The effect of body region on the canine hair cycle as defined by unit area trichogram

Evaluation of hair follicle parameters using TrichoScale Pro© in healthy dogs: a pilot study

BACKGROUND

Trichoscopy, in combination with image analysis software, is a readily available, efficient diagnostic tool for assessing hair follicle parameters of people in vivo. Systems designed for use in human dermatology must be evaluated and validated with animal skin/hair before they can be used for veterinary applications.

OBJECTIVES

To evaluate the use of a commercial software package for image analysis of canine hair follicles and to define hair follicle parameters.

ANIMALS

Thirteen client-owned healthy dogs.

METHODS

Trichoscopic images at x20 magnification were obtained from three shaved body sites (left dorsal head, left thorax, left flank) over a five day period, then analyzed by the software.

RESULTS

The image analysis software was able to identify microscopic changes in hair length on a daily basis, calculating a mean hair growth rate of 0.065 mm/day. Each of the three body sites had consistent hair growth rates across all days. Anagen and telogen percentages were consistent at each body site by Day 2 (48 h post-clipping). Data for mean hair thickness, and primary and secondary hair percentages also are reported.

CONCLUSIONS

Although it provides less useful data for canine hair coats than for human scalp hair, the system evaluated provides an easy, noninvasive, rapid means for assessing several important canine hair follicle parameters: daily hair growth rates, anagen and telogen percentages, primary and secondary hair percentages, and mean hair thickness. This diagnostic tool could serve to establish breed-specific hair coat standards, evaluating hair follicle changes in various canine alopecic conditions and monitoring coat-promoting treatments in dogs.

Trichographic features of hair from normal black Dobermann pinscher dogs

BACKGROUND

Dobermann dogs are predisposed to colour dilution alopecia and follicular dysplasia. Limited information is available regarding the trichographic features of normal canine hair shafts, including those from Dobermanns, with no studies of inter-observer agreement for canine trichographic features.

OBJECTIVES

To characterize the trichographic features of normal black Dobermann hair shafts evaluating the following variables; gross appearance, primary versus secondary hairs, colour change, tip structure, curling, twisting, bending, cuticle changes (breaks, compression, loss or abnormal overlapping), fractures and variations in hair diameter.

ANIMALS

Twenty client-owned, normal, black Dobermanns of different ages and genders.

METHODS AND MATERIALS

A systemized trichographic evaluation of hair samples from five body locations, which were evaluated independently by two observers, and inter-observer agreement evaluation. Kappa statistics, positive and negative agreement were determined.

RESULTS

Agreement between investigators ranged from 87% to 99% for each examined variable. Kappa statistics showed excellent (0.81-1.00) to substantial agreement (0.61-0.80) for all variables with the exception of moderate agreement (0.41-0.60) for cuticle compressions and variations in hair diameter. A novel finding of a "round hair tip" was made, which was more commonly found on the dorsal head. Colour change to the proximal hair shaft was more common on the thighs and flanks.

CONCLUSIONS AND CLINICAL IMPORTANCE

Trichographic features of 500 hairs collected from 20 normal black Dobermann dogs are described. A previously unreported finding of round hair tips was seen. We describe a systematic approach for evaluating hair shafts that can be applied in future studies for both normal and abnormal Dobermanns, and potentially other dog breeds.

Clinical characteristics of doxorubicin-associated alopecia in 28 dogs

BACKGROUND

Chemotherapy-induced alopecia (CIA) is common in humans, but there are limited reports describing the clinical features of CIA in dogs.

OBJECTIVES

To describe the epidemiological and clinical characteristics of doxorubicin-associated alopecia (DAA) in canine patients at a teaching hospital from 2012 to 2014.

ANIMALS

Signalment, diagnosis, treatment protocols and clinical examination findings were recorded in 150 dogs treated with doxorubicin from 2012 to 2014.

METHODS

Medical records were searched retrospectively for the keywords "alopecia" and "hypotrichosis." Dogs were excluded if the causal link of hair loss was unclear.

