Developing stratified epithelia: lessons from the epidermis and thymus

Abstract

Stratified squamous epithelial cells are found in a number of organs, including the skin epidermis and the thymus. The progenitor cells of the developing epidermis form a multilayered epithelium and appendages, like the hair follicle, to generate an essential barrier to protect against water loss and invasion of foreign pathogens. In contrast, the thymic epithelium forms a three-dimensional mesh of keratinocytes that are essential for positive and negative selection of self-restricted T cells. While these distinct stratified epithelial tissues derive from distinct embryonic germ layers, both tissues instruct immunity, and the epithelial differentiation programs and molecular mechanisms that control their development are remarkably similar. In this review, we aim to highlight some of the similarities between the thymus and the skin epidermis and its appendages during developmental specification.

Chitosan-shelled oxygen-loaded nanodroplets abrogate hypoxia dysregulation of human keratinocyte gelatinases and inhibitors: New insights for chronic wound healing

“…The epidermis is a stratified squamous epithelium consisting of several cell types, including Langerhans cells, melanocytes, and keratinocytes, that provide a physical barrier to protect the organism from external agents and pathogens, and to limit fluid loss (Roberts and Horsley, 2014). Highly specialised keratinocytes, by far the most abundant epidermal cell type, not only maintain the epidermis but also restore its integrity after injury (Pastar et al, 2014).…”

γδ T cells in homeostasis and host defence of epithelial barrier tissues

“…Epithelial tissues are comprised of a tight network of constantly renewing cells that line the body and effectively create a “wall” to the outside environment. In direct contact with the outside environment, the epithelia prevents water and nutrient loss while at the same time providing essential protection from physical damage and pathogen entry 3, 4 . Exposure to the outside environment also infers that the epithelium is in constant contact with the enormous amount of microbes that line our epithelial surfaces, collectively termed the microbiome.…”

Medullary thymic epithelial stem cells: role in thymic epithelial cell maintenance and thymic involution

“…The most typical stratified epithelial tissue is the skin epidermis. Interestingly, TECs show striking similarities to epidermis, including the expression of FoxN1 , delta‐like Notch ligands , and similar types of keratins . Additionally, some mTECs begin to express and upregulate characteristic molecules exhibited in mature keratinocytes such as involucrin, desmoglein3, and keratin 1 and 10 upon their terminal differentiation into keratinizing HBs .…”