Honoring Dr. Brigid Hogan

Dr. Brigid Hogan, Chair, Duke Cell Biology Department

Distinguished developmental biologists from just down the hall and as far away as Singapore, Japan, and England convened at Duke on Friday, March 9, for a special symposium on Developing the Mouse Embryo. Speakers at the symposium highlighted breakthroughs in cell and developmental biology and implications for human health. The day-long event was a celebration of Dr. Brigid Hogan, Chair of Duke University’s department of Cell Biology. Dr. Hogan is a world leader in developmental biology and stem cell research, and in 2002 was the first woman to be appointed as Chair of a basic science department at Duke University.

Ken Poss, Director of Duke’s Regeneration Next Initiative and Professor of Cell Biology, said, “Brigid has shown remarkable leadership for fifteen years as Department Chair. We all appreciate her vision and her support of the field, as well as her groundbreaking work in developmental biology.”

Dr. Richard Behringer, Professor of Genetics at University of Texas’ MD Anderson Cancer, was a presenter at Friday’s symposium. Dr. Behringer wrote a blog post about the Symposium on the Developmental Biology website, The Node. He recounted that many people shared touching “Brigid stories” showing how Dr. Hogan has inspired a generation of biologists. Dr. Behringer’s blog post is reposted below.

Last Friday March 9, a research symposium was held at Duke University in Durham, North Carolina to honor the career and retirement of Professor Brigid Hogan, Chair of the Department of Cell Biology. Current and former Hogan Lab members, colleagues, and friends came from across America, Japan, and the United Kingdom to join in the celebration of a truly remarkable scientist. There were 14 invited speakers, including former students, postdocs, colleagues from Brigid’s days at Vanderbilt University in Nashville, Tennessee, current members of the Department of Cell Biology at Duke, and friends in the mouse development and genetics field. More than 150 participants that included local students and postdoctoral fellows came to hear outstanding research talks. Among the participants, luminaries in the mouse developmental biology field were there to honor Brigid, including Gail Martin, Liz Robertson, Liz Lacy, Frank Costantini, Phil Soriano, Terry Magnuson, Blanche Capel, Kat Hadjantonakis, and Mary Dickinson. The symposium started with surprise videos from friends Fiona Watt (King’s College London) and Jim Smith (Francis Crick Institute), sending their congratulations to Brigid and one from Brigid’s third graduate student, Peter Holland (University of Oxford), praising her skills at inspiring his confidence as a young scientist during his thesis research. The research talks discussed current research, including gene regulatory networks, cutting-edge microscopic imaging, organogenesis, the genetic basis of human disease, novel gene manipulation approaches, embryos on a chip, organ-specific stem cells, high-throughput mouse mutant phenotyping, and tissue regeneration. The talks highlighted the advances in the field of cell and developmental biology and why this area of research is so important for basic knowledge and human health. To learn more about Brigid’s background and motivation to study mouse embryos and organs see her 2015 interview with The Node (http://bit.ly/2DqfZiM).

In addition, to the wonderful science that was presented that day, all of the speakers had a “Brigid story” that they shared with the audience. Many spoke of her drive, curiosity, generosity, patience, and for those who were trained in her lab, the lessons they learned from her. These included ‘don’t talk yourself out of an experiment, sometimes you just have to do it’, ‘be brave’, ‘finish what you start’, ‘speak up and speak out’. My favorite was ‘don’t apologize for being a tall, confident woman’. Everyone praised Brigid’s skills as a mentor. You can read about Brigid’s thoughts on mentoring in a recent interview in Cell Stem CellMentoring the Next Generation (http://bit.ly/2Dk1PiM). Yes, Brigid is “retiring” but she will still be very active. At the end of the symposium, Brigid thanked everyone for attending and participating, especially those who traveled such long distances. She said it brought “a joy to my heart” and was a “day I’ll always remember”.

Reposted from the Node, March 13, 2018 with permission.

How A Zebrafish’s Squiggly Cartilage Transforms into a Strong Spine

Blog post by Kara Manke. This article first appeared on the Duke Research Blog, and is reposted here in its entirety.

