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Are
only humans affected by alopecia areata?
Alopecia areata-like hair loss can develop in several species.
Potentially any mammal with hair could develop alopecia areata but
so far the condition has been confirmed in just a few species.
- Cats (Siamese)
- Cattle (Holstein)
- Dogs (Bernese Mountain Dog, Daschund, Doberman Pinscher,
German Shepherd, Magyar Vizsla, Miniature Poodle, Mixed Breed
Dogs)
- Horses (Appaloosa, Palomino)
- Mice (C3H/HeJ, C3H/HeJBir, A/J)
- Non-human Primates (Chimpanzee, Spider Monkey, Stump-Tailed
Macaque, White-fronted Capuchin)
- Rats (BD-IX, DEBR)
The
list is mostly based on isolated case reports from veterinarians
who have found patchy hair loss in these animals in association
with an inflammatory infiltrate around affected hair follicles.
Despite the inflammation, hair loss is non-scarring which means
that spontaneous regrowth can occur. Hair follicle-specific autoantibodies,
similar to those associated with the human condition have been
found
in alopecia areata affected mice, rats, dogs and horses. The hair
loss can be asymmetric or symmetrical and migrates, waxes and wanes
just like human alopecia areata. There is one case of a horse on
record as developing universal alopecia. There have been several
cases of daschunds with alopecia areata which might suggest this
strain is more susceptible than most to the condition. Typically,
corticosteroids are used to treat non-human alopecia areata. Response
to corticosteroids is variable, but has been shown to induce hair
regrowth for some cases in dogs, horses, non-human primates and
rodents. As for humans, once treatment is stopped relapse and renewed
alopecia frequently develops.
Confirming cases of alopecia areata in non human species can be
very difficult. There are so many other potential causes of hair
loss which must be ruled out first. A brief list of what must be
considered when indentifying cases of non-human alopecia areata
includes;
- Ringworm (Dermatophytosis)
- Psychogenic alopecia (Pilotrichomania)
- Traction alopecia (Barbering)
- Cicatrical (Scarring) alopecias (eg fungal infections,
lupus erythematosus)
- Bacterial folliculitis (eg Staphylococcosis)
- Follicular dysplasias/Hair shaft abnormalities (eg genetic
mutations)
- Endocrinopathies (eg hypothyroidism)
- Congenital alopecia
- Poisoning (eg thallium acetate)
- Sterile eosinophilic folliculitis
- Pelodera dermatitis
- Mange (Demodicosis)
- Post-rabies vaccination alopecia
- Tick bites
Animal
models for alopecia areata - rodents
Animal
models provide a vital contribution to understanding alopecia
areata. Information gained from rodent models helps define
how alopecia areata is initiated and how it progresses. The information
also provides clues as to how alopecia areata can be treated better.
Animal models, and particularly rodent models, have many advantages.
This is why animal models of human disease are the primary tool
for the study of auto-immunity.
- The small size of rodents and their rapid breeding
ability allows for large numbers to be used in research, within
a reasonable
cost, increasing the value of statistical data analysis.
- Environmental
influence on disease can be regulated and standardized for the
duration of a study.
- Many rodent models are inbred limiting
the influence of genetic variability on disease outcomes.
- Specific
genes can be studied using transgenic and knockout systems along
with controlled breeding strategies.
- Surgical manipulation can
be used as part of the research regimen, within certain ethical
limitations.
- Animal models also enable rapid screening of experimental
drug treatments in a systematic manner. This is helpful in
determining potential treatments with the greatest potency and
minimal
side effects, prior to initiating expensive and protracted clinical
trials.
Collectively the findings obtained from studies on mouse models
support the concept of alopecia areata as an autoimmune disease.
By developing a mouse with a disease similar to human alopecia
areata, researchers hope to learn more about the mechanism of
the disease and eventually develop immune system treatments for
the disease in people. Several rodent models with spontaneous
and induced alopecia areata have been identified.
- The human-SCID mouse model involves the
engraftment of alopecia areata-affected skin and hair follicles
to the back of immuno-deficient mice. Alopecia areata-affected
skin and hair follicles transplanted to SCID mice will re-grow
hair without further manipulation. These mice can then be used
for a variety of functional experiments.
- The Dundee Experimental
Bald Rat (DEBR) was the first rodent model of spontaneous alopecia
areata to be validated and is currently
being utilized to identify candidate alopecia areata susceptibility
gene loci.
- The most extensively characterized and readily accessible
alopecia areata model is the C3H/HeJ mouse model. The greatest
benefit
of using the C3H/HeJ mouse model is the ability to transfer
the disease phenotype and control the onset of alopecia areata using
a skin grafting technique. C3H/HeJ mice develop hair loss
that shows clinical, histopathological and immunohistochemical
features
of human alopecia areata. This hair loss not only develops
spontaneously, but it can also be experimentally induced in
unaffected C3H/HeJ
mice or other histocompatible strains by grafting of alopecia
areata-affected mouse skin. In short, C3H/HeJ mice with alopecia
areata can be used to study the efficacy of current treatments
of alopecia areata, to study the effectiveness and safety
profile of new treatment forms in established alopecia areata,
and to
assess the influence of various factors on the development
of alopecia areata in order to prevent the onset of the disease.
Alopecia
areata and animal models references
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can we learn from animal models of Alopecia areata? Dermatology.
2005;211(1):47-53. PMID: 15983437
- Tobin DJ, Gardner SH, Luther PB, Dunston SM, Lindsey NJ, Olivry
T. A natural canine homologue of alopecia
areata in humans. Br J Dermatol. 2003 Nov;149(5):938-50. PMID:
14632797
- McElwee KJ, Hoffmann R. Alopecia areata
- animal models. Clin Exp Dermatol. 2002 Jul;27(5):410-7. PMID:
12190642
- Smyth JR Jr, McNeil M. Alopecia areata
and universalis in the Smyth chicken model for spontaneous autoimmune
vitiligo. J Investig Dermatol Symp Proc. 1999 Dec;4(3):211-5.
PMID: 10674368
- McElwee KJ, Boggess D, Miller J, King LE Jr, Sundberg JP.
Spontaneous alopecia areata-like hair
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PMID: 10674366
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hair loss (alopecia areata) transferred by T lymphocytes to
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PMID: 9421466
- McElwee KJ, Boggess D, Olivry T, Oliver RF, Whiting D, Tobin
DJ, Bystryn JC, King LE Jr, Sundberg JP.
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species. Pathobiology. 1998;66(2):90-107. PMID: 9645633
- Sundberg JP, Cordy WR, King LE Jr.
Alopecia areata in aging C3H/HeJ mice. J Invest Dermatol. 1994
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PMID: 8006447
- Michie HJ, Jahoda CA, Oliver RF, Johnson BE. The DEBR rat:
an animal model of human alopecia areata. Br J Dermatol. 1991
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PMID: 1911310
- Gilhar A, Krueger GG. Hair growth
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