Skin plays a major role in wound healing, and reepithelialization is a crucial step. Hair-covered areas recover from skin injury sooner than do hairless areas. Studies have shown that reepithelialization spreads from the hair-follicle infundibulum, suggesting that hair follicles are important for regenerating interfollicular skin. The hair follicle bulge area is part of the outer root sheath, and recent studies have found that these cells contain keratin 15-positive keratinocytes with characteristics of epithelial stem cells. In this study, bulge-enriched keratinocytes were isolated from hair follicles, and this population of cells in vitro formed interfollicular epidermis within 2 weeks.

This is valuable translational research. Repair of major epithelial defects is limited by what is possible using skin grafts and other similar techniques. That cells harvested from the bulge area of the hair follicle can be grown in the laboratory and that they differentiate into interfollicular epidermis follicles may make surgery possible on areas where skin closure is problematic. This is a promising study for canine skin regeneration.—Karen Moriello, DVM, DACVD

Epidermal structure created by canine hair follicle keratinocytes enriched with bulge cells in a three-dimensional skin equivalent model in vitro: Implications for regenerative therapy of canine epidermis. Kobayashi T, Enomoto K, Wang YH, et al. VET DERMATOL 24:77-e20, 2013.