A patient’s own skin cells may one day treat multiple diseases

Posted by Biomechanism 

(Biomechanism.com) — UC Davis investigator provides roadmap to overcome obstacles for using induced pluripotent stem cells.

The possibility of developing stem cells from a patient’s own skin and using them to treat conditions as diverse as Parkinson’s disease, Alzheimer’s disease and cancer has generated tremendous excitement in the stem cell research community in recent years. Such therapies would avoid the controversial need for using stem cells derived from human embryos, and in theory, also bypass immunological problems inherent in using cells from one person to treat another.

The successful creation of induced pluripotent stem cells proved to the world that cellular differentiation is not a unidirectional process--with the proper instruction, cellular differentiation is bidirectional. Photo: StemCellSchool.

However, in the nearly five years since the first article describing the development of stem cells derived from adult cells — so-called induced pluripotent stem cells (iPSCs) — unique problems inherent in their use have surfaced and even their immunological safety has been called into question.

According to Paul S. Knoepfler, UC Davis associate professor of cell biology and human anatomy, finding such obstacles in such a new and novel approach is not surprising and should not dissuade investigators from actively pursuing this avenue of research. A roadmap for finding solutions to the problems identified with iPSCs, written by Knoepfler and Bonnie Barrilleaux, a postdoctoral fellow working in Knoepfler’s laboratory, is available online and will be published in the Aug. 5 issue of the journal Cell Stem Cell. Their perspective, “Inducing iPSCs to escape the dish,” suggests research strategies to advance the field more rapidly toward applications for human diseases.

“iPSCs offer the potential to treat many diseases as an alternative or adjuvant therapy to drugs or surgery,” said Knoepfler, who also is a faculty member of the UC Davis Genome Center and UC Davis Cancer Center. “Problems that have been identified with their use likely can be overcome, allowing iPSCs to jump from the laboratory dish to patients who could benefit from them.”

iPSCs were first produced in 2006 from mouse cells and in 2007 from human cells. They have many of the same regenerative properties as human embryonic stem cells, but they are derived in a lab from adult cells, such as skin cells, by inducing or forcing them to express specific genes that are normally dormant in that type of cell. In theory, a person’s skin cells could be induced to make neurons that produce the neurotransmitter dopamine, for example, and be delivered to brain regions where it is lacking in patients with Parkinson’s disease. Similarly, cells could be induced to regenerate heart muscle and blood vessels after a heart attack, or neurons following a spinal cord injury. Many labs at UC Davis, including the Knoepfler lab, are producing and studying human iPSCs.

One advantage cited for iPSCs over stem cells derived from embryos is that problems of rejection due to immunological differences between the donor (the embryo) and the patient would be eliminated, because the iPSCs would be derived from each individual patient. A recent study using iPSCs in mice found that tissue rejection may, in fact, occur in some cases. However, Knoepfler believes that particular study was conducted in the context of tumors, which tend to be highly immunogenic and not be applicable for human use. While the ability of human iPSCs to escape immune attention must be investigated further, Knoepfler says that iPSCs remain an attractive potential avenue for stem cell-based medicine, in addition to embryonic stem cells.

Another concern with using either iPSCs or embryonic stem cells is that cells with the ability to turn into many different cell types may grow out of control, producing cancerous tumors. Knoepfler points out those studies involved implanting large numbers of undifferentiated stem cells into mice that were treated with immunosuppressant drugs to reject transplants, making the conditions ideal for cancers to arise. This scenario, he argues, is unlikely to be applicable when treating humans for actual diseases. In such cases, the stem cells would be induced to have a specific function, and the body’s natural immune defenses would be present.

The “pluripotent” nature of stem cells, which potentially allow their use to repair almost any tissue, is only beginning to be harnessed for human therapies. Stem cell therapy has already been successfully used for years to treat leukemia and related bone and blood cancers. The use of iPSCs could vastly increase the spectrum of diseases that might be treated with stem cells, without the safety and ethical concerns inherent in using embryonic stem cells.

“Dr. Barrilleaux and I argue for a shift in research priorities,” said Knoepfler. “Future studies of iPSCs should increasingly focus on issues most relevant to the eventual clinical use of the cells, offering the fastest pathway to treating patients with this potentially powerful therapeutic tool.”

Knoepfler’s own research focuses on determining how stem cell behavior is controlled during normal embryonic development as well as during healing and regeneration. He also studies how control systems go awry in developmental disorders and cancer. One key direction for the Knoepfler lab is using leading genomics technology to better understand why stem cells behave the way they do and how to change that behavior for clinical use.

