Science AMA Series: I'm Thomas Hartung, a Professor at Johns Hopkins. I make mini-brains in order to study chemical toxicity & developed a computer model that maps similarities between chemicals to predict toxicity. All of this aims at shifting the field of toxicology away from animal testing. AMA!

Abstract

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Are the mini-brains you speak of organoids? If so, how accurate are they in mimicking the structure and function of a full sized brain?

Je11yDonut

Organoids is one of the words we use to describe the new technologies of cell culture, which come closer to mimicking a tissue or even an organ. This means 3D assemblies, coculture of different cell types, organ architecture and some functionalities. Often they are even perfused by liquid like an organ is with blood. Few models combine all of these aspects but there is progress on all aspects. Now there are even multi-organ-on-chip models - some projects we are currently involved with.


How are you able to account for the complex interaction between neurotransmitters, neuropeptides and hormones that are present in a full-sized human brain? Are intrinsic protective mechanisms mimicked in the mini-brains?

luckycommander

The minibrain represents at least five different types of neurons and two "helper" cells (glia). It does not represent any specific region, thus only basi functionalities can be tested. However, there are colleagues like professor Song her in Hopkins,. who also developed such region-specific models.


Could these "mini brains" be used to mimic certain neural structures, potentially for the study of neurotransmitters and neurtropic substances, with the goal of better understand in these regions, and how the brain comes together as a whole?

Edit: my Japanese is coming out, ending questions with periods and such...

jddbeyondthesky

Our model less so - we try for a very small, simple model, which can be mass-produced at low cost. This is what is needed for testing of drug candidates or substances, which damage the brain. Such specific models are emerging (see above answer).


Do the computers get sad?

AndThisIsMyPawnShop

The good thing about computers is they don't - they also do not have hangovers... always prepared to serve us, for example with predictions of toxicity. ;-)


How is encephalopathy due to toxicity generally diagnosed today? What means do we have to identify causes if we can't have a brain-in-a-jar scenario?

__andrei__

This is actually quite a problem. Typically toxicologists treat rats and then run a number of tests, whether they function well (swimming, getting out of a labyrinth etc.). For neurodevelopment, they would treat the pregnant mother animal and then test the offspring. All this is incredibly laborious: for developmental neurotoxicity for example it uses per chemical 1,400 animals and costs $1,4 million. And then we know whether it harms rats...


Hi Dr. Hartung, I will be attending JHU next year, and I was wondering what is your favorite aspect of JHU?

tomatoeseeds

The collaborative work environment. You have one of the foremost experts for everything around the corner here and I have never been turned down for help or collaboration.


How receptive have the regulatory bodies been to this? As I understand it the regulations require substantial animal testing, companies would rather use newer, better models.

nate

Both industry and regulators know that testing for brain effects (drug treatments as well as damaging side effects), animal studies are far from perfect. Until recently, we simply had not good access to human barin materials in good quantities. The stem cell technology we use, was developed only in 2006! This gives now rise to a new generation of models for all organs.


My 8-year old has a concussion; could this technology be used to better understand brain injuries?

meganlatshaw

Yes, we have a collaboration with the army, where brain trauma and interventions are addressed.


Organoid cultures are to my understanding at this point in time not robust/reproducible and composed of heterogeneous cell populations. Anything from cell passage number to cell line to specific time points can affect this. What efforts are being made to streamline these processes and how do you account for this variance in your screens?

e_swartz

You are right in general. I started actually twenty years ago the Good Cell Culture Practice movement. We just reactivated this for stem cells and organoid models. This was actually the big news about our model, that we can produce thousands of identical ones every week. Then, we also developed ways to freeze them. That is perfect: every time you test, you can go to the fridge and test on the exact same material.


Hi Thomas,

What computer models have you used? It would be also nice if you could share some insights on chemical similarities for toxicity. Did you notice a certain class of chemicals (unknown before) that had a higher change of toxicity prediction?

denzil_correa

Similar chemical structures have similar properties. The problem so far was that very few toxicity data were publicly available, even less in a computer-readable format. Now we enter the area of big data - we created last year the largest one in the world: 10,000 chemicals with 800,000 associated studies by making the one of the European Chemical Agency machine-readable. We had to train the computer to read (natural language processing). In a collaboration with Underwriters Laboratories (UL) we now strongly expanded the database and can make predictions in many cases of similar quality as running the animal study. If this stands the ongoing validation, this can dramatically reduce time and costs. The technologies used are from artificial intelligence - it is like what a webbrowser does - you find from billions of imperfect pages still the relevant piece among the first few hits.


