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

Etude des sous-populations de fibroblastes : une approche "développementaliste" de la physiologie et du vieillissement de la peau

La peau est un organe à part entière dont le rôle dépasse largement celui de barrière entre l'intérieur et l'extérieur de l'organisme. La peau comme l'ensemble du corps humain est sujette au vieillissement. Ce dernier affecte principalement la peau dans sa profondeur au niveau du compartiment dermique qui constitue sa partie matricielle. Le derme est en effet un tissu riche en matrice extracellulaire et pauvre en cellules. Il est généralement admis que ce sont des modifications de cette matrice qui contribuent le plus au vieillissement de la peau, en affectant ses propriétés biomécaniques. Traditionnellement on aborde l'étude du vieillissement de la peau en s'intéressant aux modifications des macromolécules de la matrice extracellulaire comme par exemple le collagène. Le derme est en réalité un tissu complexe matriciel et cellulaire comprenant une partie superficielle proche de l'épiderme et une partie profonde beaucoup plus épaisse qui se distinguent en histologie. Dans notre laboratoire nous avons entrepris depuis plusieurs années déjà de nous intéresser aux fibroblastes qui sont les cellules responsables de la formation et du maintien de la structure dermique et nous avons entrepris d'isoler, de cultiver et d'étudier les fibroblastes du derme superficiel dit papillaire et du derme profond dit réticulaire. Nous avons pu montrer que les deux types de fibroblastes en culture sur plastique ont un aspect et des propriétés biologiques très différentes. De plus nous avons pu confirmer et préciser ces différences dans le contexte de la peau reconstruite. La reconstitution d'une architecture tridimensionnelle est beaucoup plus proche de la peau in vivo tout particulièrement après greffe sur la souris nude. Nous posons également la question de l'apparition et du devenir de ces populations dans la peau lors de la maturation finale de la peau, c'est-à-dire, à la fin du développement et lors du vieillissement de la peau. En effet ces études pourraient se révéler très utiles pour une meilleure compréhension de la physiologie et du vieillissement de la peau et pourraient être potentiellement source d'innovation à travers de nouvelles stratégies anti-vieillissement

Vieillissement naturel et photo-induit de la peau : approches en cultures tri-dimensionnelles

La peau humaine est un organe complexe dont le rôle majeur est d’assurer la protection du corps humain contre les agressions extérieures. A cause de cette situation très particulière, le vieillissement de la peau résulte de la superposition d’un vieillissement dit « extrinsèque », dû en grande partie à l’action du rayonnement ultraviolet (UV) émis par le soleil, et de facteurs dits « intrinsèques » supposés correspondre au vieillissement chronologique. L’étude de phénomènes aussi complexes est forcément limitée quand il s’agit de mener les expériences chez l’Homme dans la mesure où il faut faire appel à des volontaires pour réaliser des biopsies. Par ailleurs, on sait très bien que les cultures classiques de cellules sur matériel plastique demeurent très éloignées des conditions physiologiques in vivo (différenciation cellulaire incomplète, absence d’interactions cellulaires, etc.). Pour se rapprocher davantage de la réalité, nous avons opté pour une approche in vitro dite « organotypique » qui consiste à reconstruire la peau à partir de cellules en culture et d’éléments matriciels. Plus précisément, notre modèle consiste à réaliser d’abord un gel en associant des fibroblastes et du collagène, lequel, après contraction et concentration des fibres de collagène par les fibroblastes, va former un « équivalent dermique » (Bell et al, 1979). Celui-ci sera ensuite le support d’ensemencement des kératinocytes de l’épiderme, qui vont produire, par multiplication et différenciation, un épithélium pluristratifié et kératinisé, histologiquement proche de l’épiderme in vivo, à condition que la culture soit réalisée avec contact avec l’atmosphère (Asselineau et al., 1985)

