Abstract 14466: Senescence-Associated microRNA-146a Suppresses Cardiomyogenic Potential by Targeting Notch1: Insights from Small Juvenile Stem Cells
Background. Stem cells are the fountain of youth, but are drained with aging. Notch1 plays an important role in muscle regeneration and its expression is diminished with aging. Recently, we discovered that a sub-population of “small juvenile stem cells (SJSCs)” exists in aged bone marrow stem cells (BMSCs) with high proliferative and differentiation potentials. By using SJSCs and aged BMSCs, we investigated the role of senescence-associated microRNAs (SA-miRs) responsible for Notch1 signaling in stem cell aging and cardiomyogenesis.
Methods and Results. SJSCs and BMSCs were isolated from young (2 months) and aged (24 months) male C57BL/6 mice. Notch1 expression was significantly reduced in aged BMSCs as compared to SJSCs (67% decrease vs SJSCs). In addition, Notch1 expression is also impaired in aged heart as compared to young heart (73% decrease vs young). To profile SA-miRs responsible for Notch1 inhibition in aged stem cells, we performed miR microarray which indicated that miR-140, miR-146a/b and miR-195 were highly expressed as validated by qRT-PCR in aged BMSCs as compared to SJSCs. Among these 3 miRs, miR-146a was predicted to directly target 3’ untranslated region of Notch1 gene by computational analysis. Transfection of anti-miR-146a significantly inhibited Notch1 protein expression in aged BMSCs as examined by Western blot (2.5 fold increase vs negative control miR transfection) and immunocytochemistry, suggesting miR-146a directly inhibits Notch1 in aged BMSCs. Interestingly, expression of cardiac lineage markers including Gata4, Nkx2.5 and Mef2c was significantly increased in aged BMSCs by knockdown of miR-146a. Furthermore, inhibition of miR-146a showed significantly lower senescence-associated β-galactosidase expression in aged BMSCs, suggesting miR-146a is involved in stem cell aging by targeting Notch1. Further in vivo studies are under investigation.
Conclusions. Increased level of SA-miR-146a is expressed in stem cells from aging animals and thus may impaire cardiomyogenic process by targeting Notch1. Therefore, inhibition of miR-146a is likely a promising therapeutic strategy for rejuvenation of aged stem cells as well as heart.
- © 2012 by American Heart Association, Inc.