Monthly Archives: April 2016

What is the benefit of blood vessels

Artificial blood vessels transplanted into three lambs grew up along with the animals, scientists reported in a study published today in Nature Communications. Made from skin cells, the grafts successfully replaced part of the pulmonary artery, which carries blood from the heart to the lungs. If these bioengineered arteries work in humans, they could spare children with heart conditions from having to endure multiple open-heart surgeries.

“Kids that have congenital heart defects can require re-plumbing of the heart basically,” says coauthor Robert Tranquillo, a biomedical engineer at the University of Minnesota in Minneapolis. “Each few years as the child grows, the tube that was implanted earlier is no longer big enough and has to be replaced.”

Surgeons have traditionally relied on synthetic materials or transplants from cadavers, Tranquillo says. He and his colleagues wanted to engineer a more adaptable graft. They started with a scaffold made of skin cells called fibroblasts, which are involved in wound healing, and fibrin, a protein found in blood clots. Over several weeks, the team guided the sheep skin cells to produce collagen, which holds tissue together.

“When you have a wound…the fibrin clot becomes replaced with something that’s very collagenous, and that’s what we’re harnessing,” Tranquillo says. “We start with a material that’s like Jell-O and far too weak to implant, and it ends up becoming a tube of cell-produced tissue that is at least as strong as the native arteries.”

The team then washed away the skin cells, leaving behind a graft made from proteins that wouldn’t set off the lambs’ immune systems. The researchers then implanted the tubes into three lambs, and monitored the animals as they grew to adulthood.

The lambs put on weight normally, and their hearts appeared to be working as expected. When the animals were nearly a year old, the scientists examined the engineered blood vessels and found that they had become larger and taken on the curving shape of natural pulmonary arteries. “Its mechanical properties were basically indistinguishable from the native artery,” Tranquillo says.

The lambs’ own cells had also taken up residence in the graft and secreted elastin, which gives tissue its ability to stretch and recoil and is found in arteries. And the grafts weren’t plagued by aneurysms, in which the blood vessel bulges and can burst–or calcification, in which hard nodules of minerals form in the tissue.

“The fact that we got…the right cells in the right places, the production of more collagen, and deposition of elastin without any bad things happening…were all very good indicators that this starting material is capable of growing,” Tranquillo says. “The artery appeared to be developing along a normal pathway.”

In the future, the team expects to test the grafts in more animals and show that the artificial vessels can be grown from human cells. They’re also testing whether their grafts can self-repair, which would make them useful for adults. Ideally, the graft will become a ready-to-use tool that can be grown and stored without needing to be customized for individual patients.

The new graft is more expensive than current alternatives. “But it would be a relatively small expense compared to multiple open-heart surgeries,” Tranquillo says. “One open heart surgery is a big enough risk.”

Baby Born Procedure

Five months ago, on April 6th of this year, a boy born to a Jordanian couple became the first baby born in the world using a new in-vitro fertilization technique that uses the DNA material from two women and one man, according to a report out today in New Scientist.

A U.S. team of doctors assisted with the birth, which took place in Mexico, according to New Scientist, as the technique has not been approved in the United States. However, its overwhelming success could help the approval process in the United States to be green-lit by the FDA soon.

The couple decided to go through with the technique after they found out that the baby boy’s mother is a carrier for Leigh syndrome, a fatal disease that afflicted her first two children; the first died at age six from the disease, and the second at just eight months. The disease-causing mutation is found in the mother’s mitochondria, and the three-parent technique avoided using her mitochondria all together.

The technique, which is called pronuclear transfer, typically involves fertilizing two eggs, one from the donor and one from the mother, with the same man’s sperm. Then, just before the eggs begin dividing, the nucleus (which contains all the genetic material except for the disease-carrying mitochondrial DNA) is removed from both eggs, and the nucleus from the mother’s egg is placed into the donor egg. But in this case, due to religious reasons, the couple opted for a different technique, called spindle nuclear transfer, in which the same nuclei swapping occurs, but only the donor’s egg is fertilized. The baby was born, healthy, with less than one percent of his mitochondria carrying the mutation, New Scientist reports.

Back in the 90s, scientists experimented with another technique that used three-parent babies where they injected donor mitochondrial DNA and sperm into a woman’s egg. However, the technique caused genetic diseases, likely from having a mix of two different mitochondrial donors, and was banned.

