Halloy2002_FollicularAutomaton

This a model from the article:
The follicular automaton model: effect of stochasticity and of synchronization
of hair cycles.

Halloy J, Bernard BA, Loussouarn G, Goldbeter A. J Theor Biol
2002 Feb 7;214(3):469-79 11846603
,
Abstract:

Human scalp hair consists of a set of about 10(5)follicles which progress
independently through developmental cycles. Each hair follicle successively goes
through the anagen (A), catagen (C), telogen (T) and latency (L) phases that
correspond, respectively, to growth, arrest and hair shedding before a new
anagen phase is initiated. Long-term experimental observations in a group of ten
male, alopecic and non-alopecic volunteers allowed determination of the
characteristics of hair follicle cycles. On the basis of these observations, we
previously proposed a follicular automaton model to simulate the dynamics of
human hair cycles and the development of different patterns of alopecia [Halloy
et al. (2000) Proc. Natl Acad. Sci. U.S.A.97, 8328-8333]. The automaton model is
defined by a set of rules that govern the stochastic transitions of each
follicle between the successive states A, T, L and the subsequent return to A.
These transitions occur independently for each follicle, after time intervals
given stochastically by a distribution characterized by a mean and a standard
deviation. The follicular automaton model was shown to account both for the
dynamical transitions observed in a single follicle, and for the behaviour of an
ensemble of independently cycling follicles. Here, we extend these results and
investigate additional properties of the model. We present a deterministic
version of the follicular automaton. We show that numerical simulations of the
stochastic version of the automaton yield steady-state level of follicles in the
different phases which approach the levels predicted by the deterministic
equations as the number of follicles progressively increases. Only the
stochastic version can successfully reproduce the fluctuations of the fractions
of follicles in each of the three phases, observed in small follicle
populations. When the standard deviation is reduced or when the follicles become
otherwise synchronized, e.g. by a periodic external signal inducing the
transition of anagen follicles into telogen phase, large-amplitude oscillations
occur in the fractions of follicles in the three phases. These oscillations are
not observed in humans but are reminiscent of the phenomenon of moulting
observed in a number of mammalian species. Copyright 2002 Elsevier Science Ltd.
This model was taken from the CellML repository
and automatically converted to SBML.
The original model was:
Halloy J, Bernard BA, Loussouarn G, Goldbeter A. (2002) - version=1.0

The original CellML model was created by:
Catherine Lloyd

[e-mail]
The University of Auckland
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