RESUMO
In the last century, human scalp hair morphology has been studied from multiple, and sometimes mutually exclusive, perspectives by anthropologists, biologists, geneticists, forensic scientists, and cosmetic scientists. Here, we review and synthesize historical and current research on hair to better understand the scientific basis and biological implications of hair microstructure and morphology. We revisit the origins of existing nomenclature regarding hair morphology and classifications, discuss the currently recognized limitations to hair analysis within the varied scientific disciplines studying hair, point out aspects of hair biology that remain unknown, and the great potential for integrating these diverse perspectives and expertise in future scientific investigations, while highlighting the benefits of combining nondestructive microscopical analysis with chemical and genomic analyses for explicating hair biology. Further, we propose consensus terminology for root growth stages through descriptions and images that will aid in the morphological and microscopical analysis of human scalp hair, thereby reducing confusion and the promulgation of inaccurate information that is presently in the literature.
Assuntos
Cabelo , Cabelo/anatomia & histologia , Cabelo/química , Cabelo/crescimento & desenvolvimento , Cabelo/ultraestrutura , Humanos , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de TransmissãoRESUMO
The complex mechanical properties of biomaterials such as hair, horn, skin, or bone are determined by the architecture of the underlying fibrous bionetworks. Although much is known about the influence of the cytoskeleton on the mechanics of isolated cells, this has been less studied in tridimensional tissues. We used the hair follicle as a model to link changes in the keratin network composition and architecture to the mechanical properties of the nascent hair. We show using atomic force microscopy that the soft keratinocyte matrix at the base of the follicle stiffens by a factor of â¼360, from 30 kPa to 11 MPa along the first millimeter of the follicle. The early mechanical stiffening is concomitant to an increase in diameter of the keratin macrofibrils, their continuous compaction, and increasingly parallel orientation. The related stiffening of the material follows a power law, typical of the mechanics of nonthermal bending-dominated fiber networks. In addition, we used X-ray diffraction to monitor changes in the (supra)molecular organization within the keratin fibers. At later keratinization stages, the inner mechanical properties of the macrofibrils dominate the stiffening due to the progressive setting up of the cystine network. Our findings corroborate existing models on the sequence of biological and structural events during hair keratinization.
Assuntos
Folículo Piloso/química , Folículo Piloso/metabolismo , Queratinas/química , Queratinas/metabolismo , HumanosRESUMO
The hair follicle is a mini-organ endowed with a unique structure and cyclic behaviour. Despite the intense research efforts which have been devoted at deciphering the hair follicle biology over the past 70 years, one must admit that hair follicle remains an enigma. In this brief review, various aspects of hair follicle biology will be addressed, and more importantly, unsolved questions and new possible research tracks will be highlighted, including hair follicle glycobiology and exosome-mediated cell-cell interactions. Even though bricks of knowledge are solidly being acquired, an integrative picture remains to emerge. One can predict that computer science, algorithms and bioinformatics will assist in fostering our understanding hair biology.
Assuntos
Doenças do Cabelo/genética , Doenças do Cabelo/fisiopatologia , Folículo Piloso/fisiopatologia , Cabelo/fisiologia , Algoritmos , Alopecia/fisiopatologia , Animais , Comunicação Celular , Biologia Computacional , Exossomos/metabolismo , Estudo de Associação Genômica Ampla , Glicômica , Humanos , Lipídeos/química , Camundongos , Modelos Biológicos , Pesquisa Translacional BiomédicaRESUMO
The decline of tissue regenerative potential of skin and hair is a hallmark of physiological ageing and may be associated with age-related changes in tissue-specific stem cells and/or their environment. Human hair follicles (hHF) contain keratinocytes having the property of stem cells such as clonogenic potential. Growth capacity of hHF keratinocytes shows that most of the colony-forming cells are classified as holoclones, meroclones or paraclones when analysed in a clonal assay (Cell, Volume 76, page 1063). Despite the well-known impact of ageing on human hair growth, little is known about changes in hHF keratinocyte clonogenic potential with age. This study aimed at assessing the clone-forming efficiency (CFE) of hHF keratinocytes from three age groups of human donors. It demonstrates that ageing affects hHF keratinocyte CFE.
