A natural canine homologue of alopecia areata in humans

Autoantigen Discovery in the Hair Loss Disorder, Alopecia Areata: Implication of Post-Translational Modifications

Alopecia areata (AA) is a chronic, multifactorial, polygenic, and heterogeneous disorder affecting growing hair follicles in susceptible individuals, which results in a non-scarring and reversible hair loss with a highly unpredictable course. Despite very considerable research effort, the nature of the precipitating factor(s) responsible for initiating AA in any given hair follicle remains unclear, due largely to significant gaps in our knowledge of the precise sequence of the etiopathogenic events in this dermatosis. However, disease-related changes in the immune-competence of the lower growing hair follicle, together with an active immune response (humoral and cellular) to hair follicle-associated antigens, are key associated phenomena. Confirmation of the hair follicle antigen(s) implicated in AA disease onset has remained stubbornly elusive. While it may be considered somewhat philosophical by some, it is also unclear whether immune-mediated hair loss in AA results from a) an ectopic (i.e., in an abnormal location) immune response to native (unmodified) self-antigens expressed by the healthy hair follicle, b) a normal immune response against modified self-antigens (or neoantigens), or c) a normal immune response against self-antigens (modified/non-modified) that were not previously visible to the immune system (because they were conformationally-hidden or sequestered) but become exposed and presentable in an MHC-I/-II molecule-restricted manner. While some candidate hair follicle antigen target(s) in AA are beginning to emerge, with a potential role for trichohyalin, it is not yet clear whether this represents the initial and immunodominant antigenic focus in AA or is simply one of an expanding repertoire of exposed hair follicle tissue damage-associated antigens that are secondary to the disease. Confirmation of autoantigen identity is essential for our understanding of AA etiopathogenesis, and consequently for developing a more informed therapeutic strategy. Major strides have been made in autoantigen discovery in other autoimmune conditions. In particular, some of these conditions may provide insights into how post-translational modifications (e.g., citrullination, deamidation, etc.) of hair follicle-restricted proteins may increase their antigenicity and so help drive the anti-hair follicle immune attack in AA.

A scoping review of autoantibodies as biomarkers for canine autoimmune disease

Background

Autoantibody biomarkers are valuable tools used to diagnose and manage autoimmune diseases in dogs. However, prior publications have raised concerns over a lack of standardization and sufficient validation for the use of biomarkers in veterinary medicine.

Objectives

Systematically compile primary research on autoantibody biomarkers for autoimmune disease in dogs, summarize their methodological features, and evaluate their quality; synthesize data supporting their use into a resource for veterinarians and researchers.

Animals

Not used.

Methods

Five indices were searched to identify studies for evaluation: PubMed, CAB Abstracts, Web of Science, Agricola, and SCOPUS. Two independent reviewers (AET and ELC) screened titles and abstracts for exclusion criteria followed by full‐text review of remaining articles. Relevant studies were classified based on study objectives (biomarker, epitope, technique). Data on study characteristics and outcomes were synthesized in independent data tables for each classification.

Results

Ninety‐two studies qualified for final analysis (n = 49 biomarker, n = 9 epitope, and n = 34 technique studies). A high degree of heterogeneity in study characteristics and outcomes reporting was observed. Opportunities to strengthen future studies could include: (1) routine use of negative controls, (2) power analyses to inform sample sizes, (3) statistical analyses when appropriate, and (4) multiple detection techniques to confirm results.

Conclusions

These findings provide a resource that will allow veterinary clinicians to efficiently evaluate the evidence supporting the use of autoantibody biomarkers, along with the varied methodological approaches used in their development.

