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| Date |
Aug 5, 2001 |
| Article |
# 160 |
| Title |
Presentations
on Hair Follicle Stem Cells Research -
3rd Intercontinental Hair Research Societies Research |
| Forums |
Please use HM forum |
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Presentation # 1 |
| Title |
An
Overview of Hair Follicle Stem Cells |
| Researchers |
Robert
M. Lavker, Tung-Tien Sun
Dept of Dermatology, University of Pennsylvania School of
Medicine; New York University School of Medicine, New York. |
Lately
everybody is turning their attention to hair follicle stem cells
because they play a critical role in governing hair growth and
maintaining the epidermis. One of the major obstacles in stem
cells research is to identify and localize their existence.
Typically, some kind of marker cells are used to distinguish hair
follicle stem cells from other transient amplifying cells. The
idea is to introduce certain marker cells into hair follicles and
evaluate the changes in existing cells once they interact with the
marker cells. Given the slow cycling nature of stem cells compared
to other cells, scientists expect that stem cells would react
differently compared to other cells when interact with certain
marker cells.
Today, the most popular approach to identify keratinocyte stem
cells relies on the slow cycling nature of stem cells. Scientists
expect that the slow cycling nature of stem cells would allow them
to be detected experimentally as the "label retaining
cells" (LRCs). In general, when it comes to hair research,
most scientific reference to LRCs are indeed referring to the
presumed stem cells.
Under this approach, scientists have been able to prove that all
or substantially all of the LRCs were confined exclusively to the
bulge, specifically the part of the outer root sheath marking the
lowest point of the upper, permanent portion of the follicle.
Studies in both mice and humans further confirmed that LRCs were
largely observed in the bulge region of the hair follicle and not
the epidermis.
In addition, cells within the follicular bulge seem to have
satisfied all the criteria for keratinocyte stem cells:
1) they have a higher proliferative capacity than other cells.
2) they have a more primitive or embryonic ultrastructure
3) they all reside in a very well protected biological environment
4) they seem to be a major target of chemical carcinogens
Some have suggested that the keratinocyte stem cells at the
follicular bulge may be bipotent in that they can give rise to not
only the hair follicle, but the epidermis as well |
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Presentation # 2 |
| Title |
Two
Distinct Reservoirs for Hair Follicle Stem Cells |
| Researchers |
Stephane
Commo, Olivier Gaillard and Bruno A. Bernard
Hair Biology Group, L'Oreal, France |
Scientists
commonly rely on 3 different yet complementary approaches to
localize hair follicle stem cells:
1) by detecting slow cycling cells
2) by detecting high colony forming cells
3) by using differential immunohistochemical staining
In this experiement, scientists use a cytokeratin marker to locate
the putative stem cells - CK19. The results of this study showed
that localization or distribution of stem cells tend to vary
throughout the anagen-telogen hair cycle. During anagen phase,
results from the CK19 marker showed that the hair follicle
contained two distinct compartments for the putative stem cells,
one at the upper third and the other at the lower third of the
follicle. However, during catagen-telogen transition, these two
distinct compartments then to fuse together until the onset of
anagen when they segregate and individualize again. |
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Presentation # 3 |
| Title |
Growth
Characteristics of Hair Follicle are Predetermined by the Previous
Anagen-Telogen Hair Cycle |
| Researchers |
Andrei
Panteleyev, Colin Jahoda, Angela Christiano
Dept of Dermatology and Genetics & Development, Columbia
University. New York / Dept of Biological Science, University of
Durham, Durham, UK |
This
experiment examined the expression patterns and basic cellular
rearrangements that pertain to the growth and cyclic regeneration
of hair through periods of anagen, catagen and telogen. The focus
of this research is on the timing when stem cells are employed in
the various stages of cyclic regeneration.
This research suggests that there are at least two separate cell
populations involved in the later stage of the telogen cycle,
namely putative stem cells in the bulge region and the hair germ
cells. Contrary to popular beliefs that the putative stem cells
initiate the whole process of cyclic regeneration, research has
shown that it is the hair germ cells that trigger the transition
to anagen before the putative stem cells participate in the hair
cycle process. The "hair germ cells give rise to the
ascending part of the growing HF, including the hair shaft and the
Inner Root Sheath, while the downgrowing Outer Root Sheath is a
product of the bulge (stem) cell activity."
