20.1 Types and properties of stem cells

Stem cells are remarkable for their ability to self-renew and differentiate into various cell types. They come in different forms, from embryonic to adult, each with unique properties and potential. Understanding stem cells is crucial for grasping cellular development and regeneration.

Stem cell potency ranges from totipotent to unipotent, determining their differentiation capabilities. Their self-renewal and differentiation are regulated by intrinsic factors and their microenvironment. This balance is key to maintaining stem cell populations while generating specialized cells.

Stem Cell Types and Properties

Key characteristics of stem cells

Top images from around the web for Key characteristics of stem cells

• 

  Stem cell - wikidoc View original

  Is this image relevant?

• 

  File:Final stem cell differentiation (1).svg - Wikimedia Commons View original

  Is this image relevant?

• 

  Cellular Differentiation | Anatomy and Physiology I View original

  Is this image relevant?

• 

  Stem cell - wikidoc View original

  Is this image relevant?

• 

  File:Final stem cell differentiation (1).svg - Wikimedia Commons View original

  Is this image relevant?

1 of 3

Top images from around the web for Key characteristics of stem cells

• 

  Stem cell - wikidoc View original

  Is this image relevant?

• 

  File:Final stem cell differentiation (1).svg - Wikimedia Commons View original

  Is this image relevant?

• 

  Cellular Differentiation | Anatomy and Physiology I View original

  Is this image relevant?

• 

  Stem cell - wikidoc View original

  Is this image relevant?

• 

  File:Final stem cell differentiation (1).svg - Wikimedia Commons View original

  Is this image relevant?

1 of 3

• Self-renewal enables stem cells to divide and produce identical daughter cells, maintaining the stem cell population
• Potency refers to the capacity of stem cells to differentiate into specialized cell types, ranging from totipotent (can form all embryonic and extraembryonic tissues) to unipotent (can form only one cell type)
• Asymmetric division produces one identical daughter cell and one differentiated cell, maintaining the stem cell population while generating specialized cells
• Niche dependency means that stem cells rely on a specific microenvironment that regulates their behavior by providing signals for self-renewal and differentiation

Types of stem cells

• Embryonic stem cells (ESCs) are derived from the inner cell mass of blastocysts and are pluripotent, meaning they can differentiate into all three germ layers (endoderm, mesoderm, ectoderm); however, their isolation raises ethical concerns
• Adult stem cells (ASCs) are found in various tissues throughout the body (bone marrow, adipose tissue) and are multipotent, meaning they can differentiate into cell types of their tissue of origin, such as hematopoietic, mesenchymal, and neural stem cells
• Induced pluripotent stem cells (iPSCs) are generated by reprogramming somatic cells (skin fibroblasts) to a pluripotent state using reprogramming factors (Oct4, Sox2, Klf4, and c-Myc), avoiding ethical issues associated with ESCs and offering potential for personalized regenerative medicine

Levels of stem cell potency

• Totipotent stem cells can give rise to all embryonic and extraembryonic tissues, such as the zygote and early blastomeres
• Pluripotent stem cells can differentiate into all three germ layers (endoderm, mesoderm, ectoderm) but cannot form extraembryonic tissues, examples include ESCs and iPSCs
• Multipotent stem cells can differentiate into multiple cell types within a specific lineage, such as hematopoietic and mesenchymal stem cells
• Unipotent stem cells can differentiate into only one cell type, such as spermatogonial stem cells

Self-renewal and differentiation potential

• Self-renewal is achieved through symmetric division, which produces two identical daughter stem cells, or asymmetric division, which produces one stem cell and one differentiated cell, and is regulated by intrinsic and extrinsic factors
• Differentiation potential refers to the capacity of stem cells to give rise to specialized cell types, determined by their potency level (totipotent, pluripotent, multipotent, or unipotent) and influenced by cell signaling pathways (Wnt, Notch) and epigenetic modifications (DNA methylation, histone modifications)
• Plasticity is the ability of some adult stem cells to transdifferentiate into cell types of another lineage under specific conditions
• Immortality refers to the extensive proliferative capacity of stem cells, maintained by telomerase activity, which prevents telomere shortening during cell division