High levels of oncomiR‐21 contribute to the senescence‐induced growth arrest in normal human cells and its knock‐down increases the replicative lifespan

Abstract

Cellular senescence of normal human cells has by now far exceeded its initial role as a model system for aging research. Many reports show the accumulation of senescent cells in vivo, their effect on their microenvironment and its double-edged role as tumour suppressor and promoter. Importantly, removal of senescent cells delays the onset of age-associated diseases in mouse model systems. To characterize the role of miRNAs in cellular senescence of endothelial cells, we performed miRNA arrays from HUVECs of five different donors. Twelve miRNAs, comprising hsa-miR-23a, hsa-miR-23b, hsa-miR-24, hsa-miR-27a, hsa-miR-29a, hsa-miR-31, hsa-miR-100, hsa-miR-193a, hsa-miR-221, hsa-miR-222 and hsa-let-7i are consistently up-regulated in replicatively senescent cells. Surprisingly, also miR-21 was found up-regulated by replicative and stress-induced senescence, despite being described as oncogenic. Transfection of early passage endothelial cells with miR-21 resulted in lower angiogenesis, and less cell proliferation mirrored by up-regulation of p21CIP1 and down-regulation of CDK2. These two cell-cycle regulators are indirectly regulated by miR-21 via its validated direct targets NFIB (Nuclear factor 1 B-type), a transcriptional inhibitor of p21CIP1, and CDC25A, which regulates CDK2 activity by dephosphorylation. Knock-down of either NFIB or CDC25A shows a phenocopy of over-expressing miR-21 in regard to cell-cycle arrest. Finally, miR-21 over-epxression reduces the replicative lifespan, while stable knock-down by sponges extends the replicative lifespan of endothelial cells. Therefore, we propose that miR-21 is the first miRNA that upon its knock-down extends the replicative lifespan of normal human cells.

miR‐125a‐5p impairs endothelial cell angiogenesis in aging mice via RTEF ‐1 downregulation

“…In addition, upregulation of mir-26a, mir-29a and mir-23a (Boon et al ., 2011; Dellago et al ., 2013) has been reported in aging mice and humans. One of the miRNAs showing the highest increase was mir-34b-3p.…”

“…RTEF-1 targets genes such as VEGF and HIF-1α in endothelial cells under hypoxia and increases vascular relaxation by modulating eNOS (Dellago et al ., 2013; Zhu et al ., 2013). In addition, previous studies have shown that VEGF promoter activity is reduced in aged animals (Rivard et al ., 1999).…”

Mir‐23a induces telomere dysfunction and cellular senescence by inhibiting TRF2 expression

“…miR-23a was previously reported to be upregulated in replicative senescent human umbilical vein endothelial cells and human umbilical cord blood-derived multipotent stem cells (Lee et al ., 2011; Dellago et al ., 2013). In senescent BJ and MC-5 human fibroblast cells, we also observed upregulated miR-23a levels; additionally, a concomitant reduction of TRF2 expression in both mRNA and protein levels was also apparent.…”

The Epigenome and Aging

“…A recent study has shown that among several up-regulated miRNA during replicative or premature senescence of normal human endothelial cells was miR-21 (Dellago et al 2013 ). Transfection of miR-21 into early passage cells induced senescence, up-regulation of p21…”