OBJECTIVETo explore the optimal methods for labeling human adipose-derived stem cells (ASCs).

METHODSASCs were isolated by collagenase digestion and density gradient centrifugation, and their cell surface markers and ability to differentiate into the adipogenic, chondrogenic, and osteogenic lineages were examined in vitro. Three different cell labeling methods, namely 5 µl DiI, 10 µg/ml BrdU and 50 MOI adenovirus carrying GFP, were used for ASC labeling, and the labeling efficiency were compared at different time points and in different passages using fluorescent microscope.

RESULTSThe isolated ASCs were capable of differentiating into adipogenic, osteogenic, chondrogenic lineages with positive stem cell marker expression. At 48 h after DiI staining, 100% of the ASCs emitted red fluorescence in the cytoplasm with fluorescent-negative nuclei, but the fluorescence intensity declined quickly after cell passaging. With 10 µg/ml BrdU, 90% of the cells showed green fluorescence in the cell nuclei at 48 h after the labeling, but the positivity rate also decreased gradually after cell passaging. Cell labeling with GFP adenovirus showed more stable labeling efficiency, and green fluorescence was detected at 24 h after labeling, and even till 5 days later more than 90% of the ASCs remained positive without an obvious attenuation of the fluorescent intensity even after cell passaging.

CONCLUSIONAll the 3 techniques are applicable for labeling ASCs. Cell labeling with DiI and BrdU can be convenient and economic and well serve the purpose of short-term labeling. Adenovirus carrying GFP gene is the optimal choice for long-term ASC tracing.