What is keratinocyte hyperproliferation?
In physiological situations the proliferation of epidermal cells (keratinocytes) in the skin is a tightly controlled process. 2. However, in many common skin diseases, such as in psoriasis, the control mechanisms go awry resulting in pathological epidermal hyperplasia (thickening).
What is keratinocyte differentiation?
Cell differentiation. During this differentiation process, keratinocytes permanently withdraw from the cell cycle, initiate expression of epidermal differentiation markers, and move suprabasally as they become part of the stratum spinosum, stratum granulosum, and eventually corneocytes in the stratum corneum.
What is epidermal hyperproliferation?
Histologically, psoriatic epidermal hyperproliferation is characterized by an overrepresentation of basaloid keratinocytes5, abnormally thick epidermal layer, or acanthosis, and the persistence of cell nuclei into the upper cornified layer (parakeratosis).
What is the structure of a keratinocyte?
Inside the epidermis, keratinocytes are arranged in four different layers — the stratum basale, stratum spinosum, stratum granulosum, and stratum corneum. The stratum basale is the basal layer of the epidermis that covers the keratinocyte stem cells and differentiating keratinocytes.
What is the function of the Merkel cell?
A special type of cell found right below the epidermis (top layer of skin). These cells are very close to the nerve endings that receive the sensation of touch and may be involved in touch. The cells also contain substances that may act as hormones.
What is the function of keratinocyte?
As the most dominant cell type constituting the epidermis, keratinocytes play multiple roles essential for skin repair. They are the executors of the re-epithelialization process, whereby keratinocytes migrate, proliferate, and differentiate to restore the epidermal barrier.
What does Proliferation mean in biology?
An increase in the number of cells as a result of cell growth and cell division.
What happens during the process of Keratinization?
Keratinization refers to the cytoplasmic events that occur in the cytoplasm of epidermal keratinocytes during their terminal differentiation. It involves the formation of keratin polypeptides and their polymerization into keratin intermediate filaments (tonofilaments).
What is the life cycle of keratinocytes?
The keratinocyte is the predominant cell of the epidermis and accounts for 70 to 80% of the cellular population. Keratinocytes are programmed to undergo cell death, this process is known as apoptosis, with a life of around 8 to 10 days from mitosis to arriving in the stratum corneum, depending on age and environment.
How is the regulation of keratinocyte proliferation complex?
The regulation of keratinocyte proliferation is an extremely complex process, which depends on the availability of growth factors, degree of cell differentiation, and cell attachment to the substrate.
Which is a potent mitogen for keratinocyte migration?
In vitro, EGF, TGFα, amphiregulin, and HB-EGF are potent mitogens and factors enhancing keratinocyte migration.
Where are the keratinocytes located in the epidermis?
The epidermis consists of several layers of keratinocytes: the basal layer facing directly the basement membrane, spinous layer, granular layer, and the outermost stratum corneum.
What can replace TGFα in a keratinocyte?
In cultured keratinocytes, the activity of TGFα can be replaced by other growth factors, such as the keratinocyte growth factor (KGF) or insulin-like growth factor-I (IGF-I) ( Gniadecki 1997 ), but it is possible that these substances indirectly stimulate EGFR.