Artificial Ovary Develops Oocytes Into Mature Human Eggs

Artificial Ovary Develops Oocytes Into Mature Human Eggs

  9:50:00 AM    Science Lover

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Researchers at Brown University and Women & Infants Hospital have invented the first artificial human ovary, an advance that provides a potentially powerful new means for conducting fertility research and could also yield infertility treatments for cancer patients. The team has already used the lab-grown organ to mature human eggs.

An artificial ovary An engineered honeycomb of cultured theca cells (top row) envelopes spheres of granulosa cells (GC). The bottom row shows the tissue after 48 hours (left) and after five days. (Credit: Carson Lab / Brown University)

"An ovary is composed of three main cell types, and this is the first time that anyone has created a 3-D tissue structure with triple cell line," said Sandra Carson, professor of obstetrics and gynecology at the Warren Alpert Medical School of Brown University and director of the Division of Reproductive Endocrinology and Infertility at Women & Infants Hospital. Carson is a senior author of a recent article in the Journal of Assisted Reproduction and Genetics that describes the innovation.

Carson said that the ovary not only provides a living laboratory for investigating fundamental questions about how healthy ovaries work, but also can act as a testbed for seeing how problems, such as exposure to toxins or other chemicals, can disrupt egg maturation and health.

Clinically, the artificial ovary could play a role in preserving the fertility of women facing cancer treatment in the future, said Stephan Krotz, a Houston fertility doctor who is the paper's lead author and a former fellow in Carson's lab. Immature eggs could be salvaged and frozen before the onset of chemotherapy or radiation, he said, and then matured outside the patient in the artificial ovary.

Building an ovary

What makes the artificial ovary a functional tissue, rather than just a cell culture, is that it brings all three ovarian cell types into a 3-D arrangement similar to a real ovary in the body. The means for making such compositions of cells was invented in the lab of Jeffrey Morgan, associate professor of medical science and engineering, who is a co-author of the paper published online Aug. 25. His so-called 3D Petri dishes are made of a moldable agarose gel that provides a nurturing template to encourage cells to assemble into specific shapes.

To create the ovary, the researchers formed honeycombs of theca cells, one of two key types in the ovary, donated by reproductive-age (25-46) patients at the hospital. After the theca cells grew into the honeycomb shape, spherical clumps of donated granulosa cells were inserted into the holes of the honeycomb together with human egg cells, known as oocytes. In a couple days the theca cells enveloped the granulosa and eggs, mimicking a real ovary.

The big test, however, was whether the structure could function like an ovary -- namely to mature eggs. In experiments the structure was able to nurture eggs from the "early antral follicle" stage to full maturity.

"[This] represents the first success in using 3-D tissue engineering principles for in vitro oocyte maturation," the researchers wrote in the journal article.

Carson said her goal was never to invent an artificial organ, per se, but merely to create a research environment in which she could study how theca and granulosa cells and oocytes interact. When she learned of Morgan's 3-D Petri dishes, they began to collaborate on creating an organ. Morgan said this is the first fully functional tissue to be made using the method.

To help fund the work, Morgan and Carson applied for and won a Collaborative Research Award from the Rhode Island Science and Technology Advisory Council (STAC). STAC grants encourage research with commercial potential. Morgan has recently founded a local Rhode Island startup, MicroTissues Inc. The company will begin selling these micro-mold tools in about a month to researchers looking to engineer 3-D tissues. Other funding came from Women & Infants Hospital.

With what appears to be a fully functional artificial organ, Carson and Morgan continue to collaborate and are now embarking on the studies she dreamed it would make possible. She's reluctant to predict what they'll turn up, however.

"This is really very, very new," she said.

The paper's other authors are Jared Robins, Toni-Marie Ferruccio, Richard Moore and Margaret Steinhoff, all of Brown University.

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Drugs Encased in Nanoparticles Travel to Tumors on the Surface of Immune-System Cells

Drugs Encased in Nanoparticles Travel to Tumors on the Surface of Immune-System Cells

  10:53:00 PM    Science Lover

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Clinical trials using patients' own immune cells to target tumors have yielded promising results. However, this approach usually works only if the patients also receive large doses of drugs designed to help immune cells multiply rapidly, and those drugs have life-threatening side effects.

pouches (yellow) to the surfaces of cells. 
(Credit: Darrell Irvine and Matthias Stephan)

Now a team of MIT engineers has devised a way to deliver the necessary drugs by smuggling them on the backs of the cells sent in to fight the tumor. That way, the drugs reach only their intended targets, greatly reducing the risk to the patient.

The new approach could dramatically improve the success rate of immune-cell therapies, which hold promise for treating many types of cancer, says Darrell Irvine, senior author of a paper describing the technique in the Aug. 15 issue of Nature Medicine.

"What we're looking for is the extra nudge that could take immune-cell therapy from working in a subset of people to working in nearly all patients, and to take us closer to cures of disease rather than slowing progression," says Irvine, associate professor of biological engineering and materials science and engineering and a member of MIT's David H. Koch Institute for Integrative Cancer Research.

The new method could also be used to deliver other types of cancer drugs or to promote blood-cell maturation in bone-marrow transplant recipients, according to the researchers.

To perform immune-cell therapy, doctors remove a type of immune cells called T cells from the patient, engineer them to target the tumor, and inject them back into the patient. Those T cells then hunt down and destroy tumor cells. Clinical trials are under way for ovarian and prostate cancers, as well as melanoma.

Although immune-cell therapy is a promising approach to treating cancer, success has been limited by difficulties in generating enough T cells that are specific to the cancer cells and getting those T cells to function properly in the patient.

