Evaluation of intraepidermal nerve fibres in the skin of normal and atopic dogs.

BACKGROUND: Interest in intraepidermal nerve fibres (IENFs) is rising in human medicine, because variations in fibre density occur in some diseases and these neurites might contribute to disease pathogenesis. An increase in IENF density is seen in human atopic dermatitis (AD); there are no such data in atopic dogs. OBJECTIVES: To compare the prevalence of IENFs in normal and atopic canine skin. METHODS: Eight millimetre skin punch biopsies were taken from six sites of 25 healthy dogs without dermatitis and compared to lesional and nonlesional skin samples of dogs with AD (23 and 14 dogs, respectively). Thirty micrometre-thick paraffin-embedded sections were stained by indirect immunofluorescence for neuronal beta-3 tubulin. Only sections with detectable dermal nerves were then screened for the presence of IENFs. RESULTS: IENFs were identified in all 25 normal nasal planum sections, but in only one biopsy collected from each of the normal canine haired skin (NCHS) sites. As there was no significant difference in IENF prevalence between NCHS areas, they were grouped together. The rate of detection of IENFs was significantly higher (one-tailed Fisher's test, P = 0.004) in lesional AD specimens (18 of 23; 78%) than in nonlesional AD (four of 14; 29%) and NCHS specimens (four of 111; 4%, P < 0.0001). The prevalence of IENF detection in nonlesional AD samples was significantly higher than in normal canine skin (P = 0.006). CONCLUSIONS AND CLINICAL IMPORTANCE: IENFs are detected more commonly in canine AD than in normal haired skin; these results are comparable to those seen for human AD.

Deficient plakophilin-1 expression due to a mutation in PKP1 causes ectodermal dysplasia-skin fragility syndrome in Chesapeake Bay retriever dogs.

In humans, congenital and hereditary skin diseases associated with epidermal cell-cell separation (acantholysis) are very rare, and spontaneous animal models of these diseases are exceptional. Our objectives are to report a novel congenital acantholytic dermatosis that developed in Chesapeake Bay retriever dogs. Nine affected puppies in four different litters were born to eight closely related clinically normal dogs. The disease transmission was consistent with an autosomal recessive mode of inheritance. Clinical signs occurred immediately after birth with superficial epidermal layers sloughing upon pressure. At three month of age, dogs exhibited recurrent superficial skin sloughing and erosions at areas of friction and mucocutaneous junctions; their coat was also finer than normal and there were patches of partial hair loss. At birth, histopathology revealed severe suprabasal acantholysis, which became less severe with ageing. Electron microscopy demonstrated a reduced number of partially formed desmosomes with detached and aggregated keratin intermediate filaments. Immunostaining for desmosomal adhesion molecules revealed a complete lack of staining for plakophilin-1 and anomalies in the distribution of desmoplakin and keratins 10 and 14. Sequencing revealed a homozygous splice donor site mutation within the first intron of PKP1 resulting in a premature stop codon, thereby explaining the inability to detect plakophilin-1 in the skin. Altogether, the clinical and pathological findings, along with the PKP1 mutation, were consistent with the diagnosis of ectodermal dysplasia-skin fragility syndrome with plakophilin-1 deficiency. This is the first occurrence of ectodermal dysplasia-skin fragility syndrome in an animal species. Controlled mating of carrier dogs would yield puppies that could, in theory, be tested for gene therapy of this rare but severe skin disease of children.

Stratum corneum removal facilitates experimental sensitization to mite allergens in atopic dogs.

