The comet assay is widely used in biomonitoring studies for the analysis of DNA damage in leukocytes and peripheral blood mononuclear cells. Rather than processing blood samples directly, it can be desirable to cryopreserve whole blood or isolated cells for later analysis by the comet assay. However, this creates concern about artificial accumulation of DNA damage during cryopreservation. In this study, 10 laboratories used standardized cryopreservation and thawing procedures of monocytic (THP-1) or lymphocytic (TK6) cells. Samples were cryopreserved in small aliquots in 50% foetal bovine serum, 40% cell culture medium, and 10% dimethyl sulphoxide. Subsequently, cryopreserved samples were analysed by the standard comet assay on three occasions over a 3-year period. Levels of DNA strand breaks in THP-1 cells were increased (four laboratories), unaltered (four laboratories), or decreased (two laboratories) by long-term storage. Pooled analysis indicates only a modest positive association between storage time and levels of DNA strand breaks in THP-1 cells (0.37% Tail DNA per year, 95% confidence interval: -0.05, 0.78). In contrast, DNA strand break levels were not increased by cryopreservation in TK6 cells. There was inter-laboratory variation in levels of DNA strand breaks in THP-1 cells (SD = 3.7% Tail DNA) and TK6 reference sample cells (SD = 9.4% Tail DNA), whereas the intra-laboratory residual variation was substantially smaller (i.e. SD = 0.4%-2.2% Tail DNA in laboratories with the smallest and largest variation). In conclusion, the study shows that accumulation of DNA strand breaks in cryopreserved mononuclear blood cell lines is not a matter of concern.

DNA strand break levels in cryopreserved mononuclear blood cell lines measured by the alkaline comet assay: results from the hCOMET ring trial / Møller, Peter; Azqueta, Amaya; Rodriguez-Garraus, Adriana; Bakuradze, Tamara; Richling, Elke; Bankoglu, Ezgi Eyluel; Stopper, Helga; Claudino Bastos, Victoria; Langie, Sabine A S; Jensen, Annie; Ristori, Sara; Scavone, Francesca; Giovannelli, Lisa; Wojewódzka, Maria; Kruszewski, Marcin; Valdiglesias, Vanessa; Laffon, Blanca; Costa, Carla; Costa, Solange; Paulo Teixeira, João; Marino, Mirko; Del Bo, Cristian; Riso, Patrizia; Zheng, Congying; Shaposhnikov, Sergey; Collins, Andrew. - In: MUTAGENESIS. - ISSN 0267-8357. - STAMPA. - 38:(2023), pp. 273-282. [10.1093/mutage/gead019]

DNA strand break levels in cryopreserved mononuclear blood cell lines measured by the alkaline comet assay: results from the hCOMET ring trial

Ristori, Sara;Scavone, Francesca;Giovannelli, Lisa;Riso, Patrizia;
2023

Abstract

The comet assay is widely used in biomonitoring studies for the analysis of DNA damage in leukocytes and peripheral blood mononuclear cells. Rather than processing blood samples directly, it can be desirable to cryopreserve whole blood or isolated cells for later analysis by the comet assay. However, this creates concern about artificial accumulation of DNA damage during cryopreservation. In this study, 10 laboratories used standardized cryopreservation and thawing procedures of monocytic (THP-1) or lymphocytic (TK6) cells. Samples were cryopreserved in small aliquots in 50% foetal bovine serum, 40% cell culture medium, and 10% dimethyl sulphoxide. Subsequently, cryopreserved samples were analysed by the standard comet assay on three occasions over a 3-year period. Levels of DNA strand breaks in THP-1 cells were increased (four laboratories), unaltered (four laboratories), or decreased (two laboratories) by long-term storage. Pooled analysis indicates only a modest positive association between storage time and levels of DNA strand breaks in THP-1 cells (0.37% Tail DNA per year, 95% confidence interval: -0.05, 0.78). In contrast, DNA strand break levels were not increased by cryopreservation in TK6 cells. There was inter-laboratory variation in levels of DNA strand breaks in THP-1 cells (SD = 3.7% Tail DNA) and TK6 reference sample cells (SD = 9.4% Tail DNA), whereas the intra-laboratory residual variation was substantially smaller (i.e. SD = 0.4%-2.2% Tail DNA in laboratories with the smallest and largest variation). In conclusion, the study shows that accumulation of DNA strand breaks in cryopreserved mononuclear blood cell lines is not a matter of concern.
2023
38
273
282
Møller, Peter; Azqueta, Amaya; Rodriguez-Garraus, Adriana; Bakuradze, Tamara; Richling, Elke; Bankoglu, Ezgi Eyluel; Stopper, Helga; Claudino Bastos, Victoria; Langie, Sabine A S; Jensen, Annie; Ristori, Sara; Scavone, Francesca; Giovannelli, Lisa; Wojewódzka, Maria; Kruszewski, Marcin; Valdiglesias, Vanessa; Laffon, Blanca; Costa, Carla; Costa, Solange; Paulo Teixeira, João; Marino, Mirko; Del Bo, Cristian; Riso, Patrizia; Zheng, Congying; Shaposhnikov, Sergey; Collins, Andrew
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Utilizza questo identificatore per citare o creare un link a questa risorsa: https://hdl.handle.net/2158/1335297
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