Better ‘Mini Brains’ Could Help Scientists Identify Treatments for Zika-Related Brain Damage

UCLA researchers develop improved technique for creating brain tissue from stem cells

UCLA researchers have developed an improved technique for creating simplified human brain tissue from stem cells. Because these so-called “mini brain organoids” mimic human brains in how they grow and develop, they’re vital to studying complex neurological diseases.

In a study published in the journal Cell Reports, the researchers used the organoids to better understand how Zika infects and damages fetal brain tissue, which enabled them to identify drugs that could prevent the virus’s damaging effects.

The research, led by senior author Ben Novitch, could lead to new ways to study human neurological and neurodevelopmental disorders, such as epilepsy, autism and schizophrenia.

“Diseases that affect the brain and nervous system are among the most debilitating medical conditions,” said Novitch, UCLA’s Ethel Scheibel Professor of Neurobiology and a member of the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA. “Mini brain organoids provide us with opportunities to examine features of the human brain that are not present in other models, and we anticipate that their similarity to the real human brain will enable us to test how various drugs impact abnormal or diseased brain tissue in far greater detail.”

For about five years, scientists have been using human pluripotent stem cells, which can create any cell type in the body, to develop mini brain organoids. But the organoids they produced have generally been difficult to use for research because they had highly variable structures and inconsistent cellular composition, and because they didn’t correctly mimic the layered structure of the brain and were too small — often no bigger than the head of a pin. They also didn’t survive very long in the laboratory and contained neural tissue that was difficult to classify in relation to real human brain tissue.

The organoids developed by Novitch’s group have a stratified structure that accurately mimics the human brain’s onion-like layers, they survive longer and have a larger and more uniform shape.

To create the brain organoids, Novitch and his team made several modifications to the methods that other scientists used previously: The UCLA investigators used a specific number of stem cells and specialized petri dishes with a modified chemical environment; previous methods used varying amounts of cells and a different type of dish. And they added a growth factor called LIF, which stimulated a cell-signaling pathway that is critical for human brain growth.

The researchers found critical similarities between the organoids they developed and real human brain tissue. Among them: The organoids’ anatomy closely resembled that of the human cortex, the region of the brain associated with thought, speech and decision making; and a diverse array of neural cell types commonly found in the cortex were all present in the organoids, and they exhibited electrical activities and network function, meaning they were capable of communicating with one another much like the neural networks in the human brain do.

The UCLA scientists also found that they could modify their methodology to make other parts of the brain including the basal ganglia, which are involved in the control of movement and are affected by neurodegenerative conditions such as Parkinson’s disease and Huntington’s disease.

“While our organoids are in no way close to being fully functional human brains, they mimic the human brain structure much more consistently than other models,” said Momoko Watanabe, a UCLA postdoctoral fellow and the study’s first author. “Other scientists can use our methods to improve brain research because the data will be more accurate and consistent from experiment to experiment and more comparable to the real human brain.”

When the team exposed the organoids to Zika, they discovered specifically how the virus destroys neural stem cells, the cells from which the brain grows during fetal development. Novitch’s team found that there are four specific molecules, called receptors, on the outer surface of neural stem cells; previous studies have indicated that the Zika virus could bind to these receptors and infect the cells. The researchers then mapped the changes that occur in the neural stem cells after Zika infection, presenting a clearer picture of how the virus infiltrates and harms fetal brain tissue.

Zika is associated with an unusually high incidence of fetal brain damage, so understanding how neural stem cells are affected by the virus could be an important new step toward a treatment.

The researchers tested several drugs on the Zika-infected organoids. They found three that are effective at blocking the virus’s entry into the brain tissue, including two that protected neural stem cells by preventing the interaction between the virus and entry receptors on the neural stem cells. In previous studies by Novitch and other UCLA colleagues, one of those drugs reduced brain damage in fetal mice infected with Zika.

“Many neurological diseases or conditions arise from defects in the way one neuron communicates with another or from the way an external factor, such as a virus, interacts with neural cells,” Novitch said. “If we can focus in at the level of cellular communication, we should be able to model those undesirable cellular interactions and counteract them with drugs or other therapies.”

The team plans to continue using its improved organoids to better understand human brain development and to learn more about autism spectrum disorders, epilepsy and other neurological conditions.

The experimental drugs used in the preclinical study have not been tested in humans or approved by the Food and Drug Administration for treating Zika in humans.

Penn Study Identifies Potent Inhibitor of Zika Entry Into Human Cells

A panel of small molecules that inhibit Zika virus infection, including one that stands out as a potent inhibitor of Zika viral entry into relevant human cell types, was discovered by researchers from the Perelman School of Medicine at the University of Pennsylvania. Publishing in Cell Reports this week, a team led by Sara Cherry, PhD, an associate professor of Microbiology, screened a library of 2,000 bioactive compounds for their ability to block Zika virus infection in three distinct cell types using two strains of the virus.