The baby was born, healthy, with less than one percent of his mitochondria carrying the mutation.

There are still obstacles before this new technique is approved. As we reported last year, many groups are concerned that this could lead the way for designer babies, where for example, parents could choose what color hair or eyes their child will certainly have. But researchers have strongly emphasized that, similar to gene-editing technologies like CRISPR-Cas9, the technique is for therapeutic use only, as it was in this case.

Safety of the procedure itself is another concern, but a review published in the journal Nature in June deemed the technique safe, and that it significantly reduces, though doesn’t guarantee 100 percent, the chances of passing fatal disease-causing mitochondrial mutations onto the carrier’s child.

Going forward, doctors and researchers will follow the baby to ensure that his levels of the mitochondrial mutation remain as low as they are now, and it’s likely the FDA could take his case into consideration in deciding whether or not to approve the technique’s use in the U.S.
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IVF embryos in vitro fertilization reproduction mutations gene mutations Health

How to teach baby

There’s now another reason for new moms to treat themselves during breastfeeding: their milk will be hard at work as a teacher. Mothers’ breast milk teaches babies’ developing cells to defend against infection, according to new research led by University of California, Riverside.

“It’s like vaccinating the baby without actually vaccinating the baby,” lead researcher Ameae Walker said in a UCR news release. This “maternal educational immunity” transfers immune cells from the mother into the milk, which then makes its way to the thymus through digestion. These cells teach baby cells to develop immunities to whatever organisms the mother been exposed. These cellular lessons are carried throughout life.

Walker sees this as a way to get babies protected against infections that are sometimes too dangerous to vaccinate against in infancy. By boosting mom’s vaccination during pregnancy, her milk will be super-charged for when the baby arrives. With some diseases like tuberculosis, immunity through milk is even more effective than through a vaccine given to the baby.

Tips To Protect Us From Starvation

ryObesity now affects more than 600 million people worldwide and is increasingly becoming a serious public health problem. But despite this, we still don’t completely understand what causes people to become obese. Scientists know it’s an interaction between our genes and our environment, including the unique environment of microbes that live in our guts, but they are still unsure of how exactly these factors come together to cause someone to become overweight and eventually obese.

A new study out in the journal Cell Metabolism suggests that a popular, yet controversial theory on why our genes make us more susceptible to being obese–known as the thrifty-gene hypothesis–might not hold water, which may cause many researchers to continue to rethink obesity’s root causes and subsequently how they will go about treating it.

The idea behind the thrifty-gene hypothesis is this: back in the day, when we routinely went through periods of famine, those individuals who had genes that made them more likely to store fat were at an advantage compared to others. But now, because we don’t experience these famines anymore, those fat storing genes are actually putting people at a disadvantage by having them store fat for fasting periods that don’t end up happening.

Despite the popularity and simplicity of the idea, researchers have continually poked holes in its thesis for years. If these genes were so advantageous, why did only some people and not others inherit them? Shouldn’t they have, by now, spread to the entire population? To figure it out, researchers in this study looked at 115 genes known to be associated with obesity and tried to identify evidence that showed the genes to be under positive selection, also called Darwinian selection, where a gene that provides an advantage to the individual sweeps through the entire population. Typically, if a gene has very little variation, then it is more likely to be under positive selection.

What they found, though, was that only nine out of those 115 gene variants showed signs of positive selection. And of those nine, only four showed positive selection for fat storage; the other five actually showed positive selection for leanness.

“This is probably the hardest evidence so far against the thrifty gene hypothesis,” John Speakman, a coauthor of the paper wrote in the release. Speakman says their goal now is for researchers to think beyond the thrifty gene hypothesis as the reason for the genetic cause of obesity.

While overall, the results do lean away from the popular hypothesis, the study did have its limitations. As a metric for obesity, the study used BMI (body mass index) which only takes into account body weight and height and isn’t often considered the best measurement for determining if a person is obese. Further, the method they used for determining if a gene variant was positively selective works best if the variant in question is focused on a single mutation where natural selection is quick to eliminate other variants. In the future, the researchers plan to test their results using other toolsets. For now, though, the results of this study could still be enough to cause scientists studying the genetic factors of obesity to focus on other reasons for obesity to arise in an individual.