Assuntos
Envelhecimento/patologia , Folículo Piloso/citologia , Queratinócitos/citologia , Adolescente , Adulto , Células-Tronco Adultas/citologia , Idoso , Ensaio de Unidades Formadoras de Colônias , Humanos , Pessoa de Meia-Idade , Adulto JovemRESUMO
The hair cycle and its control remain today an object of debate. A number of factors, which can modulate this process, have been identified but its choreography remains elusive. For years, the hunt for the conductor has been on, but nobody ever caught him. Intuitively, the process being considered as cyclic, an automaton controlling this cycle should be looked for, by analogy with a clock. However, the putative hair follicle oscillator that would control hair cycle failed to be identified and characterized. In fact, we have revealed that human hair follicle has an autonomous behaviour and that the transitions from one phase to the next occur independently for each follicle, after time intervals given stochastically by a lognormal distribution characterized by a mean and a variance. From this analysis, one can conclude that instead of a cyclical behaviour with an intrinsic automaton, a bistable steady state controls human hair follicle behaviour, which under a stochastic way jumps from the dormant to the active steady state and vice versa.
Assuntos
Folículo Piloso/fisiologia , Humanos , MorfogêneseRESUMO
Jasmonic acid is involved in plant wound repair and tissue regeneration, but no study has been reported in human skin. The effect of a jasmonic acid derivative, tetra-hydro-jasmonic acid (LR2412, 1 and 10 µm) was investigated on an in vitro reconstructed skin model, Episkin™. Using real time RTQPCR studies, results showed an increase in hyaluronan synthase 2 (HAS2) and hyaluronase synthase 3 (HAS3) expression. Furthermore, an increase in hyaluronic acid (HA) deposits in basal and suprabasal layers of the epidermis was observed. The percentage of positive Ki67 keratinocytes in the basal layer as well as the epidermis thickness were seen to increase. Immunohistochemistry studies showed that the synthesis of late differentiation proteins filaggrin and transglutaminase 1 was not modified. The human epidermis is known to thin with age while HA content has been reported to decrease. These results illustrate the potential of LR2412 in counteracting signs of skin ageing.
Assuntos
Envelhecimento/efeitos dos fármacos , Ciclopentanos/farmacologia , Epiderme/efeitos dos fármacos , Epiderme/patologia , Modelos Biológicos , Oxilipinas/farmacologia , Envelhecimento/metabolismo , Envelhecimento/patologia , Células Cultivadas , Epiderme/metabolismo , Proteínas Filagrinas , Glucuronosiltransferase/metabolismo , Humanos , Hialuronan Sintases , Técnicas In Vitro , Interleucina-8/metabolismo , Proteínas de Filamentos Intermediários/metabolismo , Queratinócitos/efeitos dos fármacos , Queratinócitos/metabolismo , Queratinócitos/patologia , Transglutaminases/metabolismoRESUMO
Congenital Horner syndrome is a rare disorder that accounts for less than 5% of all cases of Horner syndrome. Like Horner syndrome in general, it consists primarily of ptosis, miosis, and anhidrosis. Congenital Horner syndrome may manifest some special features such as iris heterochromia since the sympathetic nervous system is an essential component for the development and maintenance of eye color. We present 3 cases of unilateral straight hair in association with congenital Horner syndrome in which the patients had straight hair ipsilateral to the Horner syndrome, whereas on the contralateral side, it was curly, and we discuss possible mechanisms for this phenomenon.
Assuntos
Síndrome de Horner/congênito , Doenças da Íris/etiologia , Transtornos da Pigmentação/etiologia , Pré-Escolar , Diagnóstico Diferencial , Cor de Olho , Síndrome de Horner/complicações , Síndrome de Horner/diagnóstico , Humanos , Lactente , Recém-Nascido , Doenças da Íris/diagnóstico , Masculino , Transtornos da Pigmentação/diagnósticoRESUMO
A placebo-controlled randomized pilot study was performed on five postmenopausal women aged from 60 to 75 years. The women applied 320 mg (2 mg/cm(2)) of either placebo or 10% C-ß-D-xylopyranoside-2-hydroxy-propane (C-xyloside) cream to each outer forearm twice daily for 3 months. At the end of the treatment, skin biopsies were collected from application areas on both forearms. Transmission electron microscope examinations revealed skin ultrastructural changes at the dermal epidermal junction (DEJ) after 10% C-xyloside application for 3 months. The morphological appearance of the DEJ showed strong improvements, with more homogeneous and regular lamina densa in the C-xyloside-treated compared to the placebo treated skin areas. The number of zones showing basement membrane re-duplication was indeed strikingly reduced on C-xyloside-treated skin. These ultrastructural results were further confirmed by a statistically significant increase in the expression levels of α6-integrin the and laminin-332, as estimated by immunohistochemistry. Altogether, these data suggest that topical C-xyloside application in vivo may be efficient in inducing a better dermal-epidermal cohesion when such a junction is deficient, as is the case in photo-aged or chronologically aged skin. Moreover, a statistically significant increase in CD44 expression was noted in the epidermis of C-xyloside-treated compared to the placebo treated skin areas.
