HUMAN STEM CELLS FREE OF FOREIGN DNA

Human Stem Cells Free Of Foreign DNA
U.S. researchers have developed a method to produce human induced pluripotent stem cells, or iPS cells, which contain no foreign, potentially harmful DNA. The report of this work are published in the latest issue of the journal Science.

Stem cells are induced pluripotent human adult cells that were "reprogrammed" into embryonic stem cells.

This result is important for the use of these cells in basic research in biology and is a key step in view of producing induced pluripotent stem cells used in medical therapy without the risk that elements inserted into their genome interfere with the development normal cell. When researchers in the early days reprogrammed adult and fetal cells so they become induced pluripotent stem cells, they used viruses to insert the processed key genes in the nucleus can trigger the reprogramming process.

Jungying Yu and his colleagues at the University of Wisconsin-Madison (USA) now describe an alternative to this approach. They added genes to circular DNA fragments called plasmids generally independent of cellular chromosomes. Then they introduced the plasmids into human foreskin cells by a process called nucleofection. The proteins expressed by genes carried by plasmids were then able to reprogram cells into iPS cells. Finally, the iPS cells began to lose their plasmid during cell division and researchers were then able to isolate which carried no more.

In their article, the authors state that other teams have recently reported methods with the same objective, but that their process is currently the only producing iPS completely devoid of human vectors and transgenic sequences.
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Article: Human Induced Pluripotent Stem Cells Free of Vector and Transgene Sequences
Authors: Junying Yu, Kejin Hu, Kim Smuga-Otto, Shulan Tian, Ron Stewart, Igor I. Slukvin, James A. Thomson
Journal Publication: Science
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Source: EurekAlert
Credit: UW-Madison

STEM CELLS REPAIR HEART INJURIES

Stem Cells Repair Heart Injuries
United States - The team of Dr. Terzic of the Mayo Clinic in Rochester has succeeded for the first time to repair heart injuries caused by a heart attack using stem cells.

This is the first time that cells induced pluripotent stem (iPS), an artificially-derived non-pluripotent cell in which it induces the expression of specific genes, are used to treat heart disease. Stem cells from the mice used in this study were genetically reprogrammed so that they become stem cells capable of growth in the heart.

The iPS serve the renewal of tissues and can differentiate to produce several types of human cells. These cells are excluded from the controversy generated around embryonic cells because they are induced by the patient himself.

In four weeks, the stem cells implanted in mice have successfully stopped the progression of lesions caused by heart attacks and regenerate injured tissue.

With this study, the researchers hope to eventually be able to use own stem cells to repair the patient's heart, instead of using a heart transplant. Dr. Terzic provides the ability to change adult cells to produce on demand a cardiovascular regenerative therapy.

CREATION OF MICE FROM iPS CELLS

Live Mice Created from Adult Cells Reprogrammed

Mice were born and have even been able to procreate after being created from stem cells from reprogrammed adult cells, depending on the work of a Chinese team published in 2009.

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It is "the first definitive proof, to our knowledge, that the iPS cells are truly pluripotent, ie as versatile as embryonic stem cells, a characteristic" critical to therapeutic applications, "concluded by Qi Zhou (Chinese Academy of Sciences, Beijing) and his colleagues.

The ability of embryonic stem cells to differentiate to produce all types of human cells (blood, nerve, muscle ...) has made the challenge of medicine "regenerative" which would in future repair the heart or other organs, but their use raises ethical issues.

Thanks to the pioneering work in 2006 and 2007, Japanese researcher Shinya Yamanaka to program adult differentiated cells to become multi-purpose, cells induced pluripotent stem (iPS) are seen as an alternative to embryonic stem cells .

Since then, this technique was commonly used to reprogram the genomes of cells in a pluripotent state similar to embryonic cells, "recalls Qi Zhou in the study published online by the British scientific journal Nature.

To prove that the iPS cells are as versatile as embryonic stem cells, he showed that they could afford to produce live fertile mice.

Team Fani Qi Zeng and Zhou (Shanghai Jiao Tong University) has created 37 lines of iPS cells, three of which led to the birth of 27 mice, including the first-born named Tiny.

MAN-MADE: Tiny, live mice from iPS cells

One of them, a brown male adult was able to impregnate a female white coat and lead to second-generation mice in good health, according to researchers.

To produce viable mice, the researchers used as a cradle of biological cells called blastocysts with four sets of chromosomes (instead of two normal, one from the father and the other from the mother).

In this cradle (suitable for creating the placenta), they then injected iPS cells that have sent their own genetic heritage to all daughter cells forming the embryo. This proves, according to researchers, the iPS cells are pluripotent as embryonic stem cells.

Even if the cloning was not the objective of the experiment, it nevertheless leads to create animals with the same genetic program that the reprogrammed adult cells. The use of four sets of chromosomes (not both) to avoid mixing the DNA of the blastocyst, doomed to disappear, with iPS cells.

This technique avoids complex to create chimeras, animals whose cells all have the same genetic heritage. Small second-generation mice have uniformly brown coat, a sign that their parents are not chimeras, researchers stress.

At a press conference, they were encouraged to pursue "all forms of stem cell research, but are not limited to iPS cells."