To overcome those obstacles, researchers have tried injecting patients with adjuvant drugs that stimulate T-cell growth and proliferation. One class of drugs that has been tested in clinical trials is interleukins -- naturally occurring chemicals that help promote T-cell growth but have severe side effects, including heart and lung failure, when given in large doses.

Irvine and his colleagues took a new approach: To avoid toxic side effects, they designed drug-carrying pouches made of fatty membranes that can be attached to sulfur-containing molecules normally found on the T-cell surface.

In the Nature Medicine study, the researchers injected T cells, each carrying about 100 pouches loaded with the interleukins IL-15 and IL-21, into mice with lung and bone marrow tumors. Once the cells reached the tumors, the pouches gradually degraded and released the drug over a weeklong period. The drug molecules attached themselves to receptors on the surface of the same cells that carried them, stimulating them to grow and divide.

Within 16 days, all of the tumors in the mice treated with T cells carrying the drugs disappeared. Those mice survived until the end of the 100-day experiment, while mice that received no treatment died within 25 days, and mice that received either T cells alone or T cells with injections of interleukins died within 75 days.

Irvine's approach to delivering the adjuvant drugs is both simple and innovative, says Dranoff. "The idea of modifying T cells in the lab to make them work better is something many people are exploring through more complicated approaches such as gene modification," he says. "But here, the possibility of just attaching a carefully engineered nanoparticle to the surface of cells could be a much simpler procedure."

While he is now focusing on immune-cell therapy, Irvine believes his cell pouches could be useful for other applications, including targeted delivery of chemotherapy agents. "There are lots of people studying nanoparticles for drug delivery, especially in cancer therapy, but the vast majority of nanoparticles injected intravenously go into the liver or the spleen. Less than 5 percent reach the tumor," says Irvine, who is also a Howard Hughes Medical Institute Investigator.

With a new way to carry drugs specifically to tumors, scientists may be able to resurrect promising drugs that failed in clinical trials because they were cleared from the bloodstream before they could reach their intended targets, or had to be given in doses so high they had toxic side effects.

Irvine and his colleagues also demonstrated that they could attach their pouches to the surface of immature blood cells found in the bone marrow, which are commonly used to treat leukemia. Patients who receive bone-marrow transplants must have their own bone marrow destroyed with radiation or chemotherapy before the transplant, which leaves them vulnerable to infection for about six months while the new bone marrow produces blood cells.

Delivering drugs that accelerate blood-cell production along with the bone-marrow transplant could shorten the period of immunosuppression, making the process safer for patients, says Irvine. In the Nature Medicine paper, his team reports successfully enhancing blood-cell maturation in mice by delivering one such drug along with the cells.

Irvine is now starting to work on making sure the manufacturing process will yield nanoparticles safe to test in humans. Once that is done, he hopes the particles could be used in clinical trials in cancer patients, possibly within the next two or three years.

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New Drug Delivery Technique: Nanoblasts from Laser-Activated Nanoparticles Move Molecules, Proteins and DNA Into Cells

New Drug Delivery Technique: Nanoblasts from Laser-Activated Nanoparticles Move Molecules, Proteins and DNA Into Cells

  2:39:00 PM    Science Lover

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Using chemical "nanoblasts" that punch tiny holes in the protective membranes of cells, researchers have demonstrated a new technique for getting therapeutic small molecules, proteins and DNA directly into living cells.

A field of human prostate cancer cells is shown after exposure to laser-activated carbon nanoparticles. The cell membranes have been stained red to assist in visualization. Each of the red circles is a single cell. (Credit: Credit: Prerona Chakravarty)

Carbon nanoparticles activated by bursts of laser light trigger the tiny blasts, which open holes in cell membranes just long enough to admit therapeutic agents contained in the surrounding fluid. By adjusting laser exposure, the researchers administered a small-molecule marker compound to 90 percent of targeted cells -- while keeping more than 90 percent of the cells alive.

The research was sponsored by the National Institutes of Health and the Institute of Paper Science and Technology at Georgia Tech. It will be reported in the August issue of the journal Nature Nanotechnology.

"This technique could allow us to deliver a wide variety of therapeutics that now cannot easily get into cells," said Mark Prausnitz, a professor in the School of Chemical and Biomolecular Engineering at the Georgia Institute of Technology. "One of the most significant uses for this technology could be for gene-based therapies, which offer great promise in medicine, but whose progress has been limited by the difficulty of getting DNA and RNA into cells."

The work is believed to be the first to use activation of reactive carbon nanoparticles by lasers for medical applications. Additional research and clinical trials will be needed before the technique could be used in humans.

Researchers have been trying for decades to drive DNA and RNA more efficiently into cells with a variety of methods, including using viruses to ferry genetic materials into cells, coating DNA and RNA with chemical agents or employing electric fields and ultrasound to open cell membranes. However, these previous methods have generally suffered from low efficiency or safety concerns.

With their new technique, which was inspired by earlier work on the so-called "photoacoustic effect," Prausnitz and collaborators Prerona Chakravarty, Wei Qian and Mostafa El-Sayed hope to better localize the application of energy to cell membranes, creating a safer and more efficient approach for intracellular drug delivery.

Their technique begins with introducing particles of carbon black measuring 25 nanometers -- one millionth of an inch -- in diameter into the fluid surrounding the cells into which the therapeutic agents are to be introduced. Bursts of near-infrared light from a femotosecond laser are then applied to the fluid at a rate of 90 million pulses per second. The carbon nanoparticles absorb the light, which makes them hot. The hot particles then heat the surrounding fluid to make steam. The steam reacts with the carbon nanoparticles to form hydrogen and carbon monoxide.

