Epidermis (botany)

About: Epidermis (botany) is a research topic. Over the lifetime, 7254 publications have been published within this topic receiving 308153 citations.

Production and auto-induction of transforming growth factor-alpha in human keratinocytes.

Abstract: Transforming growth factor-alpha (TGF-alpha) is a polypeptide which is structurally related to epidermal growth factor (EGF) and binds to the EGF receptor TGF-alpha synthesis occurs in a variety of neoplastic cells and during early fetal development but has not been reported in normal cells of the adult organisms TGF-alpha has therefore been regarded as an embryonic growth factor which is inappropriately expressed during neoplasia Here we report that primary cultures of normal human keratinocytes synthesize TGF-alpha Furthermore, we show that addition of EGF or TGF-alpha to these cultures induces TGF-alpha gene expression, suggesting that a mechanism of auto-induction exists Analysis of normal skin biopsies using in situ hybridization and immunohistochemistry demonstrates the in vivo presence of TGF-alpha messenger RNA and protein in the stratified epidermis

A single type of progenitor cell maintains normal epidermis

Abstract: According to the current model of adult epidermal homeostasis, skin tissue is maintained by two discrete populations of progenitor cells: self-renewing stem cells; and their progeny, known as transit amplifying cells, which differentiate after several rounds of cell division. By making use of inducible genetic labelling, we have tracked the fate of a representative sample of progenitor cells in mouse tail epidermis at single-cell resolution in vivo at time intervals up to one year. Here we show that clone-size distributions are consistent with a new model of homeostasis involving only one type of progenitor cell. These cells are found to undergo both symmetric and asymmetric division at rates that ensure epidermal homeostasis. The results raise important questions about the potential role of stem cells on tissue maintenance in vivo.

IL-34 is a tissue-restricted ligand of CSF1R required for the development of Langerhans cells and microglia

Abstract: The differentiation of bone marrow-derived progenitor cells into monocytes, tissue macrophages and some dendritic cell (DC) subtypes requires the growth factor CSF1 and its receptor, CSF1R. Langerhans cells (LCs) and microglia develop from embryonic myeloid precursor cells that populate the epidermis and central nervous system (CNS) before birth. Notably, LCs and microglia are present in CSF1-deficient mice but absent from CSF1R-deficient mice. Here we investigated whether an alternative CSF1R ligand, interleukin 34 (IL-34), is responsible for this discrepancy. Through the use of IL-34-deficient (Il34(LacZ/LacZ)) reporter mice, we found that keratinocytes and neurons were the main sources of IL-34. Il34(LacZ/LacZ) mice selectively lacked LCs and microglia and responded poorly to skin antigens and viral infection of the CNS. Thus, IL-34 specifically directs the differentiation of myeloid cells in the skin epidermis and CNS.

Epidermal stem cells of the skin.

Abstract: The skin constantly renews itself throughout adult life, and the hair follicle undergoes a perpetual cycle of growth and degeneration. Stem cells (SCs) residing in the epidermis and hair follicle ensure the maintenance of adult skin homeostasis and hair regeneration, but they also participate in the repair of the epidermis after injuries. We summarize here the current knowledge of epidermal SCs of the adult skin. We discuss their fundamental characteristics, the methods recently designed to isolate these cells, the genes preferentially expressed in the multipotent SC niche, and the signaling pathways involved in SC niche formation, SC maintenance, and activation. Finally, we speculate on how the deregulation of these pathways may lead to cancer formation.