Genetic Profile Distinguishes Types of Stem Cells

Researchers at the The Scripps Research Institute found a new way of classifying the many cell types that fall under the category of “stem cells.” The term stem cell refers to tissue specific stem cells found in mature tissues such as blood, brain, or muscle, which are restricted to forming only cells found in those tissues, as well as to embryonic stem cells that are broadly able to form all cells of the body. The term is also used to refer to the so-called induced pluripotent stem (iPS) cells that scientists can now create out of adult skin cell and that mimic embryonic stem cells in their ability to form a variety of cell types. In this work, the researchers discovered a set of genes that are always active in the pluripotent cells – whether they were iPS cells or embryonic stem cells. As more stem cell populations become available, the gene profile discovered in this study will help researchers distinguish those cells that are truly pluripotent from those that are more restricted in the cell types they are able to form.

Nature: September 18, 2008
CIRM funding: Louise Laurent (T1-00003)

Related Information: Scripps news story, The Scripps Research Institute

Human Embryonic Stem Cells Trigger Immune Reaction in Mice

Researchers at the Stanford University School of Medicine have found that human embryonic stem cells trigger an immune response much like organ rejection when transplanted into mice. In the past, researchers had thought that transplanted embryonic stem cells might not be rejected the way transplanted organs are. Testing this theory, the team found that after transplanting human embryonic stem cells into normal mice, those cells disappeared within seven to ten days. In mice without an immune system the cells survived and even multiplied. Drugs used to prevent organ rejection also successfully prevented normal mice from rejecting the transplanted stem cells. These results suggest that any therapy involving transplanted embryonic stem cells will also require a way of preventing people from rejecting those therapeutic cells.

Proceedings of the National Academy of Sciences: September 2, 2008
CIRM funding: Joseph Wu (RS1-00322)

Related Information: Press Release, Stanford Stem Cell Biology and Regenerative Medicine Institute, Wu bio

True Location of Brain Stem Cells Discovered

Researchers at UC, Irvine identified the true location of adult stem cells in the brain. Previous studies indicated that in mammals, adult neural stem cells originate in a region of the brain called the subventricular zone. In this study, the team found evidence that stem cells exist only in a region called the ependymal layer, which is adjacent to the subventricular zone. They also coaxed the ependymal stem cells to divide in adult rats displaying Parkinson's Disease-like symptoms. This work raises the possibility that manipulating cells of the ependymal cell layer could lead to stem cell therapies for neurological diseases.

Neuroscience: July 11, 2008
CIRM funding: Darius Gleason (T1-00008)

Related Information: UC, Irvine press release, Sue and Bill Gross Stem Cell Research  Center

New Embryonic Stem Cell Lines Avoid Animal Products

Researchers at Stanford University School of Medicine derived new human embryonic stem cell lines using minimal animal products. Although numerous groups have derived stem cell lines, most were generated in the presence of animal serum and animal-derived feeder cells. These animal products are a concern because they may cause the stem cells to produce an immune response when transplanted into humans and may induce biological changes especially to the genome. In this study, the team characterized six lines that were derived with minimal use of animal products.  The researchers verified that the lines behave like normal ES cells in their ability to both self-renew and differentiate to the major cell types.  These lines may be useful for future studies that help move the field toward clinical-grade cell therapy.

Stem Cells and Development: June 17, 2008
CIRM funding: Renee Reijo Pera (RC1-00137)

Related Information: Stanford Stem Cell Biology and  Regenerative Medicine Institute, Pera lab page

Fly Stem Cells Create their Home

Researchers at the Salk Institute of Biological Studies discovered that stem cells in the testes of fruit flies are able to generate their own support cells. This work in flies could help guide researchers hoping to understand the environment surrounding resident populations of human stem cells - called the niche. The niche is difficult to study in humans but is an area of great interest because any therapy based on transplanting stem cells into a tissue will require those cells to be paced in a niche where they will thrive. This work raises the possibility that some transplanted stem cells may be able to produce their own niche.

Nature: July 20, 2008
CIRM funding: Justin Voog (T1-00003)

Related Information: Salk press release, Salk Institute for Biological Studies

Aging Muscles Inhibit Stem Cells, Prevent Repair

Researchers at UC, Berkeley identified a signaling molecule that interferes with the ability of older skeletal muscle to regenerate. After injury, adult skeletal muscle regenerates by activating muscle stem cells that fuse with the existing muscle cells to repair the damage. This ability to regenerate diminishes with age, not because of a decline in the number of resident stem cells, but because stem cells in the older muscle don’t respond when damage occurs. It turns out that older muscles release molecules that actively inhibit the resident stem cells. In this study, the team identified one of those molecules and showed that interfering with that molecule’s function restores the ability of muscle in older mice to regenerate after injury. This research illustrates the potential for recruiting adult resident stem cells in tissue repair.

Nature: June 15, 2008.
CIRM funding: Morgan Carlson (T1-00007)

Related Information: Press release, Berkeley Stem Cell Center

Mutation Revealed to Convert Blood Stem Cells to Cancer Stem Cells

Researchers at UC, Los Angeles discovered a series of mutations that can convert normal blood stem cells into cancer stem cells. It is believed that many types of cancer result from cancer stem cells created by such mutations. In this case the first mutation converted normal stem cells and then caused over expression of an oncogene, a cancer gene, resulting in a proliferation of leukemia stem cells and acute T-cell lymphoblastic leukemia in a mouse model. The team hopes that by studying these pathways they will find ways to block them with small molecule drugs and cure the often fatal disease.

Nature: May 22, 2008
CIRM funding: Wei Guo (T1-00005)

Related Information: UCLA press release, The Eli and Edythe Broad  Center of Regenerative Medicine and Stem Cell Research at UCLA