Rapamycin increases oxidative stress response gene expression in adult stem cells

Amber E Kofman,Christopher J Payne,Margeaux R Mcgraw

doi:10.18632/aging.100451

Amber E Kofman, Christopher J Payne + Show 1 more

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https://doi.org/10.18632/aging.100451

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Abstract

Balancing quiescence with proliferation is of paramount importance for adult stem cells in order to avoid hyperproliferation and cell depletion. In some models, stem cell exhaustion may be reversed with the drug rapamycin, which was shown can suppress cellular senescencein vitro and extend lifespan in animals. We hypothesized that rapamycin increases the expression of oxidative stress response genes in adult stem cells, and that these gene activities diminish with age. To test our hypothesis, we exposed mice to rapamycin and then examined the transcriptome of their spermatogonial stem cells (SSCs). Gene expression microarray analysis revealed that numerous oxidative stress response genes were upregulated upon rapamycin treatment, including superoxide dismutase 1, glutathione reductase, and delta-aminolevulinate dehydratase. When we examined the expression of these genes in 55-week-old wild type SSCs, their levels were significantly reduced compared to 3-week-old SSCs, suggesting that their downregulation is coincident with the aging process in adult stem cells. We conclude that rapamycin-induced stimulation of oxidative stress response genes may promote cellular longevity in SSCs, while a decline in gene expression in aged stem cells could reflect the SSCs' diminished potential to alleviate oxidative stress, a hallmark of aging.

Highlights

Cell senescence may contribute to adult stem cell exhaustion, compromising the maintenance of cell lineages within the body [1]
We found that mammalian target of rapamycin complex 1 (mTORC1) inhibition upregulates key genes important for Spermatogonial stem cells (SSCs) self-renewal, and elevates transcript levels of oxidative stress response genes and downregulates genes associated with growth and metabolism
In order to verify that our magnetic-activated cell sorting (MACS) selection strategy was successfully enriching undifferentiated male germ cells, we performed qRTPCR on MACS-enriched THY1+/GFRA1+ cells from non-injected mice

Summary

Introduction

Cell senescence may contribute to adult stem cell exhaustion, compromising the maintenance of cell lineages within the body [1]. Recent evidence suggests that the cumulative exposure to reactive oxygen species (ROS) and DNA damage can lead to the decline of adult stem cells both in population and in regenerative capacity. Hematopoietic stem cells (HSCs) from mice lacking forkhead box O (FOXO) family transcription factors exhibit higher levels of ROS, accompanied by short-term hyperproliferation that is followed by increased apoptosis that depletes the HSC pool [2, 3]. Neural stem cells (NSCs), decline in number and function within the subventricular zone of lateral ventricles in the aging mouse brain due to genomic instability and upregulated cyclindependent kinase inhibitor 2a (Cdkn2a; p16Ink4a), which activates DNA-damage response pathways that induce apoptosis or senescence [5, 6]. Spermatogonial stem cells (SSCs) exhibit a loss of regenerative ability during aging in vivo and in vitro, with the downregulation of several genes important for self-renewal [7, 8, 9, 10]

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