We thank members of the Demaria lab for fruitful discussions, and Thijmen van Vliet for sharing data and protocol on the UV-induced senescence.

1. General Preparation
<ol>
	<li>Prepare D10 medium. Supplement DMEM medium-Glutamax with 10% FBS and 1% penicillin/streptomycin (Final concentration: 100 U/mL).</li>
	<li>Prepare sterile PBS. Dissolve the tablets in water according to manufacturer&#8217;s instructions. Sterilize by autoclave.</li>
	<li>Prepare 1x trypsin. Dilute 5 mL of Trypsin-Versene EDTA/10x 1:10 in 45 mL of sterile PBS. 
	Note: Throughout the protocol, we use cell culture conditions that are closer to the physiological conditions for p...

<ol>
	<li>Hayflick, L., Moorhead, P. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+serial+cultivation+of+human+diploid+cell+strains.">The serial cultivation of human diploid cell strains.</a> Experimental Cell Research. 25, 585-621 (1961).</li><li>Mu&#241;oz-Esp&#237;n, D., Serrano, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellular+senescence:+from+physiology+to+pathology.+Nature+reviews.">Cellular senescence: from physiology to pathology. Nature reviews.</a> Molecular cell biology. 15, 482-496 (2014).</li><li>Sharpless, N. E., Sherr, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Forging+a+signature+of+in+vivo+senescence.">Forging a signature of in vivo senescence.</a> Nature Reviews Cancer. 15 (7), 397-408 (2015).</li><li>Correia-Melo, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitochondria+are+required+for+pro-ageing+features+of+the+senescent+phenotype.">Mitochondria are required for pro-ageing features of the senescent phenotype.</a> The EMBO Journal. 10, e201592862 (2016).</li><li>Loaiza, N., Demaria, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellular+senescence+and+tumor+promotion:+Is+aging+the+key?.">Cellular senescence and tumor promotion: Is aging the key?.</a> Biochimica et Biophysica Acta (BBA) - Reviews on Cancer. , (2016).</li><li>Coppe, J. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Senescence-associated+secretory+phenotypes+reveal+cell-nonautonomous+functions+of+oncogenic+RAS+and+the+p53+tumor+suppressor.">Senescence-associated secretory phenotypes reveal cell-nonautonomous functions of oncogenic RAS and the p53 tumor suppressor.</a> PLoS Biology. 6 (12), 2853-2868 (2008).</li><li>Baker, D. 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H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Local+clearance+of+senescent+cells+attenuates+the+development+of+post-traumatic+osteoarthritis+and+creates+a+pro-regenerative+environment.">Local clearance of senescent cells attenuates the development of post-traumatic osteoarthritis and creates a pro-regenerative environment.</a> Nature Medicine. 23 (6), 775-781 (2017).</li><li>Demaria, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellular+Senescence+Promotes+Adverse+Effects+of+Chemotherapy+and+Cancer+Relapse.">Cellular Senescence Promotes Adverse Effects of Chemotherapy and Cancer Relapse.</a> Cancer Discovery. 7 (2), 165-176 (2017).</li><li>Chang, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clearance+of+senescent+cells+by+ABT263+rejuvenates+aged+hematopoietic+stem+cells+in+mice.">Clearance of senescent cells by ABT263 rejuvenates aged hematopoietic stem cells in mice.</a> Nature Medicine. 22 (1), 78-83 (2016).</li><li>Soto-Gamez, A., Demaria, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Therapeutic+interventions+for+aging:+the+case+of+cellular+senescence.">Therapeutic interventions for aging: the case of cellular senescence.</a> Drug Discov Today. 22 (5), 786-795 (2017).</li><li>Childs, B. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Senescent+cells:+an+emerging+target+for+diseases+of+ageing.">Senescent cells: an emerging target for diseases of ageing.</a> Nature Reviews Drug Discovery. 16 (10), 718-735 (2017).</li><li>Marthandan, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Conserved+genes+and+pathways+in+primary+human+fibroblast+strains+undergoing+replicative+and+radiation+induced+senescence.">Conserved genes and pathways in primary human fibroblast strains undergoing replicative and radiation induced senescence.</a> Biological Research. 49, 34 (2016).</li><li>Marthandan, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Conserved+Senescence+Associated+Genes+and+Pathways+in+Primary+Human+Fibroblasts+Detected+by+RNA-Seq.">Conserved Senescence Associated Genes and Pathways in Primary Human Fibroblasts Detected by RNA-Seq.</a> PLoS One. 11 (5), e0154531 (2016).</li><li>Hernandez-Segura, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unmasking+Transcriptional+Heterogeneity+in+Senescent+Cells.">Unmasking Transcriptional Heterogeneity in Senescent Cells.</a> Current Biology. 27 (17), 2652-2660 (2017).</li><li>Le, O. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ionizing+radiation-induced+long-term+expression+of+senescence+markers+in+mice+is+independent+of+p53+and+immune+status.">Ionizing radiation-induced long-term expression of senescence markers in mice is independent of p53 and immune status.</a> Aging Cell. 9 (3), 398-409 (2010).</li><li>Hall, J. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=C/EBPalpha+regulates+CRL4(Cdt2)-mediated+degradation+of+p21+in+response+to+UVB-induced+DNA+damage+to+control+the+G1/S+checkpoint.">C/EBPalpha regulates CRL4(Cdt2)-mediated degradation of p21 in response to UVB-induced DNA damage to control the G1/S checkpoint.</a> Cell Cycle. 13 (22), 3602-3610 (2014).