Lipid accumulation is largely investigated
due to its role in many human diseases.
The attention is mainly focused on the lipid
droplets (LDs), spherical cytoplasmic
organelles which are devoted to the storage
of the lipids. The amount of lipid content is
often evaluated by measuring LDs size
and/or the integrated optical density (IOD) in
cultured cells. Both evaluations are directly
associated to the lipid content and therefore
they are correlated to each other, but a lack of
theoretical relationship between size and
IOD was observed in literature. Here we
investigated the size-IOD relationship of
LDs observed in microscopical images of
cultured cells. The experimental data were
obtained from immature and differentiated
3T3-L1 murine cells, which have been
extensively used in studies on adipogenesis.
A simple model based on the spherical shape
of the LDs and the Lambert-Beer law, which
describes the light absorption by an optical
thick material, leads to a mathematical relationship.
Despite only light rays’ absorption
was considered in the model, neglecting their
scattering, a very good agreement between
the theoretical curve and the experimental
data was found. Moreover, a computational
simulation corroborates the model indicating
the validity of the mathematically theoretical
relationship between size and IOD. The theoretical
model could be used to calculate the
absorption coefficient in the LDs population
and it could be applied to seek for morphologically
and functionally LDs subpopulations.
The identification of LDs dynamic by
measuring size and IOD could be related to
different pathophysiological conditions and
useful for understand cellular lipid-associated
diseases.
