Induction of hair follicle regeneration in rat ear by microencapsulated human hair dermal papilla cells

Objective: To induce hair follicle regeneration in rat ear by microencapsulated dermal papillae (DP) cells. Methods: Intact dermal papillae were obtained from human scalp follicles which were digested with collagenase I. The human hair DP cells were encapsulated with alginate-polylysine-alginate (APA) by a high-voltage electric field droplet generator. The diameters of the DP cell microcapsules were optimized by regulating the voltage, the distance between the needle head and the solution surface and the injection speed. Then DP cell microencapsulations were xenotransplanted into ears of 20 SD rats with a novel method. One rat was killed every week at the postoperative 2-12 weeks and the implantation sites were biopsied for histological observation. Results: The DP cell microencapsulations were found in a group of round, smooth and transparent microcapsules under a phase-contrast microscope. The optimal combination of parameters to obtain 0.4 mm DP cell microcapsules was voltage 7.0 kV, injection speed 55 mm/h, and distance 10 mm. After 4-12 weeks, 18 of 20 DP cell microcapsule implantations had produced high-density hair. Histological observation indicated that both large follicles and sebaceous gland structures were formed in the rat ear within 3-12 weeks. Conclusions: These findings show that the DP cell microencapsulation maintain the capacity for initiating the follicle regeneration and can be considered as a substitute for fresh isolated dermal papillae.