Histologic morphology and involucrin, filaggrin, and keratin expression in normal canine skin from dogs of different breeds and coat types

Abstract

The purpose of this study was to measure the thickness of canine epidermis at various anatomical sites according to localization of cornified envelopes (involucrin and filaggrin), keratins (keratin 10, 5), and their mRNA expression. This was done in the skin of five breeds of dogs including seven poodles, six golden retrievers, six Shih Tzus, four pugs, and four Labrador retrievers. Epidermal thickness of the stratum corneum and nucleated epidermal layer was significantly different. The greatest thickness was observed in the digital web area and the thinnest epidermis was in the axilla. Epidermal thickness was also significantly different between the breeds (p ＜ 0.05). Immunohistochemical staining scores revealed significant decreases of involucrin, filaggrin, and keratin 10 in the ventral and weight-bearing sites, and a relative increase of keratin 5 (p ＜ 0.05). q-PCR analysis showed that their the levels of mRNA were positively correlated with expression of the corresponding proteins in skin samples (p ＜ 0.05). The present study is the first to report the relationship between epidermal gene expression and histologic morphology of the skin in normal dogs. Further studies will be essential to fully understand the pathogenesis of skin barrier dysfunctions in canines.

Filaggrin in Canine Skin

“…IHC of the skin from the dogs, preand post-allergen exposure, was demonstrated. Similar to that observed by Theerawatanasirikul et al [ 18 ], the positive staining was observed not only in the S. granulosum but also in lower epidermal layers of all groups (Fig. 20.9 ).…”

“…Theerawatanasirikul et al [ 18 ] did IHC from dog skin of different breeds and coat types, including short coats (pug), medium-length coats (Labrador retriever), long coats with no undercoat (poodle and Shih Tzu), and long coats with a dense undercoat (golden retriever) at various sites of the body, including the ear pinnae (concave and convex), periocular, muzzle, axilla, ventral neck, ventral thorax, lateral thorax, ventral abdomen, dorsal back, lateral fl ank, inguinal area, perineum, forelimb, hind limb, and digital areas. The Ab was found to bind throughout the epidermal layers.…”

Abnormal keratinocyte differentiation in the nasal planum of Labrador Retrievers with hereditary nasal parakeratosis (HNPK)

“…Involucrin gene expression was significantly but less marked down-regulated, compared to loricrin. Our findings of altered involucrin expression restricted to the nasal planum are underlined by the fact that involucrin is present in paw pad and haired skin of HNPK-affected and normal dogs (S1 Fig) [12,16].…”

“…Interestingly, loricrin was present in skin and paw pads of HNPK-affected dogs and its pattern was comparable to control dogs. As there are no structural differences in the epidermis between dog breeds [12,16], we used tissue of a beagle dog as we did not have sufficient samples of LR. This finding is in line with the clinical and histological phenotype of HNPKaffected dogs where changes are restricted to the nasal planum, but no abnormalities of the haired skin or paw pads are seen.…”

“…One study showed that the healthy canine nasal planum displays a similar pattern of the differentiation markers K14 and K10, desmogleins 1 and 3, and filaggrin, compared to a canine in vitro three-dimensional skin equivalent [15]. Another study reported on comparable mRNA and protein expression of K5 and K10, filaggrin and involucrin in various haired body regions of dogs [16]. In the nasal planum of LR with HNPK, the pattern of desmoglein 1 and the number of cells positive for the proliferation marker Ki67 is similar to non-affected control dogs [5].…”