</li><li>Nitiss, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Targeting+DNA+topoisomerase+II+in+cancer+chemotherapy.">Targeting DNA topoisomerase II in cancer chemotherapy.</a> Nature Reviews Cancer. 9 (5), 338-350 (2009).</li><li>Pazolli, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chromatin+remodeling+underlies+the+senescence-+associated+secretory+phenotype+of+tumor+stromal+fibroblasts+that+supports+cancer+progression.">Chromatin remodeling underlies the senescence- associated secretory phenotype of tumor stromal fibroblasts that supports cancer progression.</a> Cancer Research. 72, 2251-2261 (2012).</li><li>Venturelli, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differential+induction+of+apoptosis+and+senescence+by+the+DNA+methyltransferase+inhibitors+5-azacytidine+and+5-aza-2'-deoxycytidine+in+solid+tumor+cells.">Differential induction of apoptosis and senescence by the DNA methyltransferase inhibitors 5-azacytidine and 5-aza-2'-deoxycytidine in solid tumor cells.</a> Molecular Cancer Therapeutics. 12, 2226-2236 (2013).</li><li>Tennant, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+the+Trypan+Blue+Technique+for+Determination+of+Cell+Viability.">Evaluation of the Trypan Blue Technique for Determination of Cell Viability.</a> Transplantation. 2, 685-694 (1964).</li><li>Livak, K. J., Schmittgen, T. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+relative+gene+expression+data+using+real-time+quantitative+PCR+and+the+2(-Delta+Delta+C(T))+Method.">Analysis of relative gene expression data using real-time quantitative PCR and the 2(-Delta Delta C(T)) Method.</a> Methods. 25 (4), 402-408 (2001).</li><li>Lee, B. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Senescence-associated+&#946;-galactosidase+is+lysosomal+&#946;-galactosidase.">Senescence-associated &#946;-galactosidase is lysosomal &#946;-galactosidase.</a> Aging Cell. 5, 187-195 (2006).</li><li>Kopp, H. G., Hooper, A. T., Shmelkov, S. V., Rafii, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Beta-galactosidase+staining+on+bone+marrow.+The+osteoclast+pitfall.">Beta-galactosidase staining on bone marrow. The osteoclast pitfall.</a> Histology and Histopathology. 22 (9), 971-976 (2007).</li><li>Dimri, G. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+biomarker+that+identifies+senescent+human+cells+in+culture+and+in+aging+skin+in+vivo.">A biomarker that identifies senescent human cells in culture and in aging skin in vivo.</a> Proceedings of the National Academy of Sciences. 92 (20), 9363-9367 (1995).</li><li>Salic, A., Mitchison, T. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+chemical+method+for+fast+and+sensitive+detection+of+DNA+synthesis+in+vivo.">A chemical method for fast and sensitive detection of DNA synthesis in vivo.</a> Proceedings of the National Academy of Sciences. 105 (7), 2415-2420 (2008).</li><li>Sherr, C. J., McCormick, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+RB+and+p53+pathways+in+cancer.">The RB and p53 pathways in cancer.</a> Cancer Cell. 2 (2), 103-112 (2002).</li><li>Bunz, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Requirement+for+p53+and+p21+to+sustain+G2+arrest+after+DNA+damage.">Requirement for p53 and p21 to sustain G2 arrest after DNA damage.</a> Science. 282 (5393), 1497-1501 (1998).</li><li>Severino, J., Allen, R. G., Balin, S., Balin, A., Cristofalo, V. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Is+beta-galactosidase+staining+a+marker+of+senescence+in+vitro+and+in+vivo.">Is beta-galactosidase staining a marker of senescence in vitro and in vivo.</a> Experimental Cell Research. 257 (1), 162-171 (2000).</li><li>Stolzing, A., Coleman, N., Scutt, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glucose-induced+replicative+senescence+in+mesenchymal+stem+cells.">Glucose-induced replicative senescence in mesenchymal stem cells.</a> Rejuvenation Research. 9 (1), 31-35 (2006).</li><li>Blazer, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+glucose-induced+replicative+senescence:+point+of+no+return+and+effect+of+telomerase.">High glucose-induced replicative senescence: point of no return and effect of telomerase.</a> Biochemical and Biophysical Research Communications. 296 (1), 93-101 (2002).</li><li>Wiley, C. 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V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MTOR+and+autophagy:+converging+on+senescence+or+quiescence.">MTOR and autophagy: converging on senescence or quiescence.</a> Autophagy. 9 (2), 260-262 (2013).</li><li>Meuter, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Markers+of+cellular+senescence+are+elevated+in+murine+blastocysts+cultured+in+vitro:+molecular+consequences+of+culture+in+atmospheric+oxygen.">Markers of cellular senescence are elevated in murine blastocysts cultured in vitro: molecular consequences of culture in atmospheric oxygen.</a> Journal of Assisted Reproduction and Genetics. 31 (10), 1259-1267 (2014).</li><li>Coppe, J. 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The protocols explained here were optimized for human primary fibroblasts, particularly BJ and WI-38 cells. The protocols for replicative senescence, ionizing radiation and doxorubicin, have been successfully applied to other types of fibroblasts (HCA2 and IMR90) and in other cell types (namely neonatal melanocytes and keratinocytes or iPSC-derived cardiomyocytes) in our laboratory. However, adaptations for additional cell types can be optimized by adjusting some details such as the number of seeded cells, the methods an...

