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Idiopathic canine chronic hepatitis has recognised breed-related differences in predisposition and prognosis, but reasons behind this are poorly understood. This retrospective study using archived post mortem tissue aimed to provide insight into liver ageing in 51 microscopically normal canine livers across seven breed categories, including those with and without increased risk of chronic hepatitis. Immunohistochemistry was conducted for \u03b3H2AX, p21, and cell proliferation marker Ki67, and the mean number of positive hepatocytes per high power field was determined. All three markers were strongly correlated to each other, but no age-dependent expression was seen in the combined study population. Overall expression levels were low in most dogs, with median values representing less than 1.5% of hepatocytes, but this increased to 20\u201330% in individual dogs at the upper end of the range. Individual breed differences were noted in two breeds that have increased risk of chronic hepatitis, with English Springer Spaniels having lower expression of Ki67 than other dogs, and Labradors having higher expression of Ki67 and \u03b3H2AX than other dogs. These results warrant further investigation in these breeds and highlight a need to validate reliable markers of cellular senescence in dogs.<\/jats:p>","DOI":"10.1007\/s11259-020-09784-x","type":"journal-article","created":{"date-parts":[[2020,12,10]],"date-time":"2020-12-10T11:03:40Z","timestamp":1607598220000},"page":"21-30","update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":8,"title":["Breed-related expression patterns of Ki67, \u03b3H2AX, and p21 during ageing in the canine liver"],"prefix":"10.1007","volume":"45","author":[{"given":"Laura J. 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All dogs were submitted to the diagnostic veterinary anatomic pathology service of the Department of Veterinary Medicine, University of Cambridge. Full owner consent was obtained for subsequent use of tissue for research purposes, and institutional ethical approval was awarded by the Departmental Ethics and Welfare Committee (reference: CR223) on 14\/12\/2018.","order":1,"name":"Ethics","group":{"name":"EthicsHeading","label":"Compliance with ethical standards"}},{"value":"The authors declare that they have no conflict of interest.\u00a0","order":2,"name":"Ethics","group":{"name":"EthicsHeading","label":"Conflicts of interest"}},{"value":"Not applicable.\u00a0","order":3,"name":"Ethics","group":{"name":"EthicsHeading","label":"Consent to participate"}},{"value":"All authors give consent for publication.","order":4,"name":"Ethics","group":{"name":"EthicsHeading","label":"Consent for publication"}},{"value":"\u00a0Not applicable.","order":5,"name":"Ethics","group":{"name":"EthicsHeading","label":"Code availability"}}]}}