In humans with atopic dermatitis and in mouse models of IgE-mediated allergic diseases, evidence is mounting that the stratum corneum (SC) provides an important barrier against environmental allergens. At this time, it is not known whether the SC has a similar role in dogs, especially in those with atopic dermatitis. The objectives of this pilot study were to determine whether SC removal led to earlier and stronger sensitization of atopic dogs to Dermatophagoides farinae (Df) house dust mites. Five Maltese-beagle atopic (MBA) dogs were sensitized epicutaneously after the SC was removed with ten tape strips (TS group), while sensitization was done without tape strips in five other MBA dogs (nontape stripping; NTS group). During this 16 week study, sensitization was assessed with allergen-specific IgE serology, intradermal testing with Df allergens and determination of stimulation indices of blood mononuclear cells cultured with Df and stained for CD4 and the activation markers CD25 or CD30. Compared with dogs from the NTS group, those of the TS group exhibited earlier rises in Df-specific IgE serum levels, usually had higher allergen-specific IgE titres, showed higher intradermal test reactivity and had earlier increases and higher percentages of CD25- or CD30-positive activated allergen-specific peripheral CD4-positive T lymphocytes. These observations implicate a role of the SC as a barrier limiting sensitization to exogenous allergens in this experimental atopic dog model.

Clinical and immunological heterogeneity of canine subepidermal blistering dermatoses with anti-laminin-332 (laminin-5) auto-antibodies.

Laminin-332 (laminin-5) is a basement membrane heterotrimeric protein composed of alpha-3, beta-3 and gamma-2 laminin chains. Laminin-332 polypeptides are targeted by auto-antibodies in human patients with mucous membrane (cicatricial) pemphigoid or, more rarely, subepidermal vesicular diseases that resemble epidermolysis bullosa acquisita (EBA) or bullous pemphigoid (BP). The objectives of this report were to characterize the clinical, histopathological and immunological characteristics of nine dogs with auto-antibodies targeting laminin-332. Immunological investigations consisted of direct immunofluorescence (IF), indirect IF with intact and salt-split canine gingival, and salt-split normal or laminin-332-deficient human skin, immunoblotting with purified human laminin-332 and immunoblotting with recombinant NC1 domain of human collagen VII. All dogs exhibited varying degrees of skin blistering and ulceration associated with microscopic subepidermal vesiculation with or without inflammatory cells. Indirect IF established that circulating IgG auto-antibodies bound the dermal side of salt-split canine lip and human skin. In five dogs, IgG variably recognized the basement membrane of laminin-332-deficient human skin (three dogs negative, two dogs positive). In all nine dogs, IgG auto-antibodies detected purified human laminin-332 by immunoblotting. In two dogs, additional targeting of collagen VII-NC1 was present. These observations establish laminin-332 as a novel basement membrane antigen in dogs with autoimmune blistering diseases with variable clinical phenotypes. The names 'acquired junctional epidermolysis bullosa', 'anti-laminin-332 mucous membrane pemphigoid (MMP)' and 'mixed auto-immune subepidermal blistering dermatosis' are proposed for dogs with clinical signs reminiscent of EBA, MMP or BP respectively.

Patch testing of experimentally sensitized beagle dogs: development of a model for skin lesions of atopic dermatitis.

In humans with atopic dermatitis (AD), the epicutaneous application of allergens (atopy patch tests or APT) to which the patients are sensitized often results in the development of inflammation resembling that of spontaneous skin lesions. Dogs are affected with a natural homologue of human AD, but information on the induction of positive patch testing reactions is limited. The objectives of this pilot study were to determine the nature and cellular dynamics of inflammation occurring after APT in dogs hypersensitive to house dust mite and flea allergens. Laboratory Beagles were sensitized experimentally to Dermatophagoides farinae house dust mites (two dogs), Ctenocephalides felis flea saliva (one dog) or both (two dogs). Two other dogs served as nonsensitized controls. Both allergens and saline were applied epicutaneously. Macroscopic evaluations and skin biopsies were performed at 4, 24, 48 and 96 h after starting allergenic challenge. Biopsies were evaluated histologically and immunohistochemically with a panel of monoclonal antibodies specific for canine leucocyte antigens. Positive macroscopic reactions consisted of erythema, oedema and induration, and they occurred between 24 and 96 h after allergen application. Macroscopic and microscopic APT reactions developed only whenever serum IgE was present against tested allergens. Microscopically, positive APT was associated with epidermal hyperplasia, Langerhans' cell hyperplasia, and eosinophil and lymphocyte epidermotropism. Dermal inflammation was mixed and arranged in a superficial perivascular to interstitial pattern. Numerous IgE+-CD1+ dendritic cells and gamma-delta T-lymphocytes were observed. Macroscopically and microscopically, APT reactions in these experimentally sensitized animals resembled those seen in lesional biopsy specimens of dogs and humans with spontaneous AD. Therefore, APT in hypersensitive dogs provides a relevant experimental model to investigate the pathogenesis and treatment of both canine and human AD skin lesions.