In 1961, Hayflick and Moorhead reported that primary fibroblasts in culture lose their proliferative potential after successive passages1. This process is caused by the sequential shortening of telomeres after each cell division. When telomeres reach a critically short length, they are recognized by the DNA-damage response (DDR) that activates an irreversible arrest of proliferation &#8212; also defined as replicative senescence. Replicative senescence is currently one of the many stimuli that are known to induce a state of permanent cell cycle arrest that renders cells insensitive both to mitogens and to apoptotic signals2,3. The senescence program is normally characterized by additional features including high lysosomal activity, mitochondrial dysfunction, nuclear changes, chromatin rearrangements, endoplasmic reticulum stress, DNA damage and a senescence-associated secretory phenotype (SASP)3,4. Senescent cells have multiple functions in the body: development, wound healing and tumor suppression2. Equally, they are known to play an important role in aging and, paradoxically, in tumor progression5. The negative, and partially contradictory, effects of senescence are often attributed to the SASP6.
Recently, it was shown that elimination of senescent cells from mice leads to lifespan extension and to elimination of many of the aging features7,8,9,10,11,12. In the same way, multiple drugs have been developed to either eliminate senescent cells (senolytics) or to target the SASP13,14. The anti-aging therapeutic potential has recently attracted more attention to the field.
The study of mechanisms associated to cellular senescence and the screenings for pharmacological interventions heavily rely on ex vivo models, particularly on human primary fibroblasts. While there are some common features activated by diverse senescence inducers, a large variability in the senescence phenotype is observed and dependent on various factors including cell type, stimulus and time point3,15,16,17. It is imperative to consider the heterogeneity for studying and targeting senescent cells. Therefore, this protocol aims to provide a series of methods used to induce senescence in primary fibroblasts by using different treatments. As it will be explained, the methods can easily be adapted to other cell types.
Apart from replicative senescence, we describe five other senescence-inducing treatments: ionizing radiation, ultraviolet (UV) radiation, doxorubicin, oxidative stress and epigenetic changes (namely promotion of histone acetylation or DNA demethylation). Both, ionizing radiation and UV-radiation cause direct DNA damage and, at the appropriate dose, trigger senescence18,19. Doxorubicin also causes senescence mainly through DNA damage by intercalating into the DNA and disrupting topoisomerase II function and thus halting DNA repair mechanisms20. The expression of genes essential for senescence is normally controlled by histone acetylation and DNA methylation. As a consequence, histone deacetylase inhibitors (e.g., sodium butyrate and SAHA) and DNA demethylating (e.g., 5-aza) agents trigger senescence in otherwise normal cells21,22.
Finally, four of the most common markers associated to senescent cells will be explained: activity of the senescence associated-&#946;-galactosidase (SA-&#946;-gal), rate of DNA synthesis by EdU incorporation assay, overexpression of the cell cycle regulators and cyclin-dependent kinase inhibitors p16 and p21, and overexpression and secretion of members of the SASP.