Explain what we know about toxins molds effects on the brain. And any other chemicals that can cause toxic encephalopathy. Thanks ! Also... How does one make a mi I brain?

Blue_Blazes

There is many ways to damage a brain - this is why you need to represent in the model a lot of the possible targets and very sensitive functions, which can be disturbed. Our model has all the major brain cell types (except the immune cells - but working on this) and we can do a type of EEG. By putting them on micro-electrode arrays, we can monitor their electrical communication, which is very sensitive to any perturbation.

How to make one - we just published (online available at www.altex.ch, Pamies et al.). We use human skin cells, which were reprogrammed to become stem cells. We keep frozen stocks. By a three-month protocol using special shakers and growth factors, thousands of these cell balls are produced. The important thing: they look all the same, from week to week. This allows to test.

Recently, we also developed a method of freezing the mini-brains. That is a big step: we can stockpile them and send them to where they are needed.


Hi Dr. Hartung!

A lot of research has been done on the link between an increased inflammatory status of the CNS and development of depression (e.g. Schedlowski et al); but do you believe there is a connection between increases in certain toxin-/toxic substance families and the increasing incidence of depression in the industrialized countries?

I.e. are there chemicals present today, to a larger degree, than say 20 yrs ago, which can be linked to increased CNS inflammatory status leading to depression?

Thank you for your reply!

EDIT: Added example of reference in first paragraph EDIT2: grammatical corrections

pyotrsolacha

I believe that almost all diseases have genetic and environmental components. Environmental can include chemicals, though we sometimes see that the fear of chemicals is out of proportion. We have tripled life expectancy while introducing all these chemicals. However, we need to find the ones, which create problems. Here all interests meet: nobody wants to poison their customers. The problem is that the current animal test are too slow and too expensive - and often not relevant for humans. This is why less than 10% of chemicals on the US market have safety data, only 3% have been intensely tested. This has to change!


"Shifting the field of toxicology away from animal testing" could be interpreted quite broadly. Anywhere from reducing to completely replacing it.

Do you have any personal beliefs that might bias the research you conduct towards a specific outcome and how do you attempt to moderate for this?

For example, you may be a vegan peta member for all I know, but the best work you do may only result on an alternative that can reduce the need for animal testing without eliminating it. You may have a personal belief that any animal testing at all is unacceptable even at the cost of quality of test results, and this could skew you to exaggerate the level of replaceability your techniques provide.

My personal bias would be it is desirable to reduce animal testing as much as possible but without sacrificing any accuracy of result certainty overall in the whole testing process for example, and I would accept a moderate cost increase to do this.

So my question is what personal beliefs about the morality of animal testing do you have, and how do you effectively keep that out of the data, and conclusions you draw?

Also on a bit of a tangent but still related slant:

We have seen significant evidence that some science is not being done in a sufficiently rigorous way recently (such as the psychology reproducibility crisis) and with the publish or perish environment that science currently is politically stuck with in many areas, how do you balance your career progression/preservation desires, with your impartiality and your ethical stance on your research as a whole?

ZeroRyuk

I love animals but I have also done my share of animal experiments on mice and rats in the past - as a pharmacologist in infectious disease unavoidable. But I needed a big glass of whisky in the evening after each of them and in retrospect some I would not have done some of them. It took me a while to learn about their limitations.

I work towards replacing animal experiments where we have something better, and actually technologies are developing so fast. Most of the animal tests in my field (safety sciences) have been developed when I was not yet born or in kindergarden. I am now 53 - this is the only field of science where use such old methods.

I am very sympathetic with some of the animal welfare organizations, have many friends there, but I was never a member. As a scientist, I work for the best of patients and consumers, but I want that we do not neglect the animals.


"Shifting the field of toxicology away from animal testing" could be interpreted quite broadly. Anywhere from reducing to completely replacing it.

Do you have any personal beliefs that might bias the research you conduct towards a specific outcome and how do you attempt to moderate for this?

For example, you may be a vegan peta member for all I know, but the best work you do may only result on an alternative that can reduce the need for animal testing without eliminating it. You may have a personal belief that any animal testing at all is unacceptable even at the cost of quality of test results, and this could skew you to exaggerate the level of replaceability your techniques provide.

My personal bias would be it is desirable to reduce animal testing as much as possible but without sacrificing any accuracy of result certainty overall in the whole testing process for example, and I would accept a moderate cost increase to do this.