Our spines begin as a flexible column called the notochord. Over time, cells on the notochord surface divide into alternating segments that go on to form cartilage and vertebrae.

In the womb, our strong spines start as nothing more than a rope of rubbery tissue. As our bodies develop, this flexible cord, called the notochord, morphs into a column of bone and cartilage sturdy enough to hold up our heavy upper bodies.

Graduate student Susan Wopat and her colleagues in Michel Bagnat’s lab at Duke are studying the notochords of the humble zebrafish to learn how this cartilage-like rope grows into a mature spine.

In a new paper, they detail the cellular messaging that directs this transformation.

It all comes down to Notch receptors on the notochord surface, they found. Notch receptors are a special type of protein that sits astride cell membranes. When two cells touch, these Notch receptors link up, forming channels that allow messages to rapidly travel between large groups of cells.

Notch receptors divide the outer notochord cells into two alternating groups – one group is told to grow into bone, while the other is told to grow into cartilage. Over time, bone starts to form on the surface of the notochord and works its way inward, eventually forming mature vertebrae.

When the team tinkered with the Notch signaling on the surface cells, they found that the spinal vertebrae came out deformed – too big, too small, or the wrong shape.

Meddling with cellular signaling on the notochord surface caused zebrafish spines to develop deformities. The first and third image show healthy spines, and the second and fourth image show deformed spines.

“These results demonstrate that the notochord plays a critical role in guiding spine development,” Wopat said. “Further investigation into these findings may help us better understand the origin of spinal defects in humans.”

Spine patterning is guided by segmentation of the notochord sheath,” Susan Wopat, Jennifer Bagwell, Kaelyn D. Sumigray, Amy L. Dickson, Leonie F. Huitema, Kenneth D. Poss, Stefan Schulte-Merker, Michel Bagnat. Cell, February 20, 2018. DOI: 10.1016/j.celrep.2018.01.084

We’re hiring: Research Technician


We are seeking a highly qualified individual with extensive experience in animal surgery and handling. The main research area of our group is regenerative therapies for cardiac injury and disease. The position will be situated in a stimulating environment that provides excellent opportunities for scientific growth in the pursuit of a variety of careers.

Principal Responsibilities:
•Perform surgical induction of myocardial infarction, transverse aortic constriction in mouse and rat hearts, microinjection into the vasculature and myocardial wall, implantation of a bioengineered cardiac tissue patch on the heart and follow-up physiological and hemodynamic studies including echocardiographic analysis and PV loops.
•Perform pre- and post-operative care and observations.
•Responsibilities may also include interpreting experimental results and guiding lab members through surgical methods and analyses, and to help prepare reports of research for presentation or publication including high-quality figures that convey new findings.

Preferred Qualifications:
•Bachelors degree in biology, physiology, veterinary medicine, medicine, or other relevant areas of biomedical sciences.
•Technical proficiency and collaborative ability as well as independent thought.
•In-depth knowledge of multiple areas and of the underlying principles and concepts.
•Strong training in small animal surgery, including cardiac injuries.
•Proficient with animal restraint, anesthesia, intubation, and ventilation.

Perform other related duties incidental to the work described herein. The above statements describe the general nature and level of work This is not intended to be an exhaustive list of all responsibilities and duties required of personnel so classified. being performed by individuals assigned to this classification.

Please send a cover letter, resume, and a list of at least 3 references to regeneration@duke.edu

Duke University is an Affirmative Action/Equal Opportunity Employer committed to providing employment opportunity without regard to an individual’s age, color, disability, gender, gender expression, gender identity, genetic information, national origin, race, religion, sex, sexual orientation, or veteran status.

Shedding light on a potential therapy for visual degenerative disease

This image shows a cross-section of the rat retina. Müller glial cells are shown in green and their reactivity is shown in red. Image credit: Sehwon Koh, Ph.D.

Age-related macular degeneration (AMD) is the leading cause of blindness in individuals aged 60 or older. No effective treatments are currently available for most of these patients, but cell transplantation-based therapies are being developed and tested in clinical trials. A new study by Regeneration Next Postdoctoral Fellow Sehwon Koh, Duke faculty member Cagla Eroglu, and colleagues is shedding light on a possible transplantation-based treatment for AMD and other diseases that cause loss of visual function.

