New Source of Multipotent Adult
Stem Cells Discovered in Human Hair Follicles
Implications for Personalized Approaches to Transplants
(Philadelphia, PA) - Researchers at the University of Pennsylvania
School of Medicine have isolated a new source of adult stem cells
that appear to have the potential to differentiate into several cell types.
If their approach to growing these cells can be scaled up and proves to
be safe and effective in animal and human studies, it could one day provide
the tissue needed by an individual for treating a host of disorders, including
peripheral nerve disease, Parkinson’s disease, and spinal cord injury.
“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
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.
Overall, the researchers showed that human embryonic stem cell media could
be used to isolate and expand a novel population of multipotent adult
stem cells from human hair follicles. “Although we are just at the
start of this research, our findings suggest that human hair follicles
may provide an accessible, individualized source of stem cells,”
says Xu. The researchers are now working on inducing other cell types
from the hair sphere cells and testing the cells in animal models.
Study co-authors are Hong Yu, Suresh M. Kumar, and Geza Acs, all from
Penn; and Dong Fang, Ling Li, Thiennga K. Nguyen, and Meenhard Herlyn,
all from the Wistar Institute, Philadelphia.
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