________________

Funding for Knoepfler’s article was provided by a grant from the California Institute for Regenerative Medicine.

ABOUT UC DAVIS STEM CELL RESEARCH

UC Davis has brought together physicians, research scientists, biomedical engineers and a range of other experts and collaborative partners to establish the UC Davis Institute for Regenerative Cures, a facility supported by the California Institute for Regenerative Medicine. The $62 million institute is housed on the university’s Sacramento campus, where collaborative, team-oriented science is advancing breakthrough discoveries and working to bring stem cell therapies and cures to patients. For more information, visit www.ucdmc.ucdavis.edu/stemcellresearch

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Regrowing Blood Vessels With a Potent Molecule

Posted by Biomechanism 

(Biomechanism.com) — Ever since the Nobel Prize for nerve growth factor was awarded more than 30 years ago, researchers have been searching for ways to use growth factor clinically.

University of Pittsburgh Professor Yadong Wang has developed a minimally invasive method of delivering growth factor to regrow blood vessels. His research, which could be used to treat heart disease, the most common cause of death in the Western world, is published this week in the Aug. 1 issue of the journal Proceedings of the National Academy of Sciences.

During a heart attack, time is muscle. When a blocked blood vessel doesn't allow enough oxygen and nutrients to the heart, the muscle dies.

Wang is a professor in the Department of Bioengineering in Pitt’s Swanson School of Engineering and the Department of Surgery in the University’s School of Medicine. He is also affiliated with the Pitt-UPMC McGowan Institute of Regenerative Medicine (MIRM). His coauthors are Johnny Huard, professor in the Department of Bioengineering and the School of Medicine’s Departments of Orthopaedic Surgery, Molecular Genetics, and Pathology, as well as MIRM; graduate student Hunghao Chu and postdoctoral fellow Jin Gao in the Departments of Bioengineering and Surgery; and Chien-Wen Chen, a Ph.D. candidate in bioengineering and surgery.

When the researchers injected their growth factor compound under the skin of mice, they saw something amazing: New blood vessels grew, and large ones, not just tiny capillaries. “We had structures that resembled arterioles—small arteries that lead to a network of capillaries,” says Wang.

Moreover, the structures stuck around. At least a month later, after only one injection of the growth factor complex, the new blood vessels were still there.

POWERFUL IN SMALL DOSES

In our bodies, growth factors control many different functions, including cell proliferation, migration, and differentiation. There are even growth factors that inhibit growth of certain cell types or cause cell suicide. “They are very potent molecules,” says Wang.

Being so powerful, growth factor is controlled very tightly by the body, which quickly destroys free-floating growth factor. The half-life for most growth factor injected under the skin is half an hour or less—very short-lived.

With this limitation in mind, the researchers investigated ways to use growth factor efficiently. They hit on a molecule called heparin, one of the molecules that bonds growth factor to its receptor on the cell’s surface. When heparin binds to the receptor and the growth factor, it actually increases the activity of growth factor and stabilizes it.

“Our idea was, ‘Let’s use heparin as is, without any modification, to stabilize the growth factor and also to present it to the receptor,’ ” says Wang.

But there was only one catch: If you bond heparin to growth factor, the resulting substance is water-soluble. Injected into the body, the complex dissolves within seconds. We are made mostly of water, after all.

The team had to figure out a way to keep the complex from dissolving long enough for it to do its work of regenerating blood vessels.

The trick, they discovered, was to use a polycation—a molecule with multiple positive charges. Heparin has many negative charges. If it’s neutralized with a polycation, it can be brought out of solution into what is called a coacervate—an aggregate of tiny oil droplets. Many other research teams use heparin in growth factor delivery as well, but the Wang lab is the first to convert the heparin/growth factor complexes into coacervates.

In this first-ever report of using coacervate for the controlled delivery of growth factor, the team delivered fibroblast growth factor-2. This led to extensive and persistent new blood vessel formation. The team used only one growth factor to induce the formation of mature blood vessels. These vessels were stabilized by special cells called mural cells.

Now, Wang has gone on to use his unique delivery platform to study the controlled release of other growth factors that bind heparin: nerve growth factor, vascular endothelial growth factor, epidermal growth factor, bone morphogenetic proteins, and many others. “In all cases, the controlled delivery using coacervate was much more effective,” says Wang.

The complex is highly efficient: Since the heparin and growth factor are both active ingredients, and polycation is added only to bring it out of the water, as much growth factor as necessary can be delivered. “High loading efficiency is important because it allows us to reduce the frequency of injections,” Wang adds.

