Posts tagged medicine

Posts tagged medicine
Using a type of human stem cell, Johns Hopkins researchers say they have created a three-dimensional complement of human retinal tissue in the laboratory, which notably includes functioning photoreceptor cells capable of responding to light, the first step in the process of converting it into visual images.

(Image caption: Rod photoreceptors (in green) within a “mini retina” derived from human iPS cells in the lab. Image courtesy of Johns Hopkins Medicine)
“We have basically created a miniature human retina in a dish that not only has the architectural organization of the retina but also has the ability to sense light,” says study leader M. Valeria Canto-Soler, Ph.D., an assistant professor of ophthalmology at the Johns Hopkins University School of Medicine. She says the work, reported online June 10 in the journal Nature Communications, “advances opportunities for vision-saving research and may ultimately lead to technologies that restore vision in people with retinal diseases.”
Like many processes in the body, vision depends on many different types of cells working in concert, in this case to turn light into something that can be recognized by the brain as an image. Canto-Soler cautions that photoreceptors are only part of the story in the complex eye-brain process of vision, and her lab hasn’t yet recreated all of the functions of the human eye and its links to the visual cortex of the brain. “Is our lab retina capable of producing a visual signal that the brain can interpret into an image? Probably not, but this is a good start,” she says.
The achievement emerged from experiments with human induced pluripotent stem cells (iPS) and could, eventually, enable genetically engineered retinal cell transplants that halt or even reverse a patient’s march toward blindness, the researchers say.
The iPS cells are adult cells that have been genetically reprogrammed to their most primitive state. Under the right circumstances, they can develop into most or all of the 200 cell types in the human body. In this case, the Johns Hopkins team turned them into retinal progenitor cells destined to form light-sensitive retinal tissue that lines the back of the eye.
Using a simple, straightforward technique they developed to foster the growth of the retinal progenitors, Canto-Soler and her team saw retinal cells and then tissue grow in their petri dishes, says Xiufeng Zhong, Ph.D., a postdoctoral researcher in Canto-Soler’s lab. The growth, she says, corresponded in timing and duration to retinal development in a human fetus in the womb. Moreover, the photoreceptors were mature enough to develop outer segments, a structure essential for photoreceptors to function.
Retinal tissue is complex, comprising seven major cell types, including six kinds of neurons, which are all organized into specific cell layers that absorb and process light, “see,” and transmit those visual signals to the brain for interpretation. The lab-grown retinas recreate the three-dimensional architecture of the human retina. “We knew that a 3-D cellular structure was necessary if we wanted to reproduce functional characteristics of the retina,” says Canto-Soler, “but when we began this work, we didn’t think stem cells would be able to build up a retina almost on their own. In our system, somehow the cells knew what to do.”
When the retinal tissue was at a stage equivalent to 28 weeks of development in the womb, with fairly mature photoreceptors, the researchers tested these mini-retinas to see if the photoreceptors could in fact sense and transform light into visual signals.
They did so by placing an electrode into a single photoreceptor cell and then giving a pulse of light to the cell, which reacted in a biochemical pattern similar to the behavior of photoreceptors in people exposed to light.
Specifically, she says, the lab-grown photoreceptors responded to light the way retinal rods do. Human retinas contain two major photoreceptor cell types called rods and cones. The vast majority of photoreceptors in humans are rods, which enable vision in low light. The retinas grown by the Johns Hopkins team were also dominated by rods.
Canto-Soler says that the newly developed system gives them the ability to generate hundreds of mini-retinas at a time directly from a person affected by a particular retinal disease such as retinitis pigmentosa. This provides a unique biological system to study the cause of retinal diseases directly in human tissue, instead of relying on animal models.
The system, she says, also opens an array of possibilities for personalized medicine such as testing drugs to treat these diseases in a patient-specific way. In the long term, the potential is also there to replace diseased or dead retinal tissue with lab-grown material to restore vision.
(Source: hopkinsmedicine.org)
New Method Reveals Key Protein Interaction For Embryonic Stem Cell Differentiation
Proteins are responsible for the vast majority of the cellular functions that shape life, but like guests at a crowded dinner party, they interact transiently and in complex networks, making it difficult to determine which specific interactions are most important.
