In vitro models to study hair follicle generation

Until Philpott and colleagues managed to grow human hair in vitro for the first time in 1990, human hair follicle (HF) research was limited to histological analysis of HF sections or complex human skin transplantation experiments onto immunocompromised mice. This breakthrough offered new opportunities to testing the effect of growth factors, hormones, or drugs on HF growth and also provided insights into hair growth disorders including alopecia areata or androgenic alopecia. Despite 25 years of ex vivo culture of human HFs and extensive research in vitro and in animal models, de novo organogenesis in vitro has remained an unattainable goal, the major reason being inability to maintain the hair-inductive properties of dermal papilla (DP) cells in culture. Only recently, novel approaches in passaging DP cells in three-dimensional culture systems allowed the formation of HF-like structures in vitro, thereby revolutionizing skin tissue engineering and providing hope for patients with alopecia or suffering from severe burns.