FLOW CYTOMETRIC ANALYSIS OF HUMAN EPIDERM AL-CELL AGING USING 2 FLUORESCENT MITOCHONDRIAL PROBES

Cardiolipin, mitochondrial transmembrane potential, cell refringence a nd cell diameter were examined in epidermal cells obtained from 42 wom en between 9- to 75-year-old. The study was carried out in situ by flo w cytometry on cells having incorporated either Nonyl Acridine Orange or Rhodamine 123, 2 mitochondria-specific dyes. Cardiolipin levels det ermined by the binding of the cardiolipin-specific probe Nonyl Acridin e Orange, decreased significantly with age, especially in young indivi duals. This suggests 2 stages in the age-dependent transformation of m itochondria (organelle number and/or size): one during childhood devel opment and to adulthood (9 to 27 years) in which cardiolipin levels de crease dramatically (slope: -3.742; p = 0.0243) and the other correspo nding to senescence (35 to 75 years) in which this decrease is less pr ononced (slope: -0.618; p = 0.0467). These changes have no effect on m itochondrial potential, measured by Rhodamine 123 incorporation, which remained constant with age. This function, controlling calcium partit ioning within the cell, might allow Keratinocytes to differentiate and maintain the skin barrier function of the epidermis. Like cardiolipin , intrinsic parameters such as cell size and refringence also signific antly decreased in epidermal cells from elderly subjects. The methodol ogy can be used to determine physiological ageing in various cell type s and to analyse human ageing and related parameters.