Now, researchers from the University of Chicago have pioneered a new technique to simplify the study of protein networks and identify the importance of individual protein interactions. By designing synthetic proteins that can only interact with a pre-determined partner, and introducing them into cells, the team revealed a key interaction that regulates the ability of embryonic stem cells to change into other cell types. They describe their findings June 5 in Molecular Cell.
“Our work suggests that the apparent complexity of protein networks is deceiving, and that a circuit involving a small number of proteins might control each cellular function,” said senior author Shohei Koide, PhD, professor of biochemistry & molecular biophysics at the University of Chicago.
For a cell to perform biological functions and respond to the environment, proteins must interact with one another in immensely complex networks, which when diagrammed can resemble a subway map out of a nightmare. These networks have traditionally been studied by removing a protein of interest through genetic engineering and observing whether the removal destroys the function of interest or not. However, this does not provide information on the importance of specific protein-to-protein interactions.
To approach this challenge, Koide and his team pioneered a new technique that they dub “directed network wiring.” Studying mouse embryonic stem cells, they removed Grb2, a protein essential to the ability of the stem cell to transform into other cell types, from the cells. The researchers then designed synthetic versions of Grb2 that could only interact with one protein from a pool of dozens that normal Grb2 is known to network with. The team then introduced these synthetic proteins back into the cell to see which specific interactions would restore the stem cell’s transformative abilities.
“The name, ‘directed network wiring,’ comes from the fact that we create minimalist networks,” Koide said. “We first remove all communication lines associated with a protein of interest and add back a single line. It is analysis by addition.”
Despite the complexity of the protein network associated with stem cell development, the team discovered that restoring only one interaction—between Grb2 and a protein known as Ptpn11/Shp2 phosphatase—was enough to allow stem cells to again change into other cell types.
“We were really surprised to find that consolidating many interactions down to a single particular connection for the protein was sufficient to support development of the cells to the next stage, which involves many complicated processes,” Koide said. “Our results show that signals travel discrete and simple routes in the cell.”
Koide and his team are now working on streamlining directed network wiring and applying it to other areas of study such as cancer. With the ability to dramatically simplify how scientists study protein interaction networks, they hope to open the door to new research areas and therapeutic approaches.
“We can now design synthetic proteins that are far more sophisticated than natural ones, and use such super-performance proteins toward advancing science and medicine,” he said.
Until now, scientists have not known exactly how inflammation weakens the Blood-Brain Barrier, allowing toxins and other molecules access to the brain. A new research report appearing in the June 2014 issue of The FASEB Journal solves this mystery by showing that a molecule, called “microRNA-155,” is responsible for cleaving epithelial cells to create microscopic gaps that let material through. Not only does this discovery help explain the molecular underpinnings of diseases like multiple sclerosis, but it also opens an entirely new avenue for developing therapies that can help penetrate the Blood-Brain Barrier to deliver lifesaving drugs.

According to Ignacio A, Romero, Ph.D., “We are beginning to understand the mechanisms by which the barrier between the blood and the brain becomes leaky in inflammatory conditions. Based on these and other findings, drugs that reduce the leakiness of the barrier have the potential to improve symptoms in many neurological conditions.” Romero is one of the researchers involved in the work from the Department of Life, Health and Chemical Sciences of the Biomedical Research Network at The Open University in the United Kingdom.
To make this discovery, Romero and colleagues first measured microRNA-155 (miR-155) levels in cultured human cells and compared them to cells under inflammatory conditions. Researchers then measured levels in the blood vessels of inflamed brain areas of patients with multiple sclerosis (MS) and compared them to non-inflamed areas. In both cases, miR-155 was elevated in inflammation. Then, in mice, normal mice were compared with mice that were genetically altered to lose miR-155. When an inflammatory reaction was induced in these two groups of mice, the mice that could not express miR-155 had a much reduced increase in “leakiness” of the Blood-Brain Barrier than normal mice. Finally, scientists investigated in cultured human cells the mechanism by which miR-155 levels cause leakiness of the barrier and concluded that miR-155 affects the organization of the complex structures that form the tight connections between endothelial cells.
