“Latest Stem Cells News”

Cells from people with premature aging disease get “younger” with the help of stem cell technology.

Premature aging is one of the most difficult-to-deal with conditions in the world. In addition to its physical consequences, its psychological impact is devastating on a person suffering from it. At this point, experts believe that the disease is caused by the fact that people predisposed to it have very short telomeres, which are repetitive stretches of DNA attached to the end of each chromosome in each cell featuring genetic material in the human body. As chromosomes multiply, the telomeres naturally get shorter, and scientists believe that this may be playing a role in aging.

UC San Diego scientists have dramatically improved the success rate of genetically modifying human embryonic stem cells. This advance brings the promise of better treatment of genetic diseases.
The new approach works in 20 percent of embryonic stem cells, compared to less than 1 percent treated with standard methods, said Yang Xu, a UCSD professor of biology, who led the study, assisted by Hoseok Song and Sun-Ku Chung, postdoctoral fellows in his lab.

The study was published Thursday in the journal Cell Stem Cell.
Some genetic diseases can’t be studied adequately in animals, Xu said, so the ability to produce human cells with the diseases will be of great help. For example, drugs to treat the diseases can be tested in the genetically modified cells, he said.

Scientists at the John Innes Centre in Norwich, UK, have shown how plants can protect themselves against genetic damage caused by environmental stresses. The growing tips of plant roots and shoots have an in-built mechanism that, if it detects damage to the DNA, causes the cell to ‘commit suicide’ rather than pass on its defective DNA.

Plants have, at the very tips of their roots and shoots, small populations of stem cells, through which they are able to grow and produce new tissue throughout the plant’s life. These stem cells are the precursors to producing plant tissues and organs. This means that any defect that arises in the stem cell’s genetic code will be passed on and persist irreversibly throughout the life of the plant, which may last thousands of years.

It is therefore critical that there are safeguards that prevent stem cell defects becoming fixed, particularly as the stem cells exist at the growing tips of shoots and roots where they are especially exposed to potentially hazardous environments.

Nick Fulcher and Robert Sablowski, with funding from the Biotechnology and Biological Sciences Research Council (BBSRC), set out to discover what these safeguards could be. By using X-rays and chemicals they were able to induce damage to DNA, and found that stem cells were much more sensitive to DNA damage than other cells. The cells are able to detect the DNA damage, triggering the death of these cells, thus preventing the damaged genetic code becoming fixed in the rest of the plant tissues.

A similar system exists in animal cells, which has been very well investigated, as the failure of this system can lead to cancer. The discovery of a similar, although distinct system in plants is therefore of great interest in the field of plant development, as well as in the efforts of scientists to develop plants better able to cope with environmental stress.

Drought, high salinity and the accumulation of hazardous chemicals in the soil are side-effects of a changing climate, so knowledge of how plants cope with theses stresses is of fundamental importance to agricultural science’s response to climate change. This is one aim of the research carried out by the John Innes Centre, an institute of the BBSRC.

from http://www.jic.ac.uk/corporate/media-and-public/current-releases/sablowskiDNAdamage.htm

The same genes that are chemically altered during normal cell differentiation, as well as when normal cells become cancer cells, are also changed in stem cells that scientists derive from adult cells, according to new research from Johns Hopkins and Harvard.

Although genetically identical to the mature body cells from which they are derived, induced pluripotent stem cells (iPSCs) are notably special in their ability to self-renew and differentiate into all kinds of cells. And now scientists have detected a remarkable if subtle molecular disparity between the two: They have distinct “epigenetic” signatures; that is, they differ in what gets copied when the cell divides, even though these differences aren’t part of the DNA sequence.

“Relatively little study has been done on the epigenetic nature of stem cells,” says Andrew Feinberg, M.D., M.P.H., a professor of medicine at the Johns Hopkins University School of Medicine. “To date, the bulk of what is known about stem cells is focused on how you create them and grow them and so forth, but not on the essence of them, and what is fundamentally different about these cells.”