So my question is what personal beliefs about the morality of animal testing do you have, and how do you effectively keep that out of the data, and conclusions you draw?

Also on a bit of a tangent but still related slant:

We have seen significant evidence that some science is not being done in a sufficiently rigorous way recently (such as the psychology reproducibility crisis) and with the publish or perish environment that science currently is politically stuck with in many areas, how do you balance your career progression/preservation desires, with your impartiality and your ethical stance on your research as a whole?

ZeroRyuk

Let me add my stance on science as a whole. I am very much concerned about quality of science and reproducibility. I mean, science works as a whole but the low quality of many pieces of the puzzle make progress often slower than possible. I have bee responsible for the European Commission's validation body for alternative methods and now I have a chair for evidence-based toxicology at Hopkins. I also pushing for quality guidance etc.. This is all to make science better and change, among others to more humane methods, faster.


Explain to me how this would ever completely eliminate animal testing. I don't buy that it could.

Hltchens

We would not claim that. You cannot study behavior in cell culture for example. And like we need to test drugs for humans in humans, veterinary drugs will have to be tested in animals. But we can do with much less. The problem is that the value of animal tests is often overestimated and people are not always aware that you can do different.


Could these mini brains realistically feed a small horde of zombies?

FuckerMan011

Zombie-flies perhaps, given the size...


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I agree that sugar is often more a problem than for example fat. Whether our model can help, I do not see yet, but it has been so versatile so far - perhaps somebody has an idea to run the experiment.


NMDA plays a role in excitotoxicity. Alzheimer's resembles TBIs. Have you tried using a glutamate reuptake inhibitor to treat Alzheimer's?

Justeserm

My group is working on a few diseases (autism, Parkinson, a few viral infections, cancer) and by providing mini-brains to others, we enable research on malaria, trauma, MS, ALS etc. Some pharma companies started to evaluate them too. Excitotoxicity will be a key thing to check. At this moment we try to add the immune cells (micro-glia) involved in this. The model is still so new... stay tuned.


Is this part of The Brain Initiative that was started by Obama?

meganlatshaw

No, though funding came from NIH. We would hope that our work fits at some point this or similar funding programs. With the biotech Organome we created, we want to supply them for anybody interested, including research in the program.


What kind of chemicals do you test? Pharmacy, chemicals in food, drugs? And also, if you come to the conclusion that the chemical isn't toxic for the mini brains, how accurate is it that it won't be toxic for a real human?

LderG

We are not mass-testing substances. We typically test substances, for which we know quite well that they are bad or good for humans to see how our model behaves and why. This builds the confidence for testing unknown ones. For example we are interested in flame retardants.


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We keep the organoids mini (one third of a mm, one sixteenth of an inch, i.e. just visible): if they get larger, the cells in the center do not get enough oxygen and nutrients and die as we have no blood system and heart. We also can produce cheap and fast, and only small amounts of test substance are needed.


I see that the brain models you use are quite small - potentially smaller than the eye can see. How do you separate the interaction of diffusion effects of potentially toxic compounds from those that are actually 'transmitted' around the brains?

Evictus

They are just visible, which is nice: you can take them with a pipette and move them into any experimental set-up. Typically, we give substances in the media they are swimming in. We can show with dyes that they reach the inner center of the mini-brain, but this is another reason, why we cannot make them very much bigger.


Hello!

I currently work in an animal research lab (primates/pharmaceuticals). Are you currently involved at all with the animal testing at John Hopkins? What does the FDA think about your ideas? Will you still have to compare them in animal models to see if the chemicals react the same?

Thank you for trying to find alternatives! But no thank you for taking my job.

EveryUNIsTaken

We work very closely with FDA, they are on our advisory board, we do joint conferences. The FDA has had strong impact in promoting these technologies and increasingly build capacities. Direct comparisons is what is needed now. The problem is, we need to be better than the animal, because they are particularly flawed in case of the barin. But how to show that you are better, as we have not enough human data...


I think it's safe to say that the brain is by far the most complicated organ in our entire body. With that in mind, do you believe that if you are able to create a brain model to predict toxicology that it would be theoretically possible to eventually create a systematic structure of the entire human body in which you could predict sickness, diseases, ect?

-If so, how do you believe this would affect the way we study disease differently from traditional animal models and clinical trials?

seth10miller

We are actually part of programs developing multi-organ "human-on-chip" models, combing a number of organ models like our mini-brain. This is far from routine and far from perfect, but so much better than a single cell type under very artificial conditions. With both industry and agencies getting more and more excited, there is a gold rush in bioengineering right now.


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