RESULTS

Doxorubicin-associated alopecia was reported in 28 of 150 dogs (19%). Two parameters were statistically associated with the development of DAA: coat-type and cumulative doxorubicin dose. Dogs with curly or wire-haired coat-type were significantly more likely to develop DAA than dogs with straight-haired coat-type [χ² (1, N = 147) = 30, P < 0.0001]. After adjusting for sex, weight and doxorubicin dose, the odds of dogs with curly or wire-haired coat-type developing DAA were 22 times higher than those with straight-haired coat-type (P < 0.0001). Dogs that developed DAA received a significantly higher median cumulative doxorubicin dose (103.0 versus 84.5 mg/m² ; P = 0.0039) than those that did not develop DAA.

CONCLUSIONS AND CLINICAL IMPORTANCE

Dogs treated with doxorubicin may be at risk for developing DAA. This risk increases as the cumulative dose of doxorubicin increases, and with a curly or wire-haired coat-type.

Glucocorticosteroid concentrations in feces and hair of captive caribou and reindeer following adrenocorticotropic hormone challenge

Climate change and industrial development are contributing to synchronous declines in Rangifer populations across the Arctic. Chronic stress has been implicated as a proximate factor associated with decline in free-ranging populations, but its role in Rangifer is unspecified. Analysis of glucocorticosteroid (GC) concentration in feces, and more recently in hair, is a non-invasive method for monitoring stress in wildlife. Adrenocorticotropic hormone (ACTH) released from the pituitary gland stimulates GC release from the adrenals and can be administered to reflect adrenal activation. In this study, we assessed concentrations of GC metabolites in feces and cortisol in hair of Alaskan caribou (Rangifer tarandus granti) and reindeer (R. t. tarandus) following ACTH treatment. We predicted that ACTH challenge would increase concentrations of fecal GCs, but not hair cortisol because steroid deposited into the hair shaft occurs over an extended period of time (months) and is likely insensitive to acute adrenal stimulation. Adult caribou (n=10; mean age, 6.5 years old) exhibited a peak increase in fecal GCs 8h following a 2 IU/kg dose of ACTH compared to pre-injection concentrations. In contrast, sub-adult reindeer (n=10, 0.8 years old) elicited a diminished response to the same dose. Quadrupling the dose (8 IU/kg) prolonged the fecal GC response in female reindeer, but male reindeer were unresponsive. Hair cortisol was unaffected by a single ACTH challenge. Further investigation is required to ascertain whether subspecific differences in adrenal sensitivity are attributed to age or sex differences, or historical selective pressures from semi-domestication and/or sedentary life cycle in reindeer.

The canine hair cycle - a guide for the assessment of morphological and immunohistochemical criteria

The hair follicle has a lifelong capacity to cycle through recurrent phases of controlled growth (anagen), regression (catagen) and quiescence (telogen), each associated with specific morphological changes. A comprehensive classification scheme is available for mice to distinguish the cycle stages anagen I-VI, catagen I-VIII and telogen. For dogs, such a classification system does not exist, although alopecia associated with hair cycle arrest is common. We applied analogous morphological criteria and various staining techniques to subdivide the canine hair cycle stages to the same extent as has been done in mice. Of all the staining techniques applied, haematoxylin and eosin stain, Sacpic, Masson Fontana and immunohistochemistry for vimentin and laminin proved to be most useful. To evaluate the applicability of our criteria, we investigated skin biopsies from healthy beagle dogs (n=20; biopsies from shoulder and thigh) kept in controlled conditions. From each biopsy, at least 50 hair follicles were assessed. Statistical analysis revealed that 30% of the follicles were in anagen (12% early and 18% late), 8% in catagen (2% early, 5% late and 1% not determinable) and 27% in telogen. Thirty-five per cent of hair follicles could not be assigned to a specific cycle stage because not all follicles within one biopsy were oriented perfectly. In conclusion, this guide will not only be helpful for the investigation of alopecic disorders and possibly their pathogenesis, but may also serve as a basis for research projects in which the comparison of hair cycle stages is essential, e.g. comparative analysis of gene expression patterns.