"This study has the potential to be a game-changer in terms of how we treat neurological conditions and how we deliver drugs to the brain," said Gerald Weissmann, M.D., Editor-in-Chief of The FASEB Journal. “Since it was first discovered, the Blood-Brain Barrier has always been a touch elusive. Now, after careful analysis, we are learning exactly how our bodies keep our brains safe and that microRNA-155 is a key player.”
(Source: eurekalert.org)
Εngineer invents safe way to transfer energy to medical chips in the body
A Stanford electrical engineer has invented a way to wirelessly transfer power deep inside the body, and then use this power to run tiny electronic medical gadgets such as pacemakers, nerve stimulators or new sensors and devices yet to be developed.
The discoveries reported May 19 in the Proceedings of the National Academy of Sciences culminate years of efforts by Ada Poon, assistant professor of electrical engineering, to eliminate the bulky batteries and clumsy recharging systems that prevent medical devices from being more widely used.
The technology could provide a path toward a new type of medicine that allows physicians to treat diseases with electronics rather than drugs.
"We need to make these devices as small as possible to more easily implant them deep in the body and create new ways to treat illness and alleviate pain," said Poon.
Poon’s team built an electronic device smaller than a grain of rice that acts as a pacemaker. It can be powered or recharged wirelessly by holding a power source about the size of a credit card above the device, outside the body.
Breakthrough: Nasal spray may soon replace the pill
Every time we have an infection or a headache and take a pill, we get a lot more drugs than our body actually needs. The reason is that only a fraction of the drugs in a pill reaches the right places in the body; the rest never reaches its destination and may cause unwelcome side effects before they are flushed out of the body again. This kind of major overdosing is especially true when doctors treat brain diseases, because the brain does not easily accept entering drugs.
"People with brain diseases are often given huge amounts of unnecessary drugs. During a long life, or if you have a chronic disease, this may become problematic for your health", says Massimiliano Di Cagno, assistant professor at the Department of Physics, Chemistry and Pharmacy, University of Southern Denmark.
He is concerned with finding more efficient ways of delivering drugs to the brain. He and his colleagues at University of Southern Denmark and Aalborg University have turned their attention to the nose - specifically the nasal wall and the slimy mucosa that covers it.
As we know from e.g. cocaine addicts, substances can be assimilated extremely quickly and directly through the nose. But many medical substances, however, need help to be transported through the nasal wall and further on to the relevant places in the brain.
Researchers have long struggled with this challenge and have come up with different kinds of transport vehicles that are very good at transporting the active ingredients through the nasal wall into the brain. The problem with these vehicles, though, is that they cannot release their cargo of drugs once they have reached the inside of the brain. The drugs stay locked inside the strong vehicles.
“If the drugs cannot get out of their vehicles, they are no help to the patient. So we needed to develop a vehicle that does not lock the drug in”, explains Massimiliano Di Cagno.
The vehicles for drug delivery through the nose are typically made of so called polymers. A polymer is a large molecule composed of a large number of repeats of one or more types of atoms or groups of atoms bound to each other. Polymers can be natural or synthetic, simple or complex.
Direct track to the brain
Massimiliano Di Cagno and his colleagues tested a natural sugar polymer and they now report that this particular polymer is not only capable of carrying the drugs through the nasal wall but also – and most importantly – releasing the drug where it is needed.
"This is an important breakthrough, which will bring us closer to delivering brain drugs by nasal spray", says Massimiliano Di Cagno.
With this discovery two out of three major challenges in nasal delivery of brain drugs have been met:
“We have solved the problem of getting the drug through the nose, and we have solved the problem of getting the drug released once it has entered the brain. Now there is a third major challenge left: To secure a steady supply of drugs over a long period. This is especially important if you are a chronic patient and need drug delivery every hour or so”, says Massimiliano Di Cagno.
When a patient sprays a solution with active drugs into his nose cavity, the solution will hit the nasal wall and wander from here through the nasal wall to the relevant places in the brain.
“But gravity also rules inside the nose cavity and therefore the spray solution will start to run down as soon as it has been sprayed up the nose. We need it to cling to the nasal wall for a long time, so we need to invent some kind of glue that will help the solution stick to the nasal wall and not run down and out of the nose within minutes”, says Massimiliano Di Cagno.

Older migraine sufferers may have more silent brain injury
Older migraine sufferers may be more likely to have silent brain injury, according to research published in the American Heart Association’s journal Stroke.
