{"id":15,"slug":"cell-viability","name":"Cell Viability","alternate_names":["세포 생존율"],"aliases":[],"locale":"en","available_locales":["en"],"localized":false,"type":"concept","description":"Cell viability is the proportion of living, functional cells in a sample; it is a key quality measure for cell preparations such as SVF before and after processing or freezing.","overview":"Cell viability is the number or proportion of living cells in a sample. It is usually reported as percent viable cells or as viable cells per unit volume. Because 'viable' is defined by what a test measures (an intact membrane, or functions such as metabolism or proliferation), results depend on the assay used. Dye-exclusion methods, such as trypan blue or fluorescent dyes read by automated counters, check whether the cell membrane is intact. Plate-based assays measure tetrazolium or resazurin reduction, protease activity or ATP. Viability is used in cytotoxicity testing, cell culture, cryopreservation research and as a release criterion for cell therapy products, where clinical trials have commonly used thresholds of 70–80%. ISO 20391 covers cell counting methods. Readers should check which assay, instrument and definition a reported figure is based on.","official_url":null,"image_url":null,"country":null,"region":null,"wikidata_id":null,"wikipedia_url":null,"verified":false,"scores":{"authority":55,"trust":0,"citation":0},"topic":{"slug":"svf","name":"SVF & Adipose-derived Cells"},"url":"https://worldwiki.io/entity/cell-viability","facts":[{"id":202,"predicate":"definition","label":"Definition of a viable cell","value":"A cell with an intact membrane or the capacity for metabolism, motility, proliferation or response to stimuli","unit":null,"confidence":80,"valid_from":"2022-01-19","valid_until":null,"verified_at":"2026-09-18 06:55:37","source_ids":[251]},{"id":203,"predicate":"measurement_principle","label":"Dye-exclusion principle","value":"Trypan blue enters cells with damaged membranes and stains them blue; unstained cells are counted as viable","unit":null,"confidence":80,"valid_from":"2022-01-19","valid_until":null,"verified_at":"2026-09-18 06:55:37","source_ids":[251]},{"id":204,"predicate":"assay_types","label":"Common plate-reader assay classes","value":"Tetrazolium reduction (MTT, MTS, XTT, WST-1), resazurin reduction, protease substrate (GF-AFC), ATP luciferase and real-time luminescent assays","unit":null,"confidence":80,"valid_from":"2016-07-01","valid_until":null,"verified_at":"2026-09-18 06:55:37","source_ids":[134]},{"id":205,"predicate":"typical_use","label":"Typical research uses","value":"Measuring cell proliferation, testing compounds for cytotoxic effects, and as an internal control for viable cell number in multiplexed assays","unit":null,"confidence":80,"valid_from":"2016-07-01","valid_until":null,"verified_at":"2026-09-18 06:55:37","source_ids":[134]},{"id":206,"predicate":"method_comparison","label":"ATP assay characteristics","value":"Described as the fastest and most sensitive viability assay and less prone to artifacts, but it is an endpoint assay that lyses cells","unit":null,"confidence":80,"valid_from":"2016-07-01","valid_until":null,"verified_at":"2026-09-18 06:55:37","source_ids":[134]},{"id":207,"predicate":"known_limitation","label":"Trypan blue measurement variability","value":"Image-based trypan blue scoring depends on microscope optics, cameras and settings; heat-killed cells took up about 50% more dye than formaldehyde-fixed cells in a NIST study","unit":null,"confidence":80,"valid_from":"2022-01-19","valid_until":null,"verified_at":"2026-09-18 06:55:37","source_ids":[251]},{"id":208,"predicate":"related_standard","label":"Related standard","value":"ISO 20391 (Biotechnology — Cell counting), cited in NIST work on traceable viability measurement","unit":null,"confidence":80,"valid_from":"2022-01-19","valid_until":null,"verified_at":"2026-09-18 06:55:37","source_ids":[251]},{"id":209,"predicate":"release_criterion_car_t","label":"CAR T (CTL019) viability release specification","value":"At least 80% for the commercial product; early clinical trials used at least 70%","unit":"%","confidence":80,"valid_from":"2019-01-01","valid_until":null,"verified_at":"2026-09-18 06:55:37","source_ids":[136]},{"id":210,"predicate":"evidence_level","label":"Viability and clinical outcome (CAR T)","value":"No link was found between product viability below 80% and response, expansion or survival in 123 pediatric ALL and 25 adult DLBCL patients","unit":null,"confidence":80,"valid_from":"2019-01-01","valid_until":null,"verified_at":"2026-09-18 06:55:37","source_ids":[136]},{"id":211,"predicate":"release_criterion_nk","label":"NK cell therapy viability acceptance range","value":"≥70% in all reviewed Phase 1/2 trials; assay protocols were not harmonized across trials","unit":"%","confidence":80,"valid_from":"2025-11-11","valid_until":null,"verified_at":"2026-09-18 06:55:37","source_ids":[137]}],"relations":[{"type":"related_to","confidence":100,"target":{"id":62,"slug":"stem-cell-fat-grafting","name":"Stem Cell Fat Grafting","type":"concept","description":"A consumer and marketing