Molecular Characterization and Functions of Senescence-Associated Extracellular Vesicles (SA-EVs)

National Institute On Aging

Investigators

Abstract

Senescent cells produce more EVs than proliferating cells. The secretome of senescent cell, generally more active than that of proliferating cells, has been extensively studied. We treated WI-38 human diploid fibroblasts with ionizing radiation (IR, 10 Gy), etoposide (50 M), or allowed them to reach replicative exhaustion to induce senescence. After reaching senescence, as monitored by SA-Gal staining, we isolated and quantified SA-EVs. Cells rendered senescent by IR and etoposide (ETO) treatments triggered a robust increase in the production of EVs, 30- to 40-fold higher than proliferating (P) EVs. Replicative senescence (S) increased EV production 2- to 3-fold more than PEV. MS analysis uncovers specific proteins differentially enriched in SA-EVs. The SA-EVs and P-EVs were used for Mass Spectrometry (MS) analysis. 5 proteins (DPP4, MYH9, RFTN1, S10AB and TERA) were enriched in SA-EV in all three groups (S/IR/ETO). DPP4 is elevated of SA-EVs. DPP4 was highly expressed in SA-EVs and specifically on the surface of SA-EV. We also investigated DPP4 levels in aging mice compare with young mice also suggesting that DPP4 may also serve as a biomarker of SA-EVs in the circulating system. Surprisingly, we found that SA-EVs are rejected by proliferating fibroblasts, and by HeLa cells. These findings indicate that SA-EVs are have altered surface molecules that make them refractory to uptake by other cells and may increase their levels in circulation. ONGOING WORK AND FUTURE PLANS 1. To study the proteome and the transcriptome of SA-EVs to identify proteins and RNAs involved in the reprogramming by senescent cells in their microenvironment. 2. Surface proteins on EVs might play roles in pharmacokinetics. We are studying how surface proteins on SA-EV influence uptake by other cells. 3. To explore the molecular role of DPP4 on SA-EVs.