Name: epidermal cell turnover and repair
Uploaded: 2023-04-30T12:09:25.000Z
Duration: 1 min 12 s
Channel: JoVE

The epidermis is the outermost protective cover of the human body.&#160; It constantly renews itself through the differentiation of epidermal stem cells or EpiSCs located in the basal layer.
EpiSCs express integrins that bind to the underlying basement membrane. The EpiSCs-basement membrane interactions regulate the proliferation and differentiation of EpiSCs.
EpiSCs self-renew and sequentially differentiate to form a multi-layered epidermis consisting of spinous cells, granular cells, and dead keratinized squames.
Two models are used to explain EpiSC differentiation.
In the hierarchical model, EpiSCs divide asymmetrically to form a proliferative daughter cell and a transit-amplifying or TA cell. The TA cells further differentiate into different epidermal cell types.&#160;
In the stochastic model, each of the daughter cells will randomly either remain proliferative or form differentiated epidermal cells.

renewal of skin epidermal stem cells

Renewal of Skin Epidermal Stem Cells

The skin is divided into epidermis, dermis, and hypodermis, the skin&#39;s outermost, middle, and inner layers. The human epidermal layer regularly undergoes renewal, where old, dead cells are replaced by new cells. Epidermal stem cells or EpiSCs divide and differentiate to restore the lost cells. For the renewal process, some EpiSCs continuously self-renew. In contrast, few others differentiate into transit-amplifying cells, which later form prickle or spinous cells, followed by granular cells, and finally, dead keratinized squames, which are routinely shed off the skin.
Many factors should be controlled and regulated to sustain the renewal process. These include stem cell and transit-amplifying or TA cell division rate, the time a cell takes to leave the basal layer and differentiate, and finally, the removal of old and dead cells. As the cells begin to differentiate, they express different keratin molecules. The basal cells express keratin markers K5 and K14, spinous cells have K1 and K10, granular cells have profilaggrin and loricrin, while the keratinized cells express filaggrin. In case of wound or tissue damage, the epithelial keratinocytes migrate to the wound site and re-epithelialize the site.
The epidermal stem cells are attached to the basal layer through &#946;1-integrins expressed by stem cells. Integrins connect the actin filaments of the basal cells with the extracellular matrix.&#160; In addition to attachment, the integrins also play a role in signaling pathways. Other signaling pathways include Wnt, Hedgehog, Notch, BMP, and EGF, which are required to renew and maintain epidermal cells. Mutation in any of these pathways might cause skin cancer.

The skin is divided into epidermis, dermis, and hypodermis, the skin&#39;s outermost, middle, and inner layers. The human epidermal layer regularly ...

Education

JoVE Core

Cell Biology

Unit 1

Stem Cell Biology And Renewal in Epithelial Tissue

stem-cell-biology-and-renewal-in-epithelial-tissue

KEY TERMS AND CONCEPTS

epidermal cell turnover and repair

The epidermis, the outer layer of skin, is constantly renewed as old cells are replaced by new ones. Skin is organized into three layers: the epidermis, dermis, and hypodermis. In this process, epidermal stem cells, or EpiSCs, divide and make the cells needed to maintain the surface.

Some EpiSCs keep self-renewing so the stem cell pool stays active. Others become transit-amplifying, or TA, cells. These cells later form prickle or spinous cells, then granular cells, and finally dead keratinized squames that are shed from the skin.

This renewal depends on careful control of cell division, the time it takes cells to leave the basal layer, and the removal of old and dead cells. As cells differentiate, they also change the keratin proteins they express. Basal cells express K5 and K14, spinous cells express K1 and K10, granular cells express profilaggrin and loricrin, and keratinized cells express filaggrin.

The process also helps skin repair after injury. When tissue is damaged, epithelial keratinocytes migrate to the wound site and re-epithelialize it. Epidermal stem cells stay attached to the basal layer through β1-integrins, which connect actin filaments in basal cells to the extracellular matrix and also take part in signaling.

Several signaling pathways help renew and maintain epidermal cells. These include Wnt, Hedgehog, Notch, BMP, and EGF. If mutations disrupt any of these pathways, skin cancer may result.

Epidermal Cell Turnover and Repair

zygotic development and stem cell formation

zygotic-development-and-stem-cell-formation

From Zygote to Blastocyst Stem Cells

Zygote development shows how a fertilized egg becomes the first stages of a new organism. When sperm and egg fuse, they form a diploid zygote. A zygote is totipotent, which means it can develop into a complete organism. The zygote then divides by cleavage to form an 8-cell mass. At this stage, the cells are still spherical, loosely attached, and totipotent. Totipotent cells can form both embryonic tissues and extraembryonic tissues. As division continues, the cells reach the 64-cell stage...

source and potency of stem cells

Stem Cell Potency and Development

Stem cells are undifferentiated cells with strong self-renewal ability. They help keep cell populations stable during fetal and adult life. They can also specialize into the cell types of the human body. Their developmental potential varies, so they are grouped into five types: totipotent, pluripotent, multipotent, oligopotent, and unipotent. The fertilized egg, or zygote, is a totipotent stem cell. It can form both embryonic tissues and extraembryonic tissues. As the zygote divides again and...

stem cell niche

How Stem Cell Niches Control Cell Fate

Stem cell niches control how stem cells stay active, rest, or begin to specialize. A niche is the local microenvironment where stem cells live. In this setting, stem cells can remain undifferentiated, renew themselves, or become lineage-specific progenitor cells. Stem cells do not work alone in a niche. They sit next to stromal cells and connect with the extracellular matrix, or ECM, the support network outside the cells. Cell-to-cell and cell-to-matrix signals move through adhesion molecules...