The retina is a complex tissue in the eye that is responsible for visual function. Photoreceptors are one of the types of retinal neurons that turn light entering the eye into nerve signals. Many retinal diseases including AMD affect photoreceptors and cause them to progressively degenerate. Koh, Eroglu, and colleagues show that transplantation of umbilical cord-derived cells into the subretinal region of the eye can preserve visual function by protecting photoreceptors. They also show that the transplanted cells help to preserve neuron-to-neuron connections (synaptic connections) that transmit important information.

Koh and colleagues also examined a different type of retinal cell, the Müller glial cell, which plays an important role in supporting retinal cell health and regulating synaptic connections. The authors found that Müller glial cells become highly reactive even before photoreceptor cell death, and may contribute to cell death. The transplanted umbilical-cord derived cells secrete factors that weaken Müller glial cell reactivity, consequently improving retinal health and synaptic connections. Koh and colleagues show how subretinal transplantation could work to preserve visual function and highlight Müller Glial cells as a potential therapeutic target for the treatment of diseases like macular degeneration.

The paper was published as an early release article in the Journal of Neuroscience and can be accessed here>

Traveling chemical waves transmit critical developmental information

An image depicting how neurons transmit chemical information in waves. Image courtesy Victoria Deneke

Ever wonder how your brain can quickly tell your hand to move? Your brain and other systems in biology that have to spread information across large distances use chemical waves to communicate rapidly. Chemical waves are traveling waves that actively transmit biochemical information through a medium. Depicted is a cartoon of a neuron, which is the road that your body uses to send information from your brain to the rest of your body. To the right is a heat map that shows a simulation of a chemical wave traveling through space. Graduate student Victoria Deneke and Dr. Stefano Di Talia highlight the advantages and numerous examples of chemical waves in biology that range from embryogenesis to regeneration in a new review article published in the Journal of Cell Biology. Read the review here >

Engineers Grow Functioning Human Muscle from Skin Cells

A cross section of a muscle fiber grown from induced pluripotent stem cells.

A cross section of a muscle fiber grown from induced pluripotent stem cells. The green indicates muscle cells, the blue is cell nuclei, and the red is the surrounding support matrix for the cells.

By Ken Kingery

This article first appeared on Duke’s Pratt School of Engineering website, and is excerpted here.

Biomedical engineers have grown the first functioning human skeletal muscle from induced pluripotent stem cells.

The advance builds on work published in 2015 when researchers at Duke University grew the first functioning human muscle tissue from cells obtained from muscle biopsies. The ability to start from cellular scratch using non-muscle tissue will allow scientists to grow far more muscle cells, provide an easier path to genome editing and cellular therapies, and develop individually tailored models of rare muscle diseases for drug discovery and basic biology studies.

The results appear online Tuesday, January 9, in Nature Communications.

“Starting with pluripotent stem cells that are not muscle cells, but can become all existing cells in our body, allows us to grow an unlimited number of myogenic progenitor cells,” said Nenad Bursac, professor of biomedical engineering at Duke University. “These progenitor cells resemble adult muscle stem cells called ‘satellite cells’ that can theoretically grow an entire muscle starting from a single cell.”

In their previous work, Bursac and his team started with small samples of human cells obtained from muscle biopsies, called “myoblasts,” that had already progressed beyond the stem cell stage but hadn’t yet become mature muscle fibers. They grew these myoblasts by many folds and then put them into a supportive 3-D scaffolding filled with a nourishing gel that allowed them to form aligned and functioning human muscle fibers.

In the new study, the researchers instead started with human induced pluripotent stem cells. These are cells taken from adult non-muscle tissues, such as skin or blood, and reprogrammed to revert to a primordial state. The pluripotent stem cells are then grown while being flooded with a molecule called Pax7—which signals the cells to start becoming muscle.

As the cells proliferated they became very similar to—but not quite as robust as—adult muscle stem cells. While previous studies had accomplished this feat, nobody has been able to then grow these intermediate cells into functioning skeletal muscle.

