Master switches found for adult blood stem cells

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Scientists clone mice from adult skin stem cells

For cells that hold so much promise, stem cells’ potential has so far gone largely untapped. But new research from Rockefeller University and Howard Hughes Medical Institute scientists now shows that adult stem cells taken from skin can be used to clone mice using a procedure called nuclear transfer. The findings are reported in the Feb. 12 online edition of the Proceedings of the National Academy of Sciences. Caption: Using a technique called nuclear transfer, mice were cloned using adult skin stem cells (right) and a more differentiated type of skin cell (left). The mouse on the right is almost two years old and the mouse on the right is one and a half. Credit: Jinsong Li, Postdoc in the Mombaerts Laboratory, Rockefeller University Embryonic stem cells have received the most press for their potential to generate healthy cells and tissues that could replace damaged or diseased organs. [lien] [EN]

Blood stem cell growth factor reverses memory decline in mice

A human growth factor that stimulates blood stem cells to proliferate in the bone marrow reverses memory impairment in mice genetically altered to develop Alzheimer’s disease, researchers at the University of South Florida and James A. Haley Hospital found. The granulocyte-colony stimulating factor (GCSF) significantly reduced levels of the brain-clogging protein beta amyloid deposited in excess in the brains of the Alzheimer’s mice, increased the production of new neurons and promoted nerve cell connections. [Plaques] Caption - Microglia (in green) attack the beta amyloid (red) deposited in the brain of a GCSF-treated Alzheimer's mouse. Credit: Photo courtesy of University of South Florida [lien] [EN]

Scientists identifies gene that regulates blood-forming fetal stem cells

In the rancorous public debate over federal research funding, stem cells are generally assigned to one of two categories: embryonic or adult. But that’s a false dichotomy and an oversimplification. A new University of Michigan study adds to mounting evidence that stem cells in the developing fetus are distinct from both embryonic and adult stem cells. In the last several years, stem cell researchers have realized that fetal stem cells comprise a separate class. They recognized, for example, that fetal blood-forming stem cells in umbilical cord blood behave differently than adult blood-forming stem cells after transplantation into patients. Now a U-M team led by Sean Morrison has identified the first known gene. [lien] [EN]

Researchers replace organ in adult mice using ’single-parent’ stem cells

Researchers at the University of Pennsylvania School of Veterinary Medicine have derived uniparental embryonic stem cells - created from a single donor’s eggs or two sperm - and, for the first time, successfully used them to repopulate a damaged organ with healthy cells in adult mice. Their findings demonstrate that single-parent stem cells can proliferate normally in an adult organ and could provide a less controversial alternative to the therapeutic cloning of embryonic stem cells. “Creating uniparental embryonic stem cells is actually much more efficient than generating embryonic stem cells by cloning,” said K. John McLaughlin, an assistant professor in Penn’s Department of Animal Biology and researcher at the Center for Animal Transgenesis and Germ Cell Research at Penn’s New Bolton Center. [lien] [EN]

Scientists find previously unknown receptors on adult stem cells

For many years, researchers believed that stem cells in the bone marrow spent most of their existence in a slumber-like state, unaware of — and unaffected by — the daily battles fought by the body's immune system. Not so. Scientists at the Oklahoma Medical Research Foundation have discovered that marrow stem cells — undifferentiated cells that eventually give rise to the blood cells that fight infection — possess receptors that recognize bacteria and viruses. When activated, these receptors kick the stem cells and immature blood cells into action, enlisting them to help fight whatever pathogen is attacking the body. The findings, which appear in the June issue of the journal Immunity, could have important implications for treating leukemias and autoimmune diseases such as lupus and rheumatoid arthritis. [lien] [EN]

Scientists create 3-D scaffold for growing stem cells

Stem cells grew, multiplied and differentiated into brain cells on a new three-dimensional scaffold of tiny protein fragments designed to be more like a living body than any other cell culture system. An MIT engineer and Italian colleagues will report the invention-which may one day replace the ubiquitous Petri dish for growing cells-in the Dec. 27th issue of the PLoS ONE. Shuguang Zhang, associate director of MIT’s Center for Biomedical Engineering, is a pioneer in coaxing tiny fragments of amino acids called self-assembling peptides to organize themselves into useful structures. Working with visiting graduate student Fabrizio Gelain from Milan, Zhang created a designer scaffold from a network of protein nanofibers, each 5,000 times thinner than a human hair and containing pores up to 20. [lien] [EN]

Scientists Discover Key to Growing New Stem Cells

Scientists at Duke University Medical Center have demonstrated they can grow human stem cells in the laboratory by blocking an enzyme that naturally triggers stem cells to mature and differentiate into specialized cells. The discovery may enable scientists to rapidly grow stem cells and transplant them into patients with blood disorders, immune defects and select genetic diseases, said the Duke researchers. Stem cells are the most flexible cells in the body, continually dividing into new stem cells or into specialized cells that carry out specific roles in the body. But little is known about how stem cells choose their fate. The Duke team focused on “hematopoietic” or blood stem cells. [lien] [EN]

