RESUMO
Epithelial-mesenchymal transitions (EMTs) are the epitome of cell plasticity in embryonic development and cancer; during EMT, epithelial cells undergo dramatic phenotypic changes and become able to migrate to form different tissues or give rise to metastases, respectively. The importance of EMTs in other contexts, such as tissue repair and fibrosis in the adult, has become increasingly recognized and studied. In this Review, we discuss the function of EMT in the adult after tissue damage and compare features of embryonic and adult EMT. Whereas sustained EMT leads to adult tissue degeneration, fibrosis and organ failure, its transient activation, which confers phenotypic and functional plasticity on somatic cells, promotes tissue repair after damage. Understanding the mechanisms and temporal regulation of different EMTs provides insight into how some tissues heal and has the potential to open new therapeutic avenues to promote repair or regeneration of tissue damage that is currently irreversible. We also discuss therapeutic strategies that modulate EMT that hold clinical promise in ameliorating fibrosis, and how precise EMT activation could be harnessed to enhance tissue repair.
Assuntos
Transição Epitelial-Mesenquimal , Fibrose , Humanos , Animais , Cicatrização/fisiologia , Regeneração/fisiologia , Células Epiteliais/patologia , Células Epiteliais/metabolismoRESUMO
BACKGROUND: The exact pathogenic mechanism causes hair miniaturization during androgenic alopecia (AGA) has not been delineated. Recent evidence has shown a role for non-coding regulatory RNAs, such as microRNAs (miRNAs), in skin and hair disease. There is no reported information about the role of miRNAs in hair epithelial cells of AGA. OBJECTIVES: To investigate the roles of miRNAs affecting AGA in normal and patient's epithelial hair cells. METHODS: Normal follicular stem and progenitor cells, as well as follicular patient's stem cells, were sorted from hair follicles, and a miRNA q-PCR profiling to compare the expression of 748 miRNA (miRs) in sorted cells were performed. Further, we examined the putative functional implication of the most differentially regulated miRNA (miR-324-3p) in differentiation, proliferation and migration of cultured keratinocytes by qRT-PCR, immunofluorescence, and scratch assay. To explore the mechanisms underlying the effects of miR-324-3p, we used specific chemical inhibitors targeting pathways influenced by miR-324-3p. RESULT: We provide a comprehensive assessment of the "miRNome" of normal and AGA follicular stem and progenitor cells. Differentially regulated miRNA signatures highlight several miRNA candidates including miRNA-324-3p as mis regulated in patient's stem cells. We find that miR-324-3p promotes differentiation and migration of cultured keratinocytes likely through the regulation of mitogen-activated protein kinase (MAPK) and transforming growth factor (TGF)-ß signaling. Importantly, pharmacological inhibition of the TGF-ß signaling pathway using Alk5i promotes hair shaft elongation in an organ-culture system. CONCLUSION: Together, we offer a platform for understanding miRNA dynamic regulation in follicular stem and progenitor cells in baldness and highlight miR-324-3p as a promising target for its treatment.
Assuntos
Alopecia/genética , Folículo Piloso/crescimento & desenvolvimento , MicroRNAs/metabolismo , Células-Tronco/metabolismo , Adulto , Alopecia/patologia , Diferenciação Celular/efeitos dos fármacos , Diferenciação Celular/genética , Linhagem Celular , Movimento Celular/efeitos dos fármacos , Movimento Celular/genética , Proliferação de Células/efeitos dos fármacos , Proliferação de Células/genética , Perfilação da Expressão Gênica , Folículo Piloso/citologia , Humanos , Queratinócitos , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Sistema de Sinalização das MAP Quinases/genética , Masculino , Pessoa de Meia-Idade , Inibidores de Proteínas Quinases/farmacologia , Receptor do Fator de Crescimento Transformador beta Tipo I/antagonistas & inibidores , Receptor do Fator de Crescimento Transformador beta Tipo I/metabolismo , Fator de Crescimento Transformador beta/metabolismoRESUMO
Aerobic glycolysis, or Warburg effect, has been associated with pathologies such as cancer. In this issue of Developmental Cell, Bhattacharya et al. show that aerobic glycolysis is required for neural crest migration in development. These findings point to a link between glucose metabolism and epithelial-mesenchymal plasticity in development and disease.
