Loss of elastic fibers causes skin wrinkles in sun-damaged human skin

BACKGROUND: Although wrinkling is the most obvious sign of aged skin, the detailed pathomechanism of wrinkle development has not been elucidated. OBJECTIVES: In this study, we investigated the role of elastic fibers in the formation of skin wrinkles. METHODS: Loss of elastic fibers was measured quantitatively in the facial skins of subjects representing seven decades, and then compared with wrinkle severities. We also investigated whether topical retinoic acid treatment to photoaged human skin can restore destroyed elastic fiber, and the correlation between wrinkle improvement with increase in elastic fibers in RA-treated facial skin. RESULTS: We found a significant correlation between decreases in the length, width, number and total area of oxytalan fibers and wrinkle severity. Furthermore, we found that topical application of retinoic acid (0.025%) to chronically photodamaged skin regenerated and restored elastic fibers, and that there was a significant positive correlation between the amount of newly regenerated elastic fiber and the wrinkle improvement caused by retinoic acid. CONCLUSIONS: Our results provide an objective insight into the role of elastic fibers in skin wrinkle formation by providing a quantitative correlation between changes in oxytalan fibers and the severity of skin wrinkling.     

Decay-accelerating factor in human skin is associated with elastic fibers

Recently a complement inhibitor, decay-accelerating factor (DAF), has been found in association with uncharacterized fibers in the extracellular matrix of human dermis. Here we show by immunohistochemistry and immunoelectronmicroscopy that DAF is on the periphery of elastic fibers, and that it appears to be associated with some microfibrillar elements that cover the fibers. That DAF is a component of these microfibrils is also suggested by studies of lesional skin from anetoderma, a disease characterized by destruction of elastic fibers. In two patients we found a network of residual fine fibers in the dermis that stain with antibodies against DAF and fibrillin (one of the proteins known to be present in the microfibrils of elastin), but do not stain with antibodies to elastin. Western blot analysis of dermal extracts with monoclonal antibodies to DAF identified a 67 kDa molecule, slightly smaller than membrane DAF, and similar in size to soluble DAF found in secretions. It is possible that together with vitronectin, an inhibitor of the membrane attack complex recently identified in association with elastin, DAF prevents damage of elastic fibers by complement.     

Marfan syndrome: demonstration of abnormal elastic fibers in skin

The back skin of a 15-year-old girl with Marfan syndrome has been investigated using scanning (SEM) and transmission (TEM) electron microscopy. The SEM showed that admixed with normal-looking portions, there were abnormal portions of the elastic fibers which were composed of many unusual fine fibers (5-22 nm in diameter), and had a cobweb-like appearance. The TEM showed that these fine fibers were substructures of the amorphous material and were surrounded by microfibrils. It is suggested that the fine fibers could be abnormal elastic fibers resulting from the incomplete fusion of the elastic units.     

Lysyl oxidase-like and lysyl oxidase are present in the dermis and epidermis of a skin equivalent and in human skin and are associated to elastic fibers

Elastic fiber formation involves the secretion of tropoelastin which is converted to insoluble elastin by cross-linking, initiated by the oxidative deamination of lysine residues by lysyl oxidase. Five lysyl oxidase genes have been discovered. This study deals with the expression of two isoforms, LOX and LOX-like (LOXL), in human foreskin and in a human skin-equivalent (SE) model that allows the formation of elastic fibers. In this model, keratinocytes are added to a dermal equivalent made of fibroblasts grown on a chitosan-cross-linked collagen-GAG matrix. LOX and LOXL were detected by immunohistochemistry in the dermis and the epidermis of both normal skin and in a SE. This expression was confirmed by in situ hybridization on the SE. LOX and LOXL expression patterns were confirmed in human skin. The ultrastructural localization of LOXL was indicative of its association with elastin-positive materials within the SE and human skin, though interaction with collagen could not be discarded. LOX was found on collagen fibers and could be associated with elastin-positive materials in the SE and human skin. LOXL and LOX were detected in keratinocytes where LOX was mainly expressed by differentiating keratinocytes, in contrast to LOXL that can be found in both proliferating and differentiating fibroblasts. These data favor a role for LOXL in elastic fiber formation, together with LOX, and within the epidermis where both enzymes should play a role in post-translational modification of yet unknown substrates.     

