Using Stem Cells to Repair Damaged Tissue
Repairing heart tissue after a heart attack is a major focus of tissue engineering. A key challenge here is keeping grafted cardiomyocytes in place within the tissue to promote repair. As we reported a couple of weeks ago, using tissue spheroids and nanowires is one approach to overcome this challenge. Another approach involves manipulating the cell cycle — the process by which normal cells reproduce, grow, and eventually die.
People and Places
An Immune Cell Atlas
The human immune system deploys a variety of cells to counteract pathogens when they enter the body. B cells are a type of white blood cell specific to particular pathogens, and they form part of the adaptive immune system. As these cells develop, the cells with the strongest reactions to antigens are favored over others. This process is called clonal selection. Given the sheer number of pathogens out there, the number of different clonal lineages for B cells is estimated to be around 100 billion. A landscape like that can be difficult to navigate without a map.
Luckily, an atlas was recently published in Nature Biotechnology. It is the work of scientists collaborating between Penn’s own Perelman School of Medicine and faculty from the School of Biomedical Engineering, Science and Health Systems at our next-door neighbor, Drexel University. Using tissue samples from an organ donor network, the authors, led by Nina Luning Prak, MD, PhD, of Penn and Uri Heshberg, Ph.D., of Drexel, submitted the samples to a process called deep immune repertoire profiling to identify unique clones and clonal lineages. In total, they identified nearly a million lineages and mapped them to two networks: one in the gastointestinal tract and one that connects the blood, bone marrow, spleen, and lungs. This discovery suggests that the networks might be less complicated than initially thought. Also, it confirms a key role for the immune system in the gut.
Not only does this B cell atlas provide valuable information to the scientific community, but it also could serve as the basis for immune-based therapies for diseases. If we can identify these lineages and how clonal selection occurs, we could identify the most effective immunological cells and perhaps engineer them in the lab. At the very least, the extent to which scientists understand how B cells are formed and develop has received an enormous push with this research.
Understanding Muscle Movement
Natural movements of limbs require the coordinated activation of several muscle groups. Although the molecular composition of muscle is known, there remains a poor understanding of how these molecules coordinate their actions to confer power, strength, and endurance to muscle tissue. New fields of synthetic biology require this new knowledge to efficiently produce naturally inspired muscle substitutes.
Responding to this challenge, scientists at Carnegie Mellon University, including Philip R. LeDuc, Ph.D., William J. Brown Professor of Mechanical Engineering and Professor of Biomedical Engineering, have developed a computational system to better understand how mixtures of specific myosins affect muscle properties. Their method, published in PNAS, uses a computer model to show that mixtures of myosins will unexpectedly produce properties that are not the average of myosin molecular properties. Instead, the myosin mixtures coordinate and complement each other at the molecular level to create emergent behaviors, which lead to a robustness in how the muscle functions across a broad range. Dr. LeDuc and his colleagues then confirmed their model in lab experiments using muscle tissue from chickens. In the future, this new computational method could be used for other types of tissue, and it could prove useful in developing treatments for a variety of disorders.
Determining Brain Connectivity
How the brain forms and keeps memories is one of the greatest challenges in neuroscience. The hippocampus is a brain region considered critical for remembering sequences and events. The connections made by the hippocampus to other brain regions is considered critical for the hippocampus to integrate and remember experiences. However, this broad connectivity of the hippocampus to other brain areas raises a critical question: What connections are essential for rewiring the brain for new memories?
To offer an explanation for this question, a team of scientists in Hong Kong published a paper in PNAS in which they report on a study conducted in rats using resting-state function MRI. The study team, led by Ed X. Wu, Ph.D., of the University of Hong Kong, found that stimulation of a region deep in the hippocampus would propagate more broadly out into many areas of the cortex. The stimulation frequency affected how far this signal propagated from the hippocampus and pointed out the ability for frequency-based information signals to selectively connect the hippocampus to the rest of the brain. Altering the frequency of stimulation could affect visual function, indicating that targeted stimulation of the brain could have widespread functional effects throughout the brain.
Although human and rodent brains are obviously different, these findings from rats offer insights into how brain connectivity emerges in general. Similar studies in humans will be needed to corroborate these findings.
