If confirmed in humans, these new heart valves could prevent the need for repeated valve replacement surgeries in thousands of children born each year with congenital heart defects. The valves can also be stored for at least six months, which means they could provide surgeons with an “off the shelf” option for treatment.

The study was published today in Science Translational Medicine, an interdisciplinary medical journal by the American Association for the Advancement of Science (AAAS). The valve-making procedure has also been patented and licensed to the University of Minnesota startup company Vascudyne, Inc. (Stillwater, Minn.).

“This is a huge step forward in pediatric heart research,” said Robert Tranquillo, the senior researcher on the study and a University of Minnesota professor in the Departments of Biomedical Engineering and the Department of Chemical Engineering and Materials Science. “This is the first demonstration that a valve implanted into a large animal model, in our case a lamb, can grow with the animal into adulthood. We have a way to go yet, but this puts us much farther down the path to future clinical trials in children. We are excited and optimistic about the possibility of this actually becoming a reality in years to come.”

Currently, researchers have not been able to develop a heart valve that can grow and maintain function for pediatric patients. The only accepted options for these children with heart defects are valves made from chemically treated animal tissues that often become dysfunctional due to calcification and require replacement because they don’t grow with the child. These children will often need to endure up to five (or more) open heart surgeries until a mechanical valve is implanted in adulthood. This requires them to take blood thinners the rest of their lives.

In this study, Tranquillo and his colleagues used a hybrid of tissue engineering and regenerative medicine to create the growing heart valves. Over an eight-week period, they used a specialized tissue engineering technique they previously developed to generate vessel-like tubes in the lab from a post-natal donor’s skin cells. To develop the tubes, researchers combined the donor sheep skin cells in a gelatin-like material, called fibrin, in the form of a tube and then provided nutrients necessary for cell growth using a bioreactor.

The researchers then used special detergents to wash away all the sheep cells from the tissue-like tubes, leaving behind a cell-free collagenous matrix that does not cause immune reaction when implanted. This means the tubes can be stored and implanted without requiring customized growth using the recipient’s cells.

The next step was to precisely sew three of these tubes (about 16 mm in diameter) together into a closed ring. The researchers then trimmed them slightly to create leaflets to replicate a structure similar to a heart valve about 19 mm in diameter.

Video: https://www.youtube.com/watch?v=zpRbFsAVofA

“After these initial steps, it looked like a heart valve, but the question then became if it could work like a heart valve and if it could grow,” Tranquillo said. “Our findings confirmed both.”

This second generation of tri-tube valves were implanted into the pulmonary artery of three lambs. After 52 weeks, the valve regenerated as its matrix became populated by cells from the recipient lamb, and the diameter increased from 19 mm to a physiologically normal valve about 25 mm. The researchers also saw a 17 to 34 percent increase in the length of the valve leaflets as measured from ultrasound images. In addition, researchers showed that the tri-tube valves worked better than current animal-derived valves with almost none of the calcification or blood clotting that the other valves showed after being implanted in lambs of the same age.

“We knew from previous studies that the engineered tubes have the capacity to regenerate and grow in a growing lamb model, but the biggest challenge was how to maintain leaflet function in a growing valved conduit that goes through 40 million cycles in a year,” said Zeeshan Syedain, the lead researcher on the study and a University of Minnesota senior research associate in Tranquillo’s lab. “When we saw how well the valves functioned for an entire year from young lamb to adult sheep, it was very exciting.”

https://www.youtube.com/watch?v=rme9CZgRgsg

Tranquillo said the next steps are to implant the tri-tube valve directly into the right ventricle of the heart to emulate the most common surgical repair and then start the process of requesting approval from the U.S. Food and Drug Administration (FDA) for human clinical trials over the next few years.

“If we can get these valves approved someday for children, it would have such a big impact on the children who suffer from heart defects and their families who have to deal with the immense stress of multiple surgeries,” Tranquillo said. “We could potentially reduce the number of surgeries these children would have to endure from five to one. That’s the dream.”

In addition to Tranquillo and Syedain, the research team included Bee Haynie (independent contractor); University of Minnesota researchers Sandra L. Johnson and Greeshma Thrivikraman (biomedical engineering), James Berry, Richard Bianco, John P. Carney, and Matthew Lahti (experimental surgical services); Jirong Li (mechanical engineering); and Ryan C. Hill and Kirk C. Hansen (University of Colorado Anschutz Medical Campus).

The research was funded by the National Institutes of Health (R01 HL107572).

To read the full research paper entitled “Pediatric tri-tube valved conduits made from fibroblast-produced extracellular matrix evaluated over 52 weeks in growing lambs,” visit the Science Translational Medicine website.

To better characterize “The Great Dying,” the team sought to understand why communities didn’t recover as quickly as other mass extinctions. The main reason was that the end-Permian crisis was much more severe than any other mass extinction, wiping out 19 out of every 20 species. With survival of only 5% of species, ecosystems had been destroyed, and this meant that ecological communities had to reassemble from scratch.

To investigate, lead author and Academy researcher Yuangeng Huang, now at the China University of Geosciences, Wuhan, reconstructed food webs for a series of 14 life assemblages spanning the Permian and Triassic periods. These assemblages, sampled from north China, offered a snapshot of how a single region on Earth responded to the crises. “By studying the fossils and evidence from their teeth, stomach contents, and excrement, I was able to identify who ate whom,” says Huang. “It’s important to build an accurate food web if we want to understand these ancient ecosystems.”