The Duke researchers succeeded where previous attempts had failed.

Full story >

Beating Heart Patch is Large Enough to Repair the Human Heart

Watch video describing the heart patch

By Ken Kingery

This article first appeared on Duke’s Pratt School of engineering, and is reposted here in its entirety.

Biomedical engineers at Duke University have created a fully functioning artificial human heart muscle large enough to patch over damage typically seen in patients who have suffered a heart attack. The advance takes a major step toward the end goal of repairing dead heart muscle in human patients.

The study appears online in Nature Communications on November 28, 2017.

“Right now, virtually all existing therapies are aimed at reducing the symptoms from the damage that’s already been done to the heart, but no approaches have been able to replace the muscle that’s lost, because once it’s dead, it does not grow back on its own,” said Ilia Shadrin, a biomedical engineering doctoral student at Duke University and first author on the study. “This is a way that we could replace lost muscle with tissue made outside the body.”

Unlike some human organs, the heart cannot regenerate itself after a heart attack. The dead muscle is often replaced by scar tissue that can no longer transmit electrical signals or contract, both of which are necessary for smooth and forceful heartbeats.

The end result is a disease commonly referred to as heart failure that affects over 12 million patients worldwide. New therapies, such as the one being developed by Shadrin and his advisor Nenad Bursac, professor of biomedical engineering at Duke, are needed to prevent heart failure and its lethal complications.

Current clinical trials are testing the tactic of injecting stem cells derived from bone marrow, blood or the heart itself directly into the affected site in an attempt to replenish some of the damaged muscle. While there do seem to be some positive effects from these treatments, their mechanisms are not fully understood. Fewer than one percent of the injected cells survive and remain in the heart, and even fewer become cardiac muscle cells.

Heart patches, on the other hand, could conceivably be implanted over the dead muscle and remain active for a long time, providing more strength for contractions and a smooth path for the heart’s electrical signals to travel through. These patches also secrete enzymes and growth factors that could help recovery of damaged tissue that hasn’t yet died.

For this approach to work, however, a heart patch must be large enough to cover the affected tissue. It must also be just as strong and electrically active as the native heart tissue, or else the discrepancy could cause deadly arrhythmias.

This is the first human heart patch to meet both criteria. “Creating individual cardiac muscle cells is pretty commonplace, but people have been focused on growing miniature tissues for drug development,” said Bursac. “Scaling it up to this size is something that has never been done and it required a lot of engineering ingenuity.”

The cells for the heart patch are grown from human pluripotent stem cells — the cells that can become any type of cell in the body. Bursac and Shadrin have successfully made patches using many different lines of human stem cells, including those derived from embryos and those artificially forced or “induced” into their pluripotent state.

Various types of heart cells can be grown from these stem cells: cardiomyocytes, the cells responsible for muscle contraction; fibroblasts, the cells that provide structural framework for heart tissue; and endothelial and smooth muscle cells, the cells that form blood vessels. The researchers place these cells at specific ratios into a jelly-like substance where they self-organize and grow into functioning tissue.

Finding the right combination of cells, support structures, growth factors, nutrients and culture conditions to grow large, fully functional patches of human heart tissue has taken the team years of work. Every container and procedure had to be sized up and engineered from scratch. And the key that brought it all together was a little bit of rocking and swaying.

“It turns out that rocking the samples to bathe and splash them to improve nutrient delivery is extremely important,” said Shadrin. “We obtained three-to-five times better results with the rocking cultures compared to our static samples.”

The results improved on the researchers’ previous patches, which were one square centimeter and four square centimeters. They successfully scaled up to 16 square centimeters and five to eight cells thick. Tests show that the heart muscle in the patch is fully functional, with electrical, mechanical and structural properties that resemble those of a normal, healthy adult heart.

“This is extremely difficult to do, as the larger the tissue that is grown, the harder it is to maintain the same properties throughout it,” said Bursac. “Equally challenging has been making the tissues mature to adult strength on a fast timescale of five weeks while achieving properties that typically take years of normal human development.”