Seeing Inside a Tumor
Years of research have yielded the knowledge that the most effective treatments for cancer are often individualized. Knowing the genetic mutation involved in oncogenesis, for instance, can provide important information about the right drug to treat the tumor. Another important factor to know is the tumor’s chemical makeup, but far less is known about this factor due to the limitations of imaging.
However, a new study published in Nature Communications is offering some hope in this regard. In the study, scientists led by Xueding Wang, Ph.D., associate professor of biomedical engineering and radiology at the University of Michigan, used pH-sensing nanoprobes and multiwavelength photoacoustic imaging to determine tumor types in phantoms and animals. This new technology is based on the principle that cancerous cells frequently lower the pH levels in tissue, and designing probes with properties that are pH sensitive provides a method to find tumors with imaging methods and also treat these tumors.
With this technology, Dr. Wang and his colleagues were able to obtain three-dimensional images of pH levels inside of tumors. Importantly, it allowed them to noninvasively view the changes in a dye injected inside the tumor. Although a clinical application is years away, the information obtained using the Michigan team’s techniques could add significantly to our knowledge about tumorigenesis and tumor growth.
The Role of Bacteria in MS
The growing awareness of how bacteria interact with humans to affect health has led to the emergence of new scientific areas (e.g., human microbiome). Research findings from scientists collaborating between Caltech and UCSF suggest bacteria can play a role in the onset of multiple sclerosis. These investigators include Sarkis K. Mazmanian, Ph.D., Luis B. and Nelly Soux Professor of Microbiology and a faculty member in the Division of Biology and Biological Engineering at Caltech. Reporting their research results in PNAS, the researchers found several bacteria elevated in the MS microbiome. Study results showed that these bacteria regulated adaptive immune responses and helped to create a proinflammatory milieu. The identification of the bacteria interacting with immunity in MS patients could result in better diagnosis and treatment of this disabling disease.
People and Places
Live Bone Cells Grown in Lab
Bone injuries and bone loss can constitute major challenges for patients and the people who treat them. Beyond the need for bone grafts or artificial implants in cases such as severe fractures, cancers metastasizing to the bones can be disabling and disfiguring. Doctors are able to use autologous bone grafts, in which patients are their own bone donors and provides grafts from other bones in their bodies. However, the grafting process compromises the bone from the donor site. In addition, there are specific problems in cases of long bones, such as those in the arms and legs. With these bones, no site of the body can provide sufficient material without becoming severely compromised itself due to bone loss.
Stem cells have been intensively investigated as a source of bone grafts. With their ability to produce a variety of cell lines from the same source, these cells have the potential to be used in a variety of clinical situations. The mechanisms underlying the determination of the type of cell that an individual stem cell will become are known. However, the ability to produce living bone cells in the laboratory had remained elusive – until now. In an article published online last week by Nature Biomedical Engineering, a group of scientists led in part by Professor Matthew Dalby, a cellular engineer with the Institute of Molecular, Cell and Systems Biology at the University of Glasgow, United Kingdom, reported its success.
Professor Dalby’s tissue engineering team used a nanoscale bioreactor to stimulate mesenchymal stem cells into osteogenesis (bone creation). The bioreactor applied vibrations on a microscopic scale of 1,000 hertz with 15 nanometers of vertical displacement. In their previous work, Professor Dalby and his colleagues could generate only one bone cell sample at a time. In the current paper, they showed the ability to generate multiple cells for three-dimensional tissue. In addition, they showed that the cells could be generated in environments with less rigidity than that in which osteogenesis normally occurs. This is an important advance because the body provides optimal conditions of stiffness for this process, but the lab does not. Should the techniques in the paper prove viable on a greater scale, they could revolutionize the field of bone grafting.
Microfluidics in the News
Since their introduction, organs on a chip (OOCs) have proliferated in the field of bioengineering. These chips use microfluidics technology to create a model of an organ system in the body. However, until now, OOCs have not been used to model the human placenta – the tissue that connects the embryonic sac to the uterine wall during pregnancy.