<table>
	<tbody>
		<tr>
			<td>DMEM Media - GlutaMAX</td>
			<td>Gibco</td>
			<td>31966-047</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum</td>
			<td>Hyclone</td>
			<td>SV30160.03</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin (P/S; 10,000 U/ml)</td>
			<td>Lonza</td>
			<td>DE17-602E</td>
			<td></td>
		</tr>
		<tr>
			<td>Dimethyl Sulfoxide (DMSO)</td>
			<td>Sigma-Aldrich</td>
			<td>SC-202581</td>
			<td></td>
		</tr>
		<tr>
			<td>Nuclease-Free Water (not DEPC-Treated)</td>
			<td>Ambion</td>
			<td>AM9937</td>
			<td></td>
		</tr>
		<tr>
			<td>T75 flask</td>
			<td>Sarstedt</td>
			<td>833911002</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin/EDTA Solution</td>
			<td>Lonza</td>
			<td>CC-5012</td>
			<td></td>
		</tr>
		<tr>
			<td>PBS tablets</td>
			<td>Gibco</td>
			<td>18912-014</td>
			<td></td>
		</tr>
		<tr>
			<td>1.5 ml microcentrifuge tubes</td>
			<td>Sigma-Aldrich</td>
			<td>T9661-1000EA</td>
			<td></td>
		</tr>
		<tr>
			<td>Corning&#160;15 mL centrifuge tubes</td>
			<td>Sigma-Aldrich</td>
			<td>CLS430791</td>
			<td></td>
		</tr>
		<tr>
			<td>6-well plate</td>
			<td>Sarstedt</td>
			<td>83.3920</td>
			<td></td>
		</tr>
		<tr>
			<td>24-well plate</td>
			<td>Sarstedt</td>
			<td>83.3922</td>
			<td></td>
		</tr>
		<tr>
			<td>13mm round coverslips</td>
			<td>Sarstedt</td>
			<td>83.1840.002</td>
			<td></td>
		</tr>
		<tr>
			<td>Steriflip</td>
			<td>Merck Chemicals</td>
			<td>SCGP00525</td>
			<td></td>
		</tr>
		<tr>
			<td>Cesium137-source</td>
			<td></td>
			<td></td>
			<td>IBL 637 Cesium-137&#947;-ray machine</td>
		</tr>
		<tr>
			<td>UV radiation chamber</td>
			<td></td>
			<td></td>
			<td>Opsytec, Dr. G&#246;bel BS-02</td>
		</tr>
		<tr>
			<td>Doxorubicin dihydrochloride&#160;</td>
			<td>BioAustralis Fine Chemicals</td>
			<td>BIA-D1202-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Hydrogen peroxide solution</td>
			<td>Sigma-Aldrich</td>
			<td>7722-84-1</td>
			<td></td>
		</tr>
		<tr>
			<td>5-aza-2&#8217;-deoxycytidine</td>
			<td>Sigma-Aldrich</td>
			<td>A3656</td>
			<td></td>
		</tr>
		<tr>
			<td>SAHA</td>
			<td>Sigma-Aldrich</td>
			<td>SML0061</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Butyrate&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>B5887</td>
			<td></td>
		</tr>
		<tr>
			<td>X-gal (5-Bromo-4-chloro-3-indolyl-&#946;-D-galactopyranoside)</td>
			<td>Fisher Scientific</td>
			<td>7240-90-6</td>
			<td></td>
		</tr>
		<tr>
			<td>Citric acid monohydrate</td>
			<td>Sigma-Aldrich</td>
			<td>5949-29-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium dibasic phosphate</td>
			<td>Acros organics</td>
