Tissue Engineering and Regeneration of the Human Hair Follicle in Androgenetic Alopecia: Literature Review

Abstract

Androgenetic alopecia (AGA) is an androgen-dependent process and represents the most frequent non-scarring alopecia. Treatments for AGA do not always achieve a satisfactory result for the patient, and sometimes cause side effects that lead to discontinuation of treatment. AGA therapeutics currently includes topical and oral drugs, as well as follicular unit micro-transplantation techniques. Tissue engineering (TE) is postulated as one of the possible future solutions to the problem and aims to develop fully functional hair follicles that maintain their cyclic rhythm in a physiological manner. However, despite its great potential, reconstitution of fully functional hair follicles is still a challenge to overcome and the knowledge gained of the key processes in hair follicle morphogenesis and biology has not yet been translated into effective replacement therapies in clinical practice. To achieve this, it is necessary to research and develop new approaches, techniques and biomaterials. In this review, present and emerging hair follicle bioengineering strategies are evaluated. The current problems of these bioengineering techniques are discussed, as well as the advantages and disadvantages, and the future prospects for the field of TE and successful hair follicle regeneration.

Application of Cell-Derived Extracellular Vesicles and Engineered Nanovesicles for Hair Growth: From Mechanisms to Therapeutics

“…Many researchers have cultured and studied DP cells (DPCs) to use for hair growth or generation of HFs. Researchers have shown that a hair structure can be created from stem cells and mice DPCs; however, this was unsuccessful in humans because of the loss of trichogenic ability and the poor functionality of the cultured human DPCs ( Ji et al, 2021 ; Llamas-Molina et al, 2022 ).…”

Treatment of androgenetic alopecia by exosomes secreted from hair papilla cells and the intervention effect of LTF

“…Exosomes are tiny particles containing cytoplasmic components that are released by cells during cell growth and cell membrane fission 21 and are an important component of paracrine signaling. They regulate the biological activity of recipient cells and mediate intercellular communication, allowing cells to grow and communicate through proteins, nucleic acids, and lipids that carry 22 . It was found that in vitro induction induced proliferation and migration of human dermal papilla cells and secretion of VEGF and IGF‐1 23 .…”

“…They regulate the biological activity of recipient cells and mediate intercellular communication, allowing cells to grow and communicate through proteins, nucleic acids, and lipids that carry. 22 It was found that in vitro induction induced proliferation and migration of human dermal papilla cells and secretion of VEGF and IGF-1. 23 Exosomes of hypoxia-pretreated adipose mesenchymal stem cells (ADSCs)…”

Skin‐on‐a‐chip strategies for human hair follicle regeneration

“…The anagen stage begins with the development of HF, in which lower HF filaments are formed with the proliferation of secondary germ cells in the hair bulge 45,46 . In the human scalp, anagen lasts 1–6 years and involves complete regeneration of the circulating portion of the HF 47 . Melanocyte stem cells swell during anagen and are activated together with HFSCs to generate pigment granules and mature melanocytes that are distributed to adjacent differentiated cells to form coloured hair fibres 48 .…”

“…45,46 In the human scalp, anagen lasts 1-6 years and involves complete regeneration of the circulating portion of the HF. 47 Melanocyte stem cells swell during anagen and are activated together with HFSCs to generate pigment granules and mature melanocytes that are distributed to adjacent differentiated cells to form coloured hair fibres. 48 Catagen can persist for 4-6 weeks, during which keratinocytes and melanocytes undergo apoptosis, while DP migrates upwards undamaged until they are placed next to stem cells in the hair bulge.…”