In a new study, people with a history of migraine headaches had double the odds of ischemic silent brain infarction compared to people who said they didn’t have migraines. Silent brain infarction is a brain injury likely caused by a blood clot interrupting blood flow to brain tissue. Sometimes called “silent strokes,” these injuries are symptomless and are a risk factor for future strokes.
Previous studies indicated migraine could be an important stroke risk factor for younger people.
“I do not believe migraine sufferers should worry, as the risk of ischemic stroke in people with migraine is considered small,” said Teshamae Monteith, M.D., lead author of the study and assistant professor of clinical neurology and chief of the Headache Division at the University of Miami Miller School of Medicine. “However, those with migraine and vascular risk factors may want to pay even greater attention to lifestyle changes that can reduce stroke risk, such as exercising and eating a low-fat diet with plenty of fruits and vegetables.”
High blood pressure, another important stroke risk factor, was more common in those with migraine. But the association between migraine and silent brain infarction was also found in participants with normal blood pressure.
Because Hispanics and African-Americans are at increased stroke risk, researchers from the Northern Manhattan Study (NOMAS) – a collaborative investigation between the University of Miami and Columbia University – studied a multi-ethnic group of older adults (41 percent men, average age 71) in New York City. About 65 percent of participants were Hispanic. Comparing magnetic resonance imaging results between 104 people with a history of migraine and 442 without, they found:
“While the lesions appeared to be ischemic, based on their radiographic description, further research is needed to confirm our findings,” Monteith said.
The research raises the question of whether preventive treatment to reduce the severity and number of migraines could reduce the risk of stroke or silent cerebral infarction.
“We still don’t know if treatment for migraines will have an impact on stroke risk reduction, but it may be a good idea to seek treatment from a migraine specialist if your headaches are out of control,” Monteith said.
Human hibernation: Secrets behind the big sleep
Imagine it: you have been rushed into the emergency room and you are dying. Your injuries are too severe for the surgeons to repair in time. Your blood haemorrhages unseen from ruptured vessels. The loss of blood is starving your organs of vital nutrients and oxygen. You are entering cardiac arrest.
But this is not the end. A decision is made: tubes are connected, machines whir into life, pumps shuffle back and forth. Ice-cold fluid flows through your veins, chilling them. Eventually, your heart stops beating, your lungs no longer draw breath. Your frigid body remains there, balanced on the knife-edge of life and death, neither fully one nor the other, as if frozen in time.
The surgeons continue their work, clamping, suturing, repairing. Then the pumps stir into life, coursing warm blood back into your body. You will be resuscitated. And, if all goes well, you will live.
Researchers Identify Genetic Marker Linked to OCD
A group of researchers led by Johns Hopkins scientists say they have identified a genetic marker that may be associated with the development of obsessive-compulsive disorder (OCD), whose causes and mechanisms are among the least understood among mental illnesses.
The results of the research are published online May 13 by the journal Molecular Psychiatry.
“If this finding is confirmed, it could be useful,” says study leader Gerald Nestadt, M.D., M.P.H., a professor of psychiatry and behavioral sciences at the Johns Hopkins University School of Medicine and director of Johns Hopkins’ Obsessive-Compulsive Disorder Program. “We might ultimately be able to identify new drugs that could help people with this often disabling disorder, one for which current medications work only 60 to 70 percent of the time.”
Nestadt and his team conducted what is known as a genome-wide association study, scanning the genomes of more than 1,400 people with OCD and more than 1,000 close relatives of people with the mental disorder. A significant association was identified in OCD patients near a gene called protein tyrosine phosphokinase (PTPRD).
OCD is a condition marked by thoughts and images that chronically intrude in the mind and by repetitive behaviors aimed at reducing the associated anxiety. Some of the least disabling forms of the disorder can add an extra hour to the day’s routine, causing distress and interfering with daily life. Some people are so disabled that they can’t leave their homes.
Experts say OCD affects an estimated 1 to 2 percent of the U.S. population, and the World Health Organization has called it one of the more disabling medical conditions worldwide. Antidepressants known as SSRIs work for some people, but not everyone; the same is true of behavioral therapy.
