Stem Cells: Nearing Goal of Using Patient's Own Cells to Make Stem Cells to Replace Lost or Diseased Tissue

Stem Cells: Nearing Goal of Using Patient's Own Cells to Make Stem Cells to Replace Lost or Diseased Tissue

  1:27:00 AM    Science Lover

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Scientists at the Salk Institute for Biological Studies have developed an improved technique for generating large numbers of blood cells from a patient's own cells. The new technique will be immediately useful in further stem cell studies, and when perfected, could be used in stem cell therapies for a wide variety of conditions including cancers and immune ailments.

Round hematopoietic (blood) cells emerge from 
differentiating human pluripotent stem cells. 
(Credit: Courtesy of Aaron Parker, Salk Institute 
for Biological Studies)

"There are further improvements that we need to make, but this takes us a significant step closer to the ultimate goal, which is to be able to take ordinary cells from a patient, induce them to become stem cells, and then use those stem cells to rebuild lost or diseased tissues, for example the patient's bone marrow," says Inder M. Verma, PhD, Irwin and Joan Jacobs Chair in Exemplary Life Science and American Cancer Society Professor of Molecular Biology at the Salk Institute Laboratory of Genetics. Verma is senior author of the report, which is published in the July edition of the journal Stem Cells.

Stem cell researchers have been racing towards this goal since 2006, when techniques for turning ordinary skin cells into induced pluripotential stem cells (iPSCs) were first reported. In principle, iPSCs mimic the embryonic stem cells (ESCs) from which organisms develop. Researchers now want to find the precise mixes and sequences of chemical compounds needed to coax iPSCs to mature into the tissue-specific stem cells of their choice. The latter are self-renewing, and can be transplanted into the body to produce the 'progenitor' cells that multiply locally and produce mature tissue cells.

However, researchers don't know yet how to induce iPSCs to become tissue-specific stem cells or mature tissue cells with high efficiency. "We've been producing these cells in quantities that are too low to enable them to be studied easily, much less used for therapies," says Aaron Parker, PhD, a former graduate student and now a postdoctoral researcher in Verma's lab. Parker is a co-lead-author of the paper, with Niels-Bjarne Woods, PhD, who was a postdoctoral researcher in the Verma lab at the outset of the project, and is now an assistant professor at Lund University in Sweden.

Like many other stem cell research laboratories, the Verma lab has been trying to find more efficient ways to turn iPSCs into blood-forming 'hematopoietic' stem cells (HSCs). These may be more valuable medically than any other tissue-specific stem cell, because they can supply not only oxygen-carrying red blood cells but also all the white blood cells of the immune system. "There would be an almost unlimited number of usages for true HSCs," says Verma.

For the present study, the research team sought to do a better job of mimicking the changing conditions that naturally direct ESCs to become HSCs in the womb. "We took seven lines of human ESCs and iPSCs, and experimented with different combinations and sequences of growth factors and other chemical compounds that are known to be present as ESCs move to the HSC state in a developing human," says Parker.



Applying cocktails of these factors, Parker and Woods and their colleagues induced the iPSCs and ESCs to form colonies of cells that bore the distinctive molecular markers of blood cells. With their best such cocktail they were able to detect blood-specific markers on 84% of their cells after three weeks. "That's a big jump in efficiency from what we saw in the field just a few years ago," says Parker.

The technique still has room for improvement. The researchers detected progenitor cells and mature cells from only one category or lineage: myeloid cells, which include red blood cells and primitive immune cells such as macrophages. "We didn't see any cells from the lymphoid lineage, meaning T-cells and B-cells," Parker says.

Another drawback was that the blood cell population they produced from ESCs and iPSCs contained short-lived progenitors and mature blood cells but no indefinitely renewing, transplantable HSCs. Their cocktail, they believed, either pushed the cells past the HSC state to the progenitor state too quickly, or made the maturing cells skip the HSC state entirely.

From this and other labs' results, the team hypothesized the existence of an intermediate, pre-hematopoietic type of stem cell, produced by ESCs and iPSCs and in turn producing HSCs. "We know that HSCs appear in a particular region of mammals during embryonic development, and our idea is that these pre-hematopoietic stem cells are there and are somehow made to mature into HSCs," says Parker. "So our lab is now going to focus on finding the precise maturation signals provided by that embryonic region to produce these true, transplantable HSCs."

Once that is done, researchers will need to make a number of further refinements to improve the safety of HSCs intended for human patients. "But we're now tantalizingly close to our ultimate goal," says Verma.

The other authors who contributed to the work were Roksana Moraghebi, of Lund University's Stem Cell Center; Margaret K. Lutz, Amy L. Firth, Kristen J. Brennand, W. Travis Berggren and Fred H. Gage of the Salk Institute Laboratory for Genetics; Juan Carlos Izpisúa Belmonte of the Salk Institute Gene Expression Laboratory; and Angel Raya of the Center of Regenerative Medicine in Barcelona, Spain.