Lymphocytic Mural Folliculitis Resembling Epitheliotropic Lymphoma in Tigers ( Panthera tigris)

A striking form of lymphocytic mural folliculitis is described in 6 tigers ( Panthera tigris). Clinically, all tigers exhibited regionally extensive chronic, variably waxing and waning alopecia with minimal scaling and crusting most pronounced over the head, neck, and shoulders. More severely affected tigers exhibited marked hyperpigmentation and lichenification. Pruritus was not a feature. Tigers generally lacked signs of systemic illness and clinical pathology findings were unremarkable. Histologic examination of skin biopsies revealed infiltrative lymphocytic mural folliculitis extending the length of the hair follicle. Mild epidermal lymphocytic infiltrates were frequent. The surrounding dermis was histologically unremarkable in 4 of 6 tigers or associated with mild perifollicular and periadnexal mixed inflammation in 2 of 6 tigers. The cause of the mural folliculitis was not identified, and tigers responded poorly to immunomodulatory therapy. Lymphocytic mural folliculitis might be a nonspecific hypersensitivity reaction pattern in tigers, and care should be taken to differentiate this reaction pattern from epitheliotropic T-cell lymphoma.

Alopecia Areata in a Dog: Clinical, Dermoscopic and Histological Features

Alopecia areata (AA)-like disease is characterized by multifocal patchy hair loss in humans, rodents, dogs, and horses. Remarkable similarities between human and nonhuman AA cases have been reported in terms of clinical presentation, histology, and immune mechanisms of the disease. Canine AA-like lesions most often consist of well-demarcated alopecic patches, frequently but not only involving the face and the head, which extend to the ear pinnae and legs. In some cases, hair loss can have a more generalized distribution. As in humans, hair regrowth is most commonly spontaneous in canine AA-like disease and the resistant cases usually respond to glucocorticoids or cyclosporine treatment. Diagnosis of AA in veterinary medicine relies on presentation, histopathology, and immunohistochemistry and on regrowth following therapy. This case report describes the first dermoscopic evaluation of AA-like disease in a dog with a clinical presentation of symmetrical hair loss.

Pilot study of safety and feasibility of DNA microseeding for treatment of spontaneous canine melanoma

Spontaneous canine malignant melanoma provides an excellent pre-clinical model to study DNA vaccines for melanoma immunotherapy. A USDA-approved xenogeneic human tyrosinase (huTYR) plasmid DNA vaccine delivered intramuscularly induces detectable immune responses and has clinical activity in some dogs with melanoma. The objective of this pilot study was to evaluate the feasibility, safety and immunogenicity of huTYR plasmid DNA administered to the skin via microseeding in dogs with spontaneous melanoma. DNA microseeding utilizes a modified tattooing device as an alternate and potentially more potent delivery method for DNA immunization. DNA was delivered to shaved inner thigh skin of six companion dogs with melanoma approximately every 14 days for a planned total of four vaccination time points. An anti-huTYR ELISA was used to test pre- and post-treatment sera. Biopsies of treated skin were obtained for detection of huTYR transgene expression. DNA microseeding was well tolerated with no significant toxicity detected beyond local site irritation, and there were no signs of autoimmunity. huTYR-expressing cells were observed in biopsies of huTYR DNA microseeding sites. Increased humoral anti-huTYR antibodies were seen in two of five evaluable dogs following microseeding compared to baseline. DNA microseeding is well tolerated in companion dogs with melanoma. Further investigation is needed to determine if combining DNA microseeding with other immunotherapy regimens potentiates this delivery platform for cancer immunotherapy.

Seasonal leukotrichia in a German shepherd dog. A case report

Leukotrichia can be caused by a variety of metabolic and inflammatory diseases. Canine alopecia areata is a rare multifactorial benign non-scarring alopecia. This case report describes a seasonally recurrent leukotrichia associated with alopecia areata in a German shepherd dog. Important differential diagnoses were ruled out and histopathology finally confirmed the diagnosis of alopecia areata. Topical tacrolimus and hydrocortisone aceponate were ineffective. The cause for the seasonal character in this case remained undetermined.

Alopecia universalis in a dog with testicular neoplasia

OBJECTIVE

To describe a case of testicular neoplasia and alopecia universalis in a dog, and successful treatment of the latter with ciclosporin.

ANIMAL

Twelve-year-old intact male wirehaired fox terrier.

METHODS

Castration, skin biopsy for histopathology, lymphocyte immunophenotyping and clonality analysis of the canine T-cell receptor gamma locus (TCRγ) rearrangement.

