RESUMO
Photodynamic therapy (PDT) is a clinical modality of photochemotherapy based on the accumulation of a photosensitizer in target cells and subsequent irradiation of the tissue with light of adequate wavelength promoting reactive oxygen species (ROS) formation and cell death. PDT is used in several medical specialties as an organ-specific therapy for different entities. In this review we focus on the current dermatological procedure of PDT. In the most widely used PDT protocol in dermatology, ROS production occurs by accumulation of the endogenous photosensitizer protoporphyrin IX after treatment with the metabolic precursors 5-methylaminolevulinic acid (MAL) or 5-aminolevulinic acid (ALA). To date, current approved dermatological indications of PDT include actinic keratoses (AK), basal cell carcinoma (BCC) and in situ squamous cell carcinoma (SCC) also known as Bowen disease (BD). With regards to AKs, PDT can also treat the cancerization field carrying an oncogenic risk. In addition, an increasing number of pathologies, such as other skin cancers, infectious, inflammatory or pilosebaceous diseases are being considered as potentially treatable entities with PDT. Besides the known therapeutic properties of PDT, there is a modality used for skin rejuvenation and aesthetic purposes defined as photodynamic photorejuvenation. This technique enables the remodelling of collagen, which in turn prevents and treats photoaging stygmata. Finally we explore a new potential treatment field for PDT determined by the activation of follicular bulge stem cells caused by in situ ROS formation.
Assuntos
Dermatologia/tendências , Fotoquimioterapia , Espécies Reativas de Oxigênio/metabolismo , Pele/efeitos da radiação , Dermatologia/métodos , Humanos , Fármacos Fotossensibilizantes , Protoporfirinas/uso terapêutico , Espécies Reativas de Oxigênio/isolamento & purificação , Pele/patologia , Dermatopatias/terapiaRESUMO
Reactive oxygen species (ROS) may severely affect the biochemical viability of most cells. However, ROS may act also as key second messengers regulating important physiological functions in eukaryotic organisms. Of special interest is the potential role of ROS in the regulation of stem cell function and tissue homeostasis and regeneration in adult mammalian tissues. In this context, the hair follicle constitutes an excellent experimental model to study this aspect of ROS biology.Here we present a robust protocol to promote a sustained growth of ex vivo cultured human hair follicles based on the induction of a transient/modulable production of nonlethal endogenous ROS levels in the tissue through a protoporphyrin IX-dependent photodynamic procedure. The light-switchable ROS production activates hair follicle stem cell niches, induces cell proliferation, and maintains the growth/anagen phase for long time. This approach constitutes a complementary experimental tool to study the physiological roles of ROS in human tissues.
Assuntos
Técnicas de Cultura de Células/métodos , Folículo Piloso/crescimento & desenvolvimento , Espécies Reativas de Oxigênio/metabolismo , Adulto , Proliferação de Células/fisiologia , Células Cultivadas , Cabelo/fisiologia , Folículo Piloso/metabolismo , Humanos , Nicho de Células-Tronco/fisiologia , Células-Tronco/fisiologiaRESUMO
The homeostatic and regenerative potential of the skin is critically impaired by an increasing accumulation of air pollutants in human ecosystems. These toxic compounds are frequently implicated in pathological processes such as premature cutaneous ageing, altered pigmentation and cancer. In this scenario, innovative strategies are required to tackle the effects of severe air pollution on skin function. Here we have used a Human Skin Organotypic Culture (HSOC) model to characterize the deleterious effects of an acute topic exposure of human skin to moderately high concentrations of common ambient pollutants, including As, Cd, Cr, dioxins and tobacco smoke. All these toxic compunds inflict severe damage in the tissue, activating the AHR-mediated response to xenobiotics. We have further evaluated the potential of an aqueous leaf extract of the polyextremophile plant Deschampsia antarctica (Edafence) to protect human skin against the acute exposure to toxic pollutants. Our results indicate that pre-treatment of HSOC samples with this aqueous extract conuterbalances the deleterious effects of the exposure to toxic comunds and triggers the activation of key genes invoved in the redox system and in the pro-inflammatory/wound healing response in the skin, suggesting that this natural compound might be effectively used in vivo to protect human skin routinely in different daily conditions.