Assuntos
Derme/crescimento & desenvolvimento , Derme/ultraestrutura , Epiderme/crescimento & desenvolvimento , Epiderme/ultraestrutura , Glicosídeos/farmacologia , Morfogênese/efeitos dos fármacos , Envelhecimento da Pele/patologia , Idoso , Moléculas de Adesão Celular/metabolismo , Derme/efeitos dos fármacos , Método Duplo-Cego , Epiderme/efeitos dos fármacos , Feminino , Humanos , Imuno-Histoquímica , Integrina alfa6/metabolismo , Pessoa de Meia-Idade , Projetos Piloto , Envelhecimento da Pele/efeitos dos fármacos , CalininaRESUMO
The stratum corneum (SC) is a superficial skin compartment that protects the body from the outside environment. Any disturbance of this function induces cascading steps of molecular and cellular repair in the whole epidermis. The aim of this study was to investigate epidermal gene expression following SC removal by tape stripping. Twenty-nine healthy male volunteers were included (27 +/- 4 years old). Tape stripping was processed on one inner forearm, the other unstripped forearm served as a control. Epidermis samples were collected at 2, 6, 19, 30 and 72 h after tape stripping. Trans-epidermal water loss measurements were performed at each step to monitor barrier restoration. Total RNA was extracted from collected epidermis samples and analysed by using DermArray cDNA microarrays. Among 4000 genes under investigation, we found that the expression of 370 genes varied significantly at least once during the time following stripping. Using an original clustering method, the modulated genes were gathered into eight groups. A functional characterization of the clusters enabled us to get a dynamic and global view of the main molecular processes taking place during epidermal recovery.
Assuntos
Epiderme/lesões , Epiderme/metabolismo , Expressão Gênica , Cicatrização/genética , Adulto , Bases de Dados Genéticas , Perfilação da Expressão Gênica , Genômica , Humanos , Cinética , Masculino , Família Multigênica , Análise de Sequência com Séries de Oligonucleotídeos , Reação em Cadeia da Polimerase , Adulto JovemRESUMO
The purpose of this study was to evaluate human hair follicle melanogenic activity using the [14C]-2-thiouracil, which was known to incorporate into nascent melanins. Results obtained on pigmented, grey and non-pigmented hair follicles demonstrated that [(14)C]-2-TU incorporation was restricted to the melanogenic compartment with a strong accumulation located around dermal papilla and within the fibre of pigmented hair follicles. Quantitative analysis of [(14)C]-2-TU incorporation showed a significant increase in pigmented hair follicles upon stimulation with 1 microm forskolin concomitant to an increase in tyrosinase levels. A strong significant decrease in [14C]-2-TU incorporation was noted, when hair follicles were incubated with the tyrosinase competitive inhibitor kojic acid (200 microm). Incubation with the MC1-R agonist alpha-MSH (0.2 microm) did not induce a significant stimulation of hair melanogenesis. The present model could thus represent a useful new tool to identify modulators of human hair pigmentation.
Assuntos
Folículo Piloso/metabolismo , Melaninas/metabolismo , Pigmentação da Pele/fisiologia , Tiouracila/metabolismo , Biópsia , Radioisótopos de Carbono , Colforsina/farmacologia , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Inibidores Enzimáticos/farmacologia , Feminino , Folículo Piloso/efeitos dos fármacos , Folículo Piloso/patologia , Humanos , Pessoa de Meia-Idade , Monofenol Mono-Oxigenase/antagonistas & inibidores , Monofenol Mono-Oxigenase/metabolismo , Pironas/farmacologia , Receptor Tipo 1 de Melanocortina/agonistas , Pigmentação da Pele/efeitos dos fármacos , alfa-MSH/farmacologiaRESUMO
Ageing is today a major societal concern that is intrinsically associated with the increase of life expectancy. Outside the context of severe degenerative diseases that affect the elderly populations, normal visible signs of ageing, notably skin sagging and wrinkles, influence the social and individual perception of peoples. Accordingly, there is a strong demand for researches on skin ageing. Deciphering the cellular and molecular processes of skin evolution through ageing is thus an active scientific domain, at the frontier of tissue developmental and ageing biology. The focus of the present article is to provide an overview of the current knowledge concerning the evolution of dermis characteristics at different life stages, from intra-uterine to post-natal life. The description will integrate stage-specific and age-related changes in dermis characteristics at the tissue, cell, and molecular levels.
