Hair follicle plasticity with complementary immunomodulation following follicular unit extraction

Int J Trichology. 2015 Jan-Mar;7(1):16-23. doi: 10.4103/0974-7753.153451.

Hair follicle transplantation was first performed by Orentreich in 1959, and its effectiveness rests on the principle of donor dominance: the donor skin graft dominates the recipient site and so keeps its donor characteristics there. In this paper, Azar et al. point to a previously overlooked influence of the recipient tissue on the donor follicle. The authors analysed follicles transplanted to the frontal area from three donor sites: the occiput, the beard and the chest. It is well known that right after transplantation hair follicles enter a dystrophic catagen phase, then telogen, before re-entering anagen. On this basis, the authors assumed that six months after transplantation the grafted follicles would have been in anagen for at least 2 months and that any immune reaction to the procedure would be gone. Six months after transplantation, they compared the grafted follicles with native ones. The dermal papilla size and the length of the transplanted follicles were significantly smaller than those of native follicles at the donor site. A large infiltrate of immune cells was also seen around the grafted follicles, which the authors believe may help regulate follicle size. The effect of dystrophic catagen on the follicle may be much greater than previously thought. Site-related changes may also reduce papilla size and follicle length after transplantation to the frontal scalp.