Biofabrication technologies in hair neoformation

Introduction The hair follicle (HF) is an exclusive adnexal structure with important cosmetic and physiological value, embodying stem cells that contribute to skin homeostasis and response to injury. Therefore, sustaining de novo hair formation in damaged skin would be a clinical breakthrough both in the management of critical wounds and in irreversible hair disorders, such as common androgenetic alopecia. However, the complex nature of hair development—hierarchically controlled by multiple cellular compartments—implicates not only the use of appropriate cells but also advanced biotechnologies and instructive matrices capable of recreating the HF specific microarchitecture and biochemical profile. Methods This chapter starts by exploring the cellular and biomaterial elements commonly considered when bioengineering the HF. Next, we reviewed strategies previously used to elicit HF neoformation, from simpler cell-based approaches to the ones assisted by microfabrication technologies, closing with a discussion on future directions. Results Earlier efforts to stimulate HF neoformation have mostly attempted to re-establish epithelial and mesenchymal interactions and respective cellular organization, while disregarding the specific nature of the HF extracellular matrix (ECM) and remaining regulatory cells. Nevertheless, the use of microfabrication technologies to mimic the spatial organization of these compartments or most recently, to regenerate HFs within skin models denote increasing efforts towards the recapitulation of the HF 3D architecture and milieu. Conclusions Despite the ever-growing number of strategies and emergent biofabrication platforms arising from tissue engineering these have just started to be considered towards HF regeneration, holding the promise of providing innovative and clinically useful solutions to promote hair neoformation in patients.