Assuntos
Envelhecimento/metabolismo , Derme/metabolismo , Matriz Extracelular/metabolismo , Envelhecimento da Pele , Envelhecimento/patologia , Animais , Derme/patologia , Matriz Extracelular/patologia , HumanosRESUMO
TRP-2 (dopachrome tautomerase) is a melanogenic enzyme whose expression was recently reported to modulate melanocyte response to different cytotoxic events. Here we studied a possible role of TRP-2 in the oxidative stress response in the amelanotic WM35 melanoma cell line. Cell viability assays showed that TRP-2 overexpression in WM35 cells reduced their sensitivity to oxidative stress. Comet assays linked TRP-2 expression to DNA damage protection, and high-performance liquid chromotography-tandem mass spectrometry experiments showed an increase in intracellular glutathione in TRP-2-overexpressing cells. These effects were specifically reversed when TRP-2 was silenced by RNA interference. Nevertheless, these properties appeared to depend on a particular cell environment because expression of TRP-2 failed to rescue HEK epithelial cells exposed to similar treatments.
Assuntos
Células Epiteliais/metabolismo , Oxirredutases Intramoleculares/metabolismo , Melanoma/metabolismo , Estresse Oxidativo/fisiologia , Western Blotting , Linhagem Celular Tumoral , Cromatografia Líquida de Alta Pressão , Ensaio Cometa , Dano ao DNA/fisiologia , Glutationa , Humanos , Imuno-Histoquímica , Interferência de RNA , Espectrometria de Massas em TandemRESUMO
Prostanoid pathway in hair follicle gained closer attention since trichogenic side-effects on hair growth has been observed concomitantly with prostaglandin F(2alpha) receptor (FP) agonist treatment of intraocular pressure. We thus investigated prostanoid receptor distribution in anagen hair follicle and different cell types from hair and skin. Using RT-PCR, Western blot and immunohistochemistry (IHC), we found that all receptors were present in hair follicle. This data shed new light on an underestimated complex network involved in hair growth control. Indeed most of these receptors showed a wide spectrum of expression in cultured cells and the whole hair follicle. Using IHC, we observed that expression of prostaglandin E(2) receptors (EP(2), EP(3), EP(4)), prostaglandin D(2) receptor (DP(2)), prostanoid thromboxane A(2) receptor (TP) and to a lesser extent EP(1) involved several hair follicle compartments. On the opposite, Prostaglandin I(2) receptor (IP) and DP(1) were more specifically expressed in hair cuticle layer and outer root sheath (ORS) basal layer, respectively. FP expression was essentially restricted to ORS companion layer and dermal papilla (DP). Although extracting a clear functional significance from this intricate network remains open challenge, FP labelling, i.e. could explain the biological effect of PGF(2alpha) on hair regrowth, by directly modulating DP function.
Assuntos
Folículo Piloso/crescimento & desenvolvimento , Folículo Piloso/metabolismo , Receptores de Prostaglandina/metabolismo , Biópsia , Células Cultivadas , Feminino , Folículo Piloso/patologia , Humanos , Pessoa de Meia-Idade , Receptores de Epoprostenol/metabolismo , Receptores Imunológicos/metabolismo , Receptores de Prostaglandina E/metabolismo , Receptores de Prostaglandina E Subtipo EP2 , Receptores de Prostaglandina E Subtipo EP3 , Receptores de Prostaglandina E Subtipo EP4 , Receptores de Tromboxano A2 e Prostaglandina H2/metabolismo , Couro Cabeludo/patologiaRESUMO
Heparanase is a heparan sulphate endo-glycosidase which was previously detected in the outer root sheath of murine hair follicles. Heparanase overexpression was reported to improve mouse hair (re)growth. In this study, we investigated its involvement in human hair biology. Immunofluorescence detection was used to explore heparanase distribution in both anagen and catagen hair follicles. Heparanase functionality was assessed in in vitro cultured hair follicles, in the presence of a heparanase activity inhibitor. Our results showed that heparanase expression was (i) primarily located in the inner root sheath (IRS) of human hair follicle, and there (ii) restricted to anagen phase. Furthermore, inhibition of heparanase in in vitro cultured hair follicles induced a catagen-like process. Hair shaft retreat upward was accompanied by a decrease in Ki67-positive cells, the formation of an epithelial strand as evidenced by K14 keratin expression, and the loss of IRS as assessed by transglutaminase 1 and desmoglein labelling. IRS distribution of heparanase and the induction of catagen-like involution of hair follicles when a potent heparanase inhibitor is added suggest that heparanase is a key actor of IRS differentiation and hair homeostasis.
