In mammals, a complex network of circadian clocks and oscillators adapts physiology and behavior to environmental changes by generating circadian rhythms. These rhythms are induced in the central pacemaker and peripheral tissues by similar transcriptional-translational feedback loops involving clock genes.

A photographic scale for the evaluation of facial skin aging in Indian women.

The process of facial skin aging differs between different ethnic populations. Standardized tools to objectively evaluate facial skin aging in clinical and epidemiological studies in different ethnic populations are needed. We designed and validated a photonumeric scale for assessment of facial aging in the Indian population.

Role of neurotrophins on dermal fibroblast survival and differentiation.

Neurotrophins (NTs) belong to a family of growth factors that play a critical role in the control of skin homeostasis. NTs act through the low-affinity receptor p75NTR and the high-affinity receptors TrkA, TrkB, and TrkC. Here we show that dermal fibroblasts (DF) and myofibroblasts (DM) synthesize and secrete all NTs and express NT receptors.

Melanin transfer in human skin cells is mediated by filopodia--a model for homotypic and heterotypic lysosome-related organelle transfer.

Transfer of the melanocyte-specific and lysosome-related organelle, the melanosome, from melanocytes to keratinocytes is crucial for the protection of the skin against harmful ultraviolet radiation (UVR)--our main physiological cutaneous stressor. However, this commonplace event remains a most enigmatic process despite several early hypotheses. Recently, we and others have proposed a role for filopodia in melanin transfer, although conclusive experimental proof remained elusive.

GammaH2AX, an accurate marker that analyzes UV genotoxic effects on human keratinocytes and on human skin.

The phosphorylated form of histone H2AX, gammaH2AX, is a component of the DNA repair system. Most studies have focused on the role of gammaH2AX during cell transformation and human cancer, but little is known about its role in keratinocytes and the skin during UV irradiation. We analyzed the response to UV irradiation focusing on the phosphorylation of histone H2AX both in vitro, in keratinocyte cultures and in artificial epidermis, and then in vivo, in human skin.

Study of fibroblast gene expression in response to oxidative stress induced by hydrogen peroxide or UVA with skin aging.

The skin aging process, implying oxidative stress, is associated with specific gene expression. Ultraviolet A (UVA) and hydrogen peroxide (H(2)O(2)) both generate reactive oxygen species (ROS) making them relevant in the study of skin cell responses to oxidative stresses. To investigate transcript expression associated with chronological skin aging and its modulation by two oxidative stresses, cDNA micro-arrays, composed of a set of 81 expressed sequence tag (EST) clones, were used to probe the patterns of transcript expression in human fibroblasts of five young (< 21 years-old) and five older (> 50 years-old) healthy females at basal levels and 24 h after exposure to UVA (7 J/cm2) and H(2)O(2) (20 mM).

Skin aquaporins: function in hydration, wound healing, and skin epidermis homeostasis.

Several aquaporins (AQPs) are expressed in mammalian skin. Some are directly involved in water transport, such as AQP5, which is involved in sweat secretion. In contrast, the physiological role of skin aquaglyceroporins, which permeate both water and glycerol, appears more and more complex.

The silver locus product (Silv/gp100/Pmel17) as a new tool for the analysis of melanosome transfer in human melanocyte-keratinocyte co-culture.

Melanosomes are melanocyte-specific lysosome-related organelles that are transferred to keratinocytes of the epidermis and anagen hair bulb. Transferred melanin forms supra-nuclear caps that protect epidermal keratinocytes against UV irradiation. The mechanism(s) responsible for melanosome transfer into keratinocytes and their subsequent intra-keratinocyte distribution has long remained one of the most enigmatic of heterotypic cell interactions.