The making of an intestinal stem cell

Researchers have found the factor that makes the difference between a stem cell in the intestine and any other cell. The discovery reported in the March 6th issue of the journal Cell, a Cell Press publication, is an essential step toward understanding the biology of the stem cells, which are responsible for replenishing all other cells in the most rapidly self-renewing tissue in mammals. It may also have implications for colon cancer, according to the researchers. The report finds evidence that a transcription factor called Achaete scute-like 2 (Ascl2) switches on the stem cell program in intestinal cells. Transcription factors are genes that control other genes. “This transcription factor makes these stem cells tick,” said Hans Clevers of Hubrecht Institute. [lien] [EN]

Neural stem cell differentiation factor discovered

Neural stem cells represent the cellular backup of our brain. These cells are capable of self-renewal to form new stem cells or differentiate into neurons, astrocytes or oligodendrocytes. Astrocytes have supportive functions in the environment of neurons, while oligodendrocytes form the myelin layer around axons in order to accelerate neuronal signal transmission. But how does a neural stem cell „know” which way it is supposed to develop? On the molecular level receptors of the Notch family play a significant role in this process. So far, only stimulating extracellular ligands of Notch receptors had been described. Biochemists of Goethe University Medical School now describe a long time assumed but not yet identified soluble Notch inhibitor. Franfurt scientists led by Mirko Schmidt and Ivan Dikic reported in the renowned journal „Nature Cell Biology” that the secreted protein EGFL7 (Epidermal Growth Factor. [lien] [EN]

Stem cell transplantation may treat type 1 diabetes

A therapy that includes stem cell transplantation induced extended insulin independence in patients with type 1 diabetes mellitus, according to a preliminary study in the April 11 issue of JAMA. Type 1 diabetes mellitus (DM) results from a cell-mediated autoimmune attack against pancreatic beta cells. At the time of clinical diagnosis, approximately 60 percent to 80 percent of the beta-cell mass has been destroyed, according to background information in the article. Beta-cell preservation has been shown to be an important target in the management of type 1 DM and in the prevention of its related complications. Julio C. Voltarelli, M.D., Ph.D., of the University of São Paulo, Ribeirão Preto, Brazil, in collaboration with Richard Burt, M.D., of the Northwestern University Feinberg School of Medicine. [lien] [EN]

Scientists unlock mystery of embryonic stem cell signaling pathway

A newly discovered small molecule called IQ-1 plays a key role in preventing embryonic stem cells from differentiating into one or more specific cell types, allowing them to instead continue growing and dividing indefinitely, according to research performed by a team of scientists who have recently joined the stem-cell research efforts at the Keck School of Medicine of the University of Southern California. Their findings are being published in the Proceedings of the National Academy of Sciences. This discovery takes scientists another step closer to being able to grow embryonic stem cells without the “feeder layer” of mouse fibroblast cells that is essential for maintaining the pluripotency of embryonic stem cells, says the study's primary investigator. [lien] [EN]

Researchers map gene that regulates adult stem cell growth

The researchers genetically mapped a stem cell gene and its protein product, Laxetin, and building on that effort, carried the investigation all the way through to the identification of the gene itself. This is the first time such a complete study on a stem cell gene has been carried out. This particular gene is important because it helps regulate the number of adult stem cells in the body, particularly in bone marrow. Now that it has been identified, researchers hope the gene, along with its protein product Latexin, can be used clinically, such as for ramping up the stem cell count in cancer patients undergoing chemotherapy and bone marrow transplantation. The researchers agreed that this very process is not only interesting, but important because of its usefulness in a wide variety of future genetics studies. [lien] [EN]

Stretching bone marrow stem cells pushes them towards becoming blood vessel

When stretched, a type of adult stem cell taken from bone marrow can be nudged towards becoming the type of tissue found in blood vessels, according to a new study by bioengineers at the University of California, Berkeley. Researchers placed mesenchymal stem cells onto a silicone membrane that was stretched longitudinally once every second. It was a cellular workout routine that helped point the bone marrow stem cell in the direction of becoming the smooth muscle tissue of vascular walls. The findings, published today (Monday, Oct. 23) in the online early edition of the Proceedings of the National Academy of Sciences, highlight the importance of mechanical forces in stem cell differentiation. Mesenchymal stem cells have the ability to turn into different types of connective tissue including bone. [lien] [EN]

Elusive pancreatic stem cells found in adult mice

Just as many scientists had given up the search, researchers have discovered that the pancreas does indeed harbor stem cells with the capacity to generate new insulin-producing beta cells. If the finding made in adult mice holds for humans, the newfound progenitor cells will represent an obvious target for therapeutic regeneration of beta cells in diabetes, the researchers report in the Jan. 25 issue of Cell, a publication of Cell Press. One of the most interesting characteristics of these [adult] progenitor cells is that they are almost indistinguishable from embryonic progenitors, said Harry Heimberg of the JDRF Center at Vrije Universiteit Brussel in Belgium and the Beta Cell Biology Consortium. �In terms of their structure and gene expression. [lien] [EN]