Bursac and Shadrin have already shown that these cardiac patches survive, become vascularized and maintain their function when implanted onto mouse and rat hearts. For a heart patch to ever actually replace the work of dead cardiac muscle in human patients, however, it would need to be much thicker than the tissue grown in this study. And for patches to be grown that thick, they need to be vascularized so that cells on the interior can receive enough oxygen and nutrients. Even then, researchers would have to figure out how to fully integrate the heart patch with the existing muscle.

“Full integration like that is really important, not just to improve the heart’s mechanical pumping, but to ensure the smooth spread of electrical waves and minimize the risk of arrhythmias,” said Shadrin.

“We are actively working on that, as are others, but for now, we are thrilled to have the ‘size matters’ part figured out,” added Bursac.

The research is part of a seven-year, $8.6 million grant from the National Institutes of Health. With the large heart patches in hand, the Bursac team is collaborating with researchers at the University of Alabama at Birmingham to develop procedures to successfully integrate the patch onto the hearts of pigs. Another affiliated team of researchers at the University of Wisconsin-Madison is working to develop improved stem cells for creating the main cell types that compose these heart patches, in the hopes of minimizing an immune response to the delivery of the engineered tissues.

This research was supported by Foundation Leducq and the National Institutes of Health (R01HL104326, R01HL12652, UG3TR002142, U01HL134764, 5T32GM007171, F30HL122079).

CITATION: “Cardiopatch platform enables maturation and scale-up of human pluripotent stem cell-derived engineered heart tissues,” Ilya Y. Shadrin, Brian W. Allen, Ying Qian, Christopher P. Jackman, Aaron L. Carlson, Mark E. Juhas, and Nenad Bursac. Nature Communications, 2017. DOI: 10.1038/s41467-017-01946-x

Star-Shaped Brain Cells Orchestrate Neural Connections

Dysfunction of intricate astrocyte cells may underlie devastating diseases like autism, schizophrenia and epilepsy

An astrocyte (blue) grown in a dish with neurons forms an intricate, star-shaped structure. Neurons’ synaptic proteins appear in green and purple. Overlapping proteins represent the locations of synapses. Credit: Jeff Stogsdill, Duke University

By Kara Manke

This article first appeared on Duke Today and is reposted here in its entirety.

Brains are made of more than a tangled net of neurons. Star-like cells called astrocytes diligently fill in the gaps between neural nets, each wrapping itself around thousands of neuronal connections called synapses. This arrangement gives each individual astrocyte an intricate, sponge-like structure.

New research from Duke University finds that astrocytes are much more than neurons’ entourage. Their unique architecture is also extremely important for regulating the development and function of synapses in the brain.

When they don’t work right, astrocyte dysfunction may underlie neuronal problems observed in devastating diseases like autism, schizophrenia and epilepsy.

The Duke team identified a family of three proteins that control the web-like structure of each astrocyte as it grows and encases neuronal structures such as synapses. Switching off one of these proteins not only limited the complexity of the astrocytes, but also altered the nature of the synapses between neurons they touched, shifting the delicate balance between excitatory and inhibitory neural connections.

“We found that astrocytes’ shape and their interactions with synapses are fundamentally important for brain function and can be linked to diseases in a way that people have neglected until now,” said Cagla Eroglu, an associate professor of cell biology and neurobiology at Duke. The research was published in the Nov. 9 issue of Nature.

Astrocytes have been around almost as long as brains have. Even simple invertebrates like the crumb-sized roundworm C. elegans has primitive forms of astrocytes cloaking their neural synapses. As our brains have evolved into complex computational machines, astrocyte structure has also grown more elaborate.

But the complexity of astrocytes is dependent on their neuronal companions. Grow astrocytes and neurons together in a dish, and the astrocytes will form intricate star-shaped structures. Grow them alone, or with other types of cells, and they come out stunted.

A 3-D-printed model of a single astrocyte from a mouse brain shows the sponge-like structure of these cells. Photo credit: Katherine King, Duke University.

To find out how neurons influence astrocyte shape, Jeff Stogsdill, a recent PhD graduate in Eroglu’s lab, grew the two cells together while tweaking neurons’ cellular signaling mechanisms. He was surprised to find that even if he outright killed the neurons, but preserved their structure as a scaffold, the astrocytes still beautifully elaborated on them.