Intraocular extramedullary plasmacytoma in a cat.

An 8-year-old, castrated male Domestic Short-haired cat was referred for evaluation of a possible intraocular neoplasm following previous ocular trauma. The eye was blind, and uveitis and an iridal mass were noted on examination. An enucleation was performed and the mandibular lymph node excised. Histopathologic examination revealed neoplastic proliferation of plasma cells in the iris and lymph node. No other evidence of disseminated disease was detected. This is the first case reported of an intraocular extramedullary plasmacytoma in the cat. The variation in clinical manifestations and potential association with multiple myeloma are not known at this time. Disseminated metastasis from a primary plasmacytoma of the uveal tract could also involve the bone marrow and be indistinguishable from multiple myeloma. Early enucleation, as in trauma-associated sarcomas, may be indicated to prevent metastasis. Periodic systemic evaluation for evidence of multiple myeloma should be performed.

Desmoglein-3 is a target autoantigen in spontaneous canine pemphigus vulgaris.

Pemphigus vulgaris (PV) is an autoimmune blistering skin disease of humans and companion animals. In human patients, PV is associated with the production of IgG autoantibodies specific for keratinocyte desmosomal glycoproteins of the cadherin family. The purpose of this study was to determine whether antikeratinocyte IgG autoantibodies were present in the skin and serum of dogs with PV, and also to identify the canine PV autoantigen(s) targeted by circulating autoantibodies. Eleven dogs were selected because of the microscopic demonstration of suprabasal epithelial acantholysis. Direct immunofluorescence revealed the presence of IgG autoantibodies bound to the membrane of keratinocytes in skin biopsy specimens of 8/9 dogs (89%). Using indirect immunofluorescence, serum-circulating IgG autoantibodies were found in 10/11 (91%) and 5/11 (45%) dogs, using normal canine gingiva and cultured canine oral keratinocytes, respectively. By immunoblotting using cultured canine oral keratinocyte protein lysates, IgG autoantibodies from 7/9 (78%) tested dogs recognized a 130-kDa antigen that comigrated with that identified by rabbit polyclonal antibodies raised against desmoglein-3. This 130 kDa antigen was confirmed to represent the canine equivalent of human desmoglein-3 by immunoprecipitation-immunoblotting. The results of these studies provide evidence that the canine desmoglein-3 homologue is a major autoantigen in dogs with PV. These observations further establish spontaneous canine PV as a natural model for research on pathogenesis, etiology and novel therapeutic approaches for this disease of humans.

A randomized controlled trial of misoprostol monotherapy for canine atopic dermatitis: effects on dermal cellularity and cutaneous tumour necrosis factor-alpha.

In this blinded randomized placebo-controlled trial, 20 dogs with atopic dermatitis (AD) were given placebo (8 dogs) or misoprostol (12 dogs) at 5 micro g kg-1, orally, three times daily for 3 weeks. Administration of the active drug, but not of placebo, led to a significant decrease in lesional and pruritus scores. The median reduction from baseline of both scores was approximately 30%. Misoprostol therapy did not lead to decreases of dermal cell counts or skin tumour necrosis factor (TNF)alpha mRNA copy numbers that were significantly different from those of placebo. Skin TNFalpha protein production, assessed using indirect immunofluorescence, decreased or remained unchanged in dogs receiving misoprostol. In contrast, post treatment TNFalpha fluorescence scores were higher in all but two dogs given placebo. The changes from baseline of TNFalpha fluorescence scores did not correlate significantly with those of lesional or pruritus indices. These observations confirm the modest efficacy of misoprostol for treatment of canine AD and suggest that its mild anti-allergic effects are not associated with either inhibition of inflammatory cell emigration or TNFalpha production.

