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Senescence-associated lncRNAs: senescence-associated long noncoding RNAs.

ABSTRACT: Noncoding RNAs include small transcripts, such as microRNAs and piwi-interacting RNAs, and a wide range of long noncoding RNAs (lncRNAs). Although many lncRNAs have been identified, only a small number of lncRNAs have been characterized functionally. Here, we sought to identify lncRNAs differentially expressed during replicative senescence. We compared lncRNAs expressed in proliferating, early-passage, 'young' human diploid WI-38 fibroblasts [population doubling (PDL) 20] with those expressed in senescent, late-passage, 'old' fibroblasts (PDL 52) by RNA sequencing (RNA-Seq). Numerous transcripts in all lncRNA groups (antisense lncRNAs, pseudogene-encoded lncRNAs, previously described lncRNAs and novel lncRNAs) were validated using reverse transcription (RT) and real-time, quantitative (q)PCR. Among the novel senescence-associated lncRNAs (SAL-RNAs) showing lower abundance in senescent cells, SAL-RNA1 (XLOC_023166) was found to delay senescence, because reducing SAL-RNA1 levels enhanced the appearance of phenotypic traits of senescence, including an enlarged morphology, positive β-galactosidase activity, and heightened p53 levels. Our results reveal that the expression of known and novel lncRNAs changes with senescence and suggests that SAL-RNAs play direct regulatory roles in this important cellular process.

ORGANISM(S): Homo sapiens

PROVIDER: GSE77675 | GEO | 2016/02/08

SECONDARY ACCESSION(S): PRJNA311196

REPOSITORIES: GEO

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Project description:BACKGROUND: Periodontal ligament mesenchymal stem cells (PDLSCs) are a promising cell resource for cell-based regenerative medicine in dentistry. PDLSCs inevitably acquire a senescent phenotype after prolonged in vitro expansion, and the key regulators of cells during replicative senescence remain unclear.METHODS: We cultured periodontal ligament stem cells to passages 4, 10 and 20 (P4, P10, P20). The senescent phenotypes, proliferation and migration ability of PDLSCs (P4, P10, P20) were detected, and non-targeted metabonomic sequencing was performed. We treated PDLSCs with AICAR and detected the expression of FOXO1, FOXO3a, FOXO6 and AMPK phosphorylation (p-AMPK) levels of replicating senescent PDLSCs to explore the correlation between the metabolic changes and the AMPK pathway.RESULTS: Immunofluorescence staining of γ-H2AX, β-galactosidase staining, cell scratch test and qPCR were performed to confirm the occurrence of replicative senescence in PDLSCs during passaging. Three groups of cells at passage 4 (P4), passage 10 (P10) and passage 20 (P20) were collected for non-targeted metabolomics analysis. Metabonomic sequencing showed that the metabolism of replicative senescence in PDLSCs varied significantly. In particular, the content of fatty acid metabolites decreased with senescence, including capric acid, stearic acid, myristic acid and dodecanoic acid. KEGG pathway analysis showed that the AMPK signaling pathway was closely related to AMP levels. The AMP:ATP ratio increased in senescent PDLSCs; however, the levels of p-AMPK and the profile of FOXO1 and FOXO3a, which are downstream of the AMPK signaling pathway, decreased with senescence. We treated PDLSCs with AICAR, an activator of the AMPK pathway, and the phosphorylated AMPK level at P20 PDLSCs was partially restored. CONCLUSION: In summary, our study suggests that the metabolic process of PDLSCs is active in the early stage of senescence, prefers to consume fatty acids, and is attenuated in the later stages of senescence. AMP accumulates in replicative senescent PDLSCs; however, the sensitivity of AMPK phosphorylation sites is impaired, causing senescent PDLSCs to fail to respond to changes in energy metabolism. Our findings provide a new basis for the clinical application of periodontal ligament stem cells.

Project description:The bipolar androgen therapy (BAT) to treat prostate cancer includes cycles of supraphysiological androgen levels (SAL) under continuous androgen deprivation therapy (ADT). We showed previously that SAL induces cellular senescence in androgen-sensitive PCa cells and ex vivo in PCa tumor samples from patients that underwent radical prostatectomy. Here, we show that SAL induces cellular senescence in both, castration sensitive (CSPC) LNCaP and castration resistant PCa (CRPC) C4-2 cells through the cell cycle inhibitor p15. Treatment with the Akt inhibitor (Akti) potently inhibited SAL-induced expression of p15 and cellular senescence in both cell lines. Proximity ligation assays (PLA) combined with high-resolution laser-scanning microscopy indicate that SAL promotes interaction of endogenous androgen receptor (AR) with endogenous Akt in cytoplasm as well as in nucleus after 72 hours hormone treatment. This suggests that the AR interacts with Akt also in a long-term manner. Transcriptome sequencing (RNA-seq) comparing the SAL-induced transcriptomes of LNCaP with C4-2 cells as well as of Akti treated cells revealed landscapes for cell senescence. Interestingly, one of the identified genes is the lncRNASAT1. SAL treatment of native patient tumor samples ex vivo results in upregulation of lncRNASAT1. The lncRNASAT1 is down-regulated in PCa tumor tissues compared to non-tumor tissues of same patients indicating a tumor suppressive function. Knockdown indicates that the lncRNASAT1 is crucial for SAL-induced cancer cell senescence and regulates LNCaP cell proliferation being an upstream factor for pAkt and for p15. Further, knockdown of lncRNASAT1 inhibits LNCaP cell proliferation by low androgen levels but enhances proliferation by SAL. This suggests that lncRNASAT1 serves as a tumor suppressor with SAL. Interestingly, immunoprecipitation of AR detected lncRNASAT1 as an AR interacting partner that regulates AR target gene expression. Thus, we identified a novel pathway of androgen signaling as the AR- lncRNASAT1- Akt- p15INK4b- axis to mediate SAL-induced cellular senescence.

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Senescence-associated lncRNAs: senescence-associated long noncoding RNAs.

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