CAAT's stem cell-derived "mini-brain"/image by Thomas Hartung (used with permission)

Researchers at HTPC partner organization CAAT create stem-cell derived mini-brains

CAAT's stem cell-derived "mini-brain"/image by Thomas Hartung (used with permission)

CAAT’s stem cell-derived “mini-brain”/image by Thomas Hartung (used with permission)


Researchers at Johns Hopkins’ Center for Alternatives to Animal Testing (CAAT) have developed a process to create “mini-brains” derived from stem cells reprogrammed from human skin cells. The resulting structures exhibit a number of cell types and cell functions of the human brain, and can be produced economically and in sufficient numbers to be especially useful for screening chemicals and drug candidates. The mini-brains will also be used to study Alzheimer’s disease, Parkinson’s disease, multiple sclerosis and autism.

From CAAT’s press release:

“[Principal investigator] Hartung and his colleagues created the brains using what are known as induced pluripotent stem cells (iPSCs). These are adult cells that have been genetically reprogrammed to an embryonic stem cell-like state and then are stimulated to grow into brain cells. Cells from the skin of several healthy adults were used to create the mini-brains, but Hartung says that cells from people with certain genetic traits or certain diseases can be used to create brains to study various types of pharmaceuticals. He says the brains can be used to study Alzheimer’s disease, Parkinson’s disease, multiple sclerosis and even autism. Projects to study viral infections, trauma and stroke have been started.

Hartung’s mini-brains are very small—at 350 micrometers in diameter, or about the size of the eye of a housefly, they are just visible to the human eye—and hundreds to thousands of exact copies can be produced in each batch. One hundred of them can grow easily in the same petri dish in the lab. After cultivating the mini-brains for about two months, the brains developed four types of neurons and two types of support cells: astrocytes and oligodendrocytes, the latter of which go on to create myelin, which insulates the neuron’s axons and allows them to communicate faster.

The researchers could watch the myelin developing and could see it begin to sheath the axons. The brains even showed spontaneous electrophysiological activity, which could be recorded with electrodes, similar to an electroencephalogram, also known as EEG. To test them, the researchers placed a mini-brain on an array of electrodes and listened to the spontaneous electrical communication of the neurons as test drugs were added.

“We don’t have the first brain model nor are we claiming to have the best one,” says Hartung, who also directs the School’s Center for Alternatives to Animal Testing.

“But this is the most standardized one. And when testing drugs, it is imperative that the cells being studied are as similar as possible to ensure the most comparable and accurate results.”

Hartung elaborated on this point to Gizmodo: “There are a handful of such models described over the last two years,” he said. “They show more fancy brain structures, but each and every one looks different, often with cells in the middle dying because of lack of oxygen as they have no blood vessels. We produce hundreds of identical mini-brains, every week. This is critical for testing and comparing substances. They have exactly the same size below a critical diameter.”

Learn more in the video embedded here.

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artistic rendering of kidney xray

A high-speed image-based system for predicting kidney toxicity

Scientists from Singapore’s A*STAR Bioinformatics Institute and the Institute of Bioengineering and Nanotechnology have developed a computerized cell imaging system that can predict with up to 90% accuracy whether a chemical will be toxic to human kidney cells. The system is more accurate than animal tests, and faster than existing in vitro methods for predicting kidney toxicity.

To create the system, the investigators screened over 2 million individual cells that had been treated with more than 40 different compounds – including industrial chemicals, agricultural chemicals, and various pharmaceuticals. They took microscopic images of the cells following each exposure and examined the images for signs of structural changes or damage to the cells. Those cells treated with compounds known to cause kidney toxicity showed a pattern of changes the team used to construct a “toxicity profile.” By training their image analysis software to look for these features in other cell images, they developed a highly accurate, high-speed, automated screening system.

Last summer the team announced a stem cell method for producing a reliable supply of human kidney cells for in vitro screening. However, they noted in the current paper that certain steps in the earlier procedure are difficult to automate.  The new image-based screening system can be completely automated, allowing investigators to screen a much larger number of chemicals in a shorter period of time.

