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

Abstract

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. Conflict of interests:The authors declare no conflict of interests.

Analysis of cortisol in dog hair - a potential biomarker of chronic stress: a review

“…Moreover, even if hair sampling may require capture or handling in certain cases, the stress potentially experienced during this event will not affect glucocorticoid concentration in the collected hair . Whereas in humans the average rate of hair growth is approximately 1 cm per month (Wennig 2000), in dogs, the normal hair growth rate depends on a number of internal and external factors, e.g., seasonal variations or body region (Muntener et al 2011). The rate of hair growth varies not only between individual dogs but also between different regions in the same dog.…”

Evaluation of Effectiveness in a Novel Wound Healing Ointment-Crocodile Oil Burn Ointment

“…The skin performs many physiological functions in the body, such as, protection, sensation, heat regulation, control of evaporation, absorption, water resistance, and so on (Madison, 2003, Proksch et al, 2008, Stucker et al, 2002. The hair follicle is a fascinating miniorgan with a complex structure, which plays an importance role in the physiological functions of the skin (Muntener et al, 2011). Wound healing is a highly regulated process that is thought to be mediated in part by stem cells (Ito et al, 2005, Levy et al, 2005), while hair follicles are the niche of various stem cell populations and are a major source of cells responsible for regeneration of the hair, sebaceous glands and epidermis (Joachimiak et al, 2012).…”

Clinical and Histologic Description of Lykoi Cat Hair Coat and Skin

“…Lykoi cats did, however, exhibit hair follicle dysplasia not seen in canine pattern baldness. A recent study on the canine hair follicle cycle suggests that the most easily visible and important feature to determine hair cycle stage is the absolute position of the dermal papilla in the dermis or subcutaneous fat 19) . Though this information has not been applied to cats, feline hair cycle stages may behave similarly to those of the canine.…”