The coacervate is not very viscous. This means that “you can use a needle as thin as a hair” to inject it, says Wang. “So if you inject that through tissue, the damage you create is very small.” It could be done through a catheter, a long tube with a needle through it. This means the chest wouldn’t have to be opened up—a huge advantage over open-heart surgery.

HEALING A BROKEN HEART

During a heart attack, time is muscle. When a blocked blood vessel doesn’t allow enough oxygen and nutrients to the heart, the muscle dies.

“After a heart attack, the muscle is dead, and what’s replacing it is scar tissue—a lot of collagen, but not many cardiac muscle cells. No muscle, no contraction,” says Wang.

Once a heart attack has happened, the patient generally has two choices: Get a stent to open the blockage, or have surgery to bypass it. The heart tries to heal itself, but its self-remodeling efforts can have deleterious effects, like dilating ventricles until they’re too big.

“If we can use growth factors to reverse that kind of adverse remodeling process, then we can probably rescue the heart function, which is the most important thing,” notes Wang.

The growth factor complex would be injected at the appropriate time—right after the heart attack, or a few days later—to change how the heart repairs itself.

“Our hope would be to reduce scarring, keep as much of the muscle alive as possible, and induce quick blood vessel formation to bring as many nutrients as possible in order to reestablish an environment for muscle growth,” Wang says.

Wang’s future research plans include eventual human clinical trials. His team will also use a disease model to investigate the efficiency of the treatment in heart attacks.

He is also interested in commercializing the treatment and is in talks with several clinicians and entrepreneurs. “This treatment is very promising in bench-to-bedside translation,” Wang says.

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Bypassing stem cells, scientists make neurons directly from human skin

Posted by Biomechanism 

(Biomechanism.com) — Researchers have come up with a recipe for making functional neurons directly from human skin cells, including those taken from patients with Alzheimer’s disease. The new method may offer a critical short cut for generating neurons for replacement therapies of the future, according to research published in the August 5th issue of the journal Cell, a Cell Press publication. Already, the converted neurons are beginning to yield insights into what goes wrong in the Alzheimer’s brain and how diseased neurons might respond to treatment.

When studied in a dish, the neurons derived from healthy skin cells could fire and receive signals, just like normal neurons. (Photo Credit: CC BY-ND/Mohammed Khazaei/Flickr)

In earlier approaches to generate neurons from skin cells, those adult cells first had to be returned to an embryonic stem cell state. Those cells, called induced pluripotent stem (iPS) cells, are hard to come by – less than one percent of cells are typically reprogrammed successfully. In addition, the entire process is time-consuming, requiring months to coax cells into iPS cells and then stimulate them to become neurons.

“iPS cells are exciting given the limits on cloning and embryonic stem cells, but it is still a roundabout and lengthy process if the goal is to take patient cells or normal cells and use them as replacement cells,” said Asa Abeliovich of Columbia University, senior author of this study.

Not only are there efficiency issues, there is also an increasing concern about the stability of iPS cells, he said. Their ability to grow and produce any cell type makes them a cancer risk. Moreover, the cells may have limited use as models for understanding disease states because the processes used to derive them “may erase or overwhelm” the natural biology of the cells.

To get around these potential pitfalls, Abeliovich’s team started with known transcriptional regulators and, through a process of trial and error, identified a cocktail of factors that could turn human skin cells into neurons. While the process was not initially very efficient, they refined the protocol, ultimately converting about 50 percent of the cells.

“It is a huge leap over the iPS-based process,” he said. It is also more efficient than a similar method recently developed by another group.

When studied in a dish, the neurons derived from healthy skin cells could fire and receive signals, just like normal neurons. What’s more, when placed into the brains of developing mice, the converted cells were able to connect up to the existing circuitry. “They really are neurons,” Abeliovich said.

The method can also produce neurons from the skin cells of patients with a rare familial form of Alzheimer’s disease (AD). The AD neurons superficially looked normal, but upon closer inspection, Abeliovich’s team saw abnormalities in the processing of amyloid precursor protein, the source for the amyloid plaques that riddle the brains of those with Alzheimer’s disease. The neurons also showed more general differences in the way proteins inside the cell move around.

Abeliovich says that to really understand what goes wrong in Alzheimer’s disease it will be important to look at what is happening in living human neurons. Earlier studies have been limited to exploring the consequences of the Alzheimer’s mutations in tumor cells, skin cells or in mouse models of the disease.

