Tissue engineering strategies to bioengineer the ageing skin phenotype in vitro

Human skin ageing is a complex and heterogeneous process, which is influenced by genetically determined intrinsic factors and accelerated by cumulative exposure to extrinsic stressors. In the current world ageing demographic, there is a requirement for a bioengineered ageing skin model, to further the understanding of the intricate molecular mechanisms of skin ageing, and provide a distinct and biologically relevant platform for testing actives and formulations. There have been many recent advances in the development of skin models that recapitulate aspects of the ageing phenotype in vitro. This review encompasses the features of skin ageing, the molecular mechanisms that drive the ageing phenotype, and tissue engineering strategies that have been utilised to bioengineer ageing skin in vitro.     

The Effect of Lactobacillus plantarum Extracellular Vesicles from Korean Women in Their 20s on Skin Aging

Extracellular vesicles, which are highly conserved in most cells, contain biologically active substances. The vesicles and substances interact with cells and impact physiological mechanisms. The skin is the most external organ and is in direct contact with the external environment. Photoaging and skin damage are caused by extrinsic factors. The formation of wrinkles is a major indicator of skin aging and is caused by a decrease in collagen and hyaluronic acid. MMP-1 expression is also increased. Due to accruing damage, skin aging reduces the ability of the skin barrier, thereby lowering the skin’s ability to contain water and increasing the amount of water loss. L. plantarum suppresses various harmful bacteria by secreting an antimicrobial substance. L. plantarum is also found in the skin, and research on the interactions between the bacteria and the skin is in progress. Although several studies have investigated L. plantarum, there are only a limited number of studies on extracellular vesicles (EV) derived from L. plantarum, especially in relation to skin aging. Herein, we isolated EVs that were secreted from L. plantarum of women in their 20s (LpEVs). We then investigated the effect of LpEVs on skin aging in CCD986sk. We showed that LpEVs modulated the mRNA expression of ECM related genes in vitro. Furthermore, LpEVs suppressed wrinkle formation and pigmentation in clinical trials. These results demonstrated that LpEVs have a great effect on skin aging by regulating ECM related genes. In addition, our study offers important evidence on the depigmentation effect of LpEVs.     

Genetic evidence for linkage with the Z and W sex chromosomes of two distinct couples of alleles controlling larval and postmetamorphic skin pigmentation in salamander

In Pleurodeles waltl, progeny resulting from a cross between 2 individuals of the Z/W sexual genotype include 25% of W/W individuals, while those issued from crossing a Z/W neomale with a W/W thelygenous female include 50% of W/W individuals. W/W individuals can be identified through the peptidase-1 zymogram since, in P. waltl, this enzyme is controlled by codominant alleles which are linked to the sex chromosomes. In such progeny, we discovered 2 mutant phenotypes affecting larval and postmetamorphic skin pigmentation in W/W individuals. These phenotypes are described herein. The study of their inheritance in several offspring provides evidence that they are controlled by 2 distinct genes, the recessive mutant alleles of which are linked to the W sex chromosome; moreover, in thelygenous W/W females, the differential segment does not prevent the occurrence of meiotic recombinations between W sex chromosomes. Mutant skin pigmentary phenotypes are easily identified and constitute a tool for rapid, efficient selection of individuals of the W/W sexual genotype.     

Arrested development of secondary sexual adornments in subordinate adult male mandrills (Mandrillus sphinx).

Previous studies of semifree-ranging mandrills identified two morphological and social variants of the adult male, based on behavioral and secondary sexual characteristics. "Fatted" males are social, with highly developed sex skin coloration, large testes, high plasma testosterone levels, and fat rumps; while "nonfatted" males are peripheral or solitary, with paler sex skin, smaller testes, lower plasma testosterone, and slimmer rumps. We present a detailed study of morphology and group association for 10 adult male mandrills, living in two semifree-ranging groups in Gabon, in order to relate differences between males to dominance rank. The results show that rather than existing as two distinct morphotypes, male mandrills represent a continuous spectrum of possibilities between social males with fully developed secondary sexual characteristics, and solitary males with muted secondary sexual characteristics. Alpha males (N = 2) had the highest testosterone levels, the most colorful sex skin, and the most active sternal glands, and were the only males to spend 100% of their time with the social group. Rank relationships between nonalpha males (N = 8) were not always clear, but all subordinate males had lower testosterone levels and less development of the secondary sexual adornments, and were less group-associated than alpha males. These findings suggest that only alpha males have sufficient testosterone to develop full secondary sexual characteristics, and we propose possible socioendocrine mechanisms underlying the suppression of testosterone and secondary sexual development in subordinate adults. We discuss differences in secondary sexual development in relation to reproductive strategies, and discuss the evolution of alternative reproductive morphs in primates.     