强脉冲光照射对小鼠皮肤胶原纤维、弹性纤维及透明质酸含量的影响

目的 探讨强脉冲光照射对昆明小鼠皮肤胶原纤维、弹性纤维、透明质酸含量的意义。方法用强脉冲光照射小鼠右侧背部皮肤,左侧为对照,取各时间点照射组和对照组皮肤进行组织学观察,包括HE染色、Ⅰ型和Ⅲ型胶原纤维饱和苦味酸-天狼猩红染色、弹性纤维Gomori醛品红法染色,同时提取皮肤组织,碱水解-分光光度法测定羟脯氨酸含量,放射免疫法测定透明质酸含量。结果 照射后2周,真皮厚度较对照组增加（t = 4.623,P < 0.05）,4周时达最大值,较对照组增加18.71%,8周时仍大于对照组,差异有统计学意义（t = 3.904,P < 0.05）。照射后1周,Ⅲ型胶原纤维较对照组增加40.54%（t = 5.129,P < 0.05）,照射后2周和4周,Ⅰ型和Ⅲ型胶原纤维均较对照组增多明显,至8周时,均大于对照组（P < 0.05）。照射后2 ~ 8周,弹性纤维均较对照组增多（P < 0.05）;照射后1 ~ 8周,羟脯氨酸含量均较对照组增多（P < 0.05）。照射后1 d和3 d,透明质酸含量显著增加,1 ~ 8周,渐进性降低,但均高于对照组（P < 0.05）。结论 强脉冲光照射小鼠皮肤可刺激真皮胶原纤维、弹性纤维、透明质酸含量增加。     

Age-related changes in the elastic properties and thickness of human facial skin

Using recently designed, commercially available, non-invasive instruments, we measured the thickness and elasticity of the skin of the face and ventral forearm in 170 women, and evaluated the effects of age and exposure to sunlight. Skin thickness decreased with age in ventral forearm skin, which has limited exposure to sunlight, but increased significantly in the skin of the forehead, corners of the eyes, and cheeks, which are markedly exposed to sunlight. Skin elasticity (U_r/U_f) decreased with age on both the face and forearm. The ratio of viscosity element to elasticity element (U_v/U_e) increased with age at all sites. However, delayed distension (U_v), immediate retraction (U_r), final distension (U_f), and immediate distention (U_e), as individual elements, decreased on the face and increased on the forearm with age. This tendency was more marked after correction for skin thickness. These results suggested the specificity of skin thickness and elasticity in the facial skin. Analysis using a four-element model showed no changes in the elasticity coefficient of Maxwell element on the forearm, but an increase on the face. This indicates quantitative or qualitative changes in elastic fibres in facial skin. Thus, sunlight appears to have a considerable effect on the thickness and physical properties of facial skin.     

Ultrastructural study of elaunin fibres in the secretory coil of human eccrine sweat glands

The basement membrane of the secretory coil of human eccrine sweat glands was studied by light and electron microscopy. With classical staining methods for the elastic system, elaunin ring fibres were observed in the basement membrane of the secretory coil. The ultrastructural study showed that elaunin fibres are formed by bundles of fibrotubules 10-12 nm in diameter surrounding aggregates of amorphous material. These fibres differ from elastic fibres which are thicker and have an amorphous material more homogeneous and abundant.     

Dermal melanocytes and elastic fibers

The relationship between dermal melanocytes and elastic fibers was studied by electron microscopy. In 3 patients with dermal melanocytosis, the long cytoplasmic processes of the melanocytes were aligned along the long axis of the elastic fiber, and encircled or embraced these fibers. The same intimacy existed between melanocytes and elastic fibers in the skin of cynomolgus macaques, who normally have dermal melanocytes. These findings suggest that dermal melanocytes, for reasons yet to be determined, interact with elastic fibers under these special conditions.     

Distribution density of intraepidermal nerve fibers in normal human skin

A total of 74 specimens was obtained from the normal human skin of patients from 3 to 90 years old. The specimens were roughly classified into 5 groups: 15 for the face group from the face; 15 for the abdomen group from the abdomen; 13 for the back group from the back; 14 for the arm group from the upper arm and forearm; and 17 for the leg group from the thigh and lower leg. They were all fixed in 4% paraformaldehyde and 14% saturated picric acid. Cryostat sections were examined by the immunoperoxidase method and indirect immunofluorescence (IF). Primary antibodies against neurofilament, neuron-specific enolase, protein gene product 9.5 (PGP 9.5) and S-100 protein were used. The most effective method was found to be the combination of IF with PGP 9.5; it visualized the intraepidermal nerve fibers easily and clearly. Of the 74 specimens, 32 (43%) had intraepidermal PGP 9.5-immunoreactive (or nerve) fibers (IPIF), and 42 (57%) did not have any. With reference to the different skin locations, the maximal rate of specimens having IPIF was 57% in the arm group, and the minimum was 23% in the back group. IPIF positive specimens had approximate surface lengths of 6 mm, in which the existence number of the IPIF was 1 to 75. Their distribution density per 1000 epidermal basal cells was highest at 9.63 in the arm group and lowest at 2.89 in the back group. Their thickness was 2.94 +/- 0.83 microns with no significant differences among the five groups. We concluded that intraepidermal nerve fibers may not be distributed evenly in the hairy portions of normal human skin, but they may be present focally. Physiologically, two-point discrimination of itch may be explained by the distribution mode of intraepidermal nerve fibers.     