Assuntos
Poluentes Atmosféricos/efeitos adversos , Exposição Ambiental , Extratos Vegetais/farmacologia , Substâncias Protetoras/farmacologia , Pele/efeitos dos fármacos , Poluição do Ar , Biomarcadores , Proliferação de Células/efeitos dos fármacos , Humanos , Imuno-Histoquímica , Pele/metabolismo , Pele/patologia , Técnicas de Cultura de TecidosRESUMO
Here, we describe a protocol to induce switchable in vivo photogeneration of endogenous reactive oxygen species (ROS) in mouse skin. This transient production of ROS in situ efficiently activates cell proliferation in stem cell niches and stimulates tissue regeneration as strongly manifested through the acceleration of burn healing and hair follicle growth processes. The protocol is based on a regulatable photodynamic treatment that treats the tissue with precursors of the endogenous photosensitizer protoporphyrin IX and further irradiates the tissue with red light under tightly controlled physicochemical parameters. Overall, this protocol constitutes an interesting experimental tool to analyze ROS biology.
Assuntos
Regeneração Nervosa/genética , Protoporfirinas/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Nicho de Células-Tronco/genética , Animais , CamundongosRESUMO
The emerging variety of signalling roles for ROS in eukaryotic cells and tissues is currently a matter of intense research. Here we make use of ex vivo cultured single human hair follicles as an experimental model to demonstrate that a transient production of non-lethal endogenous ROS levels in these mini-organs promotes efficiently the entry into the growth phase (anagen). The stimulatory process implicates the specific activation of the hair follicle stem cell niche, encompassing the induction of stem cell differentiation markers (Ck15), overall cell proliferation and sustained growth of the tissue associated with expression of gen targets (Ccnd1) concomitant with the inhibition of Wnt signaling antagonists and repressors (Dkk1, Gsk3ß) of Wnt signaling. As a whole, this observation indicates that, once activated, ROS signalling is an intrinsic mechanism regulating the hair follicle stem cell niche independently of any external signal.
Assuntos
Ciclina D1/genética , Folículo Piloso/citologia , Queratina-15/genética , Espécies Reativas de Oxigênio/metabolismo , Técnicas de Cultura de Células , Ciclo Celular , Diferenciação Celular , Proliferação de Células , Células Cultivadas , Regulação da Expressão Gênica , Folículo Piloso/metabolismo , Humanos , Modelos Biológicos , Nicho de Células-Tronco , Via de Sinalização WntRESUMO
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
RESUMO
The hair follicle is a biological oscillator that alternates growth, regression, and rest phases driven by the sequential activation of the proliferation/differentiation programs of resident stem cell populations. The activation of hair follicle stem cell niches and subsequent entry into the growing phase is mainly regulated by Wnt/ß-catenin signalling, while regression and resting phases are mainly regulated by Tgf-ß/Bmp/Smad activity. A major question still unresolved is the nature of the molecular switch that dictates the coordinated transition between both signalling pathways. Here we have focused on the role of Endoglin (Eng), a key co-receptor for members of the Tgf-ß/Bmp family of growth factors. Using an Eng haploinsufficient mouse model, we report that Eng is required to maintain a correct follicle cycling pattern and for an adequate stimulation of hair follicle stem cell niches. We further report that ß-catenin binds to the Eng promoter depending on Bmp signalling. Moreover, we show that ß-catenin interacts with Smad4 in a Bmp/Eng-dependent context and both proteins act synergistically to activate Eng promoter transcription. These observations point to the existence of a growth/rest switching mechanism in the hair follicle that is based on an Eng-dependent feedback cross-talk between Wnt/ß-catenin and Bmp/Smad signals.