Changes of the basement membrane and type IV collagen in human skin during aging

A Reproducible Laser-Wounded Skin Equivalent Model to Study the Effects of AgingIn Vitro

Skin aging involves both chronological and photoaging processes. The effects of these processes are often overlapping and include changes in both the stratified epithelium and the fibroblast-rich dermis. Wound healing is frequently delayed with aging and can result in scarring. A skin equivalent model can be used to study the role of cells and the extracellular matrix in the process of wound healing. Current studies using this model employ a full-thickness wound placed atop a nonwounded dermis to mimic a partial-thickness wound. However, a true reproducible partial-thickness wound model has yet to be described. In this study, we investigated whether a laser-wounded skin equivalent would be a useful partial-thickness wound healing model. Three lasers were compared for the ability to generate a reproducible wound: an erbium-YAG, a high-powered excimer, and a low-powered excimer laser. Reepithelialization ability was tested using newborn and adult skin keratinocytes, adult esophageal keratinocytes, and cdk4-overexpressing newborn keratinocytes. Keratinocyte compartmentalization and basement membrane formation were assessed by immunofluorescence. The erbium-YAG and high-powered excimer laser cut reproducible wounds but left the remaining surface either discolored due to thermal damage and/or ragged; keratinocytes were unable to migrate into the wound area. The low-powered excimer laser cut reproducible wounds, leaving the cut surface intact and visibly unaltered; keratinocytes reepithelialized the wound in a collagenase-dependent manner within 3 days; and return of compartmentalization and basement membrane occurred within 14 days. The laser-wounded skin equivalent is an adjustable, reproducible partial-thickness wound model where keratinocyte biology akin to in vivo can be studied, and will be useful to study the effects of aging on wound healing.

Estudo das alterações relacionadas com a idade na pele humana, utilizando métodos de histo-morfometria e autofluorescência

FUNDAMENTOS: O processo de envelhecimento tecidual é evidente nas modificações visíveis na pele, resultando em importantes implicações psicológicas para o indivíduo e crescente interesse científico. OBJETIVOS: O presente trabalho objetivou analisar as alterações da pele normal com o envelhecimento mediante estratégias de histomorfometria e autofluorescência. MÉTODOS: Foram coletadas amostras de pele do abdômen de 18 cadáveres, incluindo cinco indivíduos jovens (menos de 20 anos), sete indivíduos com idade intermediária (20-60 anos) e seis indivíduos idosos (mais de 60 anos). Foram feitos cortes histológicos em parafina seguidos de coloração pela Hematoxilina-Eosina (H&E) e pelo tricrômio de Van Gieson-elastina. Avaliaram-se a espessura da epiderme e derme, e a superfície de contato epidermo-dérmica. Investigaram-se ainda as modificações qualitativas do aparelho colágeno-elástico, considerando sua disposição espacial na derme. Espécimes corados em H&E também foram utilizados para autofluorescência. RESULTADOS: A espessura da epiderme e derme do grupo idoso foi significativamente diminuída (p<0,05) em relação aos demais grupos. Os grupos idoso e intermediário exibiram acentuada redução na superfície de contato epiderme-derme (p<0,05). Detectaram-se a perda da distribuição em rede das fibras elásticas com sua progressiva fragmentação, alterações da compactação do colágeno e espessamento da membrana basal com o envelhecimento. CONCLUSÃO: O envelhecimento leva à redução da espessura da derme e epiderme, bem como ao aplanamento da junção dermo-epidérmica. As mudanças da pele ao longo da vida nem sempre seguem um perfil linear, mostrando drásticas alterações nas últimas décadas de vida. O método de autofluorescência mostrou-se um instrumento valioso no estudo da complexa relação espacial das fibras elásticas e colágenas.

Estrogen and skin. An overview

As the population of postmenopausal women increases, interest in the effects of estrogen grows. The influence of estrogen on several body systems has been well-documented; however, one area that has not been explored is the effects of estrogen on skin. Estrogen appears to aid in the prevention of skin aging in several ways. This reproductive hormone prevents a decrease in skin collagen in postmenopausal women; topical and systemic estrogen therapy can increase the skin collagen content and therefore maintain skin thickness. In addition, estrogen maintains skin moisture by increasing acid mucopolysaccharides and hyaluronic acid in the skin and possibly maintaining stratum corneum barrier function. Sebum levels are higher in postmenopausal women receiving hormone replacement therapy. Skin wrinkling also may benefit from estrogen as a result of the effects of the hormone on the elastic fibers and collagen. Outside of its influence on skin aging, it has been suggested that estrogen increases cutaneous wound healing by regulating the levels of a cytokine. In fact, topical estrogen has been found to accelerate and improve wound healing in elderly men and women. The role of estrogen in scarring is unclear but recent studies indicate that the lack of estrogen or the addition of tamoxifen may improve the quality of scarring. Unlike skin aging, the role of endogenous and exogenous estrogen in melanoma has not been well established.

Analysis of film coating thickness and surface area of pharmaceutical pellets using fluorescence microscopy and image analysis

A method is presented which enables geometrical characterisation of pharmaceutical pellets and their film coating. It provides a high level of details on the single pellet level. Image analysis was used to determine the coating thickness (h) applied on the pellets and the surface area (A) of the pellet cores. Different definitions of A and h are evaluated. Hierarchical analysis of variance was used to resolve different sources contributing to the total variance. The variance within pellets and the variance between pellets were found as significant sources of variation. Special emphasis was put on evaluation of A/h due to its influence on the release rate of an active drug substance from the pellet core. The pellet images were thus used to predict variations in the release rate using a mathematical model as a link between the image data and the release rate. General aspects of image analysis are discussed. The method would be useful in calibration of near infrared spectra to h in process analytical chemistry.

Amyotrophic lateral sclerosis: increased hyaluronic acid in the media of the basilar artery

Hyaluronic acid in the basilar artery of 10 patients with sporadic amyotrophic lateral sclerosis (ALS) and 7 age-matched control subjects was examined histochemically and densitometrically. The intensity of staining with alcian blue was significantly increased (P=0.0007) in the media in ALS patients compared with that in control subjects. The staining was virtually eliminated by Streptomyces hyaluronidase. These results clearly indicate an increase of hyaluronic acid in the media of the basilar artery in ALS patients.