Quantitative nanohistology of aging dermal collagen.

The skin is the largest organ in the body and is essential for protecting us from environmental stressors such as UV radiation, pollution, and pathogens. As we age, our skin undergoes complex changes that can affect its function, appearance, and health. These changes result from intrinsic (chronological) and extrinsic (environmental) factors that can cause damage to the skin's cells and extracellular matrix.

Assessing the Role of Carbonyl Adducts, Particularly Malondialdehyde Adducts, in the Development of Dermis Yellowing Occurring during Skin Photoaging.

Solar elastosis is associated with a diffuse yellow hue of the skin. Photoaging is related to lipid peroxidation leading to the formation of carbonyl groups. Protein carbonylation can occur by addition of reactive aldehydes, such as malondialdehyde (MDA), 4-hydroxy-nonenal (4-HNE), and acrolein.

A mechanistic view on the aging human skin through ex vivo layer-by-layer analysis of mechanics and microstructure of facial and mammary dermis.

Age-related changes in skin mechanics have a major impact on the aesthetic perception of skin. The link between skin microstructure and mechanics is crucial for therapeutic and cosmetic applications as it bridges the micro- and the macro-scale. While our perception is governed by visual and tactile changes at the macroscopic scale, it is the microscopic scale (molecular assemblies, cells) that is targeted by topical treatments including active compounds and energies.

UVA Exposure Combined with Glycation of the Dermis Are Two Catalysts for Skin Aging and Promotes a Favorable Environment to the Appearance of Elastosis.

Skin aging is the result of superimposed intrinsic (individual) and extrinsic (e.g., UV exposure or nutrition) aging.

Author Correction: Reconstructed Skin Models Revealed Unexpected Differences in Epidermal African and Caucasian Skin.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Dietary Antioxidant Capacity and Skin Photoaging: A 15-Year Longitudinal Study.

The long-term effect of diet on skin aging is largely unknown, but evidence suggests that the antioxidants from foods may mitigate the main component of skin aging caused by sun exposure. We assessed the association between the total antioxidant capacity of foods people eat and the photoaging of their skin. In a community-based, prospective study among 777 Australian adults aged <55 years at baseline, we estimated the total dietary antioxidant capacity of participants' diets in 1992, 1994, and 1996 and graded photoaging severity using microtopography in 1992, 1996, and 2007.

Reconstructed Skin Models Revealed Unexpected Differences in Epidermal African and Caucasian Skin.

Clinical observations of both normal and pathological skin have shown that there is a heterogeneity based on the skin origin type. Beside external factors, intrinsic differences in skin cells could be a central element to determine skin types. This study aimed to understand the in vitro behaviour of epidermal cells of African and Caucasian skin types in the context of 3D reconstructed skin.

Biological Effects Induced by Specific Advanced Glycation End Products in the Reconstructed Skin Model of Aging.

Advanced glycation end products (AGEs) accumulate in the aging skin. To understand the biological effects of individual AGEs, skin reconstructed with collagen selectively enriched with N(ɛ)-(carboxymethyl)-lysine (CML), N(ɛ)-(carboxyethyl)-lysine (CEL), methylglyoxal hydroimidazolone (MG-H1), or pentosidine was studied. Immunohistochemistry revealed increased expression of α6 integrin at the dermal epidermal junction by CEL and CML (p<0.

The reconstructed skin model as a new tool for investigating in vitro dermal fillers: increased fibroblast activity by hyaluronic acid.

Background: Clinical studies on dermal fillers have essentially focused upon visible improvement of skin quality and any eventual side effects, whereas very little is known about their detailed biological effects.

Objectives: New skin equivalent models were created to investigate the biological impact of hyaluronic acid (HA) fillers on the dermal compartment in vitro.

Materials And Methods: Two different reconstructed skin models were developed to incorporate HA within the collagen fibers.

Skin aging by glycation: lessons from the reconstructed skin model.

Background: Aging is the result of several mechanisms which operate simultaneously. Among them, glycation is of particular interest because it is a reaction which affects slowly renewing tissues and macromolecules with elevated half-life, like the dermis, a skin compartment highly affected by aging. Glycation produces crosslinks between macromolecules thereby providing an explanation for the increased age-related stiffness of the skin.

