1.10 Stem Cells

Introduction

Stem cells are special cells with the potential to develop into many different types of cells in the body. They are the body's "master cells" because they can divide to produce more copies of themselves or differentiate into specialized cells with specific functions.

Definition

Stem Cells: Stem cells are cells with the potential to develop into many different types of cells in the body.

In simple words: Stem cells are unspecialized cells that can become any type of cell the body needs.

Core Concept

• Under the right conditions in the body or a laboratory, stem cells divide to form more cells called daughter cells.
• These daughter cells become either:
• Blood cells
• Nerve cells
• Liver cells
• Heart muscle cells
• Bone cells
• No other cell in the body has the natural ability to generate new cell types.
• Stem cells are so named because they can either divide to produce more copies of themselves or differentiate into more specialized types of cells.

Detailed Explanation

Definition of Stem Cells

A stem cell can be defined as:

"It is a cell with the unique ability to develop into specialized cell types in the body."

Advantages of Using Stem Cells

1. New cells are provided by the stem cells as they grow. - They replace the specialized cells that are damaged or lost.

2. They can divide again and again to produce new cells. - As the stem cells divide, they can change into the other types of cells that make up the body.

• Spinal cord injuries
• Type 1 diabetes
• Parkinson's disease
• Alzheimer's disease
• Heart disease
• Stroke
• Burns
• Cancer
• Osteoarthritis
• And many other conditions

Different Types of Stem Cells

There are several different types of stem cells, each with its own unique properties and applications in medical research and practice. The three main types are:

• Embryonic Stem Cells (ESCs)
• Adult Stem Cells
• Induced Pluripotent Stem Cells (iPSCs)

1. Adult Stem Cells

• These cells supply new cells as an organism grows and to replace cells that get damaged.
• Adult stem cells are multipotent, which means they can only change into some specific cells in the body, not any cell.
• Example: Hematopoietic stem cells in bone marrow can become red blood cells, white blood cells, or platelets.

2. Embryonic Stem Cells (ESCs)

• These cells provide new cells for a growing embryo.
• They are called pluripotent, which means they can naturally produce every type of cell in the body.
• They are derived from the inner cell mass of the blastocyst (early embryo).

3. Induced Pluripotent Stem Cells (iPSCs)

• The stem cells that scientists make in the laboratory are called induced pluripotent stem cells.
• They can develop into any cell type.
• They are created by reprogramming adult cells to behave like embryonic stem cells.
• iPSCs were first described by Shinya Yamanaka and his colleagues at Kyoto University in 2006.
• They were jointly awarded the 2012 Nobel Prize in Physiology or Medicine for their work.

Types of Stem Cells Based on Potency

Researchers categorize stem cells according to their potential to differentiate into other types of cells. The full classification includes:

Advantages of Induced Pluripotent Stem Cells (iPSCs)

The advantages are:

1. Ability to give rise to almost any cell types desired. - iPSCs can be differentiated into many different cell types for research and therapy.

2. Avoidance of ethical concerns associated with human ESCs. - iPSCs are created from adult cells, so they do not require the destruction of embryos.

3. Induced pluripotent stem cells generated from the patient themselves could be used to grow new organs that would have a lower risk of being rejected. - Because they are derived from the patient's own cells, they are less likely to be rejected by the immune system.

Disadvantages of Induced Pluripotent Stem Cells (iPSCs)

• For human iPSC production, viruses were initially used as delivery vectors for the genes required for cell reprogramming.
• The main issue is the use of retroviruses to generate iPSCs as they are associated with cancer.
• More specifically, retroviruses can insert their DNA anywhere in the genome and subsequently trigger cancer-causing gene expression.

2. Risk of overgrowth of transplanted cells: - The risk of the overgrowth of the transplanted cells, or, in other words, cancer, continues to be a major hurdle.

How to Generate Induced Pluripotent Stem Cells?

• Signals in the body tell a cell what type of specialized cell it should be by switching some genes on and some genes off.
• To generate induced pluripotent stem cells, scientists re-introduce the signals that normally tell stem cells to stay as stem cells in the early embryo.
• These switch off any genes that tell the cell to be specialized, and switch on genes that tell the cell to be a stem cell.