“It didn’t matter if the neurons were dead or alive — either way, contact between astrocytes and neurons allowed the astrocyte to become complex,” Stogsdill said. “That told us that there are interactions between the cell surfaces that are regulating the process.”

Stogsdill searched existing genetic databases for cell surface proteins known to be expressed by astrocytes, and identified three candidates that might help direct their shape. These proteins, called neuroligins, play a role in building neural synapses and have been linked to diseases like autism and schizophrenia. Previously, their functions had been primarily studied in neurons.

To find out what role neuroligins play in astrocytes, Stogsdill tinkered with astrocytes’ ability to produce these proteins. He found that when he switched off the production of neuroligins, the astrocytes grew small and blunt. But when he boosted the production of neuroligins, astrocytes grew to nearly twice the size.

“The shape of the astrocytes was directly proportional to their expression of the neuroligins,” Stogsdill said.

Tweaking the expression of neuroligins didn’t just change the size and shape of the astrocytes. They also had a drastic effect on the synapses that astrocyte touched.

When Stogsdill switched off a single neuroligin — neuroligin 2 — the number of excitatory or “go” synapses dropped by 50 percent. The number of inhibitory or “stop” synapses stayed the same, but their activity increased.

“We are learning now that one of the hallmarks of neurological disorders like schizophrenia, autism and epilepsy is an imbalance between excitation and inhibition,” Stogsdill said. “Which just drives home that these disease-associated molecules are potentially functioning in astrocytes to shift this balance.”

Ben Barres, a professor of neurobiology at Stanford University who was not involved with the study, praised the findings as “a profoundly important, revolutionary advance” for understanding how interactions between neurons and astrocytes can affect synapse formation.

“These findings vividly illustrate once again how any important process in the brain can only be understood as a dialogue between astrocytes and neurons,” Barres said. “To ignore the astrocytes, which are vastly more numerous than neurons, is always a mistake.”

Other authors on the study are Juan Ramirez, Katherine T. Baldwin, Eray Enustun, Tiffany Ejikeme from Duke University Cell Biology Department and Ru-Rong Ji, Di Liu, Yong-Ho Kim from Duke University Department of Anesthesiology.

This research was supported by grants from the National Institutes of Health (RO1 DA031833, RO1 DE022743 and F31 NS092419) and a Holland Trice Brain Research Award. Additional support was provided by the Foerster-Bernstein Family and the Hartwell Foundation.

CITATION:  “Astrocyte Neuroligins Control Astrocyte Morphogenesis and Synaptogenesis,” Jeff A. Stogsdill, Juan Ramirez, Di Liu, Yong-Ho Kim, Katherine T. Baldwin, Eray Enustun, Tiffany Ejikeme, Ru-Rong Ji and Cagla Eroglu. Nature, Nov. 9, 2017. DOI: 10.1038/nature24638

“Cell Biology of Astrocyte-Synapse Interactions,” Nicola J. Allen and Cagla Eroglu. Neuron, Nov. 1, 2017. DOI: 10.1016/j.neuron.2017.09.056

Students win travel grants

We are pleased to announced the winners of Cycle 2 of the Regeneration Next student travel grants. Congratulations to:

Shaunak Adkar (Gersbach lab) to travel to the Orthopaedic Research Society annual symposium in March 2018 to present his work: Purification of hiPSC-derived chondrocyte-like cells using a CRISPR-Cas9-generated collagen II reporter enhances chondrogenesis and cartilaginous matrix production.

Victoria Deneke (DiTalia lab) to travel to the ASCB/EMBO joint annual meeting in December 2017 to present her work: Mechanisms regulating the emergence of tissue-wide synchrony in Drosophila early embryos.

Nora Peterson (Fox lab) to travel to the ASCB/EMBO joint annual meeting in December 2017 to present her work: Cell-cell fusion facilitates aneuploidy tolerance in a developing organ.

The next round of travel grant applications will open in January 2018. All students presenting work  relevant to tissue regeneration are encouraged to apply!