RESUMEN
It has become increasingly clear that several age-associated pathologies associate with mutations in the mitochondrial genome. Experimental modeling of such events has revealed that acquisition of mitochondrial DNA (mtDNA) damage can impair respiratory function and, as a consequence, can lead to widespread decline in cellular function. This includes premature aging syndromes. By taking advantage of a mutator mouse model with an error-prone mtDNA polymerase, we here investigated the impact of an established mtDNA mutational load with regards to the generation, maintenance, and differentiation of induced pluripotent stem (iPS) cells. We demonstrate that somatic cells with a heavy mtDNA mutation burden were amenable for reprogramming into iPS cells. However, mutator iPS cells displayed delayed proliferation kinetics and harbored extensive differentiation defects. While mutator iPS cells had normal ATP levels and glycolytic activity, the induction of differentiation coincided with drastic decreases in ATP production and a hyperactive glycolysis. These data demonstrate the differential requirements of mitochondrial integrity for pluripotent stem cell self-renewal versus differentiation and highlight the relevance of assessing the mitochondrial genome when aiming to generate iPS cells with robust differentiation potential.
Asunto(s)
Diferenciación Celular/genética , ADN Mitocondrial/genética , Células Madre Pluripotentes Inducidas/metabolismo , Mutación , Adenosina Trifosfato/metabolismo , Animales , Células Cultivadas , Reprogramación Celular/genética , ADN Polimerasa gamma , ADN Polimerasa Dirigida por ADN/genética , Glucólisis/genética , Células Madre Hematopoyéticas/citología , Células Madre Hematopoyéticas/metabolismo , Células Madre Pluripotentes Inducidas/citología , Subunidad gamma Común de Receptores de Interleucina/deficiencia , Subunidad gamma Común de Receptores de Interleucina/genética , Factor 4 Similar a Kruppel , Factores de Transcripción de Tipo Kruppel/genética , Ratones Endogámicos C57BL , Ratones Endogámicos NOD , Ratones Noqueados , Ratones SCID , Microscopía Electrónica de Transmisión , Mitocondrias/genética , Mitocondrias/metabolismo , Mitocondrias/ultraestructura , Factor 3 de Transcripción de Unión a Octámeros/genética , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Factores de Transcripción SOXB1/genéticaRESUMEN
Aging of hematopoietic stem cells (HSCs) leads to several functional changes, including alterations affecting self-renewal and differentiation. Although it is well established that many of the age-induced changes are intrinsic to HSCs, less is known regarding the stability of this state. Here, we entertained the hypothesis that HSC aging is driven by the acquisition of permanent genetic mutations. To examine this issue at a functional level in vivo, we applied induced pluripotent stem (iPS) cell reprogramming of aged hematopoietic progenitors and allowed the resulting aged-derived iPS cells to reform hematopoiesis via blastocyst complementation. Next, we functionally characterized iPS-derived HSCs in primary chimeras and after the transplantation of re-differentiated HSCs into new hosts, the gold standard to assess HSC function. Our data demonstrate remarkably similar functional properties of iPS-derived and endogenous blastocyst-derived HSCs, despite the extensive chronological and proliferative age of the former. Our results, therefore, favor a model in which an underlying, but reversible, epigenetic component is a hallmark of HSC aging.
Asunto(s)
Diferenciación Celular/fisiología , Senescencia Celular/fisiología , Epigénesis Genética/fisiología , Trasplante de Células Madre Hematopoyéticas , Células Madre Hematopoyéticas/citología , Células Madre Hematopoyéticas/fisiología , Animales , Diferenciación Celular/genética , Senescencia Celular/genética , Regulación del Desarrollo de la Expresión Génica/fisiología , Estudio de Asociación del Genoma Completo , Ratones , Ratones Endogámicos C57BL , Telómero/genética , Células Madre Totipotentes/citología , Células Madre Totipotentes/fisiología , Transcripción Genética/fisiologíaRESUMEN
Somatic stem cells mediate tissue maintenance for the lifetime of an organism. Despite the well-established longevity that is a prerequisite for such function, accumulating data argue for compromised stem cell function with age. Identifying the mechanisms underlying age-dependent stem cell dysfunction is therefore key to understanding the aging process. Here, using a model carrying a proofreading-defective mitochondrial DNA polymerase, we demonstrate hematopoietic defects reminiscent of premature HSC aging, including anemia, lymphopenia, and myeloid lineage skewing. However, in contrast to physiological stem cell aging, rapidly accumulating mitochondrial DNA mutations had little functional effect on the hematopoietic stem cell pool, and instead caused distinct differentiation blocks and/or disappearance of downstream progenitors. These results show that intact mitochondrial function is required for appropriate multilineage stem cell differentiation, but argue against mitochondrial DNA mutations per se being a primary driver of somatic stem cell aging.