Preliminary study on reconstruction of hair follicle by cell mass of dermal papilla cells and bulge stem cells

The study aimed to determine the proliferation and collagen synthesis of human dermal hair papilla cells. It found that cell proliferation had a high phase on the 11th day in basal culture medium and two high phases on the 5th and 11th days in routine culture medium. Collagen synthesis did not differ among dermal hair papilla cells, dermal sheath cells, and fibroblasts, but the collagen amount was higher in fibroblast medium. This suggested different functions for these cells. The study concluded that routine culture medium was effective for cell growth and proliferation, and that dermal hair papilla and sheath cells had a lower collagen secretion ability compared to fibroblasts.

The study explored the role of dermal papillae in hair growth using in vitro cultures. It was found that outer root sheath cells (ORSCs) grew more actively when cultured with dermal papillae, suggesting the presence of papilla-derived factors that stimulate ORSC growth. Additionally, epithelial cells from the bulb matrix grew towards implanted dermal papillae, indicating that dermal papillae might produce factors that attract these cells. When the dermal papilla remained attached to the hair bulb matrix, hair and follicle elongation continued for over a week. However, detachment or damage to the papilla-matrix junction suppressed hair and follicle growth, highlighting the importance of this attachment for normal development.

The study investigated the co-culture of human hair follicles and dermal papillae in a collagen matrix. It was found that when hair follicles were cultured alone, outer root sheath cells formed spike-like structures. However, when dermal papillae were present, these spikes grew more rapidly and elongated towards the papillae, suggesting that dermal papilla cells produce factors that enhance and attract follicular epithelial cell growth. In whole excised follicles, normal hair shaft and follicle elongation occurred when the dermal papilla remained attached to the hair bulb matrix. Conversely, when detached, epithelial cells proliferated to form hair follicle-like structures. This model was considered useful for studying the interaction between follicular epithelial cells and dermal papillae, as well as hair and follicle growth in vitro.

The study explored the isolation and culture of cells from the dermal papillae of human hair follicles, highlighting their role in hair follicle development and growth. Human papilla cells exhibited unique in vitro behaviors, forming multilayered aggregates on collagen gels. Beard follicle cells grew faster than scalp follicle cells, with doubling times of 40 hours and 70-80 hours, respectively, unaffected by testosterone. These cells synthesized an extracellular matrix and released IGF-1, though its in vivo relevance was unclear. While human papilla cells did not induce hair growth in vitro, rat vibrissa cells did when implanted in animals, suggesting potential for future research in hair biology using cell culture models.