			<td>7782-85-6</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium ferrocyanide&#160;</td>
			<td>Fisher Scientific</td>
			<td>14459-95-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium ferricyanide</td>
			<td>Fisher Scientific</td>
			<td>13746-66-2</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Chloride</td>
			<td>Merck Millipore</td>
			<td>7647-14-5</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnesium Chloride</td>
			<td>Fisher Chemicals</td>
			<td>7791-18-6</td>
			<td></td>
		</tr>
		<tr>
			<td>25% glutaraldehyde</td>
			<td>Fisher Scientific</td>
			<td>111-30-8,7732-18-5</td>
			<td></td>
		</tr>
		<tr>
			<td>16% formaldehyde (w/v)</td>
			<td>Thermo-Fisher Scientific</td>
			<td>28908</td>
			<td></td>
		</tr>
		<tr>
			<td>EdU (5-ethynyl-2&#8217;-deoxyuridine)</td>
			<td>Lumiprobe</td>
			<td>10540</td>
			<td></td>
		</tr>
		<tr>
			<td>Sulfo-Cyanine3 azide (Sulfo-Cy3-Azide)</td>
			<td>Lumiprobe</td>
			<td>D1330</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium ascorbate</td>
			<td>Sigma-Aldrich</td>
			<td>A4034</td>
			<td></td>
		</tr>
		<tr>
			<td>Copper(II) sulfate pentahydrate (Cu(II)SO4.5H2O)</td>
			<td>Sigma-Aldrich</td>
			<td>209198</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Acros organics</td>
			<td>215682500</td>
			<td></td>
		</tr>
		<tr>
			<td>TRIS base</td>
			<td>Roche</td>
			<td>11814273001</td>
			<td></td>
		</tr>
		<tr>
			<td>LightCycler 480 Multiwell Plate 384, white&#160;</td>
			<td>Roche</td>
			<td>4729749001</td>
			<td></td>
		</tr>
		<tr>
			<td>Lightcycler 480 sealing foil&#160;</td>
			<td>Roche</td>
			<td>4729757001</td>
			<td></td>
		</tr>
		<tr>
			<td>Sensifast Probe Lo-ROX kit&#160;</td>
			<td>Bioline</td>
			<td>BIO-84020</td>
			<td></td>
		</tr>
		<tr>
			<td>UPL Probe Library</td>
			<td>Sigma-Aldrich</td>
			<td>Various</td>
			<td></td>
		</tr>
		<tr>
			<td>Human IL-6 DuoSet ELISA</td>
			<td>R&#38;D</td>
			<td>D6050</td>
			<td></td>
		</tr>
		<tr>
			<td>Bio-Rad TC20</td>
			<td>Bio-Rad</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Counting slides</td>
			<td>Bio-Rad</td>
			<td>145-0017</td>
			<td></td>
		</tr>
		<tr>
			<td>Dry incubator</td>
			<td>Thermo-Fisher Scientific</td>
			<td>Heratherm</td>
			<td></td>
		</tr>
		<tr>
			<td>Dimethylformamide</td>
			<td>Merck Millipore</td>
			<td>1.10983</td>
			<td></td>
		</tr>
		<tr>
			<td>Parafilm &#39;M&#39; laboratory film</td>
			<td>Bemis&#160;</td>
			<td>#PM992</td>
			<td></td>
		</tr>
		<tr>
			<td>Tweezers</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Needles</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