RESULTS

The dog presented with symmetrical generalized alopecia. Testicular enlargement was noted which on castration was determined to be caused by bilateral interstitial cell tumours, Sertoli cell tumours and a unilateral seminoma. During the four months after castration the alopecia became more severe and widespread. Histopathology of the skin showed moderate, multifocal, mural folliculitis, peribulbar mucinosis and lymphocytic bulbitis, and targeting of anagen hair follicles. Immunophenotyping of the infiltrate showed a population of well-differentiated, small CD3-positive T lymphocytes, some expressing CD4 and others CD8. Molecular analysis revealed a polyclonal lymphocytic infiltrate, substantiating the diagnosis of alopecia areata rather than lymphoma. Treatment with ciclosporin (4.6 mg/kg) and ketoconazole (4.6 mg/kg) resulted in complete hair regrowth.

CONCLUSION AND CLINICAL IMPORTANCE

Ciclosporin treatment, in combination with ketoconazole, can be effective for treatment of alopecia universalis in the dog. Alopecia universalis may present with clinically noninflammatory, symmetrical, generalized alopecia, mimicking an endocrine alopecia, and skin biopsies are needed to confirm the diagnosis.

Animal Models for Alopecia Areata: What and Where?

Disease is not limited to humans. Rather, humans are but another mammal in a continuum, and as such, often share similar if not identical diseases with other mammalian species. Alopecia areata (AA) is such a disease. Natural disease occurs in humans, nonhuman primates, many domestic animals, and laboratory rodents. However, to be useful as models of human disease, affected animals need to be readily available to the research community, closely resemble the human disease, be easy to work with, and provide reproducible data. To date, the laboratory mouse (most if not all of the C3H substrains) and the Dundee experimental bald rat fit these criteria. Manipulations using full-thickness skin grafts or specific immune cell transfers have improved the models. New mouse models that carry a variety of genetic-based immunodeficiencies can now be used to recapitulate the human immune system and allow for human full-thickness skin grafts onto mice to investigate human-specific mechanistic and therapeutic questions. These models are summarized here including where they can currently be obtained from public access repositories.

Alopecia areata universalis in a dog

BACKGROUND

Alopecia areata is a T-cell mediated autoimmune disease that occurs in humans and various other mammalian species. When the disease progresses to total alopecia it is defined as alopecia areata universalis (AAU), although this outcome has only been described in humans.

HYPOTHESIS/OBJECTIVES

To describe a case of canine alopecia areata universalis and its clinical outcome after 22 months of follow-up.

ANIMAL

A 9-year-old intact male cross-breed hunting dog was presented with generalized and complete noninflammatory alopecia of 12-14 months duration.

METHODS

Clinical examination; histopathological and immunohistochemical examination of skin biopsies.

RESULTS

There was loss of all body hair including eyelashes and vibrissae. The histopathological and immunohistochemical findings supported a diagnosis of long-standing alopecia areata. Treatment with oral ciclosporin was associated with hair regrowth but muzzle hair, most eyelashes and whiskers were still lacking after 17 months of therapy.

CONCLUSIONS AND CLINICAL IMPORTANCE

To the best of the author's knowledge this is the first documented case of canine AAU. The clinical and histopathological features were consistent with a diagnosis of AAU as defined in humans. Treatment with oral ciclosporin resulted in near complete resolution of the alopecia, but after 5 months without treatment the alopecia did not relapse and spontaneous resolution cannot be ruled out.

Efficacy of low-level laser therapy on hair regrowth in dogs with noninflammatory alopecia: a pilot study

BACKGROUND

Canine noninflammatory alopecia (CNA) is a heterogeneous group of skin diseases with different underlying pathogenesis. The therapeutic approach is challenging, and new options for treatment are desirable.

HYPOTHESIS/OBJECTIVES

To test the clinical efficacy of low-level laser therapy (LLLT) on hair regrowth in CNA.

ANIMALS

Seven dogs of different ages, breeds and genders with a clinical and histopathological diagnosis of noninflammatory alopecia.

