Back to the Future: From Appendage Development Toward Future Human Hair Follicle Neogenesis.

Hair disorders such as alopecia and hirsutism often impact the social and psychological well-being of an individual. This also holds true for patients with severe burns who have lost their hair follicles (HFs). HFs stimulate proper wound healing and prevent scar formation; thus, HF research can benefit numerous patients. Although hair development and hair disorders are intensively studied, human HF development has not been fully elucidated. Research on human fetal material is often subject to restrictions, and thus development, disease, and wound healing studies remain largely dependent on time-consuming and costly animal studies. Although animal experiments have yielded considerable and useful information, it is increasingly recognized that significant differences exist between animal and human skin and that it is important to obtain meaningful human models. Human disease specific models could therefore play a key role in future therapy. To this end, hair organoids or hair-bearing skin-on-chip created from the patient's own cells can be used. To create such a complex 3D structure, knowledge of hair genesis, i.e., the early developmental process, is indispensable. Thus, uncovering the mechanisms underlying how HF progenitor cells within human fetal skin form hair buds and subsequently HFs is of interest. Organoid studies have shown that nearly all organs can be recapitulated as mini-organs by mimicking embryonic conditions and utilizing the relevant morphogens and extracellular matrix (ECM) proteins. Therefore, knowledge of the cellular and ECM proteins in the skin of human fetuses is critical to understand the evolution of epithelial tissues, including skin appendages. This review aims to provide an overview of our current understanding of the cellular changes occurring during human skin and HF development. We further discuss the potential implementation of this knowledge in establishing a human in vitro model of a full skin substitute containing hair follicles and the subsequent translation to clinical use.

Isolation, expansion and neural differentiation of stem cells from human plucked hair: a further step towards autologous nerve recovery.

Stem cells from the adult hair follicle bulge can differentiate into neurons and glia, which is advantageous for the development of an autologous cell-based therapy for neurological diseases. Consequently, bulge stem cells from plucked hair may increase opportunities for personalized neuroregenerative therapy. Hairs were plucked from the scalps of healthy donors, and the bulges were cultured without prior tissue treatment. Shortly after outgrowth from the bulge, cellular protein expression was established immunohistochemically. The doubling time was calculated upon expansion, and the viability of expanded, cryopreserved cells was assessed after shear stress. The neuroglial differentiation potential was assessed from cryopreserved cells. Shortly after outgrowth, the cells were immunopositive for nestin, SLUG, AP-2α and SOX9, and negative for SOX10. Each bulge yielded approximately 1 × 10(4) cells after three passages. Doubling time was 3.3 (±1.5) days. Cellular viability did not differ significantly from control cells after shear stress. The cells expressed class III ß-tubulin (TUBB3) and synapsin-1 after 3 weeks of neuronal differentiation. Glial differentiation yielded KROX20- and MPZ-immunopositive cells after 2 weeks. We demonstrated that human hair follicle bulge-derived stem cells can be cultivated easily, expanded efficiently and kept frozen until needed. After cryopreservation, the cells were viable and displayed both neuronal and glial differentiation potential.

Advances in hair transplantation: longitudinal partial follicular unit transplantation.

There are different techniques of hair transplantation. The most common and known hair transplantation methods are the 'strip' method, where a strip of skin containing hair follicles is removed, cut into grafts and implanted in the recipient area, and the follicle unit extraction (FUE) method, in which whole follicle units are extracted one by one and implanted one by one back into the recipient area. The FUE method is more patient friendly and leaves only tiny scars compared to the strip method, which leaves visible linear scars at the donor area. Both methods, however, have the major disadvantage that the extracted hair follicles are removed and the availability of donor hair follicles are limited and results in a decrease in hair density, as no re-grow will occur in the donor area. Since partial longitudinal-follicular unit transplantation (PL-FUT) extracts partial longitudinal follicular units that can be used as complete follicular units to regenerate completely differentiated hair growth and the partial follicular units that remain in the dermis in the donor area can survive and produce hair, PL-FUT enables us to multiply hair follicles in vivo while preserving the donor area. Although this technique is suitable for androgenic alopecia, PL-FUT could also be suitable in persons who have a relative small donor area compared to the recipient area like burn victims, as well as scarring alopecia's like frontal fibrosing alopecia.

The influence of preservation solution on the viability of grafts in hair transplantation surgery.