Assuntos
Glicólise , Neoplasias , Glucose , Humanos , Crista Neural , Transdução de SinaisRESUMO
Billions of dollars are annually invested in pharmaceutical industry and cosmetic sector with intent to develop new drugs and treatment strategies for alopecia. Because the hair looks an important characteristic of humans-an effective appendage in perception, expression of beauty, and preservation of self-esteem-the global market for hair loss treatment products is exponentially increasing. However, current methods to treat hair loss endure yet multiple challenges, such as unfavorable outcomes, nonpermanent and patient-dependent results, as well as unpredictable impacts, which limit their application. Over recent years, remarkable advances in the fields of regenerative medicine and hair tissue engineering have raised new hopes for introducing novel cell-based approaches to treat hair loss. Through cell-based approaches, it is possible to produce hair-like structures in the laboratory setting or manipulate cells in their native niche (in vivo lineage reprogramming) to reconstruct the hair follicle. However, challenging issues still exist with the functionality of cultured human hair cells, the proper selection of nonhair cell sources in cases of shortage of donor hair, and the development of defined culture conditions. Moreover, in the case of in vivo lineage reprogramming, selecting appropriate induction factors and their efficient delivery to guide resident cells into a hair fate-with the aim of reconstructing functional hair-still needs further explorations. In this study, we highlight recent advances and current challenges in hair loss treatment using cell-based approaches and provide novel insights for crucial steps, which must be taken into account to develop reproducible, safe, and efficient cell-based treatment.
Assuntos
Cabelo/fisiologia , Regeneração/fisiologia , Alopecia/patologia , Alopecia/terapia , Folículo Piloso/crescimento & desenvolvimento , Humanos , Nicho de Células-TroncoRESUMO
The changes in cell dynamics after oncogenic mutation that lead to the development of tumours are currently unknown. Here, using skin epidermis as a model, we assessed the effect of oncogenic hedgehog signalling in distinct cell populations and their capacity to induce basal cell carcinoma, the most frequent cancer in humans. We found that only stem cells, and not progenitors, initiated tumour formation upon oncogenic hedgehog signalling. This difference was due to the hierarchical organization of tumour growth in oncogene-targeted stem cells, characterized by an increase in symmetric self-renewing divisions and a higher p53-dependent resistance to apoptosis, leading to rapid clonal expansion and progression into invasive tumours. Our work reveals that the capacity of oncogene-targeted cells to induce tumour formation is dependent not only on their long-term survival and expansion, but also on the specific clonal dynamics of the cancer cell of origin.
Assuntos
Carcinoma Basocelular/patologia , Células Clonais/patologia , Células-Tronco Neoplásicas/patologia , Neoplasias Cutâneas/patologia , Animais , Apoptose , Carcinoma Basocelular/genética , Autorrenovação Celular , Sobrevivência Celular , Progressão da Doença , Epiderme/patologia , Feminino , Proteínas Hedgehog/metabolismo , Homeostase , Masculino , Camundongos , Mutação/genética , Oncogenes/genética , Transdução de Sinais , Neoplasias Cutâneas/genética , Cauda/patologia , Proteína Supressora de Tumor p53/metabolismoRESUMO
Sox9 is a transcription factor expressed in most solid tumors. However, the molecular mechanisms underlying Sox9 function during tumorigenesis remain unclear. Here, using a genetic mouse model of basal cell carcinoma (BCC), the most frequent cancer in humans, we show that Sox9 is expressed from the earliest step of tumor formation in a Wnt/ß-catenin-dependent manner. Deletion of Sox9 together with the constitutive activation of Hedgehog signaling completely prevents BCC formation and leads to a progressive loss of oncogene-expressing cells. Transcriptional profiling of oncogene-expressing cells with Sox9 deletion, combined with in vivo ChIP sequencing, uncovers a cancer-specific gene network regulated by Sox9 that promotes stemness, extracellular matrix deposition, and cytoskeleton remodeling while repressing epidermal differentiation. Our study identifies the molecular mechanisms regulated by Sox9 that link tumor initiation and invasion.