It is suggested that during periods of hair growth (anagen),
putative stem cells from the bulge region will travel down the
Outer Root Sheath and stay near the bulb area of the follicle
until the onset of the resting phase (catagen) of hair growth when
the cells migrate and interact with the dermal papilla. The
cells will differentiate based on signals originated from the
dermal papilla and will mature in the process forming hair germ
cells. The researchers concluded that "the growth
characteristics of hair follicle and hair shaft are predetermined
by the previous hair cycle," during the time when the
putative stem cells in the bulge region travel down the Outer Root
Sheath and go through the formation process of hair germ. |
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Presentation # 4 |
| Title |
Death
of Putative Slow Cycling Stem Cells Caused by Plucking |
| Researchers |
M.Ito
and K. Kizawa
Basic Research Laboratory, Kanebo Ltd., Odawara, Japan |
| It
is widely suggested that hair follicle stem cells reside in the
bulge region of the follicle. The bulge region is a well protected
reservoir ideal for protection of follicular stem cells. However,
scientists have discovered that after plucking clubs for anagen
induction, most cells in the bulge region experienced massive cell
death. To find out if the putative slow cycling stem cells in the
bulge regions are among those cells that are directed to cell
death after plucking, scientists conducted further experiments and
confirmed that such is the case. However, "the disrupted
bulge regions were restored by 48 hours after plucking, and hair
follicle regeneration was accomplished with delay. |
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Presentation # 5 |
| Title |
Multipotent
Stem Cells and Differentiation Process for Hair Follicle |
| Researchers |
H.
Oshima and Y. Barrandon
Dept of Biology, Ecole Normale Superieure, Paris France
Dept of Plastic Surgery, ST. MArianna University School of
Medicine, Kawasaki, Japan |
More
and more researches are suggesting that hair follicle stem cells
are localized at the upper part of the follicle. In some studies,
it was confirmed that over 90% of the colony forming cells are of
rat vibrissal follicle are confined to the bulge slightly above
the upper permanent portion of the hair follicle. Studies have
shown that cells in this area are less proliferative than cells in
other regions. Many believe that the bulge may serve as a
"reservoir of stem cells to sustain hair growth and there is
a flux of stem cells from the bulge to the bulb".
In their experiements, Dr. Oshima and Dr. Barrandon have
demonstrated that 1) multipotent stem cells are found in the bulge
of vibrissal follicles of adult mice, and 2) these multipotent
stem cells can differentiate into epidermis, hair follicles and
sebaceous glands. |
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Presentation # 6 |
| Title |
Alternative
Differentiation Pathway Can Be Reprogrammed by Inducing Transient
Amplifying Cells to Stem-like Condition |
| Researchers |
C.
Ferraris, G. Chevalier, B. FAvier, C. JAhoda, D. Dhouailly
Biologie Differenciation Eputheliale, Institut A. Bonniot,
Universite J. Fourier /
Dept of Biological Sciences, University of Durham, UK |
This
experiment is the first indication that it is possible create an
alternative differentiation pathway for cells by first
inducing transient amplifying cells to stem-like conditions. It
also confirms that follicles may be the primary source for
epidermal homeostasis.
The most astounding aspect of this experiment was that it involved
nuclei of cells derived from two different species, a rabbit and a
mouse. Specifically, the corneal epithelium of an adult rabbit was
introduced to a mouse embryonic dermis derived from a hair-bearing
region. As a result of the interaction with the embryonic dermis,
the corneal epithelium of the adult rabbit then underwent a
transition to an epidermal-type phenotype and produced hair
follicles. The newly generated hair follicles retained the
characteristics and attributes of the donor embryonic skin dermis
from the mouse. |
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Presentation # 7 |
| Title |
Hair
Follicle Stem Cells in Human Skin Development |
| Researchers |
M.
Akiyama
Dept of Dermatology, Teikyo University School of Medicine,
Ichihara Hospital, Ichihara, Japan |
| This
experiment explored the sequential localization and morphological
characteristics of hair follicle stem cells. In addition, the
expression of hemidesmosomal agents such as type VII collagen,
laminin 5, and b4 integrin were also examined in the stem cell
reservoirs during the human hair follicle differentiation process.
The results lend more support to the theory that the hair follicle
stem cells reservoir is located at the hair follicle bulge. This
is the stem cell site for follicular epithelium from the bulbous
hair peg stage and suggests that hemidesmosomal agents are
continuously expressed in the stem cell sites during hair follicle
differentiation process. |
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Presentation # 8 |
| Title |
Identifying
stem cells with a new marker Cx43 - a negative marker for
epidermal stem cell |
| Researchers |
Maja
Matic, Marcia Simon
Dept of Oral Biology & Pathology, SUNY, Stony Brook, NY |
Stem
cells are known to be difficult to identify. The process of
identifying or locating stem cells usually involve the use of
certain marker cells to help pinpoint the location of the presumed
stem cells. Sometimes these marker cells for presumed stem cells
are also termed Label Retaining Cells (LRC) because of the slow
cycling nature of stem cells. Despite recent progress in stem
cells research, markers that can distinguish epidermal stem cells
are still lacking.
This goal of this experiment is to explore the possibility of
using the protein Cx43 as a negative marker for identifying stem
cells. This experiment was sparked by the discovery that certain
epithelial stem cells in the outer rim of the cornea do not
exhibit any expression of the Cx43 protein.
The experiment was conducted in mice and the goal is to prove that
the Label Retaining Cells (presumed stem cells) in the mouse
vibrissae do not show any expression of the Cx43 protein.
The results support the hypothesis that Cx43 can be used as a
negative marker for epidermal stem cells. |
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