Hair cortisol concentration as a noninvasive measure of long-term stress in free-ranging grizzly bears (Ursus arctos): considerations with implications for other wildlife

Human-caused landscape change negatively affects the sustainability of many wildlife populations. In Alberta, Canada, grizzly bears ( Ursus arctos L., 1758) live in one of the most populated and heavily exploited landscapes in which the species survives. Long-term physiological stress in individual animals may be the predominant mechanism linking landscape change with impaired wildlife population health. Hair cortisol concentration has been validated as a biomarker of long-term stress in humans and domestic animals; however, limited work has examined factors that may affect its measurement or interpretation. We have measured cortisol in as few as five guard hairs of a grizzly bear and have identified factors influencing hair cortisol concentration in this species. Hair cortisol varies with hair type, body region, and capture method. It is not influenced by colour, age, sex, environmental exposure (18 days), or prolonged laboratory storage (>1 year) and does not vary along the length of the hair shaft. Recommendations for prudent use of hair cortisol analysis in grizzly bears are discussed with implications for the development of hair cortisol concentration as a tool to monitor long-term stress in other wildlife.

Spaying-induced coat changes: the role of gonadotropins, GnRH and GnRH treatment on the hair cycle of female dogs

Although spaying can result in qualitative hair coat changes in dogs, the influence of spaying on the hair growth cycle has never been described. The study aims were to examine the effect of spaying and gonadotropin-releasing hormone (GnRH) treatment on canine hair coat, cycle stages of hair follicles, plasma gonadotropin concentrations and mRNA transcription of luteinizing hormone (LH) and GnRH receptors in hair follicles. Fifteen female dogs were examined before and 1 year after spaying and 24 spayed dogs before and after GnRH treatment. Spaying resulted in increased plasma gonadotropin concentrations and increased anagen : telogen ratio of hair follicles, but only 20% of the dogs developed coat changes. No differences were found in mRNA transcription of LH and GnRH receptors. GnRH treatment resulted in reduced plasma gonadotropin concentrations and improvement of coat changes in 79% of patients. This was associated with an increase in catagen hair follicles without changes in the anagen : telogen ratio. The present study demonstrated that spaying had an effect on the anagen : telogen ratio of hair follicles. Spaying-induced coat changes did not correlate with the anagen : telogen ratio. GnRH treatment reduced gonadotropin concentrations and reversed coat changes in some dogs, but had no effect on the hair growth cycle other than increasing the number of catagen hair follicles. A weak positive correlation between the plasma LH concentration and the anagen : telogen ratio was noted; however, our data did not suggest a direct receptor-mediated hormonal effect on the hair follicle. The present study did not identify the pathomechanism of spaying-induced coat changes.

Hair cycle in dogs with different hair types in a tropical region of Brazil

Hair cycle activity has been extensively studied in humans, sheep and laboratory animals, but there is a lack of information in dogs. Besides varying according to species, breed, sex and general health, hair growth is mainly affected by climatic variations. The aim of the study was to evaluate the follicle activity in three breeds of dogs with different hair types, in the city of Viçosa, Minas Gerais (latitude 20 degrees 45'S), Brazil. Twenty-one male dogs of boxer, labrador and schnauzer breeds were trichographically analysed monthly over 12 consecutive months. Hair percentage of telogen and anagen hairs at the different stages of the hair cycle in boxers and labradors was not significantly different, but both differed from the schnauzers. A significant correlation between hair follicle cycle and environmental temperature and photoperiod was noted in the boxers and labradors. In these breeds, a larger number of telogen hairs were observed during the hottest months of the year, and an increase in anagen hairs during the coldest months. The mean percentage of telogen hairs was 93, 90 and 55.3% for boxer, labrador and schnauzer, respectively.