Potentially the most exciting use of these Alzheimer’s neurons will be for testing new drug candidates. Abeliovich notes that when the cells were treated with one existing candidate drug that reduces beta amyloid production, the protein ‘trafficking’ problem actually worsened, raising caution about that particular treatment. Going forward, his group plans to study neurons derived from skin cells from patients with the more common, sporadic forms of Alzheimer’s disease.

“Sporadic disease accounts for 99 percent of cases and no one really knows if it is similar or different from the simpler genetic forms,” Abeliovich said. “It’s not a done deal that we’ll be able to come up with answers, but at least we can now ask the question. In that sense, this is the tip of the iceberg.”

First Opal-Like Crystals Discovered in Meteorite

Science Daily — Scientists have found opal-like crystals in the Tagish Lake meteorite, which fell to Earth in Canada in 2000. This is the first extraterrestrial discovery of these unusual crystals, which may have formed in the primordial cloud of dust that produced the sun and planets of our solar system 4.6 billion years ago, according to a report in the Journal of the American Chemical Society.

The formation of colloidal crystals in the meteorite implies that several conditions must have existed when they formed. "First, a certain amount of solution water must have been present in the meteorite to disperse the colloidal particles," the report explains. "The solution water must have been confined in small voids, in which colloidal crystallization takes place. These conditions, along with evidence from similar meteorites, suggest that the crystals may have formed 4.6 billion years ago."Katsuo Tsukamoto and colleagues say that colloidal crystals such as opals, which form as an orderly array of particles, are of great interest to for their potential use in new electronics and optical devices. Surprisingly, the crystals in the meteorite are composed of magnetite, which scientists thought could not assemble into such a crystal because magnetic attractions might pack the atoms together too tightly. "We believe that, if synthesized, magnetite colloidal crystals have promising potential as a novel functional material," the article notes.The authors acknowledge funding from the Japan Society for the Promotion of Science, the Tohoku University Global COE Program, and the Center for Interdisciplinary Research Tohoku University.

Water Flowing On Mars, NASA Spacecraft Data Suggest

Warm-Season Flows on Slope in Newton Crater: This series of images shows warm-season features that might be evidence of salty liquid water active on Mars today. (Credit: NASA/JPL-Caltech/Univ. of Arizona)

Science Daily — Observations from NASA's Mars Reconnaissance Orbiter have revealed possible flowing water during the warmest months on Mars.

Dark, finger-like features appear and extend down some Martian slopes during late spring through summer, fade in winter, and return during the next spring. Repeated observations have tracked the seasonal changes in these recurring features on several steep slopes in the middle latitudes of Mars' southern hemisphere.

"NASA's Mars Exploration Program keeps bringing us closer to determining whether the Red Planet could harbor life in some form," NASA Administrator Charles Bolden said, "and it reaffirms Mars as an important future destination for human exploration."

"The best explanation for these observations so far is the flow of briny water," said Alfred McEwen of the University of Arizona, Tucson. McEwen is the principal investigator for the orbiter's High Resolution Imaging Science Experiment (HiRISE) and lead author of a report about the recurring flows published in the journal Science.

Some aspects of the observations still puzzle researchers, but flows of liquid brine fit the features' characteristics better than alternate hypotheses. Saltiness lowers the freezing temperature of water. Sites with active flows get warm enough, even in the shallow subsurface, to sustain liquid water that is about as salty as Earth's oceans, while pure water would freeze at the observed temperatures.

"These dark lineations are different from other types of features on Martian slopes," said Mars Reconnaissance Orbiter Project Scientist Richard Zurek of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Repeated observations show they extend ever farther downhill with time during the warm season."

The features imaged are only about 0.5 to 5 yards or meters wide, with lengths up to hundreds of yards. The width is much narrower than previously reported gullies on Martian slopes. However, some of those locations display more than 1,000 individual flows. Also, while gullies are abundant on cold, pole-facing slopes, these dark flows are on warmer, equator-facing slopes.

The images show flows lengthen and darken on rocky equator-facing slopes from late spring to early fall. The seasonality, latitude distribution and brightness changes suggest a volatile material is involved, but there is no direct detection of one. The settings are too warm for carbon-dioxide frost and, at some sites, too cold for pure water. This suggests the action of brines, which have lower freezing points. Salt deposits over much of Mars indicate brines were abundant in Mars' past. These recent observations suggest brines still may form near the surface today in limited times and places.

When researchers checked flow-marked slopes with the orbiter's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), no sign of water appeared. The features may quickly dry on the surface or could be shallow subsurface flows.

