Investigating the roles of cellular senescence in embryogenesis and aging
Cellular senescence is an irreversible form of proliferative arrest, historically linked to tumour suppression and aging. Recent discoveries, however, have extended its known role to include complex biological processes such as tissue repair, tumour promotion and age-related disorders. These new ins...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2014 |
| País: | España |
| Institución: | CBUC, CESCA |
| Repositorio: | TDR. Tesis Doctorales en Red |
| OAI Identifier: | oai:www.tdx.cat:10803/289617 |
| Acceso en línea: | http://hdl.handle.net/10803/289617 |
| Access Level: | acceso abierto |
| Palabra clave: | Cellular senescence Aging Epidermal stem cells Embryonic development Tumour supression Células m Senescència cel·lular Envelliment Cèl·lules mare epidèrmiques Desenvolupament embrionari Supressió tumoral 576 |
| Sumario: | Cellular senescence is an irreversible form of proliferative arrest, historically linked to tumour suppression and aging. Recent discoveries, however, have extended its known role to include complex biological processes such as tissue repair, tumour promotion and age-related disorders. These new insights are redefining our view of cellular senescence, that unlike a static endpoint, senescence represents a collective phenotype, composed of complex networks of effector programs. The biological outcome of these effector programs varies depending on the cellular context and nature of the stress. Here, we investigated the functional role of senescence in two polar contexts: first, within the epidermal stem cell population during the aging process, and second, during embryonic development. We identified that the primitive Keratin-15 positive (Krt-15) hair follicle stem cell population increases in number in an age-dependent manner, but exhibits decreased functional capacity and an inability to tolerate stress. While there was no evidence of Krt-15 stem cells entering directly into senescence, we identified an age-associated imbalance in epidermal Jak-Stat signalling surrounding the stem cells, reminiscent of extrinsic senescent cells that inhibit stem cell function. These findings suggest that epidermal stem cell decline contributes to the aging phenotype of tissue, and that this may be directed by extrinsic senescence. Conversely, we also describe cellular senescence as a normal developmental mechanism that occurs during mammalian embryonic development, specifically in the apical ectodermal ridge (AER) and the roof plate of the hindbrain neural tube. Interestingly, developmental senescence is strictly dependent on p21, wherein mice deficient in p21 present with defects in embryonic senescence, AER maintenance and abnormal limb patterning. Additionally, we found significant gene-expression overlap between developmental and oncogene-induced senescence in the adult, suggesting a commonality in function. Furthermore, we found that the underlying mesenchyme is a source for senescence instruction, while the fate of senescent cells is both apoptosis and immune-mediated clearance. These findings indicate that senescence also functions in non-pathological states and plays an instructive role during embryonic development, and suggests that senescence may have evolved initially as a developmental mechanism that was subsequently adapted for its role in adult life. |
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