The two gases form a bubble which grows as the laser provides energy. The bubble collapses suddenly when the laser is turned off, creating a shock wave that punches holes in the membranes of nearby cells. The openings allow therapeutic agents from the surrounding fluid to enter the cells. The holes quickly close so the cell can survive.

The researchers have demonstrated that they could get the small molecule calcein, the bovine serum albumin protein and plasmid DNA through the cell membranes of human prostate cancer cells and rat gliosarcoma cells using this technique. Calcein uptake was seen in 90 percent of the cells at laser levels that left more than 90 percent of the cells alive.

"We could get almost all of the cells to take up these molecules that normally wouldn't enter the cells, and almost all of the cells remained alive," said Prerona Chakravarty, the study's lead author. "Our laser-activated carbon nanoparticle system enables controlled bubble implosions that can disrupt the cell membranes just enough to get the molecules in without causing lasting damage."

To assess how long the holes in the cell membrane remained open, the researchers left the simulated therapeutics out of the fluid when the cells were exposed to the laser light, then added the agents one second after turning off the laser. They saw almost no uptake of the molecules, suggesting that the cell membranes resealed themselves quickly.

To confirm that the carbon-steam reaction was a critical factor driving the nanoblasts, the researchers substituted gold nanoparticles for the carbon nanoparticles before exposure to laser light. Because they lacked the carbon needed for reaction, the gold nanoparticles produced little uptake of the molecules, Prausnitz noted.

Similarly, the researchers substituted carbon nanotubes for the carbon nanoparticles, and also measured little uptake, which they explained by noting that the nanotubes are less reactive than the carbon black particles.

Experimentation further showed that DNA introduced into cells through the laser-activated technique remained functional and capable of driving protein expression. When plasmid DNA that encoded for luciferase expression was introduced into the cancer cells, production of luciferase increased 17-fold.

For the future, the researchers plan to study use of a less expensive nanosecond laser to replace the ultrafast femtosecond instrument used in the research. They also plan to optimize the carbon nanoparticles so that nearly all of them are consumed during the exposure to laser light. Leftover carbon nanoparticles in the body should produce no harmful effects, though the body may be unable to eliminate them, Prausnitz noted.

"This is the first study showing proof of principle for laser-activation of reactive carbon nanoparticles for drug and gene delivery," he said. "There is a considerable path ahead before this can be brought into medicine, but we are optimistic that this approach can ultimately provide a new alternative for delivering therapeutic agents into cells safely and efficiently."

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How Do Cells Die? Biophotonic Tools Reveal Real-Time Dynamics in Living Color

How Do Cells Die? Biophotonic Tools Reveal Real-Time Dynamics in Living Color

  2:29:00 AM    Science Lover

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Apoptosis, programmed cell death, is essential to normal development, healthy immune system function, and cancer prevention. The process dramatically transforms cellular structures but the limitations of conventional microscopy methods have kept much about this structural reorganization a mystery.

Scientists have developed a biophotonic imaging 
approach capable of monitoring in real-time the 
transformations that cellular macromolecules undergo 
during apoptosis -- programmed cell death. 
(Credit: Image courtesy of University at Buffalo)

Now, in research featured on the cover of the current issue of Proceedings of the National Academy of Sciences, University at Buffalo scientists have developed a biophotonic imaging approach capable of monitoring in real-time the transformations that cellular macromolecules undergo during programmed cell death.

The work could help realize the potential of customized molecular medicine, in which chemotherapy, for example, can be precisely targeted to cellular changes exhibited by individual patients. It can also be a valuable drug development tool for screening new compounds.

"This new ability provides us with a dynamic mapping of the transformations occurring in the cell at the molecular level," says study co-author Paras N. Prasad, PhD, executive director of the UB Institute for Lasers, Photonics and Biophotonics (ILPB) and SUNY Distinguished Professor in the departments of Chemistry, Physics, Electrical Engineering and Medicine. "It provides us with a very clear visual picture of the dynamics of proteins, DNA, RNA and lipids during the cell's disintegration."

Prasad notes that molecular medicine, in which treatments or preventive measures can be tailored to cellular properties exhibited by individual patients, depends on much better methods of visualizing what's happening during critical cellular processes.

"This research helps improve our understanding of cellular events at the molecular level," he says. "If we know that specific molecular changes constitute an early signature of a disease, or what changes may predispose a patient to that disease, then we can take steps to target treatment or even prevent the disease from developing in the first place."

To capture the cellular images, the interdisciplinary UB team of biologists, chemists and physicists, led by Prasad, utilized an advanced biophotonic approach that combines three techniques: a nonlinear, optical imaging system (CARS or Coherent anti-Stokes Raman scattering), TPEF (two-photon excited fluorescence), which images living tissue and cells at deep penetration and Fluorescence Recovery after Photobleaching to measure dynamics of proteins.

"For the first time, this approach allows us to monitor in a single scan, four different types of images, characterizing the distribution of proteins, DNA, RNA and lipids in the cell," says Aliaksandr V. Kachynski, PhD, research associate professor at the ILPB and co-author.

The resulting composite image integrates in one picture the information on all four types of biomolecules, with each type of molecule represented by a different color: proteins in red, RNA in green, DNA in blue and lipids in grey, as shown on the PNAS cover.

Multiplex imaging provided new information on the rate at which proteins diffuse through the cell nucleus, the UB scientists say.

Before apoptosis was induced, the distribution of proteins was relatively uniform, but once apoptosis develops, nuclear structures disintegrate, the proteins become irregularly distributed and their diffusion rate slows down, says Artem Pliss, PhD, research assistant professor at the ILPB and co-author on the paper.

"This research gives us the unique ability to study and improve our understanding of individual subcellular structures and the transformations they go through," says Pliss.