induction and validation of cellular senescence in primary human cells

Cellular senescence is a state of permanent cell cycle arrest activated in response to different damaging stimuli. Activation of cellular senescence is a hallmark of various pathophysiological conditions including tumor suppression, tissue remodeling and aging. The inducers of cellular senescence in vivo are still poorly characterized. However, a number of stimuli can be used to promote cellular senescence ex vivo. Among them, most common senescence-inducers are replicative exhaustion, ionizing and non-ionizing radiation, genotoxic drugs, oxidative stress, and demethylating and acetylating agents. Here, we will provide detailed instructions on how to use these stimuli to induce fibroblasts into senescence. This protocol can easily be adapted for different types of primary cells and cell lines, including cancer cells. We also describe different methods for the validation of senescence induction. In particular, we focus on measuring the activity of the lysosomal enzyme Senescence-Associated &#946;-galactosidase (SA-&#946;-gal), the rate of DNA synthesis using 5-ethynyl-2&#39;-deoxyuridine (EdU) incorporation assay, the levels of expression of the cell cycle inhibitors p16 and p21, and the expression and secretion of members of the Senescence-Associated Secretory Phenotype (SASP). Finally, we provide example results and discuss further applications of these protocols.

Enrichment of SA-&#946;-gal staining in senescent fibroblasts
&#914;-galactosidase (&#946;-gal) is a lysosomal enzyme that is expressed in all cells and that has an optimum pH of 4.025,26. However, during senescence, lysosomes increase in size and, consequently, senescent cells accumulate &#946;-gal. The increased amounts of this enzyme make it possible to detect its activi...

Watch this Scientific Journal Video about Induction and Validation of Cellular Senescence in Primary Human Cells at JoVE.com

Induction and Validation of Cellular Senescence in Primary Human Cells

Here, we discuss a series of protocols for induction and validation of cellular senescence in cultured cells. We focus on different senescence-inducing stimuli and describe the quantification of common senescence-associated markers. We provide technical details using fibroblasts as a model, but the protocols can be adapted to various cellular models.

Cellular senescence is a state of permanent cell cycle arrest activated in response to different damaging stimuli. Activation of cellular senescence is a ...