Original article: Su et al. (2015) High-Throughput Imaging-Based Nephrotoxicity Prediction for Xenobiotics with Diverse Chemical Structures. [Open access]

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The Year of the Brain (Organoid)

Cultivated neural tissue (photo credit: Michael Schwartz, University of Wisconsin-Madison)

Cultivated neural tissue (photo credit: Michael Schwartz, University of Wisconsin-Madison)

What sounded like science fiction just a couple of decades ago is a rapidly advancing reality today: in 2015, a number of research teams developed and refined stem cell-derived “brain organoids” that are already being used to model neurological diseases and test potential drug treatments.

Miniaturized human brain organoid grown from re-programmed adult skin cells (photo courtesy of Ohio State University)

Miniaturized human brain organoid grown from re-programmed adult skin cells (photo courtesy of Ohio State University)

We blogged about some of these studies in August 2015, and NIH Director Dr. Francis Collins featured brain organoids in a blog column in September. The Wall Street Journal’s science columnist, Shirley Wang, has an informative round-up of stem cell-based neurological disease models in her recent column.

In its year-end “breakthrough” round-up, MIT’s Technology Review magazine names brain organoids as one of the top technology breakthroughs of 2015. As the article explains, “What makes cerebral organoids particularly useful is that their growth mirrors aspects of human brain development. The cells divide, take on the characteristics of, say, the cerebellum, cluster together in layers, and start to look like the discrete three-dimensional structures of a brain. If something goes wrong along the way—which is observable as the organoids grow—scientists can look for potential causes, mechanisms, and even drug treatments.”

In addition to modeling diseases and testing potential treatments, these brain organoids can also be used to more efficiently and affordably assess other chemicals – such as those in pesticides or industrial agents – for neurotoxicity in humans.

3D cell & tissue culture brain organoids stem cells
artistic rendering of kidney xray

A non-animal method for predicting kidney toxicity

Scientists at Singapore’s Institute of Bioengineering and Nanotechnology have created a non-animal drug screening method that uses stem cell-derived human kidney cells to predict the toxicity of drugs and other chemicals. The method improves on the reliability and availability of earlier stem cell models, promises to reduce the costs and time it takes to test and develop new drugs, and could eventually eliminate certain animal tests.

iStock_kidney-larger-cropBecause of their role in filtering blood, the kidneys are especially vulnerable to any toxic effects of drugs and other substances that pass through them, but predicting the renal toxicity of such substances has been difficult. As the authors write in their article in Scientific Reports, “Typically, compound nephrotoxicity is only detected during late stages of drug development, which is associated with high costs for the pharmaceutical industry. Animal models have limited predictivity and the development of renal in vitro models with high predictivity has been challenging.”

Using primary human kidney cells in toxicity tests is difficult, as well, due to high variability between donors, and difficulties keeping the cells fully functional during tests. For these reasons, generating a reliable supply of kidney cells from stem cells is preferable. Previous human kidney cell models (including one published by the authors) were produced from human embryonic stems cells (hESCs), which are difficult to access and which raise ethical concerns. This new method instead uses induced pluripotent stem cells (iPSCs) created from more readily available cells, such as human skin cells. iPSCs are genetically “reprogrammed” to an early developmental state, from which they can be coaxed into other kinds of cells. The team’s method produces usable kidney cells within 8 days – much faster than previous stem cell models, as well.

To learn more about using stem cells in toxicity testing, read the “primer” on AltTox.org.

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Organovo's Novogen 3D bioprinter (photo credit: Organovo)

Reading round-up

A few good links to share…

A UCLA scientist is using tiny worms – C. elegans – in a high-throughput, automated format, to screen chemicals for reproductive toxicity.

Patrick-Allard-Lab-0841_mid_credit-UCLA Fielding SPH

Patrick Allard (photo credit: UCLA Fielding School of Public Health)

“With this approach we can now simultaneously screen hundreds of compounds for their toxicity to the reproductive process, which can help to prioritize the chemicals that need further analysis,” Allard said. “Beyond that, once we find compounds that are repro-toxic, we can look further into the stages of reproduction that are affected, and how they are affected.”