METHODS

Each dog was treated twice weekly for a maximum of 2 months with a therapeutic laser producing the following three different wavelengths emerging simultaneously from 21 foci: 13 × 16 mW, 470 nm; 4 × 50 mW, 685 nm; and 4 × 200 mW, 830 nm. The fluence given was 3 J/cm(2) , frequency 5 Hz, amplitude of the irradiated area was 25 cm(2) and application time was 1.34 min. A predetermined alopecic area was left untreated and served as a control area. From one dog, post-treatment biopsies of treated and untreated sites were obtained for histological evaluation of hair density and the percentage of haired and nonhaired follicles.

RESULTS

At the end of the study, coat regrowth was greatly improved in six of seven animals and improved in one of seven. By morphometry, the area occupied by hair follicles was 18% in the treated sample and 11% in the untreated one (11%); haired follicles were (per area) 93% in the treated sample and only 9% in the control sample.

CONCLUSIONS AND CLINICAL IMPORTANCE

Our clinical and histological data document promising effects of LLLT on hair regrowth in CNA. Further studies investigating the biological mechanism underlying the effect of LLLT on hair follicle cycling are warranted.

Clinical and histological characterization of multifocal, spontaneous, noninfectious alopecia in Norwegian puffin dogs (lundehunds)

BACKGROUND

A noninfectious, spontaneous, multifocal alopecia has been recognized in Norwegian puffin dogs.

HYPOTHESIS/OBJECTIVES

This study aimed to report demographic information, history, clinical signs, histopathological features and follow-up information for alopecic Norwegian puffin dogs from Sweden.

MATERIAL AND METHODS

A questionnaire was sent out to all members of the breed association. Dogs clinically diagnosed with alopecia and biopsied were allocated to Group A. Dogs reported with alopecia for which histopathology was not available were allocated to Group B.

RESULTS

Group A included 14 dogs (11.7% of the breed population in Sweden). Information regarding 72 dogs (60% of the breed population) was collected via questionnaire, and alopecia without histopathology was reported in another five dogs (Group B). Gender distribution was equal. Median age of onset was 1.5 years (range 8 months to 7 years). Multifocal or serpiginous alopecia, follicular plugging, dry skin, slight scaling and pruritus were characteristic. Extensive, widespread alopecia was not seen, and lesions were recorded only in haired skin. A lymphoplasmacytic, mural, isthmus folliculitis/perifolliculitis with follicular and perifollicular mucin was observed. Inflammation did not involve the hair bulb; atrophy was sometimes present. The inflammation sometimes extended to sebaceous glands, resulting in atrophy and absence of glands. Follow-up ranged from 6 months to 12 years (mean 3.2 years). Spontaneous remission was rare. Estrus was associated with worsening of the disease or relapse. Oral prednisolone reduced pruritus but was not effective in resolving clinical lesions. All dogs treated with ciclosporin went into remission.

CONCLUSIONS AND CLINICAL IMPORTANCE

This is the first report of mural, mucinotic, isthmus folliculitis alopecia in Norwegian puffin dogs.

What causes alopecia areata?

The pathobiology of alopecia areata (AA), one of the most frequent autoimmune diseases and a major unsolved clinical problem, has intrigued dermatologists, hair biologists and immunologists for decades. Simultaneously, both affected patients and the physicians who take care of them are increasingly frustrated that there is still no fully satisfactory treatment. Much of this frustration results from the fact that the pathobiology of AA remains unclear, and no single AA pathogenesis concept can claim to be universally accepted. In fact, some investigators still harbour doubts whether this even is an autoimmune disease, and the relative importance of CD8(+) T cells, CD4(+) T cells and NKGD2(+) NK or NKT cells and the exact role of genetic factors in AA pathogenesis remain bones of contention. Also, is AA one disease, a spectrum of distinct disease entities or only a response pattern of normal hair follicles to immunologically mediated damage? During the past decade, substantial progress has been made in basic AA-related research, in the development of new models for translationally relevant AA research and in the identification of new therapeutic agents and targets for future AA management. This calls for a re-evaluation and public debate of currently prevalent AA pathobiology concepts. The present Controversies feature takes on this challenge, hoping to attract more skin biologists, immunologists and professional autoimmunity experts to this biologically fascinating and clinically important model disease.

