Coenzyme Q₁₀ (CoQ₁₀), also known as ubiquinone-10, is an important molecule of the mitochondrial respiratory chain that acts as an electron carrier between complexes I, II, and III and additionally functions as an antioxidant. Due to its bioenergetic properties, CoQ₁₀ is of high interest for therapeutic and cosmetic use. This study aims to characterize the metabolic impact of CoQ₁₀ on primary human dermal fibroblasts (HDF) using fluorescence lifetime imaging microscopy (FLIM) and electron microscopy.

FLIM of nicotinamide adenine dinucleotide (NADH) is a robust method to characterize cellular energy metabolism that also provides spatial information. Electron microscopy offers a way to characterize the ultrastructure of mitochondria and reveal features not visible in FLIM.

We reported a shift towards longer lifetimes of NADH in primary fibroblasts from ten different donors upon treatment with CoQ₁₀, which indicates the stimulation of oxidative phosphorylation. This is confirmed by phasor-based metabolic pattern segmentation, which showed localization of longer NADH lifetimes in CoQ₁₀-treated cells, indicating activated mitochondria in the cytoplasm. In addition, a complementary investigation of the mitochondrial ultrastructure using transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) tomography showed a reduction in stress granules in CoQ₁₀-treated cells.

Together, FLIM and electron microscopy (EM) imaging strongly imply that CoQ₁₀ stimulates cellular energy metabolism.