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Dermal papilla
It is the dermal papilla (DP) which
directs and dictates the embryonic
generation of a hair follicle and it
also retains this instructive
ability throughout the life of the
hair follicle. The DP presents as a
healthy "pear" shape in normal hair
follicles. As the name suggests,
derived from the dermis mesenchyme
the DP consists of a highly active
group of cells shown to be capable
of inducing follicle development
from the epidermis and production of
hair fiber (Oliver 1966a, Oliver
1966b, Oliver 1967).
The DP consists of a small group of
fibroblast cells derived from the
mesoderm. The cells are held close
to the base of the epidermal derived
cells that produce the hair fiber
and root sheaths but there is a thin
layer, called the basement membrane
(or basement lamina, or glassy
membrane) that separates the DP
cells from the hair fiber/sheath
cells. In other words, the basement
membrane provides a physical
dividing line between cells
descendant from embryonic ectoderm
(epidermis) and embryonic mesoderm
(dermis). This physical barrier has
a role to play in our immunological
protection. Holding the DP cells in
place is a capsule that surrounds
the DP cells in a cup and extends up
the sides of the hair follicle to
the epidermis. The whole follicle
structure sits on a pad of fibrous
tissue called the Arao-Perkins body.
Nerve fibers and blood vessels
penetrate through small gaps in the
base of the hair capsule and invade
into the DP area.
The bigger the DP, the more cells it
has, then the thicker the hair fiber
that the hair follicle produces. The
DP cells are very active with lots
of cytoplasm when the hair follicle
is producing a hair fiber although
the DP cells do not multiply and
proliferate unlike the hair
producing cells above the DP. When a
hair follicle is not producing a
fiber the DP cells lose much of
their cytoplasm and become inactive.
Oliver et al revealed that
the removal of the DP stops hair
growth but that the lower third of
the dermal sheath is capable of
supplying new cells for regeneration
of a new DP by infiltrating and
transforming at the site of the
original DP with subsequent hair
follicle re-growth (Oliver 1966a,
Oliver 1966b, Oliver 1966c, Jahoda
1992). With removal of more than the
lower third of a hair follicle,
reformation of a DP is unable to
occur and the hair follicle is
effectively permanently destroyed.
The DP cells retain their embryonic
functional abilities and are able to
induce new hair fiber growth in
mature, adult skin when implanted
into previously deactivated hair
follicles and in close association
with ORS epidermal cells (Oliver
1967, Horne 1986).
DP cells can also interact with
adult epidermis to induce the
development of new hair follicles (Jahoda
1990). In the established hair
follicle the DP cells act in
conjunction with epidermal cells via
mechanisms similar to those in
embryogenesis to permit hair
follicle cycling through hair
production and resting phases. DP
cells are almost unique in
maintaining their embryogenic
regenerative properties in adults
making them potentially attractive
for investigation with a view to
gaining an insight on organ/limb
regeneration and similar studies.
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A Hair Loss
B Type of hair loss
C What causes hair loss
D Sign and symptoms
E Introduction to skin and
biology
F Follicular structure
G Dermal papilla
H Hair fiber
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