“Blood-brain barrier on-a-chip”

Scientists at the Wyss Institute have created a 3-dimensional in vitro model of the human blood-brain-barrier (BBB)-“on-a-chip.”  The device will make it possible for researchers to test drugs, chemicals, and disease factors that interact with the BBB, without using animals – and in a 3-dimensional environment that mimics that of the human BBB in vivo.

The BBB is a semi-permeable cellular structure that allows some nutrients and substances to enter the blood flow in the brain, and keeps other elements (such as bacteria and potential toxins) out. Because it is so effective, it can also prevent useful treatments from reaching targets in the brain. Researchers need to understand how and why certain substances can pass through the barrier, in part so they can design therapeutic drugs accordingly, and so they can design other substances to prevent neurotoxicity.

From the Wyss Institute press release: "These fluorescence confocal microscopy images show both a high magnification view (left) of a region of the human brain capillary endothelium within the endothelium lined tube (shown at lower magnification at right) that, in combination with surrounding human pericytes and astrocytes, comprise the blood-brain barrier (cell junctions linking adjacent endothelial cells are shown in magenta). " Credit: Wyss Institute at Harvard University

From the Wyss Institute press release: “These fluorescence confocal microscopy images show both a high magnification view (left) of a region of the human brain capillary endothelium within the endothelium lined tube (shown at lower magnification at right) that, in combination with surrounding human pericytes and astrocytes, comprise the blood-brain barrier (cell junctions linking adjacent endothelial cells are shown in magenta). ” Credit: Wyss Institute at Harvard University

To create the device, the Wyss Institute team carved a tiny channel in a polymer chip and filled it with a gel matrix containing human astrocytes, the cells that comprise the extra-tight “barrier” around blood vessels in the brain. Another channel was tunneled through this matrix and seeded with human pericyte cells (contractile cells which control the “gaps” through which substances can enter the neurological bloodstream) and then with human endothelial cells (the cells that line the interior of a blood vessel). The cells “self-assembled” into the same layers and connections they exhibit in blood vessels in vivo.

To test the model, the team introduced a protein known to cause inflammation – one that has been associated with a number of central nervous system diseases and disorders, including Alzheimer’s, multiple sclerosis, and stroke (among others). The in vitro BBB responded by producing protective proteins. The device can thus be used to study neuroinflammation, and to test new treatments.

Read more in the Wyss Institute’s press release.

3D cell & tissue culture alternative toxicity testing disease-in-a-dish organs-on-chips toxicity testing alternatives

Chipping away at the use of animals to predict human diseases

The Wyss Institute recently announced two new human cell-based inflammatory disease models built on its rapidly expanding “organ chip” platform. Both models could speed the development of treatments for these diseases, and further reduce the use of animals in testing.

Using the “gut-on-a-chip” device first introduced in 2012, Wyss scientists co-cultured human intestinal cells with normal and pathogenic intestinal microbes, producing an in vitro model (viable for up to two weeks) of intestinal inflammation and bacterial overgrowth. These two disease features are present in a number of human intestinal disorders (such as ulcerative colitis and Crohn’s disease). Until now, it has been difficult to reproduce these disorders in the lab in order to test treatments for them. The gut-on-a-chip device “could allow breakthrough insights into how the microbial communities that flourish inside our GI tracts contribute to human health and disease.” The image below, from the Wyss Institute press release, shows how the cells in this microenvironment even reproduce normal peristalsis, the contraction/relaxation cycle of the intestinal walls that moves digested food down the tract.

The Wyss Institute also used its chip technology to create a human lung “small-airway-on-a-chip.” When the chips are lined with airway cells from patients suffering from such inflammatory disorders as chronic obstructive pulmonary disease (COPD) or asthma, the physiological features of the disease can be observed and tested in vitro. As noted in the Wyss Institute press release, “Demand for such opportunities is especially high since small airway inflammation cannot be adequately studied in human patients or animal models and, to date, there are no effective therapies that can stop or reverse the complex and widespread inflammation-driven processes.”

