Human nail stem cells are retained but hypofunctional during aging

Jia Shi,Zhengtao Lv,Changyu Liu,Hao Kang,Ranyue Ren,Ziyang Zhang,Weiwei Lu,Mingbo Nie,Guoxiang Zhang,Yong Tian,Long Li

doi:10.1007/s10735-018-9769-0

Jia Shi, Zhengtao Lv + Show 9 more

Open Access

https://doi.org/10.1007/s10735-018-9769-0

Copy DOI

Abstract

The nail is a continuous skin appendage. Cells located around the nails, which display coordinated homeostatic dynamics and release a flow of stem cells in response to regeneration, have been identified in mice. However, very few studies regarding human nail stem cells exist in the literature. Using specimens isolated from humans, we detected an unreported population of cells within the basal layer of postnatal human nail proximal folds (NPFs) and the nail matrix around the nail root. These cells were multi-expressing and expressed stem cell markers, such as keratin 15 (K15), keratin 14 (K14), keratin 19 (K19), CD29, CD34, and leucine-rich repeat-containing G protein-coupled receptor 6 (Lgr6). These cells were very similar to mouse nail stem cells in terms of cell marker expression and their location within the nail. We also found that the putative nail stem cells maintained their abundance with advancing age, but cell proliferation and nail growth rate were decreased on comparison of young and aged specimens. To summarize, we found a putative population of stem cells in postnatal human nails located at NPFs and the nail matrix. These cells may have potential for cell differentiation and be capable of responding to injury, and were retained, but may be hypofunctional during aging.

Highlights

The nail is the largest and most complex appendage of the skin in the human body
To locate and identify human nail stem cells, we used extracorporeal specimens from children with polydactyly and severed fingers from adults with trauma leading to amputation (Fig. 1a)
We observed strong keratin 15 (K15) expression (Fig. 1c–f), which was apparent in epidermal, sweat gland and hair follicle stem cells (Bose et al 2013; Leung et al 2013; Takeo et al 2013)

Summary

Introduction

The nail is the largest and most complex appendage of the skin in the human body. Skin, constituting the largest organ in our body, functions to defend against external threats, excrete waste from the body, and maintain body temperature (Johansen 2017). Skin and its appendages are in a process of permanent regeneration. Epidermal resident stem cells are found in the outermost layer of mammalian skin. These stem cells are responsible for continuous self-renewal, which sustains tissue homeostasis. There is a point in skin turnover where epidermal cells are found in the basal cell layer, forming epidermal proliferative units (Mackenzie 1970, 1997). Li et al isolated and purified epidermal stem cells from neonatal foreskin through enzymatic digestion and identified specific epidermal stem cell

Methods

Results

Conclusion