表皮干细胞英文
Introduction
Skin is the largest organ of the human body and plays a crucial role in protecting us from external injuries, infections and harmful substances. The underlying mechanism of skin repair and regeneration relies on the presence of a specific group of cells called Skin Stem Cells. Among these, Epidermal Stem Cells (ESCs) or commonly known as Epidermal Keratinocytes are found in the outermost layer of the skin’s epidermis. These unique cells have the ability to differentiate into different types of epidermal cells which facilitate the process of skin repair and regeneration.
Types of Epidermal Stem Cells
The skin’s epidermis is composed of four main cell types including Keratinocytes, Melanocytes, Langerhans cells and Merkel cells. Among these, keratinocytes have been widely studied due to their ability to contribute significantly to the regeneration of skin tissue. This is mainly due to two types of ESCs: The Basal Stem Cells and Transient Amplifying Cells.
Basal Stem Cells
Basal Stem Cells are located in the basal layer of the epidermis. They have the ability to self-renew and generate the transient amplifying cells which help in the formation of stratified layers of epidermal cells. In addition, they also play a significant role in wound repair and regeneration. Studies have shown that the activation of basal stem cells, during wound healing, can produce an increased number of basal cells which can further differentiate into mature keratinocytes to contribute to the regeneration process.
Transient Amplifying Cells
Transient Amplifying Cells are the intermediate daughter cells generated by the basal stem cells. They undergo several rounds of proliferation and differentiation, resulting in the generation of mature keratinocytes which form the outermost layer of the epidermis. These cells have a shorter lifespan compared to basal stem cells and therefore, their function is primarily focused on the regeneration of skin tissue in response to injury or damage.
Role of Epidermal Stem Cells in Skin Diseases
ESCs play a crucial role in the maintenance and repair of the skin, however, their dysfunction or depletion can lead to several skin disorders such as psoriasis, atopic dermatitis, and skin cancer. The uncontrolled proliferation of basal stem cells in addition to the impaired differentiation of keratinocytes can lead to the development of psoriatic plaques on the skin. On the other hand, the loss of function of some stem cell populations can lead to atopic dermatitis, which is characterized by abnormal skin barrier function due to the impaired differentiation of keratinocytes and defective tight junctions. Moreover, the transformation of ESCs can result in the development of skin cancer, the most common type being basal cell carcinoma. Loss-of-function mutations in genes that regulate cellular processes in ESCs have been shown to contribute to the development of skin tumors by inducing aberrant growth and unchecked proliferation of ESC populations.
Conclusion
Epidermal Stem Cells have a vital, dynamic and adaptive role in the maintenance and regeneration of the skin. Their abilities to self-renew and differentiate into different cell lines make ESCs an essential component of effective wound healing and repair process. However, their depletion or dysfunction can lead to the development of several skin disorders. Continued research in this area is essential for the understanding of tissue regeneration and the implementation of effective treatments for various skin pathologies.
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