AbstractNestin is a unique intermediate filament expressed for a short period in the developing heart. It was also documented in several cell types of the adult myocardium under pathological conditions such as myocardial infarction or fibrosis. However, circumstances of nestin re-occurrence in the diseased or aging heart have not been elucidated yet. In this work we immunohistochemically detected nestin to determine its expression and distribution pattern in the left ventricular myocardium of normotensive Wistar Kyoto (WKY) rats and in the hypertrophic ones of spontaneously hypertensive (SHR) rats, both at the age of 1 and 1.5 year. No nestin⁺ cells were identified in the intact myocardium of 1-year-old WKY rats, whereas in the aged 1.5-year-old WKY rats nestin⁺ endothelial cells in some blood vessels were discovered. In the hypertrophic myocardium of all SHR rats, nestin was rarely detected in desmin⁺ vimentin⁻ cardiomyocytes and in some vimentin⁺ interstitial cells often accumulated in clusters, varying in intensity of desmin immunoreactivity. Moreover, nestin was infrequently expressed in the endothelial cells of some myocardial blood vessels in 1-year-old SHR rats, but not in 1.5-year-old ones. Quantitative image analysis of nestin expression in the myocardium confirmed significant increase in 1.5-year-old WKY rats and in SHR rats of both ages compared to the intact 1-year-old WKY rats. This study firstly documents nestin re-expression indicating cytoskeletal remodelling in different cell types of the aging intact and chronically pressure over-loaded hypertrophied myocardium. Our findings confirm nestin involvement in complex changes during myocardial hypertrophy and progressive aging.