Watch a video demo of the small-airway-on-a-chip below:

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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

“Humans are not mice:” scientists use human cells to create a working model of a rare genetic disorder

In this TEDx talk, researchers from HemoShear Therapeutics and Children’s National Medical Center describe how they can use cells from a diseased human liver to test treatments for that disease more rapidly and effectively than they could through tests on animals.

Their patient, “Stacy,” suffers from a very rare genetic condition – proprionic acidemia (PA) – which affects her body’s ability to completely process proteins and fats. As a result, proprionic acid begins to build up to toxic levels in her blood. The condition affects 1 in 100,000 people, and can lead to a variety of serious health problems and even early death. Like other PA patients, Stacy’s liver was worn out by its efforts to clear the toxic build-up from her body, and she eventually needed a transplant.

As Brian Wamhoff from HemoShear points out in this video, scientists have tried to recreate PA in mice that have been genetically engineered to exhibit the disease – but the condition kills mice immediately, before they can be treated. And as Wamhoff says, “humans are not mice.” Researchers need a way to test treatments on viable liver cells taken from a human with proprionic acidemia. So HemoShear developed a technology that keeps cells alive in conditions that mimic those in the patient’s body. When Stacy recently got her new liver, doctors sent living cells from her diseased liver to HemoShear – allowing them to create the first working “model” of proprionic acidemia.

Says Marshall Summar, Chief of Genetics and Metabolism at Children’s National Medical Center, in the video: “What this means is we can cut literally years off the development of new treatments for our patients. Before, we would have to try to develop an animal model…that often wouldn’t work. Or we’d try serendipity – we would try, maybe there’s drug that would work here and there. Now we can take a systematic approach to developing new therapies for these patients. This literally is an order of magnitude improvement on what we’re going to be able to do. And it offers us, for the first time, hope for developing therapies rapidly for these patients with rare diseases, so we can tackle the other 6,999 of them.”

3D cell & tissue culture disease-in-a-dish non-predictive animal models

A new paper applies pathway biology to disease research and drug discovery

“Lessons from Toxicology: Developing a 21st-Century Paradigm for Medical Research,” a new paper by a team of international experts including authors from Human Toxicology Project Consortium partners Humane Society International, The Humane Society of the United States, and Unilever, calls for a systems-biology approach to biomedical research and drug discovery. The approach borrows insights from toxicology, where adverse outcome pathways (AOPs) – a framework for documenting the physiological path between chemical exposure and “adverse outcomes” such as illness, injury, or environmental harm – are being used to integrate data from a variety of new scientific technologies. The authors propose that this same framework can be expanded to disease research, and can greatly improve our ability to identify effective drugs and therapeutics.

“…[M]any human illnesses such as cancers, diabetes, immune system and neurodegenerative disorders, and respiratory and cardiovascular diseases are caused by a complicated interplay between multiple genetic and environmental factors,” the authors write. Technology developments over the last two decades have made it possible to measure how genes determine our susceptibility to diseases, as well as how genes, proteins, cells, and tissues react to various environmental exposures. Application of such developments to drug discovery “require(s) a new research paradigm to unlock their full potential.” Just as AOPs integrate these new types of information to help reveal toxicity mechanisms and protect people and the environment from potential effects of chemical exposure, disease pathways can be used to understand risk and disease mechanisms, leading to more effective cures. According to the authors, “The disease AOP approach would better exploit advanced experimental and computational platforms for knowledge discovery, since the emergence of AOP networks will identify knowledge gaps and steer investigations accordingly.”

Progress in disease research and drug discovery has been slow, the authors say, because of continued reliance on inappropriate and unproductive animal models. The AOP framework encourages the use of emerging human-specific cell- and tissue-based models – such as 3D tissue constructs and organs-on-chips – combined with increasingly advanced computational models. The powerful combination can accelerate our understanding of disease, while reducing the use of animals.

The paper was published in the open access journal, Environmental Health Perspectives: http://ehp.niehs.nih.gov/wp-content/uploads/123/11/ehp.1510345.alt.pdf

3D cell & tissue culture alternative toxicity testing AOPs drug discovery HTPC members in the news pathway-based approaches

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