Assuntos
Autorrenovação Celular/fisiologia , Transformação Celular Neoplásica/genética , Células-Tronco Neoplásicas/fisiologia , Oncogenes , Fatores de Transcrição SOX9/fisiologia , Citoesqueleto de Actina/fisiologia , Animais , Carcinogênese , Carcinoma Basocelular/etiologia , Carcinoma Basocelular/genética , Carcinoma Basocelular/fisiopatologia , Adesão Celular , Autorrenovação Celular/genética , Matriz Extracelular/fisiologia , Feminino , Deleção de Genes , Proteínas Hedgehog/fisiologia , Humanos , Masculino , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Modelos Biológicos , Mutação , Invasividade Neoplásica , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/fisiologia , Fatores de Transcrição SOX9/genética , Transdução de Sinais , Neoplasias Cutâneas/etiologia , Neoplasias Cutâneas/genética , Neoplasias Cutâneas/fisiopatologia , Receptor SmoothenedRESUMO
Basal cell carcinoma, the most frequent human skin cancer, arises from activating hedgehog (HH) pathway mutations; however, little is known about the temporal changes that occur in tumour-initiating cells from the first oncogenic hit to the development of invasive cancer. Using an inducible mouse model enabling the expression of a constitutively active Smoothened mutant (SmoM2) in the adult epidermis, we carried out transcriptional profiling of SmoM2-expressing cells at different times during cancer initiation. We found that tumour-initiating cells are massively reprogrammed into a fate resembling that of embryonic hair follicle progenitors (EHFPs). Wnt/ ß-catenin signalling was very rapidly activated following SmoM2 expression in adult epidermis and coincided with the expression of EHFP markers. Deletion of ß-catenin in adult SmoM2-expressing cells prevents EHFP reprogramming and tumour initiation. Finally, human basal cell carcinomas also express genes of the Wnt signalling and EHFP signatures.
Assuntos
Carcinoma Basocelular/patologia , Folículo Piloso/citologia , Células-Tronco Neoplásicas/citologia , Animais , Carcinoma Basocelular/metabolismo , Citometria de Fluxo , Folículo Piloso/metabolismo , Imuno-Histoquímica , Queratinócitos/citologia , Queratinócitos/metabolismo , Camundongos , Camundongos Transgênicos , Células-Tronco Neoplásicas/metabolismo , Reação em Cadeia da Polimerase em Tempo Real , Reação em Cadeia da Polimerase Via Transcriptase Reversa , beta Catenina/metabolismoRESUMO
The skin interfollicular epidermis (IFE) is the first barrier against the external environment and its maintenance is critical for survival. Two seemingly opposite theories have been proposed to explain IFE homeostasis. One posits that IFE is maintained by long-lived slow-cycling stem cells that give rise to transit-amplifying cell progeny, whereas the other suggests that homeostasis is achieved by a single committed progenitor population that balances stochastic fate. Here we probe the cellular heterogeneity within the IFE using two different inducible Cre recombinaseoestrogen receptor constructs targeting IFE progenitors in mice. Quantitative analysis of clonal fate data and proliferation dynamics demonstrate the existence of two distinct proliferative cell compartments arranged in a hierarchy involving slow-cycling stem cells and committed progenitor cells. After wounding, only stem cells contribute substantially to the repair and long-term regeneration of the tissue, whereas committed progenitor cells make a limited contribution.
