New insights into how stem cells determine what tissue to become

ANN ARBOR, Mich.---Within 24 hours of culturing adult human stem cells on a new type of matrix, University of Michigan researchers were able to make predictions about how the cells would differentiate, or what type of tissue they would become. Their results are published in the Aug. 1 edition of Nature Methods.

Differentiation is the process of stem cells morphing into other types of cells. Understanding it is key to developing future stem cell-based regenerative therapies.

"We show, for the first time, that we can predict stem cell differentiation as early as Day 1," said Jianping Fu, an assistant professor in mechanical engineering and biomedical engineering who is the first author on the paper.

"Normally, it takes weeks or maybe longer to know how the stem cell will differentiate. Our work could speed up this lengthy process and could have important applications in drug screening and regenerative medicine. Our method could provide early indications of how the stem cells are differentiating and what the cell types they are becoming under a new drug treatment."

In this study, Fu and his colleagues examined stem cell mechanics, the slight forces the cells exert on the materials they are attached to. These traction forces were suspected to be involved in differentiation, but they have not been as widely studied as the chemical triggers. In this paper, the researchers show that the stiffness of the material on which stem cells are cultivated in a lab does, in fact, help to determine what type of cells they turn into.

"Our research confirms that mechanical factors are as important as the chemical factors regulating differentiation," Fu said. "The mechanical aspects have, until now, been largely ignored by stem cell biologists."

The researchers built a novel type of stem cell matrix, or scaffold, whose stiffness can be adjusted without altering its chemical composition, which cannot be done with conventional stem cell growth matrices, Fu said.

The new scaffold resembles an ultrafine carpet of "microposts," hair-like projections made of the elastic polymer polydimethylsiloxane---a key component in Silly Putty, Fu said. By adjusting the height of the microposts, the researchers were able to adjust the rigidity of the matrix.

In this experiment, the engineers used human mesenchymal stem cells, which are found in bone marrow and other connective tissues such as fat. The stem cells differentiated into bone when grown on stiffer scaffolds, and into fat when grown on more flexible scaffolds. …

New insights into how stem cells determine what tissue to become

Technorati Tags: regenerative medicine,stem cells,biotechnology

Watching stem cells repair the human brain

There is no known cure for neurodegenerative diseases such as Huntington's, Alzheimer's and Parkinson's. But new hope, in the form of stem cells created from the patient's own bone marrow, can be found ― and literally seen ― in laboratories at Tel Aviv University.

Dr. Yoram Cohen of TAU's School of Chemistry has recently proven the viability of these innovative stem cells, called mesenchymal stem cells, using in-vivo MRI. Dr. Cohen has been able to track their progress within the brain, and initial studies indicate they can identify unhealthy or damaged tissues, migrate to them, and potentially repair or halt cell degeneration. His findings have been reported in the journal Stem Cells.

"By monitoring the motion of these cells, you get information about how viable they are, and how they can benefit the tissue," he explains. "We have been able to prove that these stem cells travel within the brain, and only travel where they are needed. They read the chemical signalling of the tissue, which indicate areas of stress. And then they go and try to repair the situation."

To test the capabilities of this innovative new stem cells, Dr. Cohen created a study to track the activity of the live cells within the brain using the in-vivo MRI at the Strauss Centre for Computational Neuro-Imaging. Watching the live, active cells has been central to establishing their viability as a therapy for neurodegenerative disease.

Dr. Cohen and his team of researchers took magnetic iron oxide nanoparticles and used them to label the stem cells they tested. When injected into the brain, they could then be identified as clear black dots on an MRI picture. The stem cells were then injected into the brain of an animal that had an experimental model of Huntington's disease. These animals suffer from a similar neuropathology as the one seen in human Huntington's patients, and therefore serve as research tool for the disease.

On MRI, it was possible to watch the stem cells migrating towards the diseased area of the brain. "Cells that go toward a certain position that needs to be rescued are the best indirect proof that they are live and viable," explains Dr. Cohen. "If they can migrate towards the target, they are alive and can read chemical signalling."

This study is based on differentiated mesenchymal cells (MSC), which were discovered at Tel Aviv University. Bone marrow cells are transformed into NTFs-secreting stem cells, which can then be used to treat neurodegenerative diseases. This advance circumvents the ethical debate caused by the use of stem cells obtained from embryos. …

Watching stem cells repair the human brain

Technorati Tags: regenerative medicine,stem cells