To compare and contrast mature connective tissue cells called fibroblasts with the pluripotent stem cells into which they were reprogrammed, the investigators focused on a chemical change known as methylation. This chemical change which, associated with silencing genes, is classified as epigenetic because, although not part of the DNA sequence, is copied when a cell divides. They identified and then measured so-called differentially methylated regions (DMRs) of genes whose expression was changed in the process of being reprogrammed from a parent cell to a stem cell.

Building on previous research that looked at where differently methylated sites were located in cancer cells, as well as on research that had shown these same sites matching up with many of the methylated areas that had been implicated in the differentiation of normal brain, liver and spleen tissues, the team discovered that the reprogramming of a cell to become a stem cell apparently involves many of the very same DMRs and genes.

“The surprise,” says Feinberg, “is that there is such a degree of overlap between the differently methylated regions and genes that are involved in turning a fibroblast into a stem cell and turning a normal cell into a cancer cell.”

The study, done jointly with George Q. Daley, M.D., Ph.D., and colleagues from Harvard University, was published Nov. 1 in the advanced online edition of Nature Genetics. The researchers suggest in the study that certain sites throughout the genome appear to be generally involved in distinguishing DNA methylation among different cell types and cancers, and these same sites are involved in reprogramming fibroblasts back into stem cells (…)

from http://newswire.ascribe.org/cgi-bin/behold.pl?ascribeid=20091104.074444&time=09%2059%20PST&year=2009&public=0

Hikers know that moss on a tree trunk always points north. According to new research by Israeli and German scientists, this ancient plant may also provide a new “compass” for stem cell research, telling scientists how better to program stem cells for medical purposes.

Dr. Nir Ohad of Tel Aviv University’s Department of Plant Sciences and Prof. Ralf Reski of the University of Freiburg have discovered a new use for the Polycomb group proteins (PcG) found in moss. They reported their findings recently in the journal Development. PcG proteins play an important role in telling stem cells how to develop, they believe. The research is being funded by the German-Israeli Foundation.

Moss is a kind of plant that shares basic development processes with those found in humans. “We may not have found the switch that turns stem cells into tissue,” comments Dr. Ohad, “but we have found a key component which makes this switch work.”

In their new paper, the researchers describe an ancient mechanism that alters the way DNA organizes inside the cell nucleus, which in turn, affects gene expression. This finding has important implications in stem cell therapies, which can go awry if implanted stem cells aren’t reprogrammed properly (…)

from http://www.sciencedaily.com/releases/2009/09/090929133242.htm

Never mind facial masks and exfoliating scrubs, skin takes care of itself. Stem cells located within the skin actively generate differentiating cells that can ultimately form either the body surface or the hairs that emanate from it. In addition, these stem cells are able to replenish themselves, continually rejuvenating skin and hair. Now, researchers at Rockefeller University have identified two proteins that enable these skin stem cells to undertake this continuous process of self-renewal.

The work, published in Nature Genetics, brings new details to the understanding of how stem cells maintain — and lose — their status as stem cells and are able to specialize into various types of cells. It also further dissects a ubiquitous Rube Goldberg-like pathway whose molecular gears and levers play an important role in activating stem cells to divide and transform into tissue-making cells.

Lead researcher Elaine Fuchs, head of the Laboratory of Mammalian Cell Biology and Development, and first author Hoang Nguyen, a former postdoc in the lab, worked with mice engineered to lack the proteins TCF3 and TCF4, which reside in the nucleus of skin stem cells, where they bind to DNA to turn genes off that would otherwise cause the stem cells to differentiate. They found that without TCF3 and TCF4, all of the layers of the mice’s skin still develop properly, but they cannot be maintained.

“The epidermal stem cells — one of the types of stem cells in the skin — lose their capacity to self-renew and replace skin cells that have died,” says Nguyen, who is now an assistant (…)

from http://www.sciencedaily.com/releases/2009/09/090927152828.htm