Assuntos
Diferenciação Celular/fisiologia , Folículo Piloso/fisiologia , Heparina Liase/metabolismo , Homeostase/fisiologia , Idoso , Desmogleína 1/metabolismo , Inibidores Enzimáticos/farmacologia , Epiderme/metabolismo , Células Epiteliais/citologia , Células Epiteliais/efeitos dos fármacos , Células Epiteliais/metabolismo , Feminino , Fibronectinas/metabolismo , Folículo Piloso/citologia , Folículo Piloso/efeitos dos fármacos , Heparina Liase/antagonistas & inibidores , Heparitina Sulfato/metabolismo , Humanos , Imuno-Histoquímica , Queratina-14/metabolismo , Queratinas Específicas do Cabelo/metabolismo , Queratinas Tipo I/metabolismo , Antígeno Ki-67/metabolismo , Pessoa de Meia-Idade , Técnicas de Cultura de Tecidos , Transglutaminases/metabolismoRESUMO
NAD(+) dependent 15-hydroxyprostaglandin dehydrogenate (15-PGDH) catalyses oxidation of 15(S)-hydroxyl group of prostaglandins and as a result inactivates their physiological potential. Positive effects of prostaglandins or prostaglandin analogues were reported on terminal hair, vellus hair or eyelash growth and a complex prostaglandin network was recently described in human hair follicle. In the present study, we showed that 15-PGDH was expressed in human hair follicle mainly in melanocytes and keratinocytes, which brought us to consider this enzyme as a possible target to sustain local prostaglandin production. Using a recombinant enzymatic strategy, specific 15-PGDH inhibitors were screened. We identified a thiazolidine dione derivative exhibiting efficacy on follicular outer root sheath keratinocytes, since it concomitantly decreased the production of deactivated 13,14 dihydro 15-ketoprostaglandin F(2alpha) and sustained prostaglandin F(2alpha)in vitro production. In the context of recent interest in prostaglandins and prostaglandin analogues as hair regrowth agents, we postulated that the use of selected 15-PGDH inhibitors could reinforce or prolong the effect of these physiological mediators on hair and skin.
Assuntos
Regulação Enzimológica da Expressão Gênica , Folículo Piloso/citologia , Folículo Piloso/enzimologia , Hidroxiprostaglandina Desidrogenases/genética , Prostaglandinas/metabolismo , Biópsia , Western Blotting , Células Cultivadas , Clonagem Molecular , Inibidores Enzimáticos/farmacologia , Feminino , Humanos , Hidroxiprostaglandina Desidrogenases/antagonistas & inibidores , Hidroxiprostaglandina Desidrogenases/metabolismo , Queratinócitos/citologia , Queratinócitos/enzimologia , Melanócitos/citologia , Melanócitos/enzimologia , Pessoa de Meia-IdadeRESUMO
The term "exposome" describes the totality of exposures to which an individual is subjected from conception to death. It includes both external and internal factors as well as the human body's response to these factors. Current exposome research aims to understand the effects all factors have on specific organs, yet today, the exposome of human skin has not received major attention and a corresponding definition is lacking. This review was compiled with the collaboration of European scientists, specialized in either environmental medicine or skin biology. A comprehensive review of the existing literature was performed using PubMed. The search was restricted to exposome factors and skin aging. Key review papers and all relevant, epidemiological, in vitro, ex vivo and clinical studies were analyzed to determine the key elements of the exposome influencing skin aging. Here we propose a definition of the skin aging exposome. It is based on a summary of the existing scientific evidence for the role of exposome factors in skin aging. We also identify future research needs which concern knowledge about the interaction of distinct exposomal factors with each other and the resulting net effects on skin aging and suggest some protective measures.