Zika is an emerging mosquito-borne virus for which there are no vaccines or specific therapeutics. The team used cells lining brain capillaries called endothelium, and cells from placenta, which represent Zika’s route across the blood-brain barrier and the transmission path from mother to child, respectively. The third type – a human osteosarcoma cell line – is a generic model cell. They tested a strain of Zika virus currently circulating in human populations in the Americas and another from Africa, which is the original strain identified in 1947.

Using a microscopy-based assay, they identified 38 molecules from the High-throughput Screening Core at Penn, which Cherry directs, that inhibited Zika virus infection in at least one cell type. Roughly half of the 2,000 molecules tested include FDA-approved molecules used to prevent viral replication in infected cells. Co-author David Schultz, PhD, the Core’s technical director, was instrumental in providing the infrastructure and expertise for this multi-level screen.

“Overall, the most important finding is that we identified nanchangmycin as a potent inhibitor of Zika virus entry across all cell types tested, including endothelial and placental cells, which are relevant to how Zika may enter the fetus,” Cherry said. Nanchangmycin – an antimicrobial indentified in China as part of a natural medicinal products survey — was also active against other medically relevant viruses, including West Nile, dengue, and chikungunya that use a similar route of entry as Zika.

These viruses enter cells using “clatherin endocytosis.” The virus binds with the host cell’s outer membrane via a pocket lined with a protein called clatherin. This protein-lined sac containing the sequestered virus pinches off to move deeper into the cytoplasm of the cell where the virus enters to replicate.

Nanchangmycin is a “stepping stone to a new class of anti-virals,” Cherry said, because it thwarts this essential mode of entry by viruses like Zika. Future studies will identify the target of this drug and current studies are testing the efficacy of nanchangmycin in animal models of Zika virus infection.

This study was supported by the National Institutes of Health NIH (R01AI074951, RO1AI122749, R01AI095500), the Linda Montague Investigator, Award, and the Burroughs Wellcome Investigators in the Pathogenesis of Infectious Disease Award.

Penn Medicine is one of the world’s leading academic medical centers, dedicated to the related missions of medical education, biomedical research, and excellence in patient care. Penn Medicine consists of the Raymond and Ruth Perelman School of Medicine at the University of Pennsylvania (founded in 1765 as the nation’s first medical school) and the University of Pennsylvania Health System, which together form a $5.3 billion enterprise.

 

Neurodevelopmental Model Of Zika May Provide Rapid Answers

A newly published study from researchers working in collaboration with the Regenerative Bioscience Center at the University of Georgia demonstrates fetal death and brain damage in early chick embryos similar to microcephaly—a rare birth defect linked to the Zika virus, now alarming health experts worldwide.

The team, led by Forrest Goodfellow, a graduate student in the UGA College of Agricultural and Environmental Sciences, developed a neurodevelopmental chick model that could mimic the effects of Zika on the first trimester. Historically, chick embryos have been extensively used as a model for human biology.

Early last spring, Goodfellow began inoculating chick embryos with a virus strain originally sourced from the Zika outbreak epicenter.

“We wanted a complete animal model, closely to that of a human, which would recapitulate the microcephaly phenotype,” said Goodfellow, who recently presented the findings at the Southern Translational Education and Research (STaR) Conference.

The RBC team, which included Melinda Brindley, an assistant professor of virology in the College of Veterinary Medicine, and Qun Zhao, associate professor of physics in the Franklin College of Arts and Sciences, suggests that the chick embryo provides a useful model to study the effects of Zika, in part because of its significant similarity to human fetal neurodevelopment and rapid embryonic process.

“Now we can look quickly, at greater numbers, to take a closer look at a multitude of different strains and possibly identify the critical window of susceptibility for Zika virus-induced birth defects,” said Brindley. “With this approach, we can continue to further design and test therapeutic efficacy.”
The challenge today is unpredictable disease outbreaks and how to ramp up process and production of therapeutic antibodies in preparation. Having an active pathogen threat like Zika that can jump across continents reinforces the need for therapeutic innovation.

Early stage chick embryos are readily available and low in cost, Goodfellow explained. Development within the egg (in ovo) provides an environment that can be easily accessed by high-speed automation. Poultry automation in the Southeast is impressive, and the industry is now using robotic technology, Goodfellow said.

“With egg injection automation and embryo viability technology, we could test tens of thousands of potential therapeutic compounds in a single day,” he said.
Since 2011, under the mentorship of Steven Stice, a Georgia Research Alliance Eminent Scholar and director of the Regenerative Bioscience Center, Goodfellow has worked extensively with eggs and chickens. In a previous project with Stice and Zhao, the team developed a unique approach of marrying stem cell biology and MRI to track and label neural stem cells.

“We knew we could look at the brain structure, shape and size with MRI, but what we captured was evidence that the infection caused MRI-visible damage, and the total brain volume was substantially smaller,” said Stice, faculty lead and principal investigator of the study. “From this finding, our data provides a rationale for targeting future therapeutic compounds in treating early-stage microcephaly to stop or slow the progress of the disease.”