Assuntos
Células Epidérmicas , Células-Tronco/citologia , Animais , Diferenciação Celular , Divisão Celular , Linhagem da Célula , Sobrevivência Celular , Células Clonais/citologia , Células Clonais/metabolismo , Integrases/genética , Integrases/metabolismo , Queratina-14/genética , Camundongos , Regiões Promotoras Genéticas/genética , Precursores de Proteínas/genética , Receptores de Estrogênio/genética , Receptores de Estrogênio/metabolismo , Células-Tronco/metabolismo , Cauda/citologia , Cicatrização/fisiologiaRESUMO
Angiogenesis is critical during tumour initiation and malignant progression. Different strategies aimed at blocking vascular endothelial growth factor (VEGF) and its receptors have been developed to inhibit angiogenesis in cancer patients. It has become increasingly clear that in addition to its effect on angiogenesis, other mechanisms including a direct effect of VEGF on tumour cells may account for the efficiency of VEGF-blockade therapies. Cancer stem cells (CSCs) have been described in various cancers including squamous tumours of the skin. Here we use a mouse model of skin tumours to investigate the impact of the vascular niche and VEGF signalling on controlling the stemness (the ability to self renew and differentiate) of squamous skin tumours during the early stages of tumour progression. We show that CSCs of skin papillomas are localized in a perivascular niche, in the immediate vicinity of endothelial cells. Furthermore, blocking VEGFR2 caused tumour regression not only by decreasing the microvascular density, but also by reducing CSC pool size and impairing CSC renewal properties. Conditional deletion of Vegfa in tumour epithelial cells caused tumours to regress, whereas VEGF overexpression by tumour epithelial cells accelerated tumour growth. In addition to its well-known effect on angiogenesis, VEGF affected skin tumour growth by promoting cancer stemness and symmetric CSC division, leading to CSC expansion. Moreover, deletion of neuropilin-1 (Nrp1), a VEGF co-receptor expressed in cutaneous CSCs, blocked VEGF's ability to promote cancer stemness and renewal. Our results identify a dual role for tumour-cell-derived VEGF in promoting cancer stemness: by stimulating angiogenesis in a paracrine manner, VEGF creates a perivascular niche for CSCs, and by directly affecting CSCs through Nrp1 in an autocrine loop, VEGF stimulates cancer stemness and renewal. Finally, deletion of Nrp1 in normal epidermis prevents skin tumour initiation. These results may have important implications for the prevention and treatment of skin cancers.
Assuntos
Carcinoma de Células Escamosas/irrigação sanguínea , Carcinoma de Células Escamosas/patologia , Neuropilina-1/metabolismo , Transdução de Sinais , Neoplasias Cutâneas/irrigação sanguínea , Neoplasias Cutâneas/patologia , Fator A de Crescimento do Endotélio Vascular/metabolismo , Animais , Diferenciação Celular , Proliferação de Células , Células Cultivadas , Modelos Animais de Doenças , Células Epiteliais/citologia , Deleção de Genes , Regulação Neoplásica da Expressão Gênica , Camundongos , Células-Tronco Neoplásicas , Neuropilina-1/genética , Fator A de Crescimento do Endotélio Vascular/genéticaRESUMO
The Keystone Symposium 'Stem Cells in Development, Tissue Homeostasis and Disease' was held between 30th January and 4th February 2011 in Santa Fe, New Mexico, USA. The organizers gathered together an impressive panel of speakers to discuss various aspects of stem-cell biology from early development to adult homeostasis, as well as the implications of stem cells for human diseases.
