Clinics in Dermatology (2012) 30, 274–276

Effects of age (neonates and elderly) on skinbarrier functionMarcia Ramos-e-Silva, MD, PhDa,⁎, Juliana Catucci Boza, MDb,Tania Ferreira Cestari, MD, PhDb

aSector of Dermatology and Post Graduation Course – HUCFF/UFRJ and School of Medicine,Federal University of Rio de Janeiro, Rua Dona Mariana 143/C-32, Rio de Janeiro 22280-020, BrazilbSector of Dermatology, Federal University of Rio Grande do Sul, Rua Ramiro Barcelos 2350, Zona 13,Rio Branco 90035-003, Porto Alegre, Rio Grande do Sul, Brazil

Abstract Skin, together with its appendages, forms an organ with several defensive roles; among them itacts as a barrier, which is one of its very important protective functions. There has been increasedinterest in studying the effects of age on these functions. There are different intensities and timinginvolved in this process and also differences between men and women, all relating to skin structure.

We review the current knowledge of the skin as a barrier in neonates and in the elderly in an attemptto explain the changes that occur with aging.© 2012 Elsevier Inc. All rights reserved.

Skin and its appendages have developed as an organ with of the stratum corneum and the permeability barrier, mainly

multiple protective functions,1 and there has been increasedinterest in studying the effects of age on skin barrier function.The purpose of this contribution is to summarize the currentknowledge on neonates and the elderly so as to clarify theskin physiology with a practical approach.

Neonates

Birth stimulates maturation of the epidermal barrier andskin surface acidification, especially in premature infants(Table 1). In full-term infants, the developed stratumcorneum accomplishes competent barrier function, incontrast with premature infants. Different environmentalfactors, as, for instance, dry and cold climate, diapers, andcosmetic care procedures, influence the postnatal develop-ment of the skin's functional parameters, such as hydration

⁎ Corresponding author. Tel.: 55 21 2864632; fax: 55 21 2864632.E-mail address: ramos.e.silva@dermato.med.br (M. Ramos-e-Silva).

0738-081X/$ – see front matter © 2012 Elsevier Inc. All rights reserved.doi:10.1016/j.clindermatol.2011.08.024

in premature infants.1

Measurement of transepidermal water loss (TEWL) isgenerally accepted as a reliable tool to assess objectivelyepidermal barrier function.2 Using TEWL, full-term neonateshave completely developed permeability barrier function atbirth.3 In preterm infants, the time required for completebarrier maturation is from 2 to 4 weeks of postnatal age.3,4

The anatomical site influences skin barrier function;TEWL was significantly higher in the soles, palms, and innerforearm.5 Apparently, there are no gender differences onpermeability barrier in the neonatal period.6 Probably thedifferences that are observable later in life can be related tohormonal factors.1

Although neonatal and adult epidermis is similar withrespect to thickness and lipid composition, skin developmentis not complete at birth. Skin function parameters wereassessed prospectively in a cohort of 202 healthy termneonates (98 boys) of Caucasian descent.7 Measurementswere performed at 3 days, 4 weeks, and 12 weeks of age andat 4 different body sites (frontal area, cheek, volar forearm,and gluteal surface). The following parameters were assessed:

Table 1 Skin structure and function in neonates

Structure/Function Neonates

Transepidermal water loss Full-term neonates have completely developed permeability barrier function at birth.Skin pH pH decreases in a steep manner in the first days of the postnatal life and then more

gradually in the rest of the neonatal period.Corneal layer hydration (capacitance) The stratum corneum hydration of term neonates in the first days is lower compared

with older children and adults.Sebum production Sebum lipids also compose vernix caseosa. Increases in the first week after birth, reaching

the excretion rate in adults.Cutaneous blood flow Capillary system is not complete at birth. Fully developed at 14-17 weeks postnatal.

275Barrier function and age

skin surface pH, corneal layer hydration (capacitance),epidermal desquamation, and surface roughness. The authorsfound that surface pH decreased, whereas desquamationincreased significantly during the observation period, butonly on the facial areas. There was a significant increase instratum corneum hydration, which was paralleled bydecreasing skin roughness, indicating smoothing of the skinsurface. No significant differences were found betweenboys and girls.

Sebum is produced by the sebaceous glands directly aftertheir development and consists predominantly of triglycer-ides, wax esters, and squalene.8 Sebum lipids also composethe vernix caseosa.9 In the first week after birth, an increasein sebum secretion is observed, reaching the excretion ratein adults.10

Another example is the cutaneous blood flow: capillaryloops are not detectable at birth except from the regions ofthe nail beds, palms, and soles. Capillary loops are firstobservable in the second week postpartum, but are notevident in all investigated skin sites until the age of 14 to17 weeks.11

Elderly

Clinical signs of maturity are reflected in the skin'shistopathological and functional findings (Table 2). Kerati-nocytes and fibroblasts are the most affected cells during thesenescence course.12-14 This process evolves in different

Table 2 Skin structure and function in the elderly

Structure/Function Elderly

Collagen and lipid content of skin Decreases with agElastin Slow degradation

abnormal elastin,Vasoconstrictor changes Irregularity of cap

thinning of the vaHormonal influences Interfering with w

reactions, and alte

intensities and times of onset, when comparing men andwomen, especially concerning skin structure.

Many authors agree that the overall lipid and collagencontent of human skin decreases with age.15,16 The “brick-and-mortar” model is often used to describe the stratumcorneum's protein-rich corneocytes embedded in a matrix ofceramides, cholesterol, and fatty acids, and smaller amountsof cholesterol sulfate, glucosylceramides, and phospholipids.These lipids contribute to the skin's function as an effectivewater barrier. The changes in the stratum corneum have beenlinked to skin conditions, such as xerosis.15

Elastin exhibits numerous age-related changes, includingslow degradation and accumulation of damage in existingelastin, increased synthesis of apparently abnormal elastin inphotoexposed areas, and abnormal localization of elastin inthe upper dermis of photodamaged skin. These factors leadto the histologically evident elastoic accumulation.17

The vascular aging process is expressed by irregularity ofcapillary loops, alterations and disorganization of horizontalvessels, thinning of the vascular walls, and changes in thewhole vascular bed. In addition, the aged population presents asignificant time delay in blood flow changes, most likelyconsequent to a decrease in function of the autonomic nervoussystem, contributing to some of the vasoconstrictor changesdetected in elderly individuals, especially women.12,18,19

Estrogen and other sex steroids have a profound influenceon skin function, and adequate levels are required to maintaincutaneous structure and functional capacity.20 Hormonalaging modifies the whole skin surface, exposed andnonexposed, but the main impact is in the dermis and in

eand accumulation of damage, increased synthesis of apparentlyelastin in the upper dermis of photodamaged skinillary loops, alterations and disorganization of horizontal vessels,scular wallsound healing, impairing immunological and inflammatoryring the protein balance

276 M. Ramos-e-Silva et al.

the biomechanical characteristics of the skin.21 Estrogensalso have a clear influence on the cutaneous vasculature. Theinfluence of androgens is especially relevant for skinappendages, such as hair follicles and sebaceous glands.12,22

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