Wake Forest researchers study urine as source for stem cells

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WINSTON-SALEM, N.C. — A daily bodily function – urinating – may become another option for collecting stem cells that can be transformed into regenerated tissue and organs.

Researchers with the Wake Forest Institute of Regenerative Medicine have identified stem cells in urine that can become multiple cell types. Their report is available on the website of the journal Stem Cells.

In a separate study released July 30, a group of researchers from the Guangzhou Institutes of Biomedicine and Health said they have been able to generate in mice tooth-like structures from urine-induced pluripotent stem cells.

Dr. Anthony Atala, director of the Wake Forest institute, said the use of urine-derived stem cells to regenerate human tissue and organs remains several years away.

“We’ve been looking at urine as a stem cell option since 2006,” Atala said. Research has been “so far, so good” in rodents.

Being able to use a patient’s own stem cells for therapy is considered advantageous because they do not induce immune responses or rejection.

However, because tissue-specific cells are a very small subpopulation of cells, they can be difficult to isolate from organs and tissues.

“The challenge has been getting the right cells and the right results every time,” Atala said. “This study reflects the promise of achieving those goals with samples that most people get rid of six times a day.”

Atala and Dr. Yuanyuan Zhang, senior Wake Forest researcher on the study, said one advantage of collecting stem cells through urine is that it is “a non-invasive, low-cost approach that avoids surgical procedures.” Other post-birth options can require drilling into bone marrow.

The researchers say they have taken stem cells from urine and transformed them into bladder-type cells, such as smooth muscle and urothelial, the cells that line the bladder.

Other possibilities include forming bone, cartilage, fat, skeletal muscle, nerve and endothelial cells, which line blood vessels.

“These stem cells represent virtually a limitless supply of autologous cells for treating not only urology-related conditions, such as kidney disease, urinary incontinence and erectile dysfunction, but could be used in other fields as well,” Zhang said.

Another advantage of urine-derived stem cells is that they do not form tumors when implanted in the body.

Researchers collected the stem cells from urine samples from 17 healthy individuals ranging in age from 5 to 75 years. As most individuals would expect, Atala said the first urine specimen of the day typically “is the best” for stem cells. Typically about a week’s worth of urine is needed.

The stem cells differentiated into three tissue layers – endoderm, ectoderm and mesoderm – that are a hallmark of true stem cells. Researchers placed cells that had been differentiated into smooth muscle and urothelial cells onto scaffolds made of pig intestine. When implanted in mice for one month, the cells formed multi-layer, tissue-like structures.

The researchers suspect the stem cells originate from the upper urinary tract, including the kidney. Female study participants who had received kidney transplants from male donors were found to have the Y chromosome in their urine-derived stem cells, suggesting the kidney as the source of the cells.

“The kidneys serve as coffee filters, if you will,” Atala said. “They get rid of stuff that the body doesn’t need, but as we have found, there’s some valuable stuff in there.”

Atala said the next goal is advancing the growth and replication process for the cells.

In the Chinese urine-derived stem-cells study, researchers said they detected the stem cells could be generated into enamel-secreting ameloblasts in the tooth-like structures, possessing physical properties such as elastic modulus and hardness found in the regular human tooth.

“It is well known that adult dental stem cells have been successfully applied in tissue-engineering research,” the Chinese researchers said. “It has proven to be possible to generate dentin pulp complexes, even whole teeth, out of isolated cells. Although these approaches could lead to tooth formation, the sources of endogenous dental epithelial stem cells seem to be scarce.

“Our results demonstrate that (the stem cells) can be used to regenerate patient-specific dental tissues or even tooth for further drug screening or regenerative therapies.”

Their study appeared in the peer-reviewed journal Cell Regeneration.

Credit: The Winston-Salem Journal

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