Market for iPSCs

• The benefits of iPSCs are catching on, which is setting the market on a course of continued expansion.
• BCC Research predicts the global market for induced pluripotent stem cells to grow from 2.8 billion in 2021** to **4.4 billion by 2026, at a compound annual growth rate of 9.3%.

Intermediate Level

Types of Stem Cells Based on Potency

Sources of Stem Cells

• Derived from the inner cell mass of the blastocyst.
• Pluripotent.
• Ethical concerns associated with their use.

• Found in various tissues (bone marrow, brain, skin, liver).
• Multipotent.
• Fewer ethical concerns.

• Created by reprogramming adult cells.
• Pluripotent.
• No ethical concerns.
• Risk of cancer.

Applications of Stem Cells

• Repair or replace damaged tissues and organs.
• Examples: Spinal cord injuries, heart disease, diabetes.

• Study diseases in the laboratory.
• Understand how diseases develop.

• Test new drugs on stem cell-derived cells.
• More accurate than animal testing.

• Correct genetic defects in stem cells.
• Transplant corrected cells back into the patient.

Ethical Considerations

Important Points

• 1. Stem cells are cells with the potential to develop into many different types of cells in the body.
• 2. Under the right conditions, stem cells divide to form more cells called daughter cells.
• 3. Daughter cells become either:
• - New stem cells
• - Specialized cells with a more specific function
• 4. Specialized cell types include:
• - Blood cells
• - Nerve cells
• - Liver cells
• - Heart muscle cells
• - Bone cells
• 5. No other cell in the body has the natural ability to generate new cell types.
• 6. Stem cells are so named because they can either divide to produce more copies of themselves or differentiate into more specialized types of cells.
• 7. Definition: "It is a cell with the unique ability to develop into specialized cell types in the body."
• 8. Advantages of using stem cells:
• - New cells are provided by the stem cells as they grow.
• - They replace the specialized cells that are damaged or lost.
• - They can divide again and again to produce new cells.
• - As the stem cells divide, they can change into the other types of cells that make up the body.
• - Benefits of stem cell therapy are in the treatment of spinal cord injuries, type 1 diabetes, Parkinson's disease, Alzheimer's disease, heart disease, stroke, burns, cancer, and osteoarthritis.
• 9. Three main types of stem cells:
• - Adult stem cells: Multipotent; supply new cells as an organism grows and replace damaged cells.
• - Embryonic stem cells (ESCs): Pluripotent; provide new cells for a growing embryo.
• - Induced pluripotent stem cells (iPSCs): Made in the laboratory; can develop into any cell type.
• 10. Classification by potency:
• - Totipotent: Can differentiate into all possible cell types.
• - Pluripotent: Can turn into almost any cell.
• - Multipotent: Can differentiate into a closely related family of cells.
• - Oligopotent: Can differentiate into a few different cell types.
• - Unipotent: Can only produce cells of one kind.
• 11. Advantages of iPSCs:
• - Ability to give rise to almost any cell types desired.
• - Avoidance of ethical concerns associated with human ESCs.
• - Patient-specific iPSCs could be used to grow new organs with lower risk of rejection.
• 12. Disadvantages of iPSCs:
• - Use of retroviruses to generate iPSCs (associated with cancer).
• - Risk of overgrowth of transplanted cells (cancer).
• 13. How to generate iPSCs:
• - Scientists re-introduce the signals that normally tell stem cells to stay as stem cells in the early embryo.
• - These switch off genes that tell the cell to be specialized and switch on genes that tell the cell to be a stem cell.
• 14. iPSCs were first described by Shinya Yamanaka and his colleagues at Kyoto University in 2006.
• - They were jointly awarded the 2012 Nobel Prize in Physiology or Medicine for their work.
• 15. Market for iPSCs:
• - BCC Research predicts the global market for induced pluripotent stem cells to grow from 2.8 billion in 2021 to4.4 billion by 2026, at a compound annual growth rate of 9.3%.

