Stem cells in urine easy to isolate, have potential for numerous therapies

In mammals, there are two broad types of stem cells: embryonic stem cell, which are isolated from the inner cell mass of blastocyst, and adult stem cell, which are found in various tissues. Now researchers at Wake Forest Baptist Medical Center’s Institute for Regenerative Medicine and colleagues have identified stem cells in urine that can be directed to become multiple cell types.

These cells can be obtained through a simple, non-invasive low-cost approach that avoids surgical procedures. It can be obtained just by collecting urine sample.

Researchers successfully directed stem cells from urine to become bladder-type cells, such as smooth muscle and urothelial, the cells that line the bladder. But the urine-derived cells could also form bone, cartilage, fat, skeletal muscle, nerve, and endothelial cells, which line blood vessels. The multipotency of the cells suggests their use in a variety of therapies.

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 sub-population of cells, they can be difficult to isolate from organs and tissues.

The team first identified the cells, which are a small subset of the many cells found in urine, in 2006. The current research builds on earlier studies by confirming the multipotency of the cells. In addition, the research found that unlike iPS cells or embryonic stem cells, the urine derived-stem cells do not form tumors when implanted in the body, indicating they may be safe for use in patients.

For their research they collected urine samples from 17 healthy individuals ranging in age from 5 to 75 years. Isolating the cells from urine involves minimal processing, according to the authors. Next, they evaluated the cells' ability to become multiple cell types.

Importantly, the cells differentiated into the three tissue layers (endoderm, ectoderm and mesoderm) that are a hallmark of true stem cells and also differentiated into the specific cell types mentioned earlier.

Next, the 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 urine-derived stem cells have markers of mesenchymal cells, which are adult stem cells from connective tissue such as bone marrow. They also have markers for pericytes, a subset of mesenchymal cells found in small blood vessels.

Researchers suspect that the 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 research is published online in the journal Stem Cells.