Immune functions of the human skin. Models of in vitro studies using Langerhans cells

Human skin constitutes the first immune defense barrier. Among the epidermal cells, the Langerhans cells, which belong to the dendritic cells, represent the pivotal cells in cutaneous immune reactions. The possibility of obtaining human Langerhans cells either from human skin or by in vitro generation from CD34+ hematopoietic precursors opens the way to studies reproducing the successive steps of the Langerhans cells' role in contact dermatitis.     

The effect of lipids on the adherence of axillary aerobic coryneform bacteria

AIMS: A wide range of lipids are present on the skin surface of human beings and bacterial lipases are known to modify them. The microflora of the underarm (axilla) is often dominated by aerobic coryneforms and whilst many require lipids for growth, they appear not to be utilized as carbon sources. The aim of this study was to investigate the adherence aerobic coryneforms to lipids present on the skin surface of the human axilla to determine whether they contribute to colonization of the skin. METHODS: Aerobic coryneforms were grown in a defined synthetic medium in the presence of (14)C-glucose to produce radio-labelled cells. Adherence to lipids was tested using a thin layer chromatography plate-based assay. SIGNIFICANCE AND IMPACT OF THE STUDY: The mechanism of bacterial adhesion to skin lipids is unknown. The results of this study show that a significant proportion of cutaneous aerobic coryneform isolates from the axilla interact with skin lipids resulting in increased adherence, which may contribute to skin colonization.     

Transcellular and paracellular elements of salt chemosensation in toad skin

Dehydrated toads absorb water by pressing a specialized (seat patch) area of the skin to moist surfaces. This behavior, the water absorption response (WR), is preceded by periods of more limited skin contact (seat patch down, SPD) in which the suitability of the rehydration source is evaluated. WR and SPD behaviors were suppressed on 250 mM NaCl and 200 mM KCl solutions. Ten micromolar amiloride partially restored SPD and WR on NaCl solutions. The addition of 5 mM La(3+) also partially restored the initiation of WR and this effect was additive to the effect of amiloride, suggesting transcellular and paracellular pathways exist in parallel. Similarly, 5 mM La(3+) partially restored the initiation of WR on KCl solutions, to levels comparable to those with K(+)gluconate, suggesting a paracellular pathway for detection of K(+). Hyperosmotic (250 mM) NaCl solutions bathing the mucosal surface rapidly and reversibly increased the paracellular conductance of isolated skin and this increase was partially inhibited by 5 mM La(3+). These results suggest that the regulation of tight junctions has a chemosensory role in toad skin.     

Polyphenols from peanut skins and their free radical-scavenging effects

Separation of the water-soluble fraction of peanut skins led to the isolation of five proanthocyanidins. Based on the spectroscopic investigation and partial acid catalyzed degradation, their structures were determined to be epicatechin-(2beta-->O -->7, 4beta -->6)-[epicatechin-(4beta-->8)]-catechin (1), epicatechin-(2beta-->O -->7, 4beta-->8) epicatechin-(4beta-->8)-catechin-(4alpha-->8)-epicatechin (2), and procyanidins B2 (3), B3 (4) and B4 (5). The absolute configuration of the new compounds was determined from their circular dichroism curves and the (1)H NMR spectra of analysis of flavan-3-ols formed by thiolytic degradation of 1 and 2 in the presence of a chiral dirhodium complex (dirhodium tetra-(R)-(trifluoromethyl) phenyl acetate).