In vivo and in vitro approaches in understanding the differences between Caucasian and African skin types: specific involvement of the papillary dermis.

Background: Most of the identified differences between Caucasian and African skin types have been related to the superficial part of the skin, the epidermis. We investigated possible implications of the dermal compartment in cutaneous differences observed between Caucasians and Africans.

Methods: In vivo and in vitro comparative studies were carried out using normal human skin biopsies and the corresponding in vitro reconstructed skin.

Distinct and complementary roles of papillary and reticular fibroblasts in skin morphogenesis and homeostasis.

To study the biological properties of dermal fibroblast sub-populations, we used a reconstructed skin model with a dermal compartment populated with either papillary or reticular fibroblasts. The histological and immunohistological characterization of these reconstructed skins revealed distinct biological and structural differences, depending on the site-matched fibroblast population incorporated. Epidermal differentiation and maturation was favored and found optimum in the presence of papillary fibroblasts with little effect on ECM, as opposed to reticular fibroblasts, which had a significant positive effect on the production of the ECM molecules of the dermal epidermal junction and the dermis.

The Caucasian and African skin types differ morphologically and functionally in their dermal component.

In the literature, most reported differences between African and Caucasian skin properties concern pigmentation and barrier function of the stratum corneum and related photoprotective properties. However, little is known about differences in morphology and possibly related biological functions. In this study, we investigated: (i) architectural differences of Caucasian and African mammary skin biopsies using microscopy, (ii) comparative constitutive expression of cytokines, matrix metalloproteinase 1 (MMP-1) and its inhibitors in papillary dermal fibroblast (pF) and reticular dermal fibroblast (rF) cultures in order to reveal biological features.

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.

Reconstructed skin modified by glycation of the dermal equivalent as a model for skin aging and its potential use to evaluate anti-glycation molecules.

Glycation is a slow chemical reaction which takes place between amino residues in protein and a reducing sugar. In skin this reaction creates new residues or induces the formation of cross-links (advanced glycation end products or AGEs) in the extracellular matrix of the dermis. Formation of such cross-links between macromolecules may be responsible for loss of elasticity or modification of other properties of the dermis observed during aging.

[Fibroblast subpopulations: a developmental approach of skin physiology and ageing].

Skin is an organ whose function is far beyond a physical barrier between the inside and the outside of the body. Skin as the whole organism is subjected to ageing which concerns skin mostly in its dermal and deepest component which is also its matricial component. The dermis is a tissue rich in matricial elements and poor in cellular content and it is generally admitted that modifications occurring in the matrix are those which mostly contribute to skin ageing, by altering its biomechanical properties.

Collagen glycation triggers the formation of aged skin in vitro.

Glycation products accumulate during the aging of many slowly renewing tissues, including skin. We have developed an in vitro model of chronologic aging of skin based on reconstructed skin modified by artificially glycating the collagen used to prepare the dermal compartment. The morphology of the modified skin is close to the morphology usually observed except that the dermis is altered in its fibrillar structure.

An in vitro approach to the chronological aging of skin by glycation of the collagen: the biological effect of glycation on the reconstructed skin model.

Glycation is a slow, nonenzymatic reaction that takes place between free amino groups in proteins primarily from lysine and a reducing sugar such as glucose or ribose. In skin, this reaction creates new residues or formations of cross-links (advanced glycation end products, AGEs) in the extracellular matrix of the dermis. The formation of these bridges between dermal molecules is supposed to be responsible for loss of elasticity or other properties of the dermis observed during aging.

[Natural and photo-induced aging of the skin: the three dimensional culture approach].

Human skin is a complex multifunctional organ which covers and surrounds the whole body ensuring a key function of protection against external injuries. Because of this unique situation, aging of skin is the result of both extrinsic factors-mostly sun exposure leading to photoaging- and intrinsic factors assumed to represent chronological aging. Studies of such complex phenomena on human volunteers is questionable and classical cultures of skin cells are not close enough to in vivo physiological conditions.