ImageJ-based semiautomatic method to analyze senescence in cell culture

β-Galactosidase accumulates in the lysosomes of senescent cells of certain tissues. Cell staining with X-gal is a common procedure to detect senescent cells in culture. However, the organelle nature of the staining makes automatic count impossible, requiring time-consuming manual counting or expensive alternative techniques such as flow cytometry to effectively determine the amount of stained cells. Here we present an analysis strategy for images of X-gal stained cells which can be implemented into a macro for the ImageJ software overcoming some of the drawbacks of computational analysis of organelle staining.