Résumé Dans cette étude randomisée en aveugle, 20 chiens présentant une dermatite atopique ont reçu un placebo (8 chiens) ou du misoprostol (12 chiens) à la posologie de 5 µg kg−1 , par voie orale, trois fois par jour pendant 3 semaines. L'administration du misoprostol mais pas du placebo a permis une diminution significative des scores de prurit et lésionnels. La réduction moyenne des 2 scores était d'environ 30%. Le misoprostol n'a pas diminué le nombre de cellules dans le derme ou le nombre de copies d'ARNm du TNF qui étaient significativement différentes du placebo. La production de TNF, determinée par immunofluorescence indirecte a diminué ou n'a pas évolué chez les chiens recevant le misoprostol. Au contraire, les scores de fluorescence pour le TNF étaient plus élevés chez tous les chiens recevant le placebo sauf deux. Les modifications des scores de fluorescence du TNF nétaient pas corrélées aux scores de prurit ou lésionnel. Ces observations confirment l'efficacité modeste du misoprostol pour le traitement de la dermatite atopique canine et suggèrent que ses effets antiallergiques modérés ne sont pas associés à une inhibition de la migration des cellules inflammatoires ou de la production de TNF.

Resumen En este ensayo ciego, al azar y controlado con placebo, a veinte perros con DA se les administró oralmente placebo (8 perros) o misoprostol (12 perros) a una dosis de 5 µg kg−1 tres veces al día durante tres semanas. La administración de la droga activa, pero no la del placebo, dio lugar a una disminución del índice de lesiones y prurito. La reducción media en ambos índices fue de aproximadamente el 30%. La terapia de misoprostol no produjo una disminución del recuento de células dérmicas o del número de copias del ARNm del FNT-α (TNFα), los cuales eran significativamente diferentes del grupo con placebo. La producción de la proteína FNTα, determinada por un método indirecto de immunofluorescencia, disminuyó o permaneció igual en perros que recibieron misoprostol. En cambio, el nivel de fluorescencia del FNTα fue más elevado en el postratamiento en todos los perros, con excepción de dos de ellos en el grupo con placebo. Los cambios en el nivel de fluorescencia, con respecto a la línea basal, no se correlacionaron significativamente con los índices de lesión o prurito. Estas observaciones confirman la modesta eficacia del misoprostol para el tratamiento de las DA caninas y sugiere que sus efectos mínimos antialérgicos no están asociados con la inhibición de la emigración de células inflamatorias o la producción del FNTα.

Absent expression of collagen XVII (BPAG2, BP180) in canine familial localized junctional epidermolysis bullosa.

Hereditary junctional epidermolysis bullosa (JEB) represents a subset of mechanobullous diseases associated with defective hemidesmosome/anchoring filament proteins leading to cleavage in the lamina lucida of the epidermal basement membrane. In humans, most cases of JEB have been related to a deficiency of either laminin-5, collagen XVII (BPAG2, BP180) or integrin ß4. We describe the existence of a previously unreported form of familial localized non-lethal JEB in German Shorthaired Pointer littermates. Acral, auricular and oral erosions and ulcers were observed. Severe ulceration of the footpads was present. Skin biopsy specimens of non-lesional and lesional skin of affected dogs were screened for a defect in basement membrane proteins using indirect immunofluorescence and immunoperoxidase testing. Epidermal staining for laminin-5 and integrin α6ß4 was similar in affected and normal control dogs. Lack of expression of collagen XVII was uniquely identified in all sections of JEB probands compared with normal control dogs. The defective expression of collagen XVII is likely to be caused by mutation(s) of the COL17A1 gene, as previously reported in humans. This is, to date, the first report of a deficient basement membrane protein in canine JEB.