Funding for this research was provided by the National Institutes for Health, the California Institute for Regenerative Medicine, the Leducq Foundation, the Merieux Foundation, the Ellison Medical Foundation, Ipsen/Biomeasure, Sanofi Aventis, the Prostate Cancer Foundation, the H.N. and Frances C. Berger Foundation, The Royal Physiographic Society of Sweden, the Lund University Medical Faculty, and the Lars Hierta Memorial Foundation, and the H.A. and Mary K. Chapman Charitable Trust.

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Carbon Nanostructures: Elixir or Poison?

Carbon Nanostructures: Elixir or Poison?

  1:15:00 AM    Science Lover

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A Los Alamos National Laboratory toxicologist and a multidisciplinary team of researchers have documented potential cellular damage from "fullerenes" -- soccer-ball-shaped, cage-like molecules composed of 60 carbon atoms. The team also noted that this particular type of damage might hold hope for treatment of Parkinson's disease, Alzheimer's disease, or even cancer.

Los Alamos National Laboratory toxicologist Jun Gao works in his laboratory using a protective fume hood. (Credit: Photo by James R. Rickman)

The research recently appeared in Toxicology and Applied Pharmacology and represents the first-ever observation of this kind for spherical fullerenes, also known as buckyballs, which take their names from the late Buckminster Fuller because they resemble the geodesic dome concept that he popularized.

Engineered carbon nanoparticles, which include fullerenes, are increasing in use worldwide. Each buckyball is a skeletal cage of carbon about the size of a virus. They show potential for creating stronger, lighter structures or acting as tiny delivery mechanisms for designer drugs or antibiotics, among other uses. About four to five tons of carbon nanoparticles are manufactured annually.

"Nanomaterials are the 21st century revolution," said Los Alamos toxicologist Rashi Iyer, the principal research lead and coauthor of the paper. "We are going to have to live with them and deal with them, and the question becomes, 'How are we going to maximize our use of these materials and minimize their impact on us and the environment?'"

Iyer and lead author Jun Gao, also a Los Alamos toxicologist, exposed cultured human skin cells to several distinct types of buckyballs. The differences in the buckyballs lay in the spatial arrangement of short branches of molecules coming off of the main buckyball structure. One buckyball variation, called the "tris" configuration, had three molecular branches off the main structure on one hemisphere; another variation, called the "hexa" configuration, had six branches off the main structure in a roughly symmetrical arrangement; the last type was a plain buckyball.

The researchers found that cells exposed to the tris configuration underwent premature senescence -- what might be described as a state of suspended animation. In other words, the cells did not die as cells normally should, nor did they divide or grow. This arrest of the natural cellular life cycle after exposure to the tris-configured buckyballs may compromise normal organ development, leading to disease within a living organism. In short, the tris buckyballs were toxic to human skin cells.

Moreover, the cells exposed to the tris arrangement caused unique molecular level responses suggesting that tris-fullerenes may potentially interfere with normal immune responses induced by viruses. The team is now pursuing research to determine if cells exposed to this form of fullerenes may be more susceptible to viral infections.

Ironically, the discovery could also lead to a novel treatment strategy for combating several debilitating diseases. In diseases like Parkinson's or Alzheimer's, nerve cells die or degenerate to a nonfunctional state. A mechanism to induce senescence in specific nerve cells could delay or eliminate onset of the diseases. Similarly, a disease like cancer, which spreads and thrives through unregulated replication of cancer cells, might be fought through induced senescence. This strategy could stop the cells from dividing and provide doctors with more time to kill the abnormal cells.

Because of the minute size of nanomaterials, the primary hazard associated with them has been potential inhalation -- similar to the concern over asbestos exposure.

"Already, from a toxicological point of view, this research is useful because it shows that if you have the choice to use a tris- or a hexa-arrangement for an application involving buckyballs, the hexa-arrangement is probably the better choice," said Iyer. "These studies may provide guidance for new nanomaterial design and development."

These results were offshoots from a study (Shreve, Wang, and Iyer) funded to understand the interactions between buckyballs and biological membranes. Los Alamos National Laboratory has taken a proactive role by initiating a nanomaterial bioassessmnet program with the intention of keeping its nanomaterial workers safe while facilitating the discovery of high-function, low-bioimpact nanomaterials with the potential to benefit national security missions. In addition to Gao and Iyer, the LANL program includes Jennifer Hollingsworth, Yi Jiang, Jian Song, Paul Welch, Hsing Lin Wang, Srinivas Iyer, and Gabriel Montaño.

Los Alamos National Laboratory researchers will continue to attempt to understand the potential effects of exposure to nanomaterials in much the same way that Los Alamos was a worldwide leader in understanding the effects of radiation during the Lab's early history. Los Alamos workers using nanomaterials will continue to follow protocols that provide the highest degree of protection from potential exposure.

Meantime, Los Alamos research into nanomaterials provides a cautionary tale for nanomaterial use, as well as early foundations for worker protection. Right now, there are no federal regulations for the use of nanomaterials. Disclosure of use by companies or individuals is voluntary. As nanomaterial use increases, understanding of their potential hazards should also increase.

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