Such precise information will be especially useful for monitoring how specific cancer drugs affect individual cells.

"For example, say drug therapy is being administered to a cancer patient; this system will allow for the monitoring of cellular changes throughout the treatment process," notes Kachynski. "Clinicians will be able to determine the optimal conditions to kill a cancer cell for the particular type of disease. An improved understanding of the drug-biomolecule interactions will help discover the optimal treatment doses so as to minimize side effects."

Andrey Kuzmin, PhD, research assistant professor at the ILPB and co-author, adds that a new paper from the UB team, forthcoming in Biophysical Journal, further extends this work.

"The benefits of the UB multiplex imaging system and its molecular selectivity have been further extended into a new fundamental cellular study, structural reorganization throughout the mitotic cell cycle," he says.

The work was supported by a grant from the John R. Oishei Foundation of Buffalo, N.Y.

The researchers are active participants in the strategic strength in Integrated Nanostructured Systems identified in the UB 2020 strategic plan for academic, research and service excellence.

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Fly Cells Flock Together, Follow the Light

Fly Cells Flock Together, Follow the Light

  12:52:00 AM    Science Lover

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Scientists at Johns Hopkins report using a laser beam to activate a protein that makes a cluster of fruit fly cells act like a school of fish turning in social unison, following the lead of the one stimulated with light.

Still image from a video clip showing a photo-activatable 
form of Rac. (Credit: Image courtesy of Denise Montell Lab)

The study of this unexpected cell movement, reported May 16 in Nature Cell Biology,holds potential importance for understanding embryonic development, wound healing and tumor metastasis -- the process by which tumor cells acquire the ability to invade surrounding tissues and migrate long distances to colonize lymph nodes, bones and other distant organs.

The research dramatically demonstrates, the researchers say, the collective direction-sensing behavior of live cells in intact tissue, and a means of controlling protein behavior in a living organism by shining a focused beam of light precisely on the parts of cells where they want the protein to be active.

"Our little system in the fruit fly is an elegant example of cells behaving socially in their natural environment -- surrounded by other cells," says Denise Montell, Ph.D., a professor of biological chemistry and director of the Center for Cell Dynamics at the Johns Hopkins University School of Medicine. "You can't capture this behavior if you look at individual cells in a culture dish."

The "social" migrating behavior among a cluster of cells in the fly ovary surprised the research team, which was using a new laser light tool to manipulate protein activity.

"People tend to think of cancer as single cells breaking off from the tumor and migrating away," Montell says, but it's likely that this collective form of movement is important, at one phase or another, in the spread of tumors."

A better understanding of how and why cells move can facilitate the development of new treatments not only for cancer but other disorders characterized by aberrant cell behavior.

Developed in the laboratory of Klaus Hahn, Ph.D., Thurman Professor of Pharmacology at the University of North Carolina at Chapel Hill, the light-activation technique previously had been shown to control cell movement in cultured mammalian cells. The Hopkins-led study provides proof of principle that a non-toxic light alone can activate a protein in live organisms, allowing researchers to safely control when and where cells move.

The Hopkins team conducted their study on a cluster of six so-called border cells in the fly ovary, cells the team has long studied and which are important to the fly because if they don't migrate, females are sterile. In addition they serve as a model for understanding the mechanisms that control collective cell movements in general, which occur during normal embryonic development, wound healing and in tumor metastasis.

First, they genetically altered the border cells so that they were lacking the ability to respond to naturally occurring chemical attractants that normally control their movement. Then they used a fly protein known as Rac, which was fused to a photoactivatable (PA) plant protein, a creation engineered by Hahn's lab. The PA-Rac, which remains inert in the dark, reacts to light because the plant protein changes shape and allows Rac to become active, causing the cells to move.

Because a beam of laser light can be much smaller than a cell, the team was able to activate Rac not only in one single cell, but also in one part of one cell, Montell says: "The other cool thing is this is reversible, so as soon as you take the light away, the PA-Rac wraps back up and turns itself off."

Following up on previous research, the team wanted to find out if Rac would be sufficient to set the direction of movement of cells within live tissue.

When they shined a laser beam on various individual cells, the entire cluster responded by moving in directions that it wouldn't under normal conditions: sideways, for instance, and even in reverse. In short, they followed the light.

"When we activated Rac in even one part of one of these cells -- and not in the cell that would be the leader if all was normal -- it was as if all the other cells said, Aha! You've got more Rac activity so we're heading your way," Montell says. "It's amazing to me that somehow the cells sense each others' levels of Rac activity and collectively decide which way to go.

Authors on the paper, in addition to Montell and Hahn, are Xiaobo Wang from Johns Hopkins and Yi Wu from UNC.

Funding was provided by the National Institutes of Health and the Cell Migration Consortium.

A video clip of a photo-activatable form of Rac is available at: http://www.icm.com/montell/MovieS5%28RacQ61Lforwardandrev%29.mov

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DNA Nanotechnology: 'Magic Bullets' Breakthrough Offers Promising Applications in Medicine

DNA Nanotechnology: 'Magic Bullets' Breakthrough Offers Promising Applications in Medicine

  12:25:00 AM    Science Lover

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A team of McGill Chemistry Department researchers led by Dr. Hanadi Sleiman has achieved a major breakthrough in the development of nanotubes -- tiny "magic bullets" that could one day deliver drugs to specific diseased cells. Sleiman explains that the research involves taking DNA out of its biological context. So rather than being used as the genetic code for life, it becomes a kind of building block for tiny nanometre-scale objects.

