Downregulation of APE1/Ref-1 Is Involved in the Senescence of Mesenchymal Stem Cells

Abstract

The senescence of human mesenchymal stem cells (hMSCs) causes disruption of tissue and organ maintenance, and is thus an obstacle to stem cell-based therapies for disease. Although some researchers have studied changes in the characteristics of hMSCs (decreases in differentiation ability and self-renewal), comparing young and old ages, the mechanisms of stem cell senescence have not yet been defined. In this study, we developed a growth curve for human bone marrow derived MSCs (hBMSCs) which changes into a hyperbolic state after passage number 7. Senescence associated b-galactosidase (SA b-gal) staining of hBMSCs showed 10% in passage 9 and 45% in passage 11. We detected an increase in endogenous superoxide levels during senescence that correlated with senescence markers (SA b-gal, hyperbolic growth curve). Interestingly, even though endogenous superoxide increased in a replicative senescence model, the expression of APE1/Ref-1, which is sensitive to intracellular redox state, decreased. These effects were confirmed in a stressinduced senescence model by exogenous treatment with H 2 O 2 . This change is related to the p53 activity that negatively regulates APE1/Ref-1. p21 expression levels, which represent p53 activity, were transiently increased in passage 9, meaning that they correlated with the expression of APE1/Ref-1. Overexpression of APE1/Ref-1 suppressed superoxide production and decreased SA b-gal in hBMSCs. In conclusion, intracellular superoxide accumulation appears to be the main cause of the senescence of hBMSCs, and overexpression of APE1/Ref-1 can rescue cells from the senescence phenotype. Maintaining characteristics of hBMSCs by regulating intracellular reactive oxygen species production can contribute to tissue regeneration and to improved cell therapy.

p16INK4A mediates age-related changes in mesenchymal stem cells derived from human dental pulp through the DNA damage and stress response

“…Moreover, flow cytometric analysis demonstrated an increasing fraction of cells arrested in G0/G1 phase with donor age. Previous studies have investigated that the growth rate of senescent MSCs is decreased (Park et al, 2005) and the percentage of SA-b-gal-positive cells is increased (Heo et al, 2009;Tokalov et al, 2007), which supports our observation (Fig. 7).…”

Maternal diabetes modulates dental epithelial stem cells proliferation and self-renewal in offspring through apurinic/apyrimidinicendonuclease 1-mediated DNA methylation

“…APEX1 is important for normal embryonic development; mouse embryos that do not express APEX1 die on embryonic day 6.521. APEX1 was also found to play a role in the senescence of mesenchymal stem cells and in the hematopoietic differentiation of embryonic stem cells5051. In addition, our previous study showed that APEX1 regulates the osteo/odontogenic differentiation of dental papilla cells through its redox function23.…”

p53, Oxidative Stress, and Aging

“…Overexpression of APE1=Ref-1 suppresses superoxide production and decreases senescence in hBMSCs (48). In addition, aging mice have an impaired induction of APE in response to oxidative damage (15).…”