"The flows are not dark because of being wet," McEwen said. "They are dark for some other reason."

A flow initiated by briny water could rearrange grains or change surface roughness in a way that darkens the appearance. How the features brighten again when temperatures drop is harder to explain.

"It's a mystery now, but I think it's a solvable mystery with further observations and laboratory experiments," McEwen said.

These results are the closest scientists have come to finding evidence of liquid water on the planet's surface today. Frozen water, however has been detected near the surface in many middle to high-latitude regions. Fresh-looking gullies suggest slope movements in geologically recent times, perhaps aided by water. Purported droplets of brine also appeared on struts of the Phoenix Mars Lander. If further study of the recurring dark flows supports evidence of brines, these could be the first known Martian locations with liquid water.

The Mars Reconnaissance Orbiter is managed by JPL for NASA's Science Mission Directorate in Washington. The University of Arizona's Lunar and Planetary Laboratory operates HiRISE. The camera was built by Ball Aerospace & Technologies Corp. in Boulder, Colo. Johns Hopkins University Applied Physics Laboratory in Laurel, Md., provided and operates CRISM. JPL is a division of the California Institute of Technology in Pasadena.

For more information about the Mars Reconnaissance Orbiter, visit: http://www.nasa.gov/mro andhttp://marsprogram.jpl.nasa.gov/mro/

DNA Strands That Select Nanotubes Are First Step to a Practical 'Quantum Wire

Wrapped up in their work: this molecular model shows a single-strand DNA molecule (yellow ribbon) coiled around an "armchair" carbon nanotube. (Credit: Roxbury, Jagota/NIST)

Science Daily   — DNA, a molecule famous for storing the genetic blueprints for all living things, can do other things as well. In a new paper, researchers at the National Institute of Standards and Technology (NIST) describe how tailored single strands of DNA can be used to purify the highly desired "armchair" form of carbon nanotubes. Armchair-form single wall carbon nanotubes are needed to make "quantum wires" for low-loss, long distance electricity transmission and wiring.

Chirality plays an important role in nanotube properties. Most behave like semiconductors, but a few are metals. One special chiral form -- the so-called "armchair carbon nanotube"* -- behaves like a pure metal and is the ideal quantum wire, according to NIST researcher Xiaomin Tu.

Single-wall carbon nanotubes are usually about a nanometer in diameter, but they can be millions of nanometers in length. It's as if you took a one-atom-thick sheet of carbon atoms, arranged in a hexagonal pattern, and curled it into a cylinder, like rolling up a piece of chicken wire. If you've tried the latter, you know that there are many possibilities, depending on how carefully you match up the edges, from neat, perfectly matched rows of hexagons ringing the cylinder, to rows that wrap in spirals at various angles -- "chiralities" in chemist-speak.

Armchair carbon nanotubes could revolutionize electric power systems, large and small, Tu says. Wires made from them are predicted to conduct electricity 10 times better than copper, with far less loss, at a sixth the weight. But researchers face two obstacles: producing totally pure starting samples of armchair nanotubes, and "cloning" them for mass production. The first challenge, as the authors note, has been "an elusive goal."

Separating one particular chirality of nanotube from all others starts with coating them to get them to disperse in solution, as, left to themselves, they'll clump together in a dark mass. A variety of materials have been used as dispersants, including polymers, proteins and DNA. The NIST trick is to select a DNA strand that has a particular affinity for the desired type of nanotube. In earlier work, team leader Ming Zheng and colleagues demonstrated DNA strands that could select for one of the semiconductor forms of carbon nanotubes, an easier target. In this new paper, the group describes how they methodically stepped through simple mutations of the semiconductor-friendly DNA to "evolve" a pattern that preferred the metallic armchair nanotubes instead.

"We believe that what happens is that, with the right nanotube, the DNA wraps helically around the tube," explains Constantine Khripin, "and the DNA nucleotide bases can connect with each other in a way similar to how they bond in double-stranded DNA." According to Zheng, "The DNA forms this tight barrel around the nanotube. I love this idea because it's kind of a lock and key. The armchair nanotube is a key that fits inside this DNA structure -- you have this kind of molecular recognition."

Once the target nanotubes are enveloped with the DNA, standard chemistry techniques such as chromatography can be used to separate them from the mix with high efficiency.

"Now that we have these pure nanotube samples," says team member Angela Hight Walker, "we can probe the underlying physics of these materials to further understand their unique properties. As an example, some optical features once thought to be indicative of metallic carbon nanotubes are not present in these armchair samples."

* From the distinctive shape of the edge of the cylinder.