Lipid droplet changes in proliferating and quiescent 3T3 fibroblasts |
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Authors: | Giacomo Diaz Barbara Batetta Francesca Sanna Sabrina Uda Camilla Reali Fabrizio Angius Marta Melis Angela Maria Falchi |
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Institution: | (1) Department of Cytomorphology, University of Cagliari, Cittadella Universitaria Monserrato, 09042 Monserrato (CA), Italy;(2) Department of Biomedical Sciences and Biotechnology, University of Cagliari, Cittadella Universitaria Monserrato, 09042 Monserrato (CA), Italy |
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Abstract: | Lipid droplets (LDs) are fat-storing organelles present in virtually all eukaryotic cells and involved in many aspects of
cell biology related to lipid metabolism and cholesterol homeostasis. In this study, we investigated the presence of LDs in
proliferating and quiescent (contact-inhibited) 3T3 fibroblasts to verify a correlation with cell growth. LDs were characterized
by Nile red staining, positivity to adipophilin and negativity to perilipin. LDs were numerous in proliferating cells, but
very few in quiescent cells. However, the fraction of quiescent cells, which resumed proliferation after scratch-wound assay,
also resumed the formation of LDs. In proliferating cells, the number of LDs correlated with the DNA content, suggesting a
continuous accumulation of LDs during cell growth. These findings were supported by biochemical data showing much higher rates
of cholesterol esterification and triglyceride synthesis in proliferating cells. Both filipin staining and the fluorescent
cholesterol analog dehydroergosterol revealed the presence of an intense traffic of free cholesterol, mediated by acidic vesicles,
in proliferating cells. Nile red ratiometric measurements revealed a different lipid composition of LDs in proliferating and
quiescent cells. Changes in the number and composition of LDs were also found in growing cells treated with inhibitors of
cholesterol esterification (Sandoz 58-035), endosomal cholesterol efflux (U18666A) and V-ATPase (bafilomycin-A1). |
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Keywords: | Cell growth Lipid droplets Cholesterol DHE 3T3 fibroblasts |
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