Researchers have created the first examples of DNA 
nanotubes that encapsulate and load cargo, and 
then release it rapidly and completely when a specific 
external DNA strand is added. 
(Credit: Image courtesy of McGill University)

Using this method, the team created the first examples of DNA nanotubes that encapsulate and load cargo, and then release it rapidly and completely when a specific external DNA strand is added. One of these DNA structures is only a few nanometres wide but can be extremely long, about 20,000 nanometres. (A nanometre is one-10,000th the diameter of a human hair.)

Until now, DNA nanotubes could only be constructed by rolling a two-dimensional sheet of DNA into a cylinder. Sleiman's method allows nanotubes of any shape to be formed and they can either be closed to hold materials or porous to release them. Materials such as drugs could then be released when a particular molecule is present.

One of the possible future applications for this discovery is cancer treatment. However, Sleiman cautions, "we are still far from being able to treat diseases using this technology; this is only a step in that direction. Researchers need to learn how to take these DNA nanostructures, such as the nanotubes here, and bring them back to biology to solve problems in nanomedicine, from drug delivery, to tissue engineering to sensors," she said.

The team's discovery was published on March 14, 2010 in Nature Chemistry. The research was made possible with funding from the National Science and Engineering Research Council and the Canadian Institute for Advanced Research.

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Nanoparticles: Golden Bullet for Cancer?

Nanoparticles: Golden Bullet for Cancer?

  10:03:00 AM    Science Lover

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In a lecture he delivered in 1906, the German physician Paul Ehrlich coined the term Zuberkugel, or "magic bullet," as shorthand for a highly targeted medical treatment.

Infrared images made while tumors were irradiated with a laser show that in nanocage-injected mice (left), the surface of the tumor quickly became hot enough to kill cells. In buffer-injected mice (right), the temperature barely budged. This specificity is what makes photothermal therapy so attractive as a cancer therapy. (Credit: WUSTL)

Magic bullets, also called silver bullets, because of the folkloric belief that only silver bullets can kill supernatural creatures, remain the goal of drug development efforts today.

A team of scientists at Washington University in St. Louis is currently working on a magic bullet for cancer, a disease whose treatments are notoriously indiscriminate and nonspecific. But their bullets are gold rather than silver. Literally.

The gold bullets are gold nanocages that, when injected, selectively accumulate in tumors. When the tumors are later bathed in laser light, the surrounding tissue is barely warmed, but the nanocages convert light to heat, killing the malignant cells.

In an article just published in the journal Small, the team describes the successful photothermal treatment of tumors in mice.

The team includes Younan Xia, Ph.D., the James M. McKelvey Professor of Biomedical Engineering in the School of Engineering and Applied Science, Michael J. Welch, Ph.D., professor of radiology and developmental biology in the School of Medicine, Jingyi Chen, Ph.D., research assistant professor of biomedical engineering and Charles Glaus, Ph.D., a postdoctoral research associate in the Department of Radiology.

"We saw significant changes in tumor metabolism and histology," says Welch, "which is remarkable given that the work was exploratory, the laser 'dose' had not been maximized, and the tumors were 'passively' rather than 'actively' targeted."

Why the nanocages get hot

The nanocages themselves are harmless. "Gold salts and gold colloids have been used to treat arthritis for more than 100 years," says Welch. "People know what gold does in the body and it's inert, so we hope this is going to be a nontoxic approach."

"The key to photothermal therapy," says Xia, "is the cages' ability to efficiently absorb light and convert it to heat. "

Suspensions of the gold nanocages, which are roughly the same size as a virus particle, are not always yellow, as one would expect, but instead can be any color in the rainbow.

They are colored by something called a surface plasmon resonance. Some of the electrons in the gold are not anchored to individual atoms but instead form a free-floating electron gas, Xia explains. Light falling on these electrons can drive them to oscillate as one. This collective oscillation, the surface plasmon, picks a particular wavelength, or color, out of the incident light, and this determines the color we see.

Medieval artisans made ruby-red stained glass by mixing gold chloride into molten glass, a process that left tiny gold particles suspended in the glass, says Xia.

The resonance -- and the color -- can be tuned over a wide range of wavelengths by altering the thickness of the cages' walls. For biomedical applications, Xia's lab tunes the cages to 800 nanometers, a wavelength that falls in a window of tissue transparency that lies between 750 and 900 nanometers, in the near-infrared part of the spectrum.

Light in this sweet spot can penetrate as deep as several inches in the body (either from the skin or the interior of the gastrointestinal tract or other organ systems).

The conversion of light to heat arises from the same physical effect as the color. The resonance has two parts. At the resonant frequency, light is typically both scattered off the cages and absorbed by them.

By controlling the cages' size, Xia's lab tailors them to achieve maximum absorption.

Passive targeting

"If we put bare nanoparticles into your body," says Xia, "proteins would deposit on the particles, and they would be captured by the immune system and dragged out of the bloodstream into the liver or spleen."

To prevent this, the lab coated the nanocages with a layer of PEG, a nontoxic chemical most people have encountered in the form of the laxatives GoLyTELY or MiraLAX. PEG resists the adsorption of proteins, in effect disguising the nanoparticles so that the immune system cannot recognize them.

Instead of being swept from the bloodstream, the disguised particles circulate long enough to accumulate in tumors.

A growing tumor must develop its own blood supply to prevent its core from being starved of oxygen and nutrients. But tumor vessels are as aberrant as tumor cells. They have irregular diameters and abnormal branching patterns, but most importantly, they have thin, leaky walls.

The cells that line a tumor's blood vessel, normally packed so tightly they form a waterproof barrier, are disorganized and irregularly shaped, and there are gaps between them.

The nanocages infiltrate through those gaps efficiently enough that they turn the surface of the normally pinkish tumor black.

