A simple hair transplantation model to investigate follicular cells and their interaction with surrounding skin.

Abstract

INTRODUCTION: Hair follicle cells contribute to wound healing, skin circulation, and skin diseases and hair transplantation is a useful technique to study the participation of hair follicle cells in skin homeostasis and wound healing. BACKGROUND: Although hair follicle transplantation is a well-established human hair restoration procedure, follicular transplantation techniques in animals have not been well described or optimized. METHOD: Vibrissae from GFP transgenic mice were harvested, micro-dissected and implanted individually into needle hole incisions in the back skin of immune-deficient nude mice. Grafts were evaluated histologically and the growth of transplanted vibrissae was observed. Migration of GFP positive cells from transplanted follicles into the inter-follicular epidermis was investigated by histological examination in animals without a wound (5 animals) and animals with an incisional wound (2 animals). RESULTS: Transplanted follicles cycled spontaneously. Ninety percent of grafted vibrissae produced a hair shaft at 6 weeks. after pluck-induced follicle cycling, growth rates were equivalent of ungrafted vibrissae. Histology examination after 6 weeks showed that transplanted follicle were innervated and connected to the host circulation system. All observed GFP-positive cells stayed in the hair follicles and had not moved into the surrounding tissue. In animals receiving an incisional would however, histology examination on day 4 showed that GFP positive cells had migrated into the inter-follicular epidermis. CONCLUSION: Established follicular vibrissae transplantation method has several advantages over current protocols for animals hair transplantation. Vibrissae are easier to micro-dissect and transplant than pelage follicles and once transplanted, are readily distinguished from host pelage hair. This facilitates measurement of hair growth. Flip-side hair follicle micro-dissection precisely separates the donor follicular tissue from inter-follicular tissue and donor cells remain confined to hair follicles. This makes it possible to investigate hair follicle epithelial cell migration during wound re-epithelialization and differentiate migrating hair follicle cells from inter-follicular epidermis in linage tracing wound experiments using genetically labelled donor follicles.