Nestadt says the genome-wide association study findings of a PTRPD-OCD link add to evidence that the genetic region they identified is important. The gene has already been shown in animals to be possibly involved in learning and memory, traits influenced by OCD in humans. Moreover, some cases of attention-deficit hyperactivity disorder (ADHD) have been associated with the gene, and OCD and ADHD have some symptoms in common. He says the gene also works with another gene family, SLITRK, which has also been associated with OCD in animals.
“OCD research has lagged behind other psychiatric disorders in terms of genetics,” Nestadt says. “We hope this interesting finding brings us closer to making better sense of it — and helps us find ways to treat it.”
(Image credit: Jennifer Soo)
Scientists have found that pressure from the fluid surrounding the brain plays a role in maintaining proper eye function, opening a new direction for treating glaucoma — the second leading cause of blindness worldwide. The research is being presented at the 2014 Annual Meeting of the Association for Research in Vision and Ophthalmology (ARVO) this week in Orlando, Fla. (Abstract Title: Effect of translaminar pressure modification on the rat optic nerve head).
Using a rat model, researchers found that elevating the pressure of the fluid surrounding the brain can counterbalance elevated pressure in the eye, preventing the optic nerve from bending backward. Rats with higher fluid pressure from the brain maintained their ability to respond to light better than rats with lower pressure.
The brain and eye are connected by the optic nerve. In diseases like glaucoma — where vision loss is associated with elevated pressure within the eye — the optic nerve bows backward, away from the eye and toward the brain. This investigation might explain why some people with normal eye pressure develop glaucoma, and why people with intraocular pressure never develop the condition.
(Source: newswise.com)
Functioning of aged brains and muscles in mice made younger
Harvard Stem Cell Institute (HSCI) researchers have shown that a protein they previously demonstrated can make the failing hearts in aging mice appear more like those of young health mice, similarly improves brain and skeletal muscle function in aging mice.
In two separate papers given early online release today by the journal Science—which is publishing the papers this coming Friday, Professors Amy Wagers, PhD, and Lee Rubin, PhD, of Harvard’s Department of Stem Cell and Regenerative Biology (HSCRB), report that injections of a protein known as GDF11, which is found in humans as well as mice, improved the exercise capability of mice equivalent in age to that of about a 70-year-old human, and also improved the function of the olfactory region of the brains of the older mice—they could detect smell as younger mice do.
Rubin, and Wagers, who also has a laboratory at the Joslin Diabetes Center, each said that, baring unexpected developments, they expect to have GDF11 in initial human clinical trials within three to five years.
Postdoctoral fellow Lida Katsimpardi, PhD, is the lead author on the Rubin group’s paper, and postdocs Manisha Sinha, PhD, and Young Jang, PhD, are the lead authors on the paper from the Wagers group.
Both studies examined the effect of GDF11 in two ways. First, by using what is called a parabiotic system, in which two mice are surgically joined and the blood of the younger mouse circulates through the older mouse. And second, by injecting the older mice with GDF11, which in an earlier study by Wagers and Richard Lee, MD, of Brigham and Women’s Hospital who is also an author on the two papers released today, was shown to be sufficient to reverse characteristics of aging in the heart.
Doug Melton, PhD, co-chair of HSCRB and co-director of HSCI, reacted to the two papers by saying that he couldn’t “recall a more exciting finding to come from stem cell science and clever experiments. This should give us all hope for a healthier future. We all wonder why we were stronger and mentally more agile when young, and these two unusually exciting papers actually point to a possible answer: the higher levels of the protein GDF11 we have when young. There seems to be little question that, at least in animals, GDF11 has an amazing capacity to restore aging muscle and brain function,” he said.
Melton, Harvard’s Xander University Professor, continued, saying that the ongoing collaboration between Wagers, a stem cell biologist whose focus has been on muscle, Rubin, whose focus is on neurodegenerative diseases and using patient generated stem cells as targets for drug discovery, and Lee, a practicing cardiologist and researcher, “is a perfect example of the power of the Harvard Stem Cell Institute as an engine of truly collaborative efforts and discovery, bringing together people with big, unique ideas and expertise in different biological areas.”
As Melton noted, GDF11 is naturally found in much higher concentrations in young mice than in older mice, and raising its levels in the older mice has improved the function of every organ system thus far studied.