This method can help answer key questions in the aging and cancer field such as how to perform common techniques to induce cellular senescence and how to evaluate the senescence phenotype. The main advantages of this technique are that it is easy to follow, highly reproducible, does not require any special or expensive equipment, and it results in the induction of senescence in at least 50%of the cellular population. Demonstrating this procedure will be Alejandra Hernandez-Segura, a graduate student from our lab.To begin, seed seven times 10 to the fifth viable primary fibroblasts with a low Population Doubling or PD in a T75 flask containing 10 milliliters of D10. Incubate the cells in a cell culture incubator at 37 degrees Celsius with 5%carbon dioxide and 5%oxygen overnight. Dilute 11 microliters of the 1, 000X doxorubicin stock solution in 11 milliliters of D10 to a final concentration of 250 nanomolar.Then aspirate the medium from the cells and replace it with 10 milliliters of D10 plus doxorubicin. Incubate the cells in a cell culture incubator at 37 degrees Celsius with 5%carbon dioxide and 5%oxygen for exactly 24 hours. Then aspirate the medium and use 10 milliliters of D10 to carefully wash the cells once.Incubate the cells in 10 milliliters of D10 for another six days replacing the medium regularly approximately every three days. To carry out beta-galactosidase staining, for each sample seed one times 10 to the fourth cells in at least one well of a 24-well plate containing 500 microliters of D10 so that the cells are sparse. Incubate the cells at 37 degrees Celsius with 5%carbon dioxide and 5%oxygen overnight.The following day, use 500 microliters of PBS to wash the cells two times. Then add 500 microliters per well of 2%formaldehyde plus 0.2%glutaraldehyde in PBS and incubate the cells at room temperature for three to five minutes to fix them. Then use 500 microliters of PBS to wash the cells twice.Next, after preparing fresh staining solution, add 500 microliters per well and use parafilm to seal the plate to avoid evaporation which can cause crystals to form. Incubate the cells in the dark at 37 degrees Celsius in a dry incubator without carbon dioxide for 12 to 16 hours. Then use 500 microliters of PBS to wash the cells twice.Check the cells under a normal light microscope to assess the results where positive cells will appear with blue paranuclear staining. To facilitate visualization and quantification of individual cells, use DAPI as a counterstain. Then using a fluorescent microscope, determine the percentage of positive cells versus total number of cells taking multiple pictures of the same sample to evaluate at least 100 single cells.For each sample or condition, place one coverslip per well into a 24-well plate. Seed one times 10 to the fourth cells with 500 microliters of D10 per well so that the cells are sparse. Incubate the cells at 37 degrees Celsius with 5%carbon dioxide and 5%oxygen overnight.Prepare enough of a 20 micromolar EdU solution and D10 so that each sample receives 250 microliters. Remove half of the medium from each well being treated and replace it with EdU D10 solution. The final EdU concentration is 10 micromolar.Incubate the samples at 37 degrees Celsius with 5%carbon dioxide and 5%oxygen for 18 to 24 hours. Use the same incubation time for control and senescent cells. After the incubation, use 500 microliters of PBS to wash the cells twice.Then add 500 microliters of 4%formaldehyde in PBS and incubate the cells for 10 minutes to fix them. Following fixation, add 500 microliters of 100 millimolar Tris pH 7.6 to the samples and incubate them for five minutes. Next, add 500 microliters of 0.1%Triton X-100 in PBS to the cells and permeabilize them for 10 minutes.Then use PBS to wash the samples three times. Prepare 50 microliters of label mix for each coverslip, adding the components in the following order, 44.45 microliters of PBS, 0.5 microliters of copper(II)sulfate, 0.05 microliters of sulfo-cy3-azide, and five microliters of sodium ascorbate. Pipette 50 microliters of the label mix on a piece of parafilm.Then using tweezers and a needle, lift the coverslip and rest it cell side down on top of the label mix. Ensure that there are no bubbles and that the whole surface of the coverslip is touching the label mix. Incubate the sample in the dark for 30 minutes.Put the cells back in the wells of the 24-well plate and use PBS to wash them three times. Then use mounting medium with DAPI to mount the samples and let them dry overnight. To begin, seed seven times 10 to the fifth viable primary fibroblasts with a low Population Doubling or.Image at least 100 cells per condition. Finally, quantify the percentage of cells that incorporated EdU by using the following formula. Carry out gene and protein expression studies according to the text protocol.Shown here are representative images of SA-beta-gal staining in proliferating versus senescent primary fibroblasts. Senescent cells look enlarged within a regular cell body. As mentioned, it can be hard to distinguish individual cells.Therefore, co-staining with DAPI facilitates visualization and cell counting. In this experiment, suflo-cy3-azide was used to perform copper catalyzed azide-alkyne cycloaddition to population. If the coupling of the azide to the alkyne has taken place, cells will display fluorescence under a cy3 filter distinguishing proliferating from non-proliferating cells.Once mastered, this technique can be done in 36 hours if performed properly. While attempting this procedure, it is important to remember to be as quick as possible while handling cells outside the incubator as oscillations in the oxygen concentration might affect their results. Following this procedure, other methods like cytokine array or Western blot can be performed in order to answer additional questions like the levels of secreted proteins or understanding specific signaling pathways.After its development, this technique paved the way for researchers in the aging and cancer field to explore how senescent cells are involved in physiological and pathological conditions in mammals. After watching this video, you should have a good understanding on how to reproducibly induce senescence in primary cells and how to assess their senescence status.

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16.3K vistas.  University of Groningen, University Medical Center Groningen. This method can help answer key questions in the aging and cancer field such as how to perform common techniques to induce cellular senescence and how to evaluate the senescence phenotype. The main advantages of this technique are that it is easy to follow, highly reproducible, does not require any special or expensive equipment, and it results in the induction of senescence in at least 50%of the cellular population. Demonstrating this procedure will be Alejandra Hernandez-Segura, a graduate ...