Assuntos
Exposição Ambiental/efeitos adversos , Envelhecimento da Pele , Pesquisa Translacional Biomédica , Cosméticos/efeitos adversos , Dieta , Exposição Ambiental/normas , Temperatura Alta/efeitos adversos , Humanos , Fatores de Risco , Privação do Sono/complicações , Fumar/efeitos adversos , Estresse Psicológico/complicaçõesRESUMO
The human hair follicle is a unique appendage which results from epithelio-mesenchymal interactions initiated around the 3rd month of development. This appendage has a very complex structure, with a dermal compartment and an epithelial compartment. The dermal compartment comprises the connective tissue sheath and the dermal papilla, both of which are irrigated by microvessels. The epithelial compartment is made of highly replicating matrix cells giving rise to three concentrical domains, namely the outer root sheath, the inner root sheath and the hair shaft. The pigmentation unit, responsible for hair color, is made of fully active melanocytes located on top of the dermal papilla. Altogether a hair follicle contains more than 20 different cell types, engaged in different differentiation pathways and/or interacting with each other. This complex appendage has a unique behavior in mammals since, after a hair production phase, it involutes in place before entering a resting phase after which it renews itself under a cyclical but stochastic way, out of a double reservoir of pluripotent stem cells able to also regenerate epidermis. For yet unknown reasons, this well ordered process can be disturbed, provoking alopecia. The pigmentation unit also renews itself under a cyclical way, out of a melanocyte progenitor reservoir which progressively declines with time, provoking the hair whitening process. Finally, the shape of the hair shaft is programmed from the bulb. What makes this appendage unique and fascinating is its high degree of autonomy, its incredibly complex though stable structure, the number of different cell types interacting under an equilibrated way and its potential of regeneration. It represents a true paradigm of tissue homeostasis, exemplifying in a small living cylinder all the fundamental laws of cell-cell and tissue interactions. This life is revealed in this short synthesis.
Assuntos
Folículo Piloso/fisiologia , Substâncias de Crescimento/fisiologia , Cabelo/crescimento & desenvolvimento , Cor de Cabelo , Folículo Piloso/embriologia , Folículo Piloso/ultraestrutura , Humanos , Oxirredutases Intramoleculares/metabolismo , Melanócitos/fisiologia , Morfogênese , Glândulas Sebáceas/ultraestruturaRESUMO
In this short review, I introduce an integrated vision of human hair follicle behavior and describe opposing influences that control hair follicle homeostasis, from morphogenesis to hair cycling. The interdependence and complementary roles of these influences allow us to propose that the hair follicle is a true paradigm of a "Yin Yang" type, that is a cold/slow-hot/fast duality. Moreover, a new promising field is emerging, suggesting that glycans are key elements of hair follicle growth control.
RESUMO
With aging, epidermal homeostasis and barrier function are disrupted. In a previous study, we analyzed the transcriptomic response of young skin epidermis after stratum corneum removal, and obtained a global kinetic view of the molecular processes involved in barrier function recovery. In the present study, the same analysis was performed in aged skin in order to better understand the defects which occur with aging. Thirty healthy male volunteers (67 ± 4 years old) were involved. Tape-strippings were carried out on the inner face of one forearm, the other unstripped forearm serving as control. At 2, 6, 18, 30 and 72 h after stripping, TEWL measurements were taken, and epidermis samples were collected. Total RNA was extracted and analyzed using DermArray(®) cDNA microarrays. The results highlighted that barrier function recovery and overall kinetics of gene expression were delayed following stripping in aged skin. Indeed, the TEWL measurements showed that barrier recovery in the young group appeared to be dramatically significant during the overall kinetics, while there were no significant evolution in the aged group until 30 h. Moreover, gene expression analysis revealed that the number of modulated genes following tape stripping increased as a function of time and reached a peak at 6 h after tape stripping in young skin, while it was at 30 h in aged skin, showing that cellular activity linked to the repair process may be engaged earlier in young epidermis than in aged epidermis. A total of 370 genes were modulated in the young group. In the aged group, 382 genes were modulated, whose 184 were also modulated in the young group. Only eight genes that were modulated in both groups were significantly differently modulated. The characterization of these genes into 15 functional families helped to draw a scenario for the aging process affecting epidermal repair capacity.