180 Autism and Exposure to Environmental Chemicals
We have searched for an affordable and realistic technology that would be as
valid as the Ames test that can detect mutagenic and carcinogenic chemicals
with a reasonable degree of certainty [45]. As shown below, we have developed
an assay that can estimate the neuromodifying effects of a chemical(s) that can
damage a developing fetus.
We have evaluated neuroblastoma cells that, in our opinion, represent vari
ous stages of developing fetal brain progenitor neurons and react to various
environmental insults very similar to what one would expect for a fetal brain
exposed to an exogenous chemical. As mentioned previously, we are able to
identify a large array of neuronal progenitor cells that are present in different
NBCs. For example, we carried out single‐cell cloning of two NBCs – one from
each gender – that we screened to determine if each of these cell lines carried
large repertoires of human fetal brain progenitor cells. In the single‐cell clon
ing method, each cell from the cell line was isolated and then allowed to grow
into an individual cell line (Figure 7.1).
By utilizing this single‐cell cloning method, we were able to grow and char
acterize numerous cell lines to determine if each of them represents a unique
type of fetal brain progenitor cell. An example is shown below where three
different single‐cell clones were characterized by immunological markers. In
addition, the cell lines were exposed to retinoic acid to induce differentiation.
As shown in Figure 7.1, each of the cell lines developed by single‐cell cloning
represents a unique progenitor cell with a specific array of immunological
markers and differentiation.
In addition, this in vitro model may also be able to assist us in determining gen
der bias. Just as the Ames test can be used to screen for mutagenic/carcinogenic
agents, we believe that this model can be used to screen for neuromodifying
chemicals. This technology could also be adapted for high throughput screening of
neurotoxic agents. We believe that this is an excellent in vitro model to study fetal
progenitor cells. By utilizing this model, one can test the precise amount of a
chemical by exposing the neuronal cells to even a fentomolar concentration of
putative neurotoxic agent, thereby exposing them to similar amounts of synthetic
or natural chemicals that would be found in a fetus’s amniotic fluid at various
stages of gestation. Our approach is highly appropriate to study gender bias, pre
cise exposure measurement, and reliable timing of exposure in relation to critical
developmental periods. It should also take into account the dynamic interplay
between genes and the environment by using genetic analyses, receptor expression
dynamics, and gene and environmental factor interactions [1–6,18,20] (Figure 7.2).
In addition to neuroblastoma cells having a similar morphology to those in
an ASD brain when exposed to synthetic chemicals, they also appear to exhibit
a similar immunological profile, where oxytocin‐ and arginine vasopressin
(AVP)‐receptor positive neurons are reduced and axons are significantly
affected. Such an outcome was observed in our recent study where all five
male NBCs exposed to fentomolar concentrations of fragrances exhibited