All Stanford University & Hospital ID holders are now welcome to visit Lane Library! Learn More
Today's Hours: 8:00am - 8:00pm
Filters applied
Did You Mean?
  • Book
    John Ramunas.
    One of our long-term goals with this work is to extend the human health span, the period of life when humans are relatively free from age-related disease. Molecular mechanisms that limit the human health span include epigenetic drift, accumulation of cellular waste products, DNA damage, and telomere shortening, and here we demonstrate a method to address telomere shortening. Telomeres comprise DNA sequences that protect the ends of chromosomes but shorten over time due to oxidative damage and incomplete DNA replication during S phase of the cell cycle. Short telomeres can lead to activation of p53, cell cycle arrest or apoptosis, chromosome-chromosome fusions, or malignancy. Short telomeres are implicated not only in age-related diseases including cancer and heart disease, but in diseases in which cells are under high replicative demand, such as muscular dystrophy. The nucleoprotein telomerase comprising the protein component TERT and RNA component TERC extends telomeres, and several efforts at extending telomeres have focused on increasing the amount of telomerase in cells, which conveys proliferative capacity to cells in culture and can reverse phenotypes of aging in animal models. Currently small molecule activators of telomerase are in use by humans, but have no detectable effects on telomere length in many subjects. Adeno-associated viral delivery of TERT is another promising approach, one that extends rodent lifespan without increasing the incidence of cancer possibly because it is usually episomal and diluted out in fast-dividing cells, but risks genomic integration and resulting constitutive TERT expression which may not be acceptable in longer-lived species. Here we present an alternative method for telomere extension made possible by the recent discovery that delivery of mRNA comprising modified nucleotides such as pseudouridine modulates the Toll-like receptor mediated innate immune response that is activated in most cells in response to unmodified mRNA. Nucleoside modifications occur naturally in mammalian RNA and provide a means of distinguishing endogenous from exogenous RNA such as bacterial RNA which have fewer or no such modifications. We find that delivery of modified mRNA encoding TERT to fibroblasts and myoblasts results in transient elevation of telomerase activity, telomere extension, and increased proliferative capacity. All cells treated to date have eventually senesced and expressed markers of senescence to the same degree as untreated cells, important for the safety of our approach. Repeated treatment increases proliferative capacity further, suggesting that the approach may be useful over a prolonged period. We have taken initial steps at delivering mRNA in vivo and this work continues.
    Digital Access   2014