Multipotent Adult Stem Cells--More Sources

UPenn School of Medicine researchers have learned how to coax adult stem cells from hair follicles to grow into smoothe muscle cells, nerve cells, and melanocytes. While it has long been known that hair follicles contain adult stem cells, no one had succeeded in causing them to differentiate into different cell types until now.

“We are very excited about this new source of adult stem cells that has the potential for a variety of applications,” says senior author Xiaowei (George) Xu, MD, PhD, Assistant Professor of Pathology. “A number of reports have pointed to the fact that adult stem cells may be more flexible in what they become than previously thought, so we decided to look in the hair follicle bulge, a niche for these cells.” Xu and colleagues report their findings in the latest issue of the American Journal of Pathology.

Hair follicles are well known to be a source for adult stem cells. Using human embryonic stem cell culture conditions, the researchers isolated and grew a new type of multipotent adult stem cell from scalp tissue obtained from the National Institute of Health’s Cooperative Human Tissue Network.

The mutipotent stem cells grow as masses the investigators call hair spheres. After growing the “raw” cells from the hair spheres in different types of growth factors, the investigators were able to differentiate the stem cells into multiple lineages, including nerve cells, smooth muscle cells, and melanocytes (skin pigment cells).

The differentiated cells acquired lineage-specific markers and demonstrated appropriate functions in tissue culture, according to each cell type. For example, after 14 days, 20% to 40% of the cells in the melanocyte media took on a weblike shape typical of melanocytes. The new cells also expressed biomarkers typical of pigment cells and when placed in an artificial human skin construct, produced melanin and responded to chemical cues from normal epidermis skin cells.

After 14 days, about 10% of the stem cells in the neuronal cell line -- a type of cell not present in skin or hair -- grew dendrites, the long extensions typical of nerve cells and expressed neuronal proteins. The neurotransmitter glutamate was also present in the cells, but the neurotransmitter dopamine was not detected.

Thirdly, about 80% of the stem cells grown in the muscle media differentiated into smooth muscle cells. These new muscle cells also contracted when placed in a collagen matrix.

Source.

The selection of different growth media to bring about the differentiation of specific cell types is an art that is gradually developing into a science. As these tricks are tried on more adult stem cell types, it is possible that a fairly full palette of cell types might come available, from adult stem cells alone.

While multiple differentiation from embryonic stem cells has been studied and utilised by researchers for several years, the possibilities for multiple differentiation of adult stem cells has not been nearly as intensively looked into. This report indicates a slow trend that seems to be developing, to correct that ommission.