Wagers first began using the parabiotic system in mice 14 years ago as a postdoctoral fellow at Stanford University, when she and colleagues Thomas Rando, MD, PhD, of Stanford, Irina Conboy, PhD, of the University of California, Berkley, and Irving Weissman, MD, of Stanford, observed that the blood of young mice circulating in old mice seemed to have some rejuvenating effects on muscle repair after injury.
Last year, she and Richard Lee published a paper in which they reported that when exposed to the blood of young mice, the enlarged, weakened hearts of older mice returned to a more youthful size, and their function improved. And then working with a Colorado firm, the pair reported that GDF11 was the factor in the blood apparently responsible for the rejuvenating effect. That finding has raised hopes that GDF11 may prove, in some form, to be a possible treatment for diastolic heart failure, a fatal condition in the elderly that now is irreversible, and fatal.
“From the previous work it could have seemed that GD11 was heart specific,” said Wagers, “but this shows that it is active in multiple organs and cell types. Prior studies of skeletal muscle and the parabiotic effect really focused on regenerative biology. Muscle was damaged and assayed on how well it could recover,” Wagers explained.
She continued: “The additional piece is that while prior studies of young blood factors have shown that we achieve restoration of muscle stem cell function and they repair the muscle better, in this study, we also saw repair of DNA damage associated with aging, and we got it in association with recovery of function, and we saw improvements in unmanipulated muscle. Based on other studies, we think that the accumulation of DNA damage in muscle stem cells might reflect an inability of the cells to properly differentiate to make mature muscle cells, which is needed for adequate muscle repair.”
Wagers noted that there is still a great deal to be learned about the mechanics of aging in muscle, and its repair. “I don’t think we fully understand how this happening or why. We might say that the damage is modification to the genetic material; the genome does have breaks in it. But whether it’s damaging, or a necessary part of repair, we don’t know yet.”
Rubin, whose primary research focus is on developing treatment for neurodegenerative diseases, particularly in children, said that when his group began its GDF11 experiments, “we knew that in the old mouse things were bad in the brain, there is a reduced amount of neurogenesis (the development of neurons), and it’s well known that cognition goes down. It wasn’t obvious to me that those things that can be repaired in peripheral tissue could be fixed in the brain.”
Rubin said that postdoctoral fellow Lida Katsimpardi, the lead author on his group’s paper, was taught the parabiotic experimental technique by Wagers, but conducted the Rubin group’s experiments independently of the Wagers group, and “she saw an increase in neural stem cells, and increased development of blood vessels in the brain.” Rubin said that 3D reconstruction of the brain, and magnetic resonance imaging (MRI) of the mouse brain showed “more new blood vessels and more blood flow,” both of which are normally associated with younger, healthier brain tissue.”
Younger mice, Rubin said, “have a keen sense of olfactory discrimination,” they can sense fine differences in odor. “When we tested the young mice, they avoided the smell of mint; the old mice didn’t. But the old mice exposed to the blood of the young mice, and those treated with GDF11 did.”
“We think an effect of GDF11 is the improved vascularity and blood flow, which is associated with increased neurogenesis,” Rubin said. “However, the increased blood flow should have more widespread effects on brain function. We do think that, at least in principle, there will be a way to reverse some of the cognitive decline that takes place during aging, perhaps even with a single protein. It could be that a molecule like GDF11, or GDF11 itself, could” reverse the damage of aging.
“It isn’t out of question that GDF11,” or a drug developed from it, “might be capable of slowing some of the cognitive defects associated with Alzheimer’s disease, a disorder whose main risk factor is aging itself,” Rubin said. It is even possible that this could occur without directly changing the “plaque and tangle burden” that are the pathological hallmarks of Alzheimer’s. Thus, a future treatment for this disease might be a combination of a therapeutic that reduces plaques and tangles, such as an antibody directed against the β-amyloid peptide, with a potential cognition enhancer like GDF11.
Wagers said that the two research groups are in discussions with a venture capital group to obtain funding to “be able to do the additional preclinical work” necessary before moving GDF11 into human trials.
“I would wager that the results of this work, together with the other work, will translate into a clinical trial and a treatment,” said the stem cell biologist. “But of course that’s just a wager.”