70
be released from orthopedic prosthesis, and the organic nano carriers of polylactic
acid are potentially useful for drug transport across the placenta. The iron oxide
nanoparticles, neutral or functionalized with anion, crossed the barrier, but disrupted
the tight junctions and induced apoptosis. Cationic nanoparticles accumulated in
co-coltured cells (Faust et al. 2014; Müller et al. 2018).
In TransWell® B, the cobalt and chrome nanoparticles, at low concentrations,
did not cross or alter the barrier permeability; however, the upper layer of BeWo
cells showed signs of impaired lysosomal function and autophagosomal clearance.
The DNA was damaged, with double- or single-strand breaks and tetraploidy (Parry
et al. 2010; Sood et al. 2011). The nanoparticle-free media collected in the outer
compartment damaged neural cell lineage, which differentiated into an excess of
glial astrocytes and endangered neurons (Hawkins et al. 2018). Some organic
nanoparticles were instead safe, able to cross the barrier from mother to fetus, and
could efficiently carry and release molecules, such as dexamethasone, digoxin, and
antiepileptic drugs. These results open a promising perspective for prenatal care
(Ali et al. 2013; Albekairi et al. 2015; Lopalco et al. 2015).
Ilekis et al. (2016) reviewed the mechanisms of placental permeability to potentially toxic agents, including nanomaterials.
3.5 Embryonic Exposure and Embryotoxicity
Once the nanoparticles have crossed the placenta, whenever possible, they meet the
zygote, the final product of the reproductive process. Therefore, direct toxicity tests
of on in vitro developing whole embryos can give important information on the
protection by the placenta.
Living mammalian embryos for in vitro studies can be obtained in two ways:
from eggs fertilized in vitro, or with the whole embryo culture test. The former
assay can study very early zygote only, during the preimplantation period, while the
latter requires the necessary sacrifice of the mother. This poses ethical questions;
therefore, the studies in vitro with whole mammalian embryos are few and usually
limited to mice and rats. The method, while not properly alternative to in vivo
experiments, nevertheless bridges the gap between in vitro and in vivo studies and
agrees at least with the principles of reduction and refinement.
A valuable alternative test is the zebrafish embryonic test, which meets all the
three main principles of reduction/refinement/replacement concepts. The many
advantages of using this small fish will be discussed in a dedicated section; here, it
is enough to mention that the zebrafish embryonic test has good predictability in
mammals and humans (Ball et al. 2014; He et al. 2014).
Another way to study in vitro the embryonic toxicity is the embryonic stem cells
test. Undifferentiated, pluripotent cells lines are obtained from the inner cell mass
of the 3.5-day mouse blastocyst, or embryos of corresponding age in other species,
such as bovine and humans. Genschow et al. (2004) validated the test for the
European Centre for the Validation of Alternative Methods. They exposed cells to
A. G. Cattaneo
be released from orthopedic prosthesis, and the organic nano carriers of polylactic
acid are potentially useful for drug transport across the placenta. The iron oxide
nanoparticles, neutral or functionalized with anion, crossed the barrier, but disrupted
the tight junctions and induced apoptosis. Cationic nanoparticles accumulated in
co-coltured cells (Faust et al. 2014; Müller et al. 2018).
In TransWell® B, the cobalt and chrome nanoparticles, at low concentrations,
did not cross or alter the barrier permeability; however, the upper layer of BeWo
cells showed signs of impaired lysosomal function and autophagosomal clearance.
The DNA was damaged, with double- or single-strand breaks and tetraploidy (Parry
et al. 2010; Sood et al. 2011). The nanoparticle-free media collected in the outer
compartment damaged neural cell lineage, which differentiated into an excess of
glial astrocytes and endangered neurons (Hawkins et al. 2018). Some organic
nanoparticles were instead safe, able to cross the barrier from mother to fetus, and
could efficiently carry and release molecules, such as dexamethasone, digoxin, and
antiepileptic drugs. These results open a promising perspective for prenatal care
(Ali et al. 2013; Albekairi et al. 2015; Lopalco et al. 2015).
Ilekis et al. (2016) reviewed the mechanisms of placental permeability to potentially toxic agents, including nanomaterials.
3.5 Embryonic Exposure and Embryotoxicity
Once the nanoparticles have crossed the placenta, whenever possible, they meet the
zygote, the final product of the reproductive process. Therefore, direct toxicity tests
of on in vitro developing whole embryos can give important information on the
protection by the placenta.
Living mammalian embryos for in vitro studies can be obtained in two ways:
from eggs fertilized in vitro, or with the whole embryo culture test. The former
assay can study very early zygote only, during the preimplantation period, while the
latter requires the necessary sacrifice of the mother. This poses ethical questions;
therefore, the studies in vitro with whole mammalian embryos are few and usually
limited to mice and rats. The method, while not properly alternative to in vivo
experiments, nevertheless bridges the gap between in vitro and in vivo studies and
agrees at least with the principles of reduction and refinement.
A valuable alternative test is the zebrafish embryonic test, which meets all the
three main principles of reduction/refinement/replacement concepts. The many
advantages of using this small fish will be discussed in a dedicated section; here, it
is enough to mention that the zebrafish embryonic test has good predictability in
mammals and humans (Ball et al. 2014; He et al. 2014).
Another way to study in vitro the embryonic toxicity is the embryonic stem cells
test. Undifferentiated, pluripotent cells lines are obtained from the inner cell mass
of the 3.5-day mouse blastocyst, or embryos of corresponding age in other species,
such as bovine and humans. Genschow et al. (2004) validated the test for the
European Centre for the Validation of Alternative Methods. They exposed cells to
A. G. Cattaneo