term used for fat grafting that is enriched with cells isolated from adipose tissue. It is not a standardised academic term and does not denote culture-expanded stem cell therapy.","url":"https://worldwiki.io/entity/stem-cell-fat-grafting"}}],"questions":[{"slug":"how-is-cell-viability-percentage-calculated","question":"How is cell viability percentage calculated?","intent":"procedure","language":"en","short_answer":"Viability percentage = viable cells ÷ total cells counted × 100. With dye exclusion, unstained cells count as viable and stained cells as dead. This can be done manually on a hemocytometer or with an automated counter using trypan blue or AO/PI. The viable cell count, as an absolute number or concentration, is usually reported alongside the percentage, because a high percentage can still mean too few cells [2][3].","url":"https://worldwiki.io/q/how-is-cell-viability-percentage-calculated"},{"slug":"what-is-an-acceptable-cell-viability-for-cell-therapy-products","question":"What is an acceptable cell viability for cell therapy products?","intent":"informational","language":"en","short_answer":"For cell therapy products, the FDA generally expects a minimum viability specification above 70%, and sponsors must justify a lower limit with data [2]. NK-cell trials in the US and Europe used ≥70% across the board [4]. Some products use stricter limits. The commercial specification for the CAR T product tisagenlecleucel is at least 80%, although a 2019 analysis found no link between viability below 80% and remission rates [3].","url":"https://worldwiki.io/q/what-is-an-acceptable-cell-viability-for-cell-therapy-products"},{"slug":"trypan-blue-vs-mtt-which-cell-viability-assay-should-i-use","question":"Trypan blue vs MTT: which cell viability assay should I use?","intent":"informational","language":"en","short_answer":"Trypan blue classifies individual cells by membrane integrity and gives a viable count and percentage. That suits cell suspensions and product release. MTT and other tetrazolium assays measure average metabolic activity per well over 1–4 hours. That suits plate-based proliferation or cytotoxicity screening [1]. Trypan blue can overestimate viability compared with AO/PI and struggles with debris [2]. Metabolic assays can be skewed by reducing or fluorescent compounds [1].","url":"https://worldwiki.io/q/trypan-blue-vs-mtt-which-cell-viability-assay-should-i-use"},{"slug":"why-does-cell-viability-drop-after-thawing-cryopreserved-cells","question":"Why does cell viability drop after thawing cryopreserved cells?","intent":"informational","language":"en","short_answer":"Freezing and thawing damage cells, and part of the cell death is delayed. In a 2020 study of bone marrow mesenchymal stromal cells, viability fell most at 2–4 hours after thawing and recovered to 93.1–97.6% by 24 hours. Metabolic activity and adhesion were still impaired at that point [8]. Viability measured right after thawing can therefore miss later cell loss and does not show function.","url":"https://worldwiki.io/q/why-does-cell-viability-drop-after-thawing-cryopreserved-cells"},{"slug":"does-higher-cell-viability-mean-better-fat-graft-survival","question":"Does higher cell viability mean better fat graft survival?","intent":"informational","language":"en","short_answer":"Not necessarily. Adipocyte or SVF viability is a laboratory measure taken before grafting, and results depend strongly on the assay. For example, trypan blue can count dead adipocytes as live [7]. Studies use viability to compare harvesting and processing methods; one study reported median adipocyte viability of 73–85% depending on the liposuction technique [7]. Graft retention in the patient is a separate clinical outcome that depends on many other factors.","url":"https://worldwiki.io/q/does-higher-cell-viability-mean-better-fat-graft-survival"}],"sources":[{"id":251,"title":"Quantitative, traceable determination of cell viability using absorbance microscopy","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC8769294/","publisher":"PLoS One","type":"journal","publication_date":"2022-01-19","accessed_at":"2026-11-10 18:01:21"},{"id":134,"title":"Cell Viability Assays (Assay Guidance Manual)","url":"https://www.ncbi.nlm.nih.gov/books/NBK144065/","publisher":"National Center for Biotechnology Information (NCBI Bookshelf), Riss TL et al.","type":"journal","publication_date":"2013-05-01","accessed_at":"2026-11-09 18:01:08"},{"id":136,"title":"CAR T cell viability release testing and clinical outcomes: is there a lower limit?","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC6872962/","publisher":"Blood (Chong EA et al.), 134(21):1873–1875","type":"journal","publication_date":"2019-09-25","accessed_at":"2026-11-09 18:01:07"},{"id":137,"title":"Quality standards for NK cell immunotherapies","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC12644036/","publisher":"Frontiers in Bioengineering and Biotechnology (von Werz et al.)","type":"journal","publication_date":null,"accessed_at":"2026-11-09 18:01:06"}],"providers":[],"published_at":"2026-09-14 13:42:07","updated_at":"2026-11-12 05:20:00","verified_at":null}