Responding to the lack of a OOC model of the placenta, two professors at Florida International University (FAU) have developed a placenta OOC. Sarah E. Du, Ph.D., assistant professor of ocean and mechanical engineering, and Andrew Oleinkov, Ph.D., associate professor of biomedical science, have collaborated to create this chip, which they to intend to use to determine the effects of malaria on the placental microenvironment. A $400,000 grant from the NIH will certainly help.
With malaria causing more than 200,000 perinatal deaths annually, beyond the burden we cited last week, there is an urgent need to determine the exact effects of this parasitic infection on the placenta. Without this knowledge, the development of technologies to mitigate or even prevent these effects will be much more difficult. In addition, because of the obvious ethical constraints on prospective testing in natural history studies, the placenta OOC offers an ideal model.
Elsewhere in the field of microfluidics, an NIH grant to scientists at the University of Illinois, Urbana-Champaign, has gone toward the development of a new test chip to detect sepsis, a condition in which the body’s reaction to infection results in inflammation of the blood vessels and which can cause lethal shock unless detected and treated promptly. The UIUC team developing this more rapid diagnostic technology is led by Rashid Bashir, Ph.D., professor of bioengineering and associate dean of UIUC’s Carle Illinois College of Medicine. Dr. Bashir was lead author on a paper published over the summer in Nature Communications.
Among the more remarkable aspects of the chip developed by Professor Bashir and his colleagues is that it can diagnose sepsis with a single drop of blood. Therefore, in addition to the device’s portability and size, which allows it to be used at the point of care, it is only necessary to use 10 microliters of blood to complete the test. Other available lab tests for sepsis can require as much as 300 times as much blood. Testing its device against the gold standard of flow cytometry, the UIUC team found that the findings obtained with its biochip were strongly correlated with those from flow cytometry. Unlike the new chip, flow cytometry cannot be performed outside the lab.
Since a large proportion of sepsis patients are treated in intensive care units, the ICU is a likely setting in which the biochip could be used, particularly because some ICUs might be in hospitals where the staff does not have 24-hour lab access. The ability to use this chip at the bedside immediately, rather than waiting until the next morning or longer, could make a key difference in detecting and treating sepsis.
Brains on the Internet
For years, Ray Kurzweil, the computer scientist turned author and inventor, has been discussing a future in which, he claims, the distinction between human and artificial intelligence will disappear. For example, Kurweil imagines brains being uploaded to computers. While what Kurzeil imagines has yet to materialize, scientists in South Africa have created the “Brainternet,” which streams brain waves onto the Internet in real time.
As a student project at the School of Electrical and Information Engineering of the University of Witerstand in Johannesburg led by Adam Pantanowitz, a lecturer in the school, the Brainternet was developed from pre-existing technology. The project starts with portable electroencephalography (EEG), which is worn by the subject and which transmits its signal by telemetry to a Raspberry Pi computer. Then, using open source software, the computer live streams the data to an application programming interface, which in turn allows the data to be published at a website accessible to others.
Beyond being an innovative use of these technologies, the Brainternet could be used in telemedicine applications. For instance, it could be helpful in situations where a specialist neurologist is not in the immediate geographic vicinity. Moreover, for research projects involving EEG measurement during tasks or under certain types of external stimulation, the Brainternet could allow for a much larger sample size to be enrolled, owing to its portability and use of the Internet.
People and Places
Dawn Elliott, Ph.D., chair of the Department of Biomedical Engineering at the University of Delaware, has been elected president of the Biomedical Engineering Society (BMES), for which she had served as treasurer. Dr. Elliott’s term as president will begin in October 2018 and last for two years. As president, she plans to take a closer look at education in the field to determine how bioengineering and biomedical engineering departments can graduate the most successful students. We wish her the best of luck and hearty congratulations.
A Breath of Fresh Air
At Columbia, a new way of treating lung disease is under development. As reported recently in Science Advances, a Columbia research group, headed by Gordana Vunjak-Novakovic, Ph.D., from the Department of Biomedical Engineering, developed a way to prepare grafted lung tissue for transplantation that could make the process easier. The challenge has been removing the epithelial cells, which ultimately make up the surface of the organ, from potential grafts without damaging the blood vessels. Applying a detergent solution to lung tissue from rats, Dr. Vunjak-Novakovic’s team was able to obtain grafts that could subsequently be used as scaffolds for human pulmonary cells and stem cell-derived lung epithelial cells. Although this approach remains in a very early state, the results here indicate promise for this technology for end-stage lung diseases such as emphysema.