SUMMARY: Hair transplantation techniques have changed in the last decades. Partial longitudinal follicular unit transplantation is a new hair transplantation technique, which differs from all other hair transplantation techniques by the size of the graft and therefore much more vulnerable grafts compared to the conventional hair transplantation grafts. In this study, we reveal the influence of the preservation solution on the viability of the grafts. We have extracted 15 hair transplantation grafts of 0.6 mm and 15 hair transplantation grafts of 0.7 mm from 3 different patients and investigated the influence of 2 commercially available preservation media, saline solution (Braun, Melsungen, Germany) and Ringer's lactate (Braun), on the viability of grafts and compared these solutions with the preservation solution developed by Hair Science Institute with trypan blue. The grafts stored in the preservation solution developed by Hair Science Institute showed a significant better viability compared with the 2 commercially available preservation media saline solution and Ringer's lactate. This study shows that a preservation solution could influence the viability of the grafts which could be essential for hair transplantations with small grafts such as in partial longitudinal follicular unit transplantation.

[Therapeutic options for androgenetic alopecia]. / Therapeutische opties bij androgenetische alopecia.

Androgenetic alopecia (AGA) is the most common type of hair loss. There are different treatment possibilities for the prevention of and as a remedy for AGA. The broad spectrum of possibilities varies from doing nothing to hair transplantation. Treating AGA is difficult because it is a natural, ongoing and personal process. The progression of AGA can be slowed down by medication. If one desires a full head of hair and immediate results, however, a hairpiece could be an option. A permanent result is only attainable by hair transplantation. In terms of cost effectiveness over the short term (1 year) and intermediate term (10 years), medication is the best option. Hair transplantation, however, remains the best solution for a permanent result over the long term (more than 10 years). Given the advantages of partial longitudinal follicle unit transplantation (PL-FUT) in comparison with traditional hair transplantation techniques, our preferences go out to PL-FUT and medicinal treatment.

Improved hair restoration method for burns.

BACKGROUND: Extracted partial longitudinal follicular units can be used as complete follicular units to regenerate completely differentiated hair growth. The partial follicular units that remained in the dermis in the donor area can survive and produce hairs. This technique enables us to multiply hair follicles in vivo, while preserving the donor area and therefore is suitable in persons, who have a relative small donor area compared to the recipient area, as in scalp burns. OBJECTIVES: With this study, we try to determine if partial longitudinal follicular unit transplantation (PL-FUT) can be used for facial and/or scalp burns. MATERIALS AND METHODS: Four burn victims (age 22-39 years, mean 27.75 years) were treated in the face (eyebrows, and beard) and/or on the scalp with PL-FUT. The grafts were harvested with hollow wave-tipped needles with an inner diameter of 0.6mm from the occipital area of the scalp. The suitable longitudinal partial follicular units were impregnated with a preservative medium, and implanted into the recipient area. Hair growth in the donor area as well as the recipient area was observed before treatment, and at intervals of 1 week, 3 months and 1 year after the treatment. RESULTS: After evaluation of the donor area, sometimes a few little white spots were visible, but almost all hair follicles in the donor site re-produce hairs after 2 years. All treated patients had satisfactory or very satisfactory cosmetic results in the treated area. CONCLUSIONS: Longitudinal partial follicular unit transplantation (LP-FUT) may represent the first reliable patient-friendly method to generate two hair follicles from one hair follicle with consistent results and preservation of the donor area. Therefore, this method is very suitable for people with facial and/or scalp burns.

Donor hair follicle preservation by partial follicular unit extraction. A method to optimize hair transplantation.

BACKGROUND: There are different stem cell pools located in the hair follicle. OBJECTIVE: To try to determine whether follicular units can survive a partial extraction and whether this partial extracted follicular unit can regenerate new hairs. METHODS: From five individuals, between 100 and 150 grafts were harvested from the occipital area of the scalp. Suitable grafts were implanted into the recipient area. Hair growth and characteristics in the donor area and the recipient area were observed at different intervals. RESULTS: After 3 months, between 92.1% and 104.1% (mean 97.7%) of the partial follicular units in the donor sites survived and produced hairs with the same characteristics. After 1 year, 91.1­101.7% (mean 95.9%) of the implanted partial follicular units regenerated hair growth with the same characteristics as the hairs in the donor area. CONCLUSIONS: We revealed that extracted partial longitudinal follicular units transplanted to the recipient area can be used as complete follicular units to regenerate completely differentiated hair growth with the same characteristics as in the donor area. We also revealed that the partial follicular units in the donor area can survive and produce the same number of hairs with the same characteristics. This technique enables us to generate two hair follicles from one follicle with consistent results and preserve the donor area.