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October 2005
Hair-raising Stem Cells Identified: Swiss Study Shows That Hair Follicles Contain Bonafide Multipotent Stem Cells
October 2005
Using an animal model, a research team led by Yann Barrandon at the EPFL (Ecole Polytechnique Federale de Lausanne) and the CHUV (Lausanne University Hospital) has discovered that certain cells inside the hair follicle are true multipotent stem cells, capable of developing into the many different cell types needed for hair growth and follicle replacement.
In an article appearing in the Oct 3
advance online edition of the Proceedings of the National Academy of Sciences,
they demonstrate that these holoclones can be used for long-term follicle
renewal.
In 2001, Barrandon was part of a French research team who reported in the
scientific journal Cell that stem cells could be used to generate skin
containing hair and sebaceous glands in mice.
But at that time it was unclear
whether the stem cells in hair follicles were true stem cells, capable of
long-term renewal, or multipotent progenitor cells that would not permanently
engraft in the follicle.
In the current PNAS study, the Swiss researchers have answered that question,
using rat whisker hair follicles to demonstrate that the clonogenic
keratinocytes in hair follicles are true stem cells.
Barrandon's group isolated stem cells from rat whisker follicles, labelled them,
and grew them in culture for 140 generations. They then implanted progeny cells
into the skin of newborn mice whose hair follicles were just being formed. This
skin was then grafted onto athymic (nude) mice.
Some cells were incorporated
into developing follicles, but other follicles were completely made up of
labelled cells. Each progeny cell contributed to the formation of eight
different types of cell in the follicle, including those of the outer root
sheath, inner root sheath, the hair shaft, the sebaceous gland and the
epidermis.
After 125 days, a biopsy was taken from the graft, and labelled stem cells were
isolated, subcloned, cultivated and then once again transplanted.
The rat whisker stem cells participated again in forming all the cell types needed to form the hair follicle and sebaceous glands, resulting in hair bulbs that underwent repeated normal phases of growth, rest and regeneration.
The fact that
the transplanted cells participate in the hair cycle over long periods of time
shows that they are true multipotent stem cells and not progeniture cells.
"With the progeny of a single stem cell, it would be theoretically possible to
generate the complete hair bulb of a human being, and one that would last for
years," explains Barrandon.
The ability of the stem cells in hair follicles to repeatedly regenerate all the
different cell types of the follicle and sebaceous glands has important
implications for regenerative medicine.
The method could one day be used to regenerate hair on patients with severe burns. This study is a logical complement to other work in Barrandon's Laboratory of Stem Cell Dynamics, recognized for research into the reconstruction of injured tissues and organs.