A trial run

In Welch's lab, mice bearing tumors on both flanks were randomly divided into two groups. The mice in one group were injected with the PEG-coated nanocages and those in the other with buffer solution. Several days later the right tumor of each animal was exposed to a diode laser for 10 minutes.

The team employed several different noninvasive imaging techniques to follow the effects of the therapy. (Welch is head of the oncologic imaging research program at the Siteman Cancer Center of Washington University School of Medicine and Barnes-Jewish Hospital and has worked on imaging agents and techniques for many years.)

During irradiation, thermal images of the mice were made with an infrared camera. As is true of cells in other animals that automatically regulate their body temperature, mouse cells function optimally only if the mouse's body temperature remains between 36.5 and 37.5 degrees Celsius (98 to 101 degrees Fahrenheit).

At temperatures above 42 degrees Celsius (107 degrees Fahrenheit) the cells begin to die as the proteins whose proper functioning maintains them begin to unfold.

In the nanocage-injected mice, the skin surface temperature increased rapidly from 32 degrees Celsius to 54 degrees C (129 degrees F).

In the buffer-injected mice, however, the surface temperature remained below 37 degrees Celsius (98.6 degrees Fahrenheit).

To see what effect this heating had on the tumors, the mice were injected with a radioactive tracer incorporated in a molecule similar to glucose, the main energy source in the body. Positron emission and computerized tomography (PET and CT) scans were used to record the concentration of the glucose lookalike in body tissues; the higher the glucose uptake, the greater the metabolic activity.

The tumors of nanocage-injected mice were significantly fainter on the PET scans than those of buffer-injected mice, indicating that many tumor cells were no longer functioning.

The tumors in the nanocage-treated mice were later found to have marked histological signs of cellular damage.

Active targeting

The scientists have just received a five-year, $2,129,873 grant from the National Cancer Institute to continue their work with photothermal therapy.

Despite their results, Xia is dissatisfied with passive targeting. Although the tumors took up enough gold nanocages to give them a black cast, only 6 percent of the injected particles accumulated at the tumor site.

Xia would like that number to be closer to 40 percent so that fewer particles would have to be injected. He plans to attach tailor-made ligands to the nanocages that recognize and lock onto receptors on the surface of the tumor cells.

In addition to designing nanocages that actively target the tumor cells, the team is considering loading the hollow particles with a cancer-fighting drug, so that the tumor would be attacked on two fronts.

But the important achievement, from the point of view of cancer patients, is that any nanocage treatment would be narrowly targeted and thus avoid the side effects patients dread.

The TV and radio character the Lone Ranger used only silver bullets, allegedly to remind himself that life was precious and not to be lightly thrown away. If he still rode today, he might consider swapping silver for gold.

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Breakthrough Reveals Blood Vessel Cells Are Key to Growing Unlimited Amounts of Adult Stem Cells

Breakthrough Reveals Blood Vessel Cells Are Key to Growing Unlimited Amounts of Adult Stem Cells

  2:22:00 AM    Science Lover

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In a leap toward making stem cell therapy widely available, researchers at the Ansary Stem Cell Institute at Weill Cornell Medical College have discovered that endothelial cells, the most basic building blocks of the vascular system, produce growth factors that can grow copious amounts of adult stem cells and their progeny over the course of weeks. Until now, adult stem cell cultures would die within four or five days despite best efforts to grow them.

Diagram showing the location of endothelial cells. (Credit: Courtesy of Wikimedia Commons / Stijn A.I. Ghesquiere)

"This is groundbreaking research with potential application for regeneration of organs and inhibition of cancer cell growth," said Dr. Antonio M. Gotto Jr., the Stephen and Suzanne Weiss Dean of Weill Cornell Medical College and Provost for Medical Affairs of Cornell University.

This new finding sets forth the innovative concept that blood vessels are not just passive conduits for delivery of oxygen and nutrients, but are also programmed to maintain and proliferate stem cells and their mature forms in adult organs. Using a novel approach to harness the potential of endothelial cells by "co-culturing" them with stem cells, the researchers discovered the means to manufacture an unlimited supply of blood-related stem cells that may eventually ensure that anyone who needs a bone marrow transplant can get one.

The vascular-cell model established in this study could also be used to grow abundant functional stem cells from other organs such as the brain, heart, skin and lungs. An article detailing these findings appears in the March 5 issue of the journal Cell Stem Cell.

In adult organs, there are few naturally occurring stem cells, so using them for organ regeneration is impractical. Until now, strategies to expand cultures of adult stem cells, which invariably used animal-based growth factors, serum, and genetically manipulated feeder cells, have only been marginally successful. This study, which employs endothelial cells to propagate stem cells without added growth factors and serum, will likely revolutionize the use of adult stem cells for organ regeneration, as well as decipher the complex physiology of the adult stem cells.

"This study will have a major impact on the treatment of any blood-related disorder that requires a stem cell transplant," says the study's senior author, Dr. Shahin Rafii, the Arthur B. Belfer Professor in Genetic Medicine, co-director of the Ansary Stem Cell Institute and a Howard Hughes Medical Institute Investigator, at Weill Cornell Medical College. Currently, stem cells derived from bone marrow or umbilical cord blood are used to treat patients who require bone marrow transplants. Most stem cell transplants are successful, but because of the shortage of genetically matched bone marrow and umbilical cord blood cells, many patients cannot benefit from the procedure.

"Over the last few decades, substantial funding has been spent to develop platforms to expand adult stem cell cultures, but these efforts have never been able to coax an authentic adult stem cell to self-renew beyond a few days," continues Dr. Rafii. "Most stem cells, even in the presence of multiple growth factors, serum, and support from generic non-endothelial stromal cells, die after a few days. Now, employing our endothelial stem cell co-cultures, we can propagate bona fide adult stem cells in the absence of external factors and serum beyond 21 days with an expansion index of more than 400-fold."