Eliminating Obesity and Diabetes With Injections
You’ve probably heard that there’s an epidemic of obesity in the United States. Obesity carries an enormous health cost because it is linked to a variety of major health complications, including diabetes and heart disease. At a cell level, white fat cells require more energy to work off than brown fat cells. Approaches to fight obesity now include efforts to increase the number of brown fat cells. Scientists at Purdue University might have found a significant shortcut to creating more brown fat cells. By inhibiting the Notch signaling pathway, Meng Deng, Ph.D., of the Weldon School of Biomedical Engineering and his colleagues were able to cause white fat cells to convert into brown cells. Reporting their results in Molecular Therapy, the team used nanoparticles loaded with dibenazapine, a chemical used widely in pharmacology, to treat obese mice with targeted injections of the drug-laden nanoparticles. Results showed that the reduction of white fat in the mice was correlated with improved glucose metabolism and reduced body weight. While it’s not yet time to cancel the gym membership, an easier way to combat obesity could be on the horizon.
Diabetes is a chronic health condition with treatments that include diet management and/or insulin injections. In a new twist on diabetes treatments, scientists at the University of Toronto have shown, in a recent PNAS study, that pancreatic islets cells, which produce insulin, could be injected subcutaneously to reverse diabetes in mice. While the idea of transplanting islets into the pancreas has been investigated for some time, this is the first time that transplants were placed under the skin, far away from the pancreas. Impressively, the modules could be retrieved and reused. If future investigations are successful, these modules could form the basis of a treatment for type 1 (so-called juvenile) diabetes, which is caused by autoimmune destruction of the pancreatic islets.
News from New England
Feng Zhang, Ph.D., associate professor in the Departments of Brain and Cognitive Sciences and of Biological Engineering at MIT, is one of five scientists to receive the Albany Medical Prize in Medicine and Biomedical Research for his work on CRISPR-Cas9 gene editing technology. We offer Dr. Zhang our heartfelt congratulations.
Across the river from Cambridge in Medford, Tufts University has announced that its newly completed Science and Engineering Complex (SEC) will open this semester and will combine classrooms and laboratories — specifically what the developers are calling “lab neighborhoods,” or spaces for collaboration among laboratories working on related research questions. Bruce Panilaitis, Ph.D., a research assistant professor in the Department of Biomedical Engineering, is the director of the SEC, and his department will also have offices there.
Continuing with our series of interviews with new faculty members, we feature this interview with Dr. Joel Boerckel, who has a dual appointment in the Department of Bioengineering at Penn and the Perelman School of Medicine’s Department of Orthopaedic Surgery. Dr. Boerckel’s research concerns the mechanobiology of development and regeneration. Here, he speaks with Andrew Mathis about his career to this point and where he sees the fields of tissue engineering and regenerative medicine heading over the future. Enjoy!
Synthetic biology (SynBio) is an important field within bioengineering. Now, SynBio and its relationships with nanotechnology and microbiology will get a big boost with a $6 million grant from the National Science Foundation awarded to the lab of Jason Gleghorn, Ph.D., assistant professor of biomedical engineering at the University of Delaware. The grant, which comes from the NSF’s Established Program to Stimulate Competitive Research, will fund research to determine the interactions between a single virus and single microbe, using microfluidics technology so that the lab staff can examine the interactions in tiny droplets of fluid, rather than using pipettes and test tubes. They believe their research could impact healthcare broadly, as well as perhaps help agriculture by increasing crop yields.
