Hirsutism Induced by Facial Autologous Fat Grafting

Autologous adipose tissue injection in the treatment of alopecia: A mini-review

BACKGROUND

Alopecia may decrease patients' quality of life and self-confidence by limiting their social life. Therefore, the main goal of the treatment is to limit or halt the progression of inflammation, scarring, and hair loss. The promising effect of fat injection on hair regrowth, limited adverse effects, and subsiding inflammation can be proof of its efficacy and safety in treating alopecia.

AIMS

This review sought to assess the role of autologous fat tissue injection in scarring and non-scarring alopecia.

METHODS

Accordingly, a thorough search was performed on the Web of Science, Scopus, and PubMed/Medline databases, as well as the Google Scholar search engine, for studies published from inception until September 1st, 2023, using the related keywords.

RESULTS

Autologous fat grafting (AFG) is a novel and potentially effective modality for treating alopecia, particularly primary and secondary cicatricial alopecia. AFG can be an effective semi-invasive option for treating refractory lichen planopilaris because it induces angiogenesis, which supports hair regrowth. In addition to cicatricial alopecia, AFG held promise for treating non-scarring alopecia, including androgenic alopecia and alopecia areata. The adipose-derived regenerative cells (ADRCs) in adipose tissue (AT) secrete different growth factors, further supporting hair regeneration. Moreover, different anti-inflammatory and anti-oxidative agents are known in AT, preventing further damage to hair follicles.

CONCLUSIONS

AFG can significantly control inflammatory processes, improve signs and symptoms, and increase hair density and diameter.

What Do We Know About Hair Growth Induced by Wounding and Its Therapeutic Applications?

BACKGROUND

Many studies have reported the role of hair follicles (HFs) in the wound healing response, and vice versa, the creation of superficial injuries may stimulate hair growth, which has encouraged new treatments for hair loss.

OBJECTIVE

To review the phenomenon of wound-induced hair growth and the usefulness of therapeutic procedures based on skin wounding in androgenetic alopecia (AGA).

METHODS

A literature search was conducted to review cases of localized hypertrichosis induced by wounds and the role of microneedling, fractional laser, and scalp threading as monotherapy for AGA.

RESULTS

Localized hypertrichosis has been extensively reported after bone fractures, burn injury, chronic venous ulcer, etc. Only 2 cases of wound-induced hair neogenesis in humans have been reported. As monotherapy for AGA, 1 of 3 studies of microneedling, 4 of 6 of fractional lasers, and 2 of 3 studies of scalp threading show good efficacy.

CONCLUSION

Certain types of wounds seem to stimulate localized hair growth in humans, but the underlying mechanism is unclear. Reports on wound-induced HF neogenesis in humans are anecdotal and questions remain as to whether this is a true phenomenon in humans. Further clinical studies are needed before recommending wound-induced hair growth procedures as therapies for AGA.

Effective and economical cell therapy for hair regeneration

We reviewed and summarized the latest reports on the characteristics of stem cells and follicular cells that are under development for hair loss treatment. Compared with conventional medicine, cell therapy could be effective in the long term with a single treatment while having mild adverse effects. Adipose-derived stem cells (ASCs) have the advantages of easy access and large isolation amount compared with dermal papilla cells (DPCs) and dermal sheath cup cells (DSCs), and promote hair growth through the paracrine effect. ASCs have a poor potential in hair neogenesis, therefore, methods to enhance trichogenecity of ASCs should be developed. DSCs can be isolated from the peribulbar dermal sheath cup, while having immune tolerance, and hair inductivity. Therefore, DSCs were first developed and finished the phase II clinical trial; however, the hair growth was not satisfactory. Considering that a single injection of DSCs is effective for at least 9 months in the clinical setting, they can be an alternative therapy for hair regeneration. Though DPCs are not yet studied in clinical trials, we should pay attention to DPCs, as hair loss is associated with gradual reduction of DPCs and DP cell numbers fluctuate over the hair cycle. DPCs could make new hair follicles with epidermal cells, and have an immunomodulatory function to enable allogeneic transplantation. In addition, we can expand large quantities of DPCs with hair inductivity using spheroid culture, hypoxia condition, and growth factor supplement. 'Off-the-shelf' DPC therapy could be effective and economical, and therefore promising for hair regeneration.

Dermal Adipose Tissue Secretes HGF to Promote Human Hair Growth and Pigmentation

Hair follicles (HFs) are immersed within dermal white adipose tissue (dWAT), yet human adipocyte‒HF communication remains unexplored. Therefore, we investigated how perifollicular adipocytes affect the physiology of human anagen scalp HFs. Quantitative immunohistomorphometry, X-ray microcomputed tomography, and transmission electron microscopy showed that the number and size of perifollicular adipocytes declined during anagen‒catagen transition, whereas fluorescence-lifetime imaging revealed increased lipid oxidation in adipocytes surrounding the bulge and/or sub-bulge region. Ex vivo, dWAT tendentially promoted hair shaft production, and significantly stimulated hair matrix keratinocyte proliferation and HF pigmentation. Both dWAT pericytes and PREF1/DLK1⁺ adipocyte progenitors secreted HGF during human HF‒dWAT co-culture, for which the c-Met receptor was expressed in the hair matrix and dermal papilla. These effects were reproduced using recombinant HGF and abrogated by an HGF-neutralizing antibody. Laser-capture microdissection‒based microarray analysis of the hair matrix showed that dWAT-derived HGF upregulated keratin (K) genes (K27, K73, K75, K84, K86) and TCHH. Mechanistically, HGF stimulated Wnt/β-catenin activity in the human hair matrix (increased AXIN2, LEF1) by upregulating WNT6 and WNT10B, and inhibiting SFRP1 in the dermal papilla. Our study demonstrates that dWAT regulates human hair growth and pigmentation through HGF secretion, and thus identifies dWAT and HGF as important novel molecular and cellular targets for therapeutic intervention in human hair growth and pigmentation disorders.

Deciphering the Emerging Roles of Adipocytes and Adipose-Derived Stem Cells in Fat Transplantation

Autologous fat transplantation is widely regarded as an increasingly popular method for augmentation or reshaping applications in soft tissue defects. Although the fat transplantation is of simple applicability, low donor site morbidity and excellent biocompatibility, the clinical unpredictability and high resorption rates of the fat grafts remain an inevitable problem. In the sites of fat transplantation, the most essential components are the adipocyte and adipose-derived stem cells (ADSCs). The survival of adipocytes is the direct factor determining fat retention. The efficacy of fat transplantation is reduced by fat absorption and fibrosis due to the inadequate blood flow, adipocyte apoptosis and fat necrosis. ADSCs, a heterogeneous mixture of cells in adipose tissue, are closely related to tissue survival. ADSCs exhibit the ability of multilineage differentiation and remarkable paracrine activity, which is crucial for graft survival. This article will review the recent existing research on the mechanisms of adipocytes and ADSCs in fat transplantation, especially including adipocyte apoptosis, mature adipocyte dedifferentiation, adipocyte browning, ADSCs adipogenic differentiation and ADSCs angiogenesis. The in-depth understanding of the survival mechanism will be extremely valuable for achieving the desired filling effects.