The food webs are made up of plants, molluscs, and insects living in ponds and rivers, as well as the fishes, amphibians, and reptiles that eat them. The reptiles range in size from that of modern lizards to half-ton herbivores with tiny heads, massive barrel-like bodies, and a protective covering of thick bony scales. Sabre-toothed gorgonopsians also roamed, some as large and powerful as lions and with long canine teeth for piercing thick skins. When these animals died out during the end-Permian mass extinction, nothing took their place, leaving unbalanced ecosystems for ten million years. Then, the first dinosaurs and mammals began to evolve in the Triassic. The first dinosaurs were small — bipedal insect-eaters about one meter long — but they soon became larger and diversified as flesh- and plant-eaters.

“Yuangeng Huang spent a year in my lab,” says Peter Roopnarine, Academy Curator of Geology. “He applied ecological modelling methods that allow us to look at ancient food webs and determine how stable or unstable they are. Essentially, the model disrupts the food web, knocking out species and testing for overall stability.”

“We found that the end-Permian event was exceptional in two ways,” says Professor Mike Benton from the University of Bristol. “First, the collapse in diversity was much more severe, whereas in the other two mass extinctions there had been low-stability ecosystems before the final collapse. And second, it took a very long time for ecosystems to recover, maybe 10 million years or more, whereas recovery was rapid after the other two crises.”

Ultimately, characterizing communities — especially those that recovered successfully — provides valuable insights into how modern species might fare as humans push the planet to the brink.

“This is an amazing new result,” says Professor Zhong-Qiang Chen of the China University of Geosciences, Wuhan. “Until now, we could describe the food webs, but we couldn’t test their stability. The combination of great new data from long rock sections in North China with cutting-edge computational methods allows us to get inside these ancient examples in the same way we can study food webs in the modern world.”

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Materials provided by California Academy of Sciences. Note: Content may be edited for style and length.

In a study published in Nano Letters, physicists from Michigan Technological University explore alternative materials to improve capacity and shrink the size of digital data storage technologies. Ranjit Pati, professor of physics at Michigan Tech, led the study and explains the physics behind his team’s new nanowire design.

“Thanks to a property called spin, electrons behave like tiny magnets,” Pati said. “Similar to how a bar magnet’s magnetization is dipolar, pointing from south to north, the electrons in a material have magnetic dipole moment vectors that describe the material’s magnetization.”

When these vectors are in random orientation, the material is nonmagnetic. When they are parallel to each other, it’s called ferromagnetism and antiparallel alignments are antiferromagnetism. Current data storage technology is based on ferromagnetic materials, where the data are stored in small ferromagnetic domains. This is why a strong enough magnet can mess up a mobile phone or other electronic storage.

Depending on the direction of magnetization (whether pointing up or down), data are recorded as bits (either a 1 or 0) in ferromagnetic domains. However, there are two bottlenecks, and both hinge on proximity. First, bring an external magnet too close, and its magnetic field could alter the direction of magnetic moments in the domain and damage the storage device. And, second, the domains each have a magnetic field of their own, so they can’t be too close to each other either. The challenge with smaller, more flexible, more versatile electronics is that they demand devices that make it harder to keep ferromagnetic domains safely apart.

“Ultrahigh-density data packing would be a daunting task with ferromagnetic memory domains,” Pati said. “Antiferromagnetic materials, on the other hand, are free from these issues.”

On their own antiferromagnetic materials aren’t great for electronic devices, but they’re not influenced by outside magnetic fields. This ability to resist magnetic manipulation started getting more attention from the research community and Pati’s team used a predictive quantum many-body theory that considers electron-electron interactions. The team found that chromium-doped nanowires with a germanium core and silicon shell can be an antiferromagnetic semiconductor.

Several research groups have recently demonstrated manipulation of individual magnetic states in antiferromagnetic materials using electrical current and lasers. They observed spin dynamics in the terahertz frequency — much faster than the frequency used in our current data storage devices. This observation has opened up a plethora of research interests in antiferromagnetism and could lead to faster, higher-capacity data storage.

“In our recent work, we have successfully harnessed the intriguing features of an antiferromagnet into a low-dimensional, complementary metal-oxide compatible semiconductor (CMOS) nanowire without destroying the semiconducting property of the nanowire,” Pati said. “This opens up possibilities for smaller and smarter electronics with higher capacity data storage and manipulation.”

Pati adds that the most exciting part of the research for his team was uncovering the mechanism that dictates antiferromagnetism. The mechanism is called superexchange and it controls the spin of electrons and the antiparallel alignment that makes them antiferromagnetic. In the team’s nanowire, germanium electrons act as a go-between, an exchanger, between unconnected chromium atoms.

“The interaction between the magnetic states of the chromium atoms is mediated by the intermediate atoms they are bonded to. It is a cooperative magnetic phenomenon,” Pati said. “In a simple way, let us say there are two people A and B: They are far apart and cannot communicate directly. But A has a friend C and B has a friend D. C and D are close friends. So, A and B can interact indirectly through C and D.”

Better understanding how electrons communicate between atomic friends enables more experiments to test the potential of materials like chromium-doped nanowires. Better understanding the germanium-silicon nanowire material’s antiferromagnetic nature is what boosts potential for smaller, smarter, higher capacity electronics.

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Materials provided by Michigan Technological University. Original written by Allison Mills. Note: Content may be edited for style and length.