John Bovill Stem Cell

Stem Cell Overview

What Are Stem Cells?

• Stem cells are a population of cells within the body that are capable of differentiating into other cell types. Differentiation is the process of transitioning from one cell type to another. By differentiating, the cell specializes in what functions it is capable of performing, but also limits what it is capable of differentiating into in the future. Each transition between cell types is irreversible. Stem cells exist in two forms within the body, embryonic and adult stem cells.
• Embryonic stem cells are the cells that are generated during the development of an embryo. They are totipotent and develop into every cell type that eventually exists in the adult body of the organism. Totipotency is the ability of a cell to differentiate into any other cell type. While an embryonic stem cell can differentiate into any type of cell, intermediate cell types or terminally differentiated cells (differentiated to the point where it will not transition cell types any further), cannot dedifferentiate back into an embryonic stem cell. Stem cells of this type can only be found within embryos, mostly very early in development.
• Adult stem cells exist within the fully developed adult body, where embryonic stem cells cannot be found. They have varying levels of potency, but are not totipotent. Many are pluripotent, meaning that they are capable of differentiation into several cell types. One type of adult stem cell is hematopoietic stem cells. These are still present in adult organisms and differentiate into every blood cell type that is observed in the body.
• While naturally, stem cells are only capable of differentiating in a single direction, it is possible to induce adult body cells to pluripotency, effectively dedifferentiating them. This leads to the creation of stem cell populations that function identically to naturally existing pluripotent stem cells, and are then capable of differentiation into a variety of cell types, based on how much they were de-differentiated. These are referred to as induced pluripotent stem cells.

Where Do They Come From?

• Embryonic stem cells are created during fertilization. Upon successful combination of two gametes, a zygote is formed. This single cell organism then copies its information and divides into numerous, smaller cells, doubling the number of cells after each division. This initial population of cells is completely undifferentiated, and totipotent, as they will later develop and differentiate to form the various cell types that exist in the body of an organism.
• Adult stem cell populations are created during
• Induced pluripotent stem cell origin

What Is Their Primary Function?

• POSSIBLY ADD PHOTOS OF FATE MAP AND/OR OF STEPS OF DIFFERENTIATION
• The primary function of embryonic stem cells are to be totipotent and be responsible for being progenitors to every cell in the body during development.
  • These embryonic stem cells or inner cells that are found in the 3- to 5-day-old embryo (blastocyst) and give rise to the entire body of the organism:
    • Ex: All of the many specialized cell types and organs such as the heart, lungs, skin, sperm, eggs and other tissues.
• The function of adult stem cells are to be pluripotent and have the capacity to maintain or repair the tissue that they are found in due to normal wear and tear, injury, or disease (bone marrow, muscle, brain, etc). To divide for a long period of time and when called upon give rise to mature cell types that have specific functions, structures, or shapes for distinctive tissues.
  • Ex: Hematopoietic cells
    • Non-terminally differentiated stem cells that contribute to the blood cell population while also self-replenishing.
    • Give rise to red blood cells, T and B lymphocytes, natural killer cells, neutrophils, basophils, eosinophils, monocytes, and macrophages.
  • Ex: Non-Hematopoietic cells
    • Small portion of stromal cell population in bone marrow that have the ability to generate cartilage, bone, and fat cells that aid in the formation of blood and fibrous connective tissue.
  • Ex. Neural Stem Cells
    • Found in the brain that give rise to nerve cell, astrocytes, and oligodendrocytes.
  • Ex. Skin stem cells
    • Most notably referenced to show the regenerative properties of stem cells
    • Found in the basal layer of epidermis. These cells lead to keratinocyte formation, which eventually find their way to surface of the skin. Once at the surface, the keratinocytes can form a protective layer (epidermis).
    • This process is easily seen when a minor cut or lesion occurs on the epidermis.

Why Are They Important?

• Induced pluripotent cells
  • Used medically for treatments

More Information

Potential Uses

• Stem cells have potential applications in cell based therapies and drug testing.

Obstacles

• While stem cells are promising, some problems faced today include immune rejection and the difficult process involved in stem cell therapies.

Table of Contents

• Stem Cell Overview
• Potential Uses
  • Stem Cells As a Research Tool
  • Cell Based Therapy
• Obstacles
  • Immune Rejection
  • Difficulties in Creating Stem Cells
• References