Surgical Methods for Full-Thickness Skin Grafts to Induce Alopecia Areata in C3H/HeJ Mice

Alopecia areata is a cell-mediated autoimmune disease of humans and many domestic and laboratory animal species. C3H/HeJ inbred mice spontaneously develop alopecia areata at a low frequency (approximately 20% by 12 mo of age). Transferring full-thickness skin grafts from affected, older mice to young mice of the same strain reliably reproduces alopecia areata, thus enabling investigators to study disease pathogenesis or intervention with a variety of therapeutic approaches. We here describe in detail how to perform full-thickness skin grafts and the follow-up procedures necessary to consistently generate mice with alopecia areata. These engrafted mice can be used to study the pathogenesis of cell-mediated autoimmune disease and for drug-efficacy trials. This standard protocol can be used for many other purposes when studying abnormal skin phenotypes in laboratory mice.Abbreviations: AA, alopecia areata; DEBR, Dundee experimental bald ratAlopecia areata (AA) is a nonscarring, cell-mediated, autoimmune disease that causes hair loss in humans. At any time, between 0.05% and 0.1% of people express some form of the disease.^3,19,20 Hair loss has been characterized as patchy (alopecia areata), total loss on the top of the head (alopecia totalis), or total loss of all body hair (alopecia universalis). Progress in understanding the pathogenesis and genetics of AA as well as the means to develop and test new therapies was severely hampered until the development of a spontaneous mouse (C3H/HeJ) disease model that very closely mimics the adult-onset form of AA.^23,26 In addition to the laboratory mouse, several other species have been proposed as models for AA, but most are poorly characterized or not readily available. These include hair loss syndromes in dogs, cats, horses, cattle, and nonhuman primates and even a feather-loss syndrome in chickens.¹¹ The Dundee experimental bald rat (DEBR) also has many features of AA.^15-17C3H/HeJ mice develop a spontaneous, complex polygenic, AA-like hair loss.^25,30 Mouse AA undergoes stages of waxing and waning in terms of clinically evident areas of alopecia, and the extent of alopecia varies greatly between subjects, thus complicating the use of these spontaneous models as drug-screening tools. Full-thickness skin grafts initially were used as a tool to decipher whether the inflammation seen histologically was driving the skin lesions or whether the skin abnormalities caused changes that resulted in localized, chronic inflammation.¹⁰ To this end, we grafted affected skin to severely immunodeficient (Prkdc^scid) mutant mice congenic on the C3H/HeJ background and to histocompatible C3H/HeJ mice of the same sex as the donor. We found that full-thickness skin grafts could be used to initiate AA in histocompatible recipients in a controlled and predictable manner. Hair regrew in the immunodeficient mice, but it regrew white rather than agouti,¹⁰ a feature also seen in human AA and in injured mouse skin because of damage to melanocyte stem cells.¹³ Both the spontaneous and graft-induced forms of this mouse model have been used extensively to test hypotheses regarding disease mechanisms and responses to various treatments and to refute the association of AA with suspected infectious or antigenic challenges.^5,9,22,27 This graft-initiated mouse model is now readily available as individual mice or for contract drug-efficacy trials (The Jackson Laboratory, West Sacramento, CA; http://jaxmice.jax.org/services/alopecia_areata.html;http://jaxmice.jax.org/library/notes/504/504b.html).We here describe how to perform full-thickness skin grafts in mice, to enable investigators to reliably reproduce this AA model system in their own laboratories.