Mitochondrial function in fibroblasts with aging in culture and/or Alzheimer's disease

Abstract 

Mitochondrial membrane potentials (MMP) reflect the functional state of the mitochondria within cells. Our recently published method provides a quantitative estimate of the MMP of populations of mitochondrial-like particles (MLP) within living cells at 37°C using the combination of conventional fluorescence microscopy, 3D-deconvolution and exhaustive photon reassignment (EPR). Although the method does not provide an absolute measure of MMP, these relative MMP allow direct comparison between various mitochondria in cells at various ages in culture and in different cell lines from multiple patients. Fibroblasts lines from four Alzheimer's disease (AD) patients bearing the presenilin-1 (PS-1) mutation and four appropriate controls were evaluated at different ages in culture. The results showed a large variation in the relative MMP, cell size and sum of relative MMP of all MLP within each cell or within each cell line. Nevertheless, combining the values of relative MMP for the cell lines in each group revealed changes in distribution with age in culture. The relative MMP decreased while the cell sizes and sum of relative MMP within each cell increased with age in fibroblasts. Values did not differ between controls and the AD patients bearing PS-1 mutation at any age in cultures. This new, sensitive and quantitative estimate of relative MMP indicates that under non-stressed conditions relative MMP change with aging in culture, but relative MMP do not differ between controls and AD subjects.

Abbreviations: BSS, balanced salt solution, CPDL, cumulative population doubling level, DIC, differential interference contrast, DMEM, Dulbecco's modified Eagle's medium, ER, endoplasmic reticulum, EPR, exhaustive photon reassignment, MLP, mitochondrial-like particles, MMP, mitochondrial membrane potential, PBS, phosphate-buffered saline, PS1, presenilin-1, PSF, point spread function, TMRM, tetramethylrhodamine methyl ester

Keywords: Mitochondria, Membrane potential, Alzheimer's disease, Aging, Fibroblasts, Tetramethylrhodamine methyl ester