While must SynBio research is medical, the technology is now also being used in making commercial products that will compete with other natural or chemically synthesized products. Antony Evans’s company Taxa Biotechnologies has developed a fragrant moss that he hopes can compete against the sprays and other chemicals you see on the store shelves. Using SynBio principles, Taxa isolates the gene in plants causing odor and transplants these genes to a simple moss in a glass terrarium that, with sufficient sunlight, water, carbon dioxide, will provide one of three scents completely naturally. Technically, the mosses are genetically modified organisms (GMOs), but since people aren’t eating them, they aren’t likely to generate the controversy raised by GMO foods. Taxa has also been working on transplanting bioluminescence genes to plants to provide light without requiring electricity, all as a part of a larger green campaign.
A Few Good Brains
A division of the U.S. Department of Defense, the Targeted Neuroplasticity Training (TNT) program of the Defense Advanced Research Projects Agency (DARPA) will fund the research of Stephen Helms Tillery, Ph.D., of the School of Biological & Health Systems Engineering at Arizona State University, who is investigating methods of enhancing cognitive performance using external stimulation. The ASU project is using transdermal electrical neuromodulation to apply electrical stimulation via electrodes placed on the scalp to determine the effects on awareness and concentration. DARPA hopes to obtain insight into how to improve decision making among troops who are actively deployed. The high-stress environment of a military deployment, combined with the fact that soldiers tend to get suboptimal amounts of sleep, leaves them with fatigue that can cloud judgment in moments of life or death. If the DARPA can find a way to alleviate that fatigue and clarify decision-making processes, it would likely save lives.
End-stage organ failure can be treated by transplantation, but waiting lists are long and the number of donors still insufficient, so alternatives are continually sought. In the field of regenerative medicine, which is partly dedicated to finding alternatives, scientists at Ohio State have developed a technology called tissue nanotransfection, which can generate any cell type within a patient’s own body. In a paper published in Nature Nanotechnology, professors Chandan Sen and James Lee and their research team describe how they used nanochip technology to reprogram skin cells into vascular cells. After injecting these cells into the injured legs and brains of mice and pigs, they found the cells could help to restore blood flow. The applications to organ systems is potentially limitless.
For cardiac patients whose conditions can be treated without need for a transplant, who make up the vast majority of this cohort, stents and valve prostheses are crucial tools. However, these devices and the procedures to implant them have high complication rates. Currently, patients receiving prosthetic valves made in part of metal must take blood thinners to prevent clots, and these drugs can greatly diminish quality of life and limit activity, particularly in younger patients. At Cornell, Jonathan Butcher, Ph.D., associate professor of biomedical engineering, is developing a prosthetic heart valve with small niches in the material loaded with biomaterials to maintain normal heart function and prevent clotting. While it has been possible for some time to coat the surface of an implant with a drug or chemical to facilitate its integration and function, these niches allow for a larger depot of such a material to be distributed over a longer period of time, increasing the durability of the positive effects of these procedures.
A number of medical diagnoses are accomplished by testing of bodily fluids, and spectrometry is a key technology in this process. However, spectrometers are expensive and usually not very portable, posing a challenge for health professionals working outside of traditional care settings. Now, a team led by Brian Cunningham, Ph.D., from the University of Illinois, Urbana-Champaign, has published in Lab on a Chip a paper detailing their creation of a smartphone-integrated spectroscope. Called the spectral Transmission-Reflectance-Intensity (TRI)-Analyzer, it uses microfluidics technology to provide point-of-care analysis to facilitate treatment decisions. The authors liken it to a Swiss army knife in terms of versatility and stress that the TRI Analyzer is less a specialized device than a mobile laboratory. The device costs $550, which is several times less than common lab-based instruments.
New Chair at Stanford
One of the more interesting tissue engineering stories to emerge this past month was the successful finding of a team at Worcester Polytechnic Institute (WPI), which used the veins in spinach leaves as a scaffold that was then recellularized with stem cells that produce heart muscle cells. After three weeks, the transplanted cells showed the ability to contract like the heart does when it beats.
“Proper vascularization of artificial living tissues has been one of the most critical challenges of tissue engineering for decades. This is particularly problematic when the size of the engineered tissue increases.,” said Dongeun (Dan) Huh, PhD, Wilf Family Term Assistant Professor in the Department of Bioengineering at the University of Pennsylvania “This work takes an unusual yet ingenious approach to solving this long-standing problem.”
Below you can watch a short video of some of the investigators on the study talking about it.