RESUMO
Impaired mitochondrial function is a hallmark of aging and a major contributor to neurodegenerative diseases. We have shown that disrupted mitochondrial dynamics typically found in aging alters the fate of neural stem cells (NSCs) leading to impairments in learning and memory. At present, little is known regarding the mechanisms by which neural stem and progenitor cells survive and adapt to mitochondrial dysfunction. Using Opa1-inducible knockout as a model of aging and neurodegeneration, we identify a decline in neurogenesis due to impaired stem cell activation and progenitor proliferation, which can be rescued by the mitigation of oxidative stress through hypoxia. Through sc-RNA-seq, we identify the ATF4 pathway as a critical mechanism underlying cellular adaptation to metabolic stress. ATF4 knockdown in Opa1-deficient NSCs accelerates cell death, while the increased expression of ATF4 enhances proliferation and survival. Using a Slc7a11 mutant, an ATF4 target, we show that ATF4-mediated glutathione production plays a critical role in maintaining NSC survival and function under stress conditions. Together, we show that the activation of the integrated stress response (ISR) pathway enables NSCs to adapt to metabolic stress due to mitochondrial dysfunction and metabolic stress and may serve as a therapeutic target to enhance NSC survival and function in aging and neurodegeneration.
Assuntos
Sobrevivência Celular , Mitocôndrias , Células-Tronco Neurais , Células-Tronco Neurais/metabolismo , Mitocôndrias/metabolismo , Animais , Camundongos , Doenças Neurodegenerativas/metabolismo , Doenças Neurodegenerativas/patologia , Doenças Neurodegenerativas/genética , Fator 4 Ativador da Transcrição/metabolismo , Fator 4 Ativador da Transcrição/genética , Estresse Fisiológico , Estresse OxidativoRESUMO
Alzheimer's disease (AD) is a progressive neurodegenerative disorder leading to dementia. The hippocampus, which is one of the sites where neural stem cells reside and new neurons are born, exhibits the most significant neuronal loss in AD. A decline in adult neurogenesis has been described in several animal models of AD. However, the age at which this defect first appears remains unknown. To determine at which stage, from birth to adulthood, the neurogenic deficits are found in AD, we used the triple transgenic mouse model of AD (3xTg). We show that defects in neurogenesis are present as early as postnatal stages, well before the onset of any neuropathology or behavioral deficits. We also show that 3xTg mice have significantly fewer neural stem/progenitor cells, with reduced proliferation and decreased numbers of newborn neurons at postnatal stages, consistent with reduced volumes of hippocampal structures. To determine whether there are early changes in the molecular signatures of neural stem/progenitor cells, we perform bulk RNA-seq on cells sorted directly from the hippocampus. We show significant changes in the gene expression profiles at one month of age, including genes of the Notch and Wnt pathways. These findings reveal impairments in neurogenesis very early in the 3xTg AD model, which provides new opportunities for early diagnosis and therapeutic interventions to prevent neurodegeneration in AD.
Assuntos
Doença de Alzheimer , Camundongos , Animais , Doença de Alzheimer/metabolismo , Neurogênese/genética , Camundongos Transgênicos , Hipocampo/metabolismo , Neurônios/metabolismo , Modelos Animais de DoençasRESUMO
Long-term maintenance of the adult neurogenic niche depends on proper regulation of entry and exit from quiescence. Neural stem cell (NSC) transition from quiescence to activation is a complex process requiring precise cell-cycle control coordinated with transcriptional and morphological changes. How NSC fate transitions in coordination with the cell-cycle machinery remains poorly understood. Here we show that the Rb/E2F axis functions by linking the cell-cycle machinery to pivotal regulators of NSC fate. Deletion of Rb family proteins results in activation of NSCs, inducing a transcriptomic transition toward activation. Deletion of their target activator E2Fs1/3 results in intractable quiescence and cessation of neurogenesis. We show that the Rb/E2F axis mediates these fate transitions through regulation of factors essential for NSC function, including REST and ASCL1. Thus, the Rb/E2F axis is an important regulator of NSC fate, coordinating cell-cycle control with NSC activation and quiescence fate transitions.
