Lipofuscin: detection and quantification by microscopic techniques.

Since lipofuscin, the so-called "aging pigment", turned out to play a fundamental role in the aging process, particularly in the postmitotic senescence of muscle or neuronal cells, it became a focus of aging and stress research. During normal aging, lipofuscin accumulates in a nearly linear way, whereas its rate of formation can increase in the final stages of senescence or in the progress of several pathologic processes. Thus, both in senescence and pathologic processes, lipofuscin can be used as a detectable "marker" to estimate the remaining lifetime of single cells, the amount of long-term oxidative stress cells were subjected to or to quantify and qualify a pathologic progress in vivo or in vitro. To enable this, a quick and easy applicable method of detection and quantification of lipofuscin has to be used, as is provided by fluorescence microscopy determining the autofluorescence via of the "aging pigment". In this review, we take a look at different methods of detection and quantification of lipofuscin in single cells by using its physical or chemical features.