Genome-wide analysis in German shepherd dogs reveals association of a locus on CFA 27 with atopic dermatitis

Humans and dogs are both affected by the allergic skin disease atopic dermatitis (AD), caused by an interaction between genetic and environmental factors. The German shepherd dog (GSD) is a high-risk breed for canine AD (CAD). In this study, we used a Swedish cohort of GSDs as a model for human AD. Serum IgA levels are known to be lower in GSDs compared to other breeds. We detected significantly lower IgA levels in the CAD cases compared to controls (p = 1.1 × 10(-5)) in our study population. We also detected a separation within the GSD cohort, where dogs could be grouped into two different subpopulations. Disease prevalence differed significantly between the subpopulations contributing to population stratification (λ = 1.3), which was successfully corrected for using a mixed model approach. A genome-wide association analysis of CAD was performed (n cases = 91, n controls = 88). IgA levels were included in the model, due to the high correlation between CAD and low IgA levels. In addition, we detected a correlation between IgA levels and the age at the time of sampling (corr = 0.42, p = 3.0 × 10(-9)), thus age was included in the model. A genome-wide significant association was detected on chromosome 27 (praw = 3.1 × 10(-7), pgenome = 0.03). The total associated region was defined as a ~1.5-Mb-long haplotype including eight genes. Through targeted re-sequencing and additional genotyping of a subset of identified SNPs, we defined 11 smaller haplotype blocks within the associated region. Two blocks showed the strongest association to CAD. The ~209-kb region, defined by the two blocks, harbors only the PKP2 gene, encoding Plakophilin 2 expressed in the desmosomes and important for skin structure. Our results may yield further insight into the genetics behind both canine and human AD.

Bilaterally Symmetrical Alopecia With Reticulated Hyperpigmentation

An adult castrated male Doberman Pinscher was presented with a 6-month history of well-demarcated alopecic patches with reticulated hyperpigmentation and fine peripheral scaling on the axillae, thorax, abdomen, inguinal region, and thighs. The dog later developed hyperthermia, lethargy, apparent joint pain, peripheral lymphadenomegaly, vomiting, and diarrhea. Relevant laboratory tests results included anemia, thrombocytopenia, proteinuria, and an elevated antinuclear antibodies serum titer. Histologically, skin biopsy specimens had a lymphocyte-rich interface dermatitis and interface mural folliculitis ending in follicular destruction. Altogether, these signs were consistent with a unique alopecic variant of chronic cutaneous lupus erythematosus, eventually associated with the development of systemic lupus erythematosus. This rare form of chronic cutaneous lupus needs to be added to the expanding list of lymphocyte-mediated autoimmune alopecias in dogs.

Alopecia areata in Eringer cows

Alopecia areata is a hair loss disorder in humans, dogs and horses with a suspected autoimmune aetiology targeting anagen hair follicles. Alopecia areata is only sporadically reported in cows. Recently, we observed several cases of suspected alopecia areata in Eringer cows. The aim of this study was to confirm the presumptive diagnosis of alopecia areata and to define the clinical phenotype and histopathological patterns, including characterization of the infiltrating inflammatory cells. Twenty Eringer cows with alopecia and 11 Eringer cows without skin problems were included in this study. Affected cows had either generalized or multifocal alopecia or hypotrichosis. The tail, forehead and distal extremities were usually spared. Punch biopsies were obtained from the centre and margin of alopecic lesions and normal haired skin. Histological examination revealed several alterations in anagen hair bulbs. These included peri- and intrabulbar lymphocytic infiltration, peribulbar fibrosis, degenerate matrix cells with clumped melanosomes and pigmentary incontinence. Mild lymphocytic infiltrative mural folliculitis was seen in the inferior segment and isthmus of the hair follicles. Hair shafts were often unpigmented and dysplastic. The large majority of infiltrating lymphocytes were CD3(+) T cells, whereas only occasional CD20(+) lymphocytes were present in the peribulbar infiltrate. Our findings confirm the diagnosis of T-cell-mediated alopecia areata in these cows. Alopecia areata appears to occur with increased frequency in the Eringer breed, but distinct predisposing factors could not be identified.

