Renewal
of Hair Follicles from Adult Multipotent Stem Cells
Stem cells able to reconstitute the skin, as well as hair follicles,
were identified for the first time in an adult mammal by a French
team of researchers. "Starting from a small group of about 500 stem
cell stocks, we grew a piece of skin with hair follicles and sebaceous
glands for the first time," said Dr Yann Barrandon, a cell specialist
at the National Institute for Science and Medical Research and Paris's
elite Ecole Normale Supérieure.
Stem cells are premature cells that develop into various organs.
The most spectacular are found in embryos at their very earliest
days of development. Embryo stem cells can grow into almost any
part of the body, a finding that raises hopes they can eventually
be "programmed" into growing replacement limbs or organs in a laboratory.
This work, "provides the first direct proof of the existence
of these cells and their capacities to reproduce skin", said
Yann Barrandon the leader of the research team. These results, so
far only obtained using mice, open significant prospects in dermatology
to replace the skin in badly burned persons or to combat skin cancer,
and also represent a new hope for bald people.
Humans have approximately five hair follicles per square centimeter
of skin, against 50 for the mouse. These stem cell stocks, located
close to the root of the hair, are able to give rise to all the
lines of cells necessary to reconstitute the skin epidermis, sebaceous
glands, and the hair follicles. These invaluable cells are mainly
located in the hair follicle structure. The follicles represent
"reseviors" of cell stocks of the skin. In humans as in
rats, each one of these follicules would contain some 1500 stem
cells. The cell stocks can migrate in different directions, to the
bottom (towards the root of the hair) or the top of the follicle.
According to the path followed, the cells specialize in the manufacture
of hair follicles, secaceous glands or the keratinocyte cells of
the skin.
Researchers hope to be able to find the molecules that guide these
cells to become one of the three different structures (hair, sebaceous
gland or skin). There are several potential applications for this
research including potential new therapies for pattern baldness,
by supporting the growth of the hair, or to solve an excess of hair
growth (hypertrichosis) by the selective destruction of hair follicle
stem cells. "Half of humanity wants to have more hair on the
head and the other less hair on the legs", summarizes Dr Ariane
Rochat, joint author of this 5 year long research project.
The research may also be useful for developing skin grafts containing
hair and sebaceous glands for badly burned persons, explains Ariane
Rochat. This research "could also contribute to the understanidng
of cutaneous cancers and the recent increase in numbers affected,
as 700000 cases were counted this year in the United States alone",
said Yann Barrandon. The Parisian team had already isolated from
the stem cell stocks of human skin, published in Cell medical journal
in 1994, but were unable to show the potential of the cells to reconstitute
skin. Thus the next stage is, "to make the same thing with
human stem cells".
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