September 28, 2008
Blood Vessel Stem Cell Source Found

Pericytes can become blood vessels, bone, muscles, and cartilage.

In a promising finding for the field of regenerative medicine, stem cell researchers at Children's Hospital of Pittsburgh of UPMC have identified a source of adult stem cells found on the walls of blood vessels with the unlimited potential to differentiate into human tissues such as bone, cartilage and muscle.

The scientists, led by Bruno Péault, PhD, deputy director of the Stem Cell Research Center at Children's Hospital, identified cells known as pericytes that are multipotent, meaning they have broad developmental potential. Pericytes are found on the walls of small blood vessels such as capillaries and microvessels throughout the body and have the potential to be extracted and grown into many types of tissues, according to the study.

Sources of adult stem cells have obvious applications for the creation of therapies. But a discovery such as this one has other benefits which are less immediately obvious. Notably, we need to know all the cell types in our bodies and their distribution and function in order to know all the cell types we need to target with rejuvenation therapies. Obviously, if a discovery such as this one is possible to make in 2008 we do not know all the cell types we have or all the places these cell types are found.

The ability to isolate all the stem cells and progenitor cells from human bodies makes it easier to study key cell types to measure how much they've aged. For example, we need to know whether stem cell aging plays a big role in artery clogging with atherosclerotic plaques. If we could grow large numbers of youthful pericytes outside of the body would injecting these cells into the body cut the risks of stroke and heart attack? Or are the existing pericytes getting suppressed by chemicals that build up in the blood as we age?

Since pericytes are found in so many tissue types they will be easy to extract.

"This finding marks the first direct evidence of the source of multipotent adult stem cells known as mesenchymal stem cells. We believe pericytes represent one of the most promising sources of multipotent stem cells that scientists have been searching for in the quest to make regenerative medicine possible," Dr. Péault said. "The encouraging aspect of this source is that blood vessels are the one structure that all tissues in the human body have in common. These cells can be extracted easily and painlessly from convenient sources such as fat tissue, dental pulp, umbilical cord and placental tissue, then grown in culture to large numbers and, possibly, re-injected into the patient to heal a broken bone, a failing joint or an injured muscle."

Results of the study are published in the September issue of the journal Cell Stem Cell.

Could pericytes or cells grown from pericytes be injected into joints to repair worn cartilage? We are all wearing out. Many of us will some day start feeling pains from cartilage wearing (and some of you already feel such pains). So the ability to manipulate pericytes to get them to do our bidding will probably some day help us avoid a lot of suffering.

Update: Some Stanford researchers also just discovered a muscle stem cell that exists among muscle satellite cells.

A single cell can repopulate damaged skeletal muscle in mice, say medical school scientists who devised a way to track the cell's fate in living animals. The research is the first to confirm that the so-called satellite cells, which encircle muscle fibers, harbor an elusive muscle stem cell.

Identifying and isolating such a cell in humans would have therapeutic implications for disorders such as muscular dystrophy, muscle injury and muscle wasting due to aging, disuse or disease.

"We were able to show at the single-cell level that these cells are true, multipotent stem cells," said Helen Blau, PhD, the Donald E. and Delia B. Baxter Professor of Pharmacology. "They fit the classic definition: they can both self-renew and give rise to specialized progeny." Blau is the senior author of the study, published Sept. 17 in the online issue of Nature.

Alessandra Sacco, PhD, senior research scientist in Blau's laboratory and the article's first author, added, "It's been known that these satellite cells are crucial for the regeneration of muscle tissue, but this is the first demonstration of self-renewal of a single cell."

The transplanted individual cells went on to replicate into thousands and even tens of thousands of cells. But these researchers were not able to tell which satellite cells are really stem cells. So they have more work to do in order to know when a particular cell is really a stem cell.

I am especially interested to learn whether these stem cells, satellite cells, and other progenitor cells show signs of serious aging. Or do muscles, blood vessels, and other tissue decay because the signaling gets lost or muffled that should tell the stem cells to produce replacement repair cells?

Share |      Randall Parker, 2008 September 28 01:43 PM  Biotech Stem Cells

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