Assuntos
Células-Tronco/metabolismo , Envelhecimento/genética , Envelhecimento/metabolismo , Animais , Diferenciação Celular , Regulação da Expressão Gênica no Desenvolvimento , Heterogeneidade Genética , Humanos , New Mexico , Transdução de Sinais , Células-Tronco/citologiaRESUMO
Squamous cell carcinoma (SCC) is the second most frequent skin cancer. The cellular origin of SCC remains controversial. Here, we used mouse genetics to determine the epidermal cell lineages at the origin of SCC. Using mice conditionally expressing a constitutively active KRas mutant (G12D) and an inducible CRE recombinase in different epidermal lineages, we activated Ras signaling in different cellular compartments of the skin epidermis and determined from which epidermal compartments Ras activation induces squamous tumor formation. Expression of mutant KRas in hair follicle bulge stem cells (SCs) and their immediate progeny (hair germ and outer root sheath), but not in their transient amplifying matrix cells, led to benign squamous skin tumor (papilloma). Expression of KRas(G12D) in interfollicular epidermis also led to papilloma formation, demonstrating that squamous tumor initiation is not restricted to the hair follicle lineages. Whereas no malignant tumor was observed after KRas(G12D) expression alone, expression of KRas(G12D) combined with the loss of p53 induced invasive SCC. Our studies demonstrate that different epidermal lineages including bulge SC are competent to initiate papilloma formation and that multiple genetic hits in the context of oncogenic KRas are required for the development of invasive SCC.
Assuntos
Carcinoma de Células Escamosas/fisiopatologia , Linhagem da Célula/fisiologia , Células Epidérmicas , Neoplasias Cutâneas/fisiopatologia , Animais , Bromodesoxiuridina , Carcinoma de Células Escamosas/genética , Primers do DNA/genética , Citometria de Fluxo , Folículo Piloso/citologia , Integrases/metabolismo , Camundongos , Camundongos Transgênicos , Proteínas Proto-Oncogênicas p21(ras)/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Neoplasias Cutâneas/genética , Células-Tronco/metabolismoRESUMO
Adult stem cells (SCs) are at high risk of accumulating deleterious mutations because they reside and self-renew in adult tissues for extended periods. Little is known about how adult SCs sense and respond to DNA damage within their natural niche. Here, using mouse epidermis as a model, we define the functional consequences and the molecular mechanisms by which adult SCs respond to DNA damage. We show that multipotent hair-follicle-bulge SCs have two important mechanisms for increasing their resistance to DNA-damage-induced cell death: higher expression of the anti-apoptotic gene Bcl-2 and transient stabilization of p53 after DNA damage in bulge SCs. The attenuated p53 activation is the consequence of a faster DNA repair activity, mediated by a higher non-homologous end joining (NHEJ) activity, induced by the key protein DNA-PK. Because NHEJ is an error-prone mechanism, this novel characteristic of adult SCs may have important implications in cancer development and ageing.
Assuntos
Reparo do DNA , Folículo Piloso/citologia , Células-Tronco Multipotentes/citologia , Células-Tronco Multipotentes/fisiologia , Células-Tronco/metabolismo , Adulto , Envelhecimento , Animais , Fenômenos Bioquímicos , Morte Celular , DNA/metabolismo , Dano ao DNA , Epiderme/metabolismo , Folículo Piloso/metabolismo , Folículo Piloso/fisiologia , Humanos , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos , Camundongos Knockout , Camundongos SCID , Células-Tronco Multipotentes/metabolismo , Proteína Supressora de Tumor p53/metabolismoRESUMO
For most types of cancers, the cell at the origin of tumour initiation is still unknown. Here, we used mouse genetics to identify cells at the origin of basal cell carcinoma (BCC), which is one of the most frequently occurring types of cancer in humans, and can result from the activation of the Hedgehog signalling pathway. Using mice conditionally expressing constitutively active Smoothened mutant (SmoM2), we activated Hedgehog signalling in different cellular compartments of the skin epidermis and determined in which compartments Hedgehog activation induces BCC formation. Activation of SmoM2 in hair follicle bulge stem cells and their transient amplifying progenies did not induce cancer formation, demonstrating that BCC does not originate from bulge stem cells, as previously thought. Using clonal analysis, we found that BCC arises from long-term resident progenitor cells of the interfollicular epidermis and the upper infundibulum. Our studies uncover the cells at the origin of BCC in mice and demonstrate that expression of differentiation markers in tumour cells is not necessarily predictive of the cancer initiating cells.