Biochemistry of epidermal stem cells

Abstract

Background The epidermis is an important protective barrier that is essential for maintenance of life. Maintaining this barrier requires continuous cell proliferation and differentiation. Moreover, these processes must be balanced to produce a normal epidermis. The stem cells of the epidermis reside in specific locations in the basal epidermis, hair follicle and sebaceous glands and these cells are responsible for replenishment of this tissue. Scope of review A great deal of effort has gone into identifying protein epitopes that mark stem cells, in identifying stem cell niche locations, and in understanding how stem cell populations are related. We discuss these studies as they apply to understanding normal epidermal homeostasis and skin cancer. Major conclusions An assortment of stem cell markers have been identified that permit assignment of stem cells to specific regions of the epidermis, and progress has been made in understanding the role of these cells in normal epidermal homeostasis and in conditions of tissue stress. A key finding is the multiple stem cell populations exist in epidermis that give rise to different structures, and that multiple stem cell types may contribute to repair in damaged epidermis. General significance Understanding epidermal stem cell biology is likely to lead to important therapies for treating skin diseases and cancer, and will also contribute to our understanding of stem cells in other systems. This article is part of a Special Issue entitled Biochemistry of Stem Cells.

Stacking the DEK: From chromatin topology to cancer stem cells

“…2 An additional complicating factor is that several tissues, including intestine and skin, have multiple distinct stem cell populations that proliferate at different rates and in response to different environmental cues. 1,22,23 The cancer stem cell hypothesis postulates that tumor formation is initiated and advances due to aberrant stem-like cells, also referred to as tumor-initiating cells. The origin of cancer stem cells is still hotly debated, but there are two prevailing theories.…”

Kinetics of the maintenance of the epidermis

“…However, this subject is beyond the scope of this article.) Experimental studies of the epidermis are numerous [4]. Understanding the mechanisms that govern the maintenance of the epidermis is, however, still limited.…”

“…Stem cells are also available in hair follicles. Under normal physiological conditions, the former and latter stem cell populations seem to function independently [4]. During cutaneous wound healing, follicular stem cells appear to play an important role in skin regeneration [5].…”

“…One of the general concepts in this field is that the maintenance and stability of biological systems is often based on negative feedback loops. In order to clarify the principles that govern the function of a biological system, generic kinetic models offer Stem cells are also found in the hair follicles (not shown), but while they have the potential to generate epidermis in circumstances such as wounding, they do not appear to contribute to maintaining normal epidermis [4]. a method to describe the interplay between corresponding subsystems.…”

“…From these general perspectives, we focus our present work on the skin epidermis. The epidermis is a self-renewing tissue between 0.05 and 1.5 mm thick that helps living organisms to avoid infection by pathogens, repel chemical and physical assaults, and prevent unregulated loss of water and solutes [4]. Structurally, the epidermis can be divided into four layers including, in respective order: (i) the basal monolayer containing stem and partially differentiated cells; [(ii) and (iii)] the spinous and granular layers composed of differentiated cells; and (iv) the cornified layer of dead cells (Fig.…”