Assuntos
Células-Tronco Adultas , Células-Tronco Neurais , Células-Tronco Neurais/metabolismo , Células-Tronco Adultas/metabolismo , Neurogênese/fisiologia , Divisão Celular , Ciclo Celular , Proteína do Retinoblastoma/genética , Proteína do Retinoblastoma/metabolismoRESUMO
Leukocyte transmigration can be affected by shear stress; however, the mechanisms by which shear stress modulates transmigration are unknown. We found that adhesion of eosinophils or an eosinophilic cell line to intereukin 4-stimulated endothelial cells led to a shear-dependent increase in endothelial cell intracellular calcium and increased phosphorylation of extracellular signal-regulated kinase (ERK) 2, but not c-Jun NH2-terminal kinase or p38 mitogen-activated protein kinase. Latex beads coated with antibodies were used to characterize the role of specific endothelial cell surface molecules in initiating signaling under shear conditions. We found that ligation of either vascular cell adhesion molecule-1 or E-selectin, but not major histocompatibility complex class I, induced a shear-dependent increase in ERK2 phosphorylation in cytokine-stimulated endothelial cells. Disassembly of the actin cytoskeleton with latrunculin A prevented ERK2 phosphorylation after adhesion under flow conditions, supporting a role for the cytoskeleton in mechano-sensing. Rapid phosphorylation of focal adhesion kinase and paxillin occurred under identical conditions, suggesting that focal adhesions were also involved in mechanotransduction. Finally, we found that Rho-associated protein kinase and calpain were both critical in the subsequent transendothelial migration of eosinophils under flow conditions. These data suggest that ligation of leukocyte adhesion molecules under flow conditions leads to mechanotransduction in endothelial cells, which can regulate subsequent leukocyte trafficking.
Assuntos
Movimento Celular/imunologia , Células Endoteliais/fisiologia , Eosinófilos/fisiologia , Mecanotransdução Celular/imunologia , Actinas/metabolismo , Adulto , Cálcio/fisiologia , Calpaína/fisiologia , Adesão Celular/imunologia , Linhagem Celular , Movimento Celular/fisiologia , Citoesqueleto/metabolismo , Selectina E/metabolismo , Células Endoteliais/enzimologia , Endotélio Vascular/citologia , Endotélio Vascular/enzimologia , Endotélio Vascular/imunologia , Humanos , Interleucina-4/fisiologia , Peptídeos e Proteínas de Sinalização Intracelular , Proteína Quinase 1 Ativada por Mitógeno/metabolismo , Fosforilação , Proteínas Serina-Treonina Quinases/fisiologia , Proteínas Tirosina Quinases/fisiologia , Molécula 1 de Adesão de Célula Vascular/metabolismo , Quinases Associadas a rhoRESUMO
Here, we asked whether we could identify pharmacological agents that enhance endogenous stem cell function to promote skin repair, focusing on skin-derived precursors (SKPs), a dermal precursor cell population. Libraries of compounds already used in humans were screened for their ability to enhance the self-renewal of human and rodent SKPs. We identified and validated five such compounds, and showed that two of them, alprostadil and trimebutine maleate, enhanced the repair of full thickness skin wounds in middle-aged mice. Moreover, SKPs isolated from drug-treated skin displayed long-term increases in self-renewal when cultured in basal growth medium without drugs. Both alprostadil and trimebutine maleate likely mediated increases in SKP self-renewal by moderate hyperactivation of the MEK-ERK pathway. These findings identify candidates for potential clinical use in human skin repair, and provide support for the idea that pharmacological activation of endogenous tissue precursors represents a viable therapeutic strategy.
