Hair follicle: a novel source of multipotent stem cells for tissue engineering and regenerative medicine

Abstract

The adult body harbors powerful reservoirs of stem cells that enable tissue regeneration under homeostatic conditions or in response to disease or injury. The hair follicle (HF) is a readily accessible mini organ within the skin and contains stem cells from diverse developmental origins that were shown to have surprisingly broad differentiation potential. In this review, we discuss the biology of the HF with particular emphasis on the various stem cell populations residing within the tissue. We summarize the existing knowledge on putative HF stem cell markers, the differentiation potential, and technologies to isolate and expand distinct stem cell populations. We also discuss the potential of HF stem cells for drug and gene delivery, tissue engineering, and regenerative medicine. We propose that the abundance of stem cells with broad differentiation potential and the ease of accessibility makes the HF an ideal source of stem cells for gene and cell therapies.

FIG. 1.

Schematic drawing of hair follicle. DS, dermal sheath; ORS, outer root sheath; IRS, inner root sheath; DP, dermal papilla; SG, sebaceous gland; APM, arrector pilli muscle. The illustration is not drawn in scale. Color images available online at www.liebertpub.com/teb

FIG. 2.

Cells comprising the DS of hair follicle are positive for smooth muscle alpha-actin (ACTA2). (A) H&E staining from neonatal ovine dermis. (B) Immunohistochemistry showing ACTA2⁺ cells in the DS of hair follicles. Image taken from Ref. Color images available online at www.liebertpub.com/teb