In this module, you will learn about read-across.

What is read-across?

Imagine the following scenario: you're a group leader at Dow,

the major chemical company,

and you produced a new chemical you want to bring to the market.

There is zero information on its toxicity,

so all toxicity tests should be run to get this chemical accepted by the EPA.

It will take a lot of time and cost

a lot of money to run all these tests regulators require.

In addition, you are under time pressure by TSCA,

newly-passed update of Toxic Substances Control Act.

So what can you do at first?

Yes, you can run read-aross.

Read-across will allow you to place your new chemical in a chemical universe,

and predict its toxicity based on its nearest neighbors.

Basically, based on chemical structure and properties,

you can see where the chemical is located in the chemical universe.

Chemical universe is filled with toxicity information for thousands of chemicals,

and you can see whether your new chemical smells like a problem.

For example, if your chemical's nearest neighbors are

skin synthesizers producing allergic reactions,

there is a high chance your chemical will be skin synthesizer, too.

This first computational screen will allow you to probe

prototypes and see what tests to conduct first.

This will drastically reduce Dow's time and dollars spent.

Dr. Harton will explain in the lesson newly-developed

tools which allow you to perform read-across basically with one click.

The lesson on organotypic cultures given by Dr. Holbeck will guide you through

the existing cell culture-based models for in-vitro toxicity testing,

highlighting the advantages and disadvantages.

You might know this children's book series,

Flat Stanley by Jeff Brown.

Flat Stanley's two-dimensional guy walking around.

So Flat Stanley is unique,

and we humans are rather three-dimensional.

The traditional cell culture models, however,

are like Flat Stanley, two-dimensional.

The cells seated on culture dishes in monolayers is a pan fried eggs.

They are quite bored with limited cell-to-cell interactions,

and they cannot recapitulate the physiology of two-dimensional organism.

So, current trends in toxicology and modern biology is

the development of

3-D human-relevant organotypic cultures and macrophysiological systems,

so-called organ on a chip,

to better recapitulate human physiology on a dish.

Welcome to Module 4