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. Previous works have reported a relationship between UV irradiation and glycation in the aging process, leading, for example, to modified radical species production and the appearance of AGEs (advanced glycosylation end products) in increasing quantities, particularly glycoxidation products like pentosidine. In addition, the colocalization of AGEs and elastosis has also been observed. We first investigated the combination of the glycation reaction and UVA effects on a reconstructed skin model to explain their cumulative biological effect. We found that UVA exposure combined with glycation had the ability to intensify the response for specific markers: for example, MMP1 or MMP3 mRNA, proteases involved in extracellular matrix degradation, or proinflammatory cytokine, IL1α, protein expression. Moreover, the association of glycation and UVA irradiation is believed to promote an environment that favors the onset of an elastotic-like phenomenon: mRNA coding for elastin, elastase, and tropoelastin expression is increased. Secondly, because the damaging effects of UV radiation in vivo might be more detrimental in aged skin than in young skin due to increased accumulation of pentosidine and the exacerbation of alterations related to chronological aging, we studied the biological effect of soluble pentosidine in fibroblasts grown in monolayers. We found that pentosidine induced upregulation of CXCL2, IL8, and MMP12 mRNA expression (inflammatory and elastotic markers, respectively). Tropoelastin protein expression (elastin precursor) was also increased. In conclusion, fibroblasts in monolayers cultured with soluble pentosidine and tridimensional in vitro skin constructs exposed to the combination of AGEs and UVA promote an inflammatory state and an alteration of the dermal compartment in relation to an elastosis-like environment.</jats:p

In vitro beneficial effects of a flax extract on papillary fibroblasts define it as an anti-aging candidate

Objective: During aging, skin undergoes structural, cellular and molecular changes, which not only alter skin mechanical properties but also biological and physiological functions. Structurally the epidermis becomes thinner, the dermal epidermal junction flattens and the extra-cellular matrix component of the dermis is disorganized and degraded. The dermis is composed of two compartments: The Reticular dermis is the deepest and thickest part while the upper layer, the papillary dermis, which is much thinner and is in close contact with epidermis, plays an important role in the structure and function of the skin. We have recently shown that the papillary dermis was preferentially affected by skin aging because the activity of fibroblasts in this region was especially altered as a function of age. The purpose of this study was to investigate the capacity of a flax extract as anti-aging component. Method: We investigated the capacity of a flax extract to stimulate or restore the activity of papillary fibroblasts from young and old donors in cultured monolayers and in reconstructed skin. Several biological markers of extracellular matrix homeostasis and mechanical properties were investigated. Results: The tested flax extract seemed to improve parameters known to change with age: I/ In monolayers after treatment the number of aged fibroblasts increased II/ In reconstructed skin the flax extract appears to positively regulate some biological activities; particularly in aged fibroblasts where the deposition of laminin 5, fibrillin 1, procollagen I were increased in the dermis and the secretion of specific soluble factors like MMP1, MMP3 and KGF were regulated to levels similar to those observed in young fibroblasts III/ Mechanical properties were improved particularly for elastics parameters (R5, R2 and R7). Conclusion: The flax extract is a promising anti-aging compound. The treatment of aged papillary fibroblasts resulted in a return to a younger-like profile for some of the studied parameters

In vitro beneficial effects of a flax extract on papillary fibroblasts define it as an anti-aging candidate

Objective: During aging, skin undergoes structural, cellular and molecular changes, which not only alter skin mechanical properties but also biological and physiological functions. Structurally the epidermis becomes thinner, the dermal epidermal junction flattens and the extra-cellular matrix component of the dermis is disorganized and degraded. The dermis is composed of two compartments: The Reticular dermis is the deepest and thickest part while the upper layer, the papillary dermis, which is much thinner and is in close contact with epidermis, plays an important role in the structure and function of the skin. We have recently shown that the papillary dermis was preferentially affected by skin aging because the activity of fibroblasts in this region was especially altered as a function of age. The purpose of this study was to investigate the capacity of a flax extract as anti-aging component. Method: We investigated the capacity of a flax extract to stimulate or restore the activity of papillary fibroblasts from young and old donors in cultured monolayers and in reconstructed skin. Several biological markers of extracellular matrix homeostasis and mechanical properties were investigated. Results: The tested flax extract seemed to improve parameters known to change with age: I/ In monolayers after treatment the number of aged fibroblasts increased II/ In reconstructed skin the flax extract appears to positively regulate some biological activities; particularly in aged fibroblasts where the deposition of laminin 5, fibrillin 1, procollagen I were increased in the dermis and the secretion of specific soluble factors like MMP1, MMP3 and KGF were regulated to levels similar to those observed in young fibroblasts III/ Mechanical properties were improved particularly for elastics parameters (R5, R2 and R7). Conclusion: The flax extract is a promising anti-aging compound. The treatment of aged papillary fibroblasts resulted in a return to a younger-like profile for some of the studied parameters.</jats:p