Canine follicle stem cell candidates reside in the bulge and share characteristic features with human bulge cells

The hair follicle bulge has attracted great interest as a stem cell repository. Previous studies have focused on rodent or human bulge stem cells, and our understanding of those in other species is limited. In this study, we attempted to localize and characterize stem cell candidates in canine hair follicles. The canine skin xenografting study located label-retaining cells in the outer root sheath around the insertion point of the arrector pili muscle, where the immunoreactivity of human bulge markers, keratin 15 and follistatin, were detected. Canine bulge cell-enriched keratinocytes up-regulated human bulge biomarkers CD200 and DIO2, and conserved key cell regulators of bulge stem cells, such as SOX9 and LHX2. Importantly, canine bulge-derived keratinocytes were highly proliferative in vitro and, when combined with trichogenic dermal cells, reconstituted pilosebaceous structures as well as the epidermis in vivo. Successful detection of canine specific DNA sequences suggested that the regenerated tissue was of canine origin. In addition, canine specific bulge cell and sebocyte lineage markers were expressed in reconstituted pilosebaceous units, implying the multipotency of canine bulge cells. Our findings demonstrate a unique strategy utilizing canine bulge cells to investigate human stem cell biology and intractable hair disorders that involve the bulge region.

Alopecia in a black Labrador retriever associated with focal sub-follicular panniculitis and sebaceous adenitis

A 6-year-old entire male black Labrador retriever was presented with nonpruritic multicentric, well-demarcated alopecia of 12-weeks duration. Skin biopsies from the margins of alopecic regions showed sebaceous adenitis and sub-follicular panniculitis. Biopsies from alopecic areas showed severe follicular atrophy with residual fibrous tracts, loss of sebaceous glands and lymphohistiocytic panniculitis beneath individual atrophic hair follicle groups. These features differed from previous reports of pilosebaceous diseases of dogs and appeared to extend the spectrum of inflammatory patterns in presumed immune-mediated adnexal diseases of this species. During the 12-month follow-up, there was partial hair regrowth without treatment but alopecia was permanent in the centre of larger lesions.

What Can We Learn from Animal Models of Alopecia areata?

Alopecia areata (AA) is a hair loss disease marked by a focal inflammatory infiltrate of dystrophic anagen stage hair follicles by CD4+ and CD8+ lymphocytes. Although AA is thought to be an autoimmune disorder, definitive proof is lacking. Moreover, characterization of the primary pathogenic mechanisms by which hair loss is induced in AA is limited. In this context, animal models may provide a vital contribution to understanding AA. Recent research using animal models of AA has focused on providing evidence in support of a lymphocyte-mediated pathogenic mechanism consistent with AA as an autoimmune disease. In the future, research with both humans and animal models shall likely concentrate on identifying the primary antigenic epitopes involved in AA and the genetics of AA susceptibility. With a comprehensive understanding of the key elements in AA pathogenesis, new avenues for therapeutic research and intervention will be defined.

S100 Proteins in the Epidermis

The S100 proteins comprise a family of 21 low molecular weight (9-13 kDa) proteins that are characterized by the presence of two calcium-binding EF-hand motifs. Fourteen S100 protein genes are located within the epidermal differentiation complex on human chromosome 1q21 and 13 S100 proteins (S100A2, S100A3, S100A4, S100A6, S100A7, S100A8, S100A9, S100A10, S100A11, S100A12, S100A15, S100B, and S100P) are expressed in normal and/or diseased epidermis. S100 proteins exist in cells as anti-parallel hetero- and homodimers and upon calcium binding interact with target proteins to regulate cell function. S100 proteins are of interest as mediators of calcium-associated signal transduction and undergo changes in subcellular distribution in response to extracellular stimuli. They also function as chemotactic agents and may play a role in the pathogenesis of epidermal disease, as selected S100 proteins are markedly overexpressed in psoriasis, wound healing, skin cancer, inflammation, cellular stress, and other epidermal states.