renewal of intestinal stem cells

Intestinal Stem Cells and Gut Lining Repair

Intestinal stem cells help repair and replace the gut lining every 4 to 5 days. They sit at the base of the crypt, a gland at the bottom of each villus. From this niche, they divide asymmetrically to make one new stem cell and one progenitor daughter cell. The daughter cells are called transit-amplifying, or TA, cells. They move upward through the crypt and then mature into absorptive cells or secretory cells. The secretory group includes goblet cells, enteroendocrine cells, and Paneth cells. <br...

role of ephrin-eph signalling in intestinal stem cell renewal

role-of-ephrin-eph-signalling-in-intestinal-stem-cell-renewal

Ephrin-Eph Signalling in Gut Cell Positioning

Ephrin-Eph signalling helps intestinal cells stay in the right place as the gut lining renews itself. Eph receptors and their Ephrin ligands were first found in a human carcinoma cell line, which is how they got their names. This signalling system is also important in the immune system because it supports immune cell migration, adhesion, and activation. Eph receptors are grouped into two classes, EphA and EphB. Ephrins are also divided into two groups, EphrinA and EphrinB. EphrinA ligands...

role of notch signalling in intestinal stem cell renewal

role-of-notch-signalling-in-intestinal-stem-cell-renewal

Notch Signaling in Gut Stem Cell Fate

Notch signaling helps control how intestinal stem cells renew and decide what cell type to become. In the intestine, this pathway acts through Atoh1, also called atonal homolog 1. Atoh1 pushes cells to become secretory cells. When Notch signaling is active, it limits Atoh1 and keeps the stem cell pool balanced. This pathway depends on direct contact between neighboring cells. It begins when a Notch ligand binds to a receptor on an adjacent cell, which is called trans-binding. If the ligand...

The epidermis, the outer layer of skin, is constantly renewed as old cells are replaced by new ones. Skin is organized into three layers: the epidermis, dermis, and hypodermis. In this process, epidermal stem cells, or EpiSCs, divide and make the cells needed to maintain the surface. Some EpiSCs keep self-renewing so the stem cell pool stays active. Others become transit-amplifying, or TA, cells. These cells later form prickle or spinous cells, then granular cells, and finally dead keratinized...

multipotency and niche of bulge stem cell

multipotency-and-niche-of-bulge-stem-cell

Hair Follicle Bulge and Stem Cell Cycles

The hair follicle bulge is the stem cell niche that helps control hair growth and renewal. A hair follicle is a small part of the skin that produces the hair shaft. Paul Gerson Unna was the first to observe the bulge in the outer root sheath, or ORS. The bulge sits between the sebaceous gland and the arrector pili muscle. It houses hair follicle stem cells, or HFSCs, and it also serves as a niche for melanocyte stem cells. When melanocyte stem cells are lost, hair can turn gray. HFSCs express...

clinical applications of epidermal stem cells

clinical-applications-of-epidermal-stem-cells

How Epidermal Stem Cells Aid Skin Repair

Epidermal stem cells help the skin repair minor injuries and replace dead skin cells. These cells are found mainly in the basal layer of the epidermis, the outer layer of skin. For severe wounds, such as major burns or skin damage linked to diabetes or inherited disorders, the body may need help beyond its own repair system. In these cases, epidermal stem cells can be grown from the patient in the lab. Skin taken from an unaffected area can be used to make cultured epidermal autografts, or...

distinctive features of adult stem cells vs cancer stem cells

distinctive-features-of-adult-stem-cells-vs-cancer-stem-cells

Adult and Cancer Stem Cell Traits

Adult stem cells and cancer stem cells share the ability to renew and make specialized cells, but they behave differently in the body. Adult stem cells are unspecialized cells that can divide as needed and, under the right conditions, become specialized cells. Cancer stem cells are a small group of cells inside tumors that also renew and differentiate. Adult stem cells are tissue-specific, which means they help build the tissue where they are found. For example, epithelial stem cells give rise...

stem cell culture

Stem Cell Sources and Therapy

Stem cells can help the body replace damaged cells and repair tissues. Most adult cells lose some ability to divide and heal as they age. Stem cells are different because they do not have a fixed shape or one set job. Adult stem cells are a small group of cells in many tissues, and they keep dividing while also making specialized cells for that same tissue. Scientists still do not fully understand how an unspecialized cell becomes a specialized one. In the lab, stem cells can be pushed to...

tissue renewal without stem cells

Liver and Pancreas Renewal by Cell Division

Liver and pancreas tissues can renew themselves through cell division, even when stem cells are not the main repair source. After tissue damage, some organs rely on resident stem cells to help rebuild lost cells. In the liver and pancreas, however, pre-existing cells can also take part in repair. Pancreas beta cells and liver hepatocytes are two key examples. Beta cells in the pancreas and hepatocytes in the liver can divide to replace cells and regenerate tissue. This process depends on...

unrenewable cells

Permanent Damage to Eye and Ear Cells

Permanent damage to eye and ear cells can affect vision and hearing because some sensory cells cannot be replaced. In humans, the photoreceptor cells of the eye and the sensory hair cells of the ear lack stem cells. That means these cells are unrenewable, so they cannot be replaced after they are damaged or destroyed. The retina contains specialized photoreceptors called rods and cones. These cells change membrane potential when they are stimulated by light energy. Rods and cones differ in the...

key terms and concepts

Learn how epidermal stem cells renew skin, form keratinized layers, and help repair wounds. Explore key keratin markers, integrins, and signaling pathways.

Epidermal Cell Turnover and Repair | JoVE K12

cell biology

JoVE Core Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

Epidermal Cell Turnover and Repair

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