Amniotic membranes (AM) have anti-fibrotic activity. Exosomes (nano-sized vesicles) function as conduits for intercellular transfer and contain all the necessary components to induce the resolution of fibrosis. In this study, we tested the hypothesis that the anti-fibrotic activity of AM is mediated by exosomes. AM-derived exosomes or amniotic stromal cell-derived exosomes were isolated and characterized. Anti-fibrotic activity of exosomes was evaluated using human hepatic stellate cells (LX-2), an in vitro model of fibrosis. Exosomes isolated from AM tissue-conditioned media had an average size of 75 nm. Exosomes significantly inhibited the proliferation of TGFβ1-activated LX-2 but had no effect on the proliferation of non-activated LX-2 cells. Exosomes also reduced the migration of LX-2 in a scratch wound assay. Furthermore, exosomes reduced the gene expression of pro-fibrotic markers such as COL1A1, ACTA, and TGFβ1 in LX-2 cells. Interestingly, exosomes isolated from AM tissue under hypoxic conditions seemed to show a stronger anti-fibrotic activity than exosomes isolated from tissue under normoxic conditions. Exosomes released by in vitro cultured AM stromal cells were smaller in size compared with tissue exosomes and also showed anti-fibrotic activity on LX-2 cells. In conclusion, AM-tissue-released exosomes contribute to the anti-fibrotic activity of AM. This is the first report of isolation, characterization, and functional evaluation of exosomes derived from amniotic tissues with the direct comparison between tissue-derived exosomes and cultured cell-derived exosomes.
Polymeric nanospheres have the ability to encapsulate
drugs and
are therefore widely used in drug delivery applications. Structural
transformations that affect drug release from nanospheres are governed
by the surrounding environment. To understand these effects, we investigated
the adsorption behavior of three types of nanospheres onto model surfaces
using quartz crystal microbalance with dissipation (QCM-D) and by
atomic force microscopy (AFM). Substrates were prepared from polymers
with different degrees of PEGylation (0, 1, and 15%). Nanospheres
were prepared via self-assembly of block copolymers. Tyrosine-derived
nanospheres are A–B–A triblock copolymers with methoxy
poly(ethylene glycol) (PEG) as the A-blocks and an alternating copolymer
of desaminotyrosyl-tyrosine octyl ester and suberic acid oligo(DTO-SA)
as the B-block. On non-PEGylated substrates, these nanospheres assembled
into a close-packed structure; on PEGylated substrates, the adsorbed
nanospheres formed a continuous film, thinner than the size of the
nanospheres suggesting unraveling of the PEG corona and disassembly
of the nanospheres. Also, the adsorption was concentration-dependent,
the final thickness being attained at exponentially longer times at
lower concentrations. Such substrate- and concentration-dependent
behavior was not observed with Pluronic F-127 and PEG-poly(caprolactone)
(PCL) nanospheres. Since the essential difference among the three
nanospheres is the composition of the core, we conclude that the core
influences the adsorption characteristics of the nanospheres as a
consequence of their disassembly upon adsorption. These results are
expected to be useful in designing nanospheres for their efficient
transport across vascular barriers and for delivering drugs to their
targets.
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