Organovo's Novogen 3D bioprinter (photo credit: Organovo)

Organovo’s Novogen 3D bioprinter (photo credit: Organovo)

Chemistry World has a good overview of the growing skin 3D-bioprinting industry, noting that while the initial push is coming from cosmetics companies, “The expertise gained could feed into pharmaceutical research, and even help enable patients’ own cells to be made into almost perfectly compatible skin grafts and eventually replacement organs.”

And in the NIH Director’s Blog, Francis Collins describes NIH-funded efforts to develop neural tissue chips that predict neurotoxicity:

Cultivated neural tissue (photo credit: Michael Schwartz, University of Wisconsin-Madison

Cultivated neural tissue (photo credit: Michael Schwartz, University of Wisconsin-Madison

Each cultured 3D “organoid”—which sits comfortably in the bottom of a pea-sized well on a standard laboratory plate—comes complete with its very own neurons, support cells, blood vessels, and immune cells! As described in Proceedings of the National Academy of Sciences [2], this new tool is poised to predict earlier, faster, and less expensively which new or untested compounds—be they drug candidates or even ingredients in cosmetics and pesticides—might harm the brain, particularly at the earliest stages of development.

Collins also co-authored a Nature commentary summarizing six important lessons learned from Human Genome Project, on its 25th anniversary: embrace partnerships, maximize data-sharing, plan for data analysis, prioritize technology development, address the societal implications of advances, be audacious yet flexible… Read the details here.

3D bioprinting 3D cell & tissue culture alternative toxicity testing organs-on-chips stem cells
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Brain-in-a-dish: researchers create “the most complete model of a human brain ever grown in a lab”

Photo courtesy of Ohio State University

Photo courtesy of Ohio State University

Ohio State University researchers Rene Anand and Susan McKay say they have grown a miniaturized human brain from re-programmed adult skin cells. The structure is described in this Washington Post story as “no bigger than a pencil eraser” and is said to contain “all the major structures and 99 percent of the genes present in the brain of a five-week-old fetus.”

“It’s a scalable model that can be engineered to carry the genetic variants that give rise to all these diseases … and it gives us incredible access to things we never have done before,” lead researcher Anand told The Washington Post. “We can screen drugs, we can ask questions, we can follow the development at every stage.”

Because the researchers are patenting their process, they have not released data describing their methods. (They have also formed a commercial startup.) But according to an OSU press release, the team has already used the technique to model autism, Alzheimer’s, and Parkinson’s disease “in-a-dish,” and hopes to receive funding from the Small Business Technology Transfer program to use the model in drug development.

The announcement comes on the heels of another advance in organotypic brain modeling – a 3D bioprinted structure developed by Rodrigo Lozano and colleagues at the University of Wollongong in Australia. A functional brain “organoid” that can be subjected to environmental manipulations, or genetically engineered to reproduce inherited conditions, holds great promise for human-relevant toxicity testing, more efficient drug-candidate screening, and the study of neurodevelopmental and neurodegenerative diseases.

3D bioprinting 3D cell & tissue culture disease-in-a-dish drug discovery stem cells
Rod photoreceptors (in green) within a "mini retina" derived from human iPS cells in the lab.

3D “mini retina” from stem cells

Scientists at Johns Hopkins University School of Medicine have cultivated functional 3-dimensional human retinal tissue in vitro from induced human pluripotent stem cells.  And in a significant technical advance over previous cultured retina studies, the resulting tissue exhibits mature cell differentiation and organization, and is able to detect light.

From the JHU press release:

(Lead investigator M. Valeria Canto-Soler) says that the newly developed system gives them the ability to generate hundreds of mini-retinas at a time directly from a person affected by a particular retinal disease such as retinitis pigmentosa. This provides a unique biological system to study the cause of retinal diseases directly in human tissue, instead of relying on animal models.

The system, she says, also opens an array of possibilities for personalized medicine such as testing drugs to treat these diseases in a patient-specific way. In the long term, the potential is also there to replace diseased or dead retinal tissue with lab-grown material to restore vision.

The study appears in last week’s issue of Nature Communications.

(To learn more about stem cells – especially about their potential in toxicity testing – see this stem cell “primer” on AltTox.org.)

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