If this vascular-based stem cell expansion strategy continues to be validated, physicians could use any source of hematopoietic (blood-producing) stem cells, propagate them exponentially, and bank the cells for transplantation into patients.

In a true first, the study demonstrates how this novel vascular cell platform or "vascular niche" can self-renew adult hematopoietic stem cells for weeks, both in vitro and in vivo, by co-culturing them on a bed of endothelial cells. The researchers chose endothelial cells because they are in close contact with blood stem cells, and previous work from Dr. Rafii's lab had demonstrated that endothelial cells produce novel stem-cell-active growth factors. However, maintenance of the endothelial cells is cumbersome and if they are not "fed" specific substances, such as growth factors known as "angiogenic factors," they immediately die. To get around this problem, the researchers genetically engineered the endothelial cells to stay in a long-term survival state by inserting a recently discovered gene cloned from adenoviruses, which does not promote oncogenic transformation of the human cells. This earlier discovery, using a single gene to put endothelial cells into a long-lasting "suspended animation" state without harming their ability to produce blood vessels, was also discovered in Dr. Rafii's lab and published in the journal Proceedings of National Academy Sciences in 2008.

Endothelial Cells Could Generate Stem Cells and Their Differentiated Progeny

In this study, the researchers also discovered that endothelial cells not only could expand stem cells, but also instruct stem cells to generate mature differentiated progeny that could form immune cells, platelets, and red and white blood cells, all of which constitute functioning blood.

"We are the first group to demonstrate that endothelial cells elaborate a repertoire of stem-cell-active growth factors that not only stimulate stem cell expansion but also orchestrate differentiation of these stem cells into their mature progeny," says Dr. Jason Butler, a senior investigator at Weill Cornell Medical College and first author of the study. "For example, we have found that expression of specific stem-cell-active factors, namely Notch-ligands, by the endothelial cells lining the wall of working blood vessels promote proliferation of the blood-forming stem cells. Inhibition of these specific factors on the endothelial cells resulted in the failure of the regeneration of the blood-forming stem cells. These findings suggest that endothelial cells directly, through expression of stem-cell-active cytokines, promote stem cell reconstitution."

Further describing this innovative concept, in a high-impact article published in the January 2010 issue of Nature Reviews Cancer, Drs. Rafii and Butler, and Dr. Hideki Kobayashi, who is also a co-author of the current study, have elaborated on specific endothelial cell-produced growth factors that promote the growth of tumor cells besides stem cells.

Development of the vascular-cell technology that supports long-lasting growth of stem cells will also allow scientists to generate abundant sources of functional and malignant stem cells for genetic and basic studies. This study has also resolved a long-standing controversy in which several groups had claimed that bone-forming cells (osteoblasts) exclusively support the expansion of blood-forming stem cells. "However, using a highly sophisticated molecular imaging approach, we show that regenerating blood-forming stem cells in the bone marrow are in intimate contact with the blood vessels, indicating that endothelial cells are the predominant regulator of stem cell repopulation in the adult bone marrow," states Dr. Daniel Nolan, a senior scientist in Dr. Rafii's lab and a co-author of the new study.

One other important concern addressed in this study was whether forced expansion of the stem cells over a long period of time would induce cancerous mutations in the stem cells. However, the authors of this study show that, even after one year, there was no indication of tumor formation, such as leukemias, when the expanded stem cells were transplanted back into mice. This suggests that the endothelial cells provide a milieu that proliferates stem cells without creating cancer risk.

The current breakthrough represents the culmination of many years of work by Dr. Rafii and his lab, including their research in converting adult mouse spermatogonial stem cells to endothelial cells (Nature, September 2007) and in deriving stable, copious endothelial cells from human embryonic stem cells (Nature Biotechnology, Jan. 17, 2010).

The ability to generate many stable endothelial cells from human embryonic stem cells leads to new research opportunities, according to Dr. Zev Rosenwaks, who is a co-author in this study and director and physician-in-chief of the Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine, as well as the director of the Tri-Institutional Stem Cell Initiative Derivation Unit at Weill Cornell Medical College.

Dr. Rosenwaks says, "Generation of endothelial cells derived from diseased embryonic stem cells that are being propagated in our Derivation Unit will open up new avenues of research to molecularly eavesdrop on the communication between vascular cells and stem cells. This innovative line of investigation -- to determine how normal and abnormal human vascular cells induce the formation of organs during development of embryos and how dysfunction of endothelial cells results in developmental defects -- will lay the foundation for novel platforms for therapeutic organ regeneration."

Dr. Rafii sees even more opportunities. "Identification of as yet unrecognized growth factors produced by human embryonic cell-derived endothelium and adult endothelial cells that support stem cell expansion and differentiation will establish a new arena in stem cell biology. We will be able to selectively activate endothelial cells not only to induce organ regeneration, but also to inhibit specifically the production of endothelial cell-derived factors in order to block the growth of tumors. Our findings are the first steps toward such goals and they highlight the potential of vascular cells for generating sufficient stem cells for therapeutic organ regeneration, tumor targeting, and gene therapy applications," concludes Dr. Rafii.

Co-authors include Daniel J. Nolan, Eva L. Vertes, Hideki Kobayashi, Andrea T. Hooper, Koji Shido, Ian A. White, Mariko Kobayashi, Yuki Kimura and Marco Seandel of the Howard Hughes Medical Institute and the Department of Genetic Medicine and Ansary Stem Cell Institute at NewYork-Presbyterian Hospital/Weill Cornell Medical Center; Zev Rosenwaks, Chad May and Larry Witte of NewYork-Presbyterian Hospital/Weill Cornell Medical Center; Carrie Shawber and Jan Kitajewski at NewYork-Presbyterian Hospital/Columbia University Medical Center; Barbara Varnum-Finney of ImClone Systems Incorporated; and Irwin D. Bernstein at Fred Hutchinson Cancer Research Center, Seattle. The study received funding from the Howard Hughes Medical Institute.

