Hair Follicle Plasticity with Complemented Immune-modulation Following Follicular Unit Extraction

Abstract

Background: During hair transplantation as an effective therapy for androgenetic alopecia, hair follicles were typically trans-located from the nonaffected occipital to the balding frontal or vertex region of the scalp. Although this is an autologous intervention, the donor and recipient hair follicle tissue differ in composition and local environment.

Settings and design: In two case studies, we investigated the changes in hair follicle morphology and the immune status of scalp and body hair follicles from different origins transplanted to the eyebrows and the frontal scalp using follicular unit extraction.

Results: Quantitative histomorphometry and immunohistochemistry revealed a transformation in hair follicle length and dermal papilla size of the scalp, chest and beard hair follicles, which had been re-extracted after a 6-month period posttransplantation. Furthermore, a significant infiltration of B and T lymphocytes as well as macrophages could be observed most prominently in the infundibulum of transplanted hair follicles.

Conclusion: The presented results demonstrate that hair follicle units from different body sites are capable to replace miniaturized or degraded hair follicles in different recipient areas like scalp or eyebrows as they keep their intrinsic capability or acquire the potential to readjust plastically within the beneficiary skin region. The essential secretory crosstalk underlying the observed tissue remodeling is possibly mediated by the infiltrating immune cells.

Keywords: Dermal papilla; hair follicle plasticity; hair transplantation; intermittent follicular unit extraction.

Figure 1

Recipient area of transplanted body, beard and scalp hair follicles. Beard, chest and scalp hair follicles were transplanted into defined areas of the frontal region of the scalp (a and b). (a) Is showing the occipital view of the scalp before and (b) after follicular unit extraction transplantation of differentially originated hair follicle units. Recipient sites for autologous beard (red), chest (white) and scalp (yellow) hair follicle units are highlighted, respectively. (c) Photograph of patient two who received beard hair follicle transplantation. After 6 months, selected hair follicles were extracted from defined sites of transplantation area for further investigations

Figure 2

Native beard, chest and scalp hair follicles have different morphological features that are characteristic for the body site they are derived from. The morphology of grafted hair follicles is changing independently on the follicles' former site of origin. (a) Photomicrographs showing the comparison of the measured follicle lengths of native beard, chest and scalp hair follicles. Dashed arrows demarcates lengthdetermination. (b and c) Quantification of the measured follicle length of native and transplanted hair follicles from different body sites to the scalp (b) and eyebrows (c). (d) Representative microscopic images showing hair bulbs of native beard, chest and scalp hair follicles with analyzed DP cross-section area highlighted by dashed lines. (e and f) DP sizes of native and transplanted hair follicles from different body sites to the scalp (e) and eyebrows (f) as determined by measuring the maximum area of longitudinal DP cross-sections. Scale bars indicate 100 μm (a) or 200 μm (d), respectively. DP: Dermal papilla

Figure 3

Quantification of immune cells in native and transplanted hair follicles. B and T lymphocytes as well as macrophages are differently distributed in native and grafted hair follicles as determined by area measurement of CD3⁺, CD20⁺ and CD68⁺ regions. Quantification of B cells (a), T cells (c) and macrophages (e) in native and transplanted hair follicles from different body sites with the scalp as the recipient site for the grafts. Quantification of B cells (b) and T cells (d) in native and transplanted beard hair follicles with the eyebrows as the recipient site for the grafts

Figure 4

Immunohistological staining reveals a massive infiltration of immune cells preferentially in the infundibulum of grafted hair follicles. Prominent staining for CD3⁺, CD20⁺ and CD68⁺ cells is more widespread in grafted hair follicles compared to controls. (a‑c) Representative photographs of native scalp hair follicles stained for CD20 (B cells), CD3 (T cells) and CD68 (macrophages). Positively stained regions are marked by arrows and scale bars indicate 200 μm in (a-c) and 150 μm in (d-f), respectively