Assuntos
Preparações Farmacêuticas/administração & dosagem , Pele/efeitos dos fármacos , Células-Tronco/efeitos dos fármacos , Cicatrização/efeitos dos fármacos , Alprostadil/administração & dosagem , Alprostadil/farmacologia , Animais , Animais Recém-Nascidos , Western Blotting , Diferenciação Celular/efeitos dos fármacos , Diferenciação Celular/genética , Autorrenovação Celular/efeitos dos fármacos , Autorrenovação Celular/genética , Células Cultivadas , Meios de Cultura/química , Meios de Cultura/farmacologia , Perfilação da Expressão Gênica/métodos , Ontologia Genética , Humanos , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Camundongos , Células NIH 3T3 , Análise de Sequência com Séries de Oligonucleotídeos , Ratos , Pele/metabolismo , Pele/fisiopatologia , Esferoides Celulares/efeitos dos fármacos , Esferoides Celulares/metabolismo , Esferoides Celulares/fisiologia , Células-Tronco/metabolismo , Células-Tronco/fisiologia , Trimebutina/administração & dosagem , Trimebutina/farmacologia , Cicatrização/genéticaRESUMO
Adult mammals have lost multi-tissue regenerative capacity, except for the distal digit, which is able to regenerate via mechanisms that remain largely unknown. Here, we show that, after adult mouse distal digit removal, nerve-associated Schwann cell precursors (SCPs) dedifferentiate and secrete growth factors that promote expansion of the blastema and digit regeneration. When SCPs were dysregulated or ablated, mesenchymal precursor proliferation in the blastema was decreased and nail and bone regeneration were impaired. Transplantation of exogenous SCPs rescued these regeneration defects. We found that SCPs secrete factors that promote self-renewal of mesenchymal precursors, and we used transcriptomic and proteomic analysis to define candidate factors. Two of these, oncostatin M (OSM) and platelet-derived growth factor AA (PDGF-AA), are made by SCPs in the regenerating digit and rescued the deficits in regeneration caused by loss of SCPs. As all peripheral tissues contain nerves, these results could have broad implications for mammalian tissue repair and regeneration.
Assuntos
Desdiferenciação Celular , Extremidades/fisiologia , Mamíferos/fisiologia , Células-Tronco Neurais/citologia , Comunicação Parácrina , Regeneração , Células de Schwann/citologia , Envelhecimento/fisiologia , Animais , Desdiferenciação Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Autorrenovação Celular/efeitos dos fármacos , Denervação , Extremidades/inervação , Deleção de Genes , Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , Mesoderma/citologia , Camundongos , Camundongos Knockout , Células-Tronco Neurais/transplante , Oncostatina M/farmacologia , Comunicação Parácrina/efeitos dos fármacos , Fator de Crescimento Derivado de Plaquetas/farmacologia , Ratos , Regeneração/efeitos dos fármacos , Fatores de Transcrição SOXB1/metabolismo , Células de Schwann/transplante , Pele/patologia , Cicatrização/efeitos dos fármacosRESUMO
Recent reports of directed reprogramming have raised questions about the stability of cell lineages. Here, we have addressed this issue, focusing upon skin-derived precursors (SKPs), a dermally derived precursor cell. We show by lineage tracing that murine SKPs from dorsal skin originate from mesenchymal and not neural crest-derived cells. These mesenchymally derived SKPs can, without genetic manipulation, generate functional Schwann cells, a neural crest cell type, and are highly similar at the transcriptional level to Schwann cells isolated from the peripheral nerve. This is not a mouse-specific phenomenon, since human SKPs that are highly similar at the transcriptome level can be made from neural crest-derived facial and mesodermally derived foreskin dermis and the foreskin SKPs can make myelinating Schwann cells. Thus, nonneural crest-derived mesenchymal precursors can differentiate into bona fide peripheral glia in the absence of genetic manipulation, suggesting that developmentally defined lineage boundaries are more flexible than widely thought.