Penicillamine-induced elastosis perforans serpiginosa with abnormal "lumpy-bumpy" elastic fibers in lesional and non-lesional skin

Four types of elastosis perforans serpiginosa (EPS) have been described in literature: 1) idiopathic EPS, 2) reactive perforating elastosis associated with connective tissue disorders, 3) in some instances of pseudoxanthoma elasticum (PXE), disease-specific calcified elastic tissue is extruded, producing a clinical picture indistinguishable from other types, may also be seen in patients undergoing hemodialysis and 4) EPS induced by long-term treatment with D-penicillamine is observed in patients suffering from Wilson's disease. Long term D-penicillamine therapy causes an alteration in the dermal elastic tissue. D-penicillamine induced EPS has a distinctive histopathologic feature - serrated appearance of elastic fibers due to perpendicular budding from their surface giving a "lumpy-bumpy" look. D-penicillamine induced elastic fiber alteration may not always manifest clinically as EPS. We report a case of D-penicillamine induced widespread alteration in skin elastic tissue with distinct histopathologic features.     

Morphological architecture and distribution of blood capillaries and elastic fibres in the human skin

This study was undertaken to clarify the morphological features in the blood capillary and elastic fibre distribution of the human skin in terms of susceptibility to pressure sore development. Skin tissues were obtained from bony areas: the sacrum and ischial tuberosity and non-bony area: the centre of the gluteus maximus of 5 aged subjects post mortem for examination using light and scanning electron microscopy. It was observed that the sacral skin had finger-like papillae and underneath the blood capillary loops were most numerous. In the ischial skin the dermal papillae consisted of a combination of finger-like and trapezoid shapes having moderate density of blood capillaries. In contrast, the dermal papillae in the gluteal skin were almost flat, so that the blood capillaries were scattered. The size of elastic bundles in the papillary layer of the sacral, ischial and gluteal skin ranged from 2 to 3 microns, 5 to 10 microns, and 3 to 5 microns, respectively. The elastic fibres were densely distributed in the ischial skin while less so in the sacral skin.     

Fibulin-5 accelerates elastic fibre assembly in human skin fibroblasts

Fibulin-5 null mice display abnormalities in the elastic fibres in the dermis. We postulated, therefore, that fibulin-5 might be a regulator of elastic fibre assembly and stability. To clarify the role of fibulin-5 in elastic fibre formation, we employed in vitro systems that allowed increasing expression of elastic fibre components by gene transduction using retroviral vector constructs. First, the human tropoelastin gene (ELN) was transduced into human dermal fibroblasts, which resulted in elevated gene expression. These cells were then cultured in monolayer, but the overexpression of ELN in this system did not alter the assembly of elastic fibres. However, incubation of fibroblasts with TGF-beta1 resulted in elastic fibre accumulation, and the expression of fibulin-5 was enhanced by TGF-beta1. Thus, we overexpressed human fibulin-5 cDNA in dermal fibroblasts using a retroviral vector containing a cytomegalovirus (CMV) promoter. These cells deposited elastic fibres. These results suggest that fibulin-5 is a critical component in the control of elastic fibre assembly by dermal fibroblasts.     

Maturation and aging of elastic fibers

We give a review of the maturation and aging processes of elastic fibers. Elastic fibers of adult human skin are composed of elastin (amorphous matrix) and surrounded by microfibrils (structural glycoproteins). The physiological aging of elastic fibers is a continuous process starting at the age of 40 or 50 and reaching its final state in the senium. This process is characterized by the following morphological changes: (1) decreasing number of microfibrils, (2) occurrence of osmiophilic inclusions, and (3) fragmentation and disintegration of the fibers. These alterations are due to reduced synthesis of elastin and increased deposits of lipids and calcium. As a result, the elastic fibres show increased susceptibility towards proteolytic enzymes.     

Fibulin-2 and fibulin-5 alterations in tsk mice associated with disorganized hypodermal elastic fibers and skin tethering

The Tight skin (Tsk) mouse is an important model of skin fibrosis that occurs in systemic sclerosis. These mice develop skin tethering and thickening associated with expression of a mutant fibrillin-1 gene. We show that Tsk fibrillin-1 leads to marked alterations in elastic fibers of the hypodermis of Tsk animals. In Tsk mice, a prominent elastic fiber layer found normally at the interface between hypodermal muscle and connective tissue was absent from an early age. The lack of elastic fibers at the hypodermal muscle-connective tissue (M-CT) interface was associated with a loss of staining for fibulin-5 in the same region. These mice also formed disorganized elastic fibers throughout hypodermal connective tissue as they aged. The increased elastic fibers in Tsk hypodermal connective tissue was associated with increased fibrillin-1 and fibulin-2 matrices. These results suggest that Tsk fibrillin-1 causes skin tethering by altering matrix protein composition in Tsk hypodermal connective tissues. The closely parallel alterations in elastogenesis associated with increased fibulin-2 in hypodermal connective tissues and decreased fibulin-5 at the hypodermal M-CT interface suggest that these proteins mediate the effect of Tsk-fibrillin-1 on elastogenesis.