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New 'Nanoburrs' Could Help Fight Heart Disease

New 'Nanoburrs' Could Help Fight Heart Disease

  1:03:00 AM    Science Lover

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Building on their previous work delivering cancer drugs with nanoparticles, MIT and Harvard researchers have turned their attention to cardiovascular disease, designing new particles that can cling to damaged artery walls and slowly release medicine.

Researchers have built targeted nanoparticles that can cling to artery walls and slowly release medicine, an advance that potentially provides an alternative to drug-releasing stents in some patients with cardiovascular disease. (Credit: Image courtesy of Massachusetts Institute of Technology)

The particles, dubbed "nanoburrs," are coated with tiny protein fragments that allow them to stick to damaged arterial walls. Once stuck, they can release drugs such paclitaxel, which inhibits cell division and helps prevent growth of scar tissue that can clog arteries.

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Broken Genomes Behind Breast Cancers, Research Finds

Broken Genomes Behind Breast Cancers, Research Finds

  11:26:00 PM    Science Lover

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The first detailed search of breast cancer genomes to uncover genomic rearrangements is published December 23. The team characterised the ways in which the human genome is broken and put back together in 24 cases of breast cancer.

Breast cancer cell. (Credit: Lorna McInroy, Wellcome Images)

Rearrangements involve reshuffling and reorganisation of the genome and include deletions, duplications and novel juxtaposition of DNA sequences. The study shows that breast cancer samples can differ greatly in the extent to which they are subject to genomic rearrangements: some are relatively undisturbed whereas others are fractured extensively and then reassembled with more than 200 rearrangements present.

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First Evidence Of Virus In Malignant Prostate Cells: XMRV Retrovirus Linked To More Aggressive Tumors

First Evidence Of Virus In Malignant Prostate Cells: XMRV Retrovirus Linked To More Aggressive Tumors

  9:53:00 PM    Science Lover

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In a finding with potentially major implications for identifying a viral cause of prostate cancer, researchers at the University of Utah and Columbia University medical schools have reported that a type of virus known to cause leukemia and sarcomas in animals has been found for the first time in malignant human prostate cancer cells.

Histopathology of adenocarcinoma of the prostate. (Credit: CDC/Dr. Edwin P. Ewing, Jr.)

If further investigation proves the virus, XMRV (Xenotropic murine leukemia virus-related virus), causes prostate cancer in people, it would open opportunities for developing diagnostic tests, vaccines, and therapies for treating the cancer, according to the study published Sept. 7 online in the Proceedings of the National Academy of Sciences. Prostate cancer is expected to strike nearly 200,000 U.S. males this year, making it the second most common form of cancer, outside of skin cancers, among men.


"We found that XMRV was present in 27 percent of prostate cancers we examined and that it was associated with more aggressive tumors," said Ila R. Singh, M.D., Ph.D., associate professor of pathology at University of Utah and the study's senior author. "We still don't know that this virus causes cancer in people, but that is an important question we're going to investigate."


Singh, also a member of the U of U's Huntsman Cancer Institute and associate medical director at ARUP Laboratories, moved to Utah from Columbia University Medical Center in 2008, where she began this research. She remains an adjunct faculty member at Columbia.


Along with providing the first proof that XMRV is present in malignant cells, the study also confirmed that XMRV is a gammaretrovirus, a simple retrovirus first isolated from prostate cancers in 2006 by researchers at the University of California, San Francisco (UCSF), and the Cleveland Clinic. Gammaretroviruses are known to cause cancer in animals, but have not been shown to do so in humans. The UCSF study did not examine benign (non-malignant) prostate tissues, so could not link XMRV to prostate cancer. They also did not find the virus in malignant cells.


Singh and her fellow researchers examined more than 200 human prostate cancers, and compared them to more than 100 non-cancerous prostate tissues. They found 27 percent of the cancers contained XMRV, compared to only 6 percent of the benign tissues. The viral proteins were found almost exclusively in malignant prostatic cells, suggesting that XMRV infection may be directly linked to the formation of tumors.


Retroviruses insert a DNA copy of their genome into the chromosomes of the cells they infect. Such an insertion sometimes occurs adjacent to a gene that regulates cell growth, disrupting normal cell growth, resulting in more rapid proliferation of such a cell, which eventually develops into a cancer. This mechanism of carcinogenesis is followed by gammaretroviruses in general. Singh is currently examining if a similar mechanism might be involved with XMRV and prostate cancer.


In another important finding of the study, Singh and her colleagues also showed that susceptibility to XMRV infection is not enhanced by a genetic mutation, as was previously reported. If XMRV were caused by the mutation, only the 10 percent of the population who carry the mutated gene would be at risk for infection with virus. But Singh found no connection between XMRV and the mutation, meaning the risk for infection may extend to the population at large.


While the study answers important questions about XMRV, it also raises a number of other questions, such as whether the virus infects women, is sexually transmitted, how prevalent it is in the general population, and whether it causes cancers in tissues other than the prostate.


"We have many questions right now," Singh said, "and we believe this merits further investigation."


Viruses have been shown to cause cancer of the cervix, connective tissues (sarcomas), immune system (lymphoma), and other organs. If the retrovirus is shown to cause prostate cancer, this could have important implications for preventing viral transmission and for developing vaccines to prevent XMRV infection in people.


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