Remember

• - Stem cells = unspecialized cells that can become specialized cells
• - Self-renewal = divide to produce more stem cells
• - Differentiation = become specialized cells
• - Three main types: Adult, Embryonic, Induced pluripotent
• - Adult stem cells = multipotent
• - Embryonic stem cells = pluripotent
• - iPSCs = made in lab; pluripotent
• - Potency classification: Totipotent, Pluripotent, Multipotent, Oligopotent, Unipotent
• - Advantages of iPSCs: No ethical concerns, patient-specific, lower risk of rejection
• - Disadvantages of iPSCs: Retroviruses (cancer risk), overgrowth (cancer)
• - iPSCs discovered by: Shinya Yamanaka (2006); Nobel Prize 2012
• - Market: 2.8 billion (2021) →4.4 billion (2026); CAGR 9.3%

Common Mistakes

• 1. Confusing stem cells with specialized cells – Stem cells are unspecialized; they can become specialized cells.
• 2. Thinking all stem cells are the same – There are different types: adult, embryonic, iPSCs. They have different potencies.
• 3. Confusing multipotent and pluripotent – Multipotent = can become a few related cell types; Pluripotent = can become almost any cell type.
• 4. Thinking iPSCs are the same as embryonic stem cells – iPSCs are made in the lab from adult cells; ESCs are derived from embryos.
• 5. Forgetting the advantages of iPSCs – No ethical concerns, patient-specific, lower risk of rejection.
• 6. Forgetting the disadvantages of iPSCs – Retroviruses (cancer risk), overgrowth (cancer).
• 7. Thinking stem cell therapy is already widely available – Many stem cell therapies are still in clinical trials.
• 8. Confusing totipotent and pluripotent – Totipotent = can become all cell types including placenta; Pluripotent = can become almost all cell types but not placenta.
• 9. Thinking adult stem cells are pluripotent – Adult stem cells are multipotent.
• 10. Forgetting the scientist who discovered iPSCs – Shinya Yamanaka (2006); Nobel Prize 2012.
• 11. Confusing the market growth rate – CAGR is 9.3%.
• 12. Thinking stem cells can only be obtained from embryos – Stem cells can also be obtained from adult tissues and generated in the lab (iPSCs).

Quick Revision

• Stem cells are cells with the potential to develop into many different types of cells in the body.
• Under the right conditions in the body or a laboratory, stem cells divide to form more cells called daughter cells.
• These daughter cells become either new stem cells or specialized cells (differentiation) with a more specific function, such as blood cells, nerve cells, liver cells, heart muscle cells, or bone cells.
• No other cell in the body has the natural ability to generate new cell types.
• Stem cells are so named because they can either divide to produce more copies of themselves or differentiate into more specialized types of cells.
• Definition: "It is a cell with the unique ability to develop into specialized cell types in the body."
• Advantages of using stem cells:
• New cells are provided by the stem cells as they grow.
• They replace the specialized cells that are damaged or lost.
• They can divide again and again to produce new cells.
• As the stem cells divide, they can change into the other types of cells that make up the body.
• Benefits of stem cell therapy are in the treatment of spinal cord injuries, type 1 diabetes, Parkinson's disease, Alzheimer's disease, heart disease, stroke, burns, cancer, and osteoarthritis.
• Three main types of stem cells:
• Classification by potency:
• Totipotent: Can differentiate into all possible cell types.
• Pluripotent: Can turn into almost any cell.
• Multipotent: Can differentiate into a closely related family of cells.
• Oligopotent: Can differentiate into a few different cell types.
• Unipotent: Can only produce cells of one kind.
• Advantages of iPSCs:
• Ability to give rise to almost any cell types desired.
• Avoidance of ethical concerns associated with human ESCs.
• Patient-specific iPSCs could be used to grow new organs with lower risk of rejection.
• Disadvantages of iPSCs:
• Use of retroviruses to generate iPSCs (associated with cancer).
• Risk of overgrowth of transplanted cells (cancer).
• How to generate iPSCs:
• Scientists re-introduce the signals that normally tell stem cells to stay as stem cells in the early embryo.
• These switch off genes that tell the cell to be specialized and switch on genes that tell the cell to be a stem cell.
• iPSCs were first described by Shinya Yamanaka and his colleagues at Kyoto University in 2006.
• They were jointly awarded the 2012 Nobel Prize in Physiology or Medicine for their work.
• Market for iPSCs:
• BCC Research predicts the global market for induced pluripotent stem cells to grow from 2.8 billion in 2021 to4.4 billion by 2026, at a compound annual growth rate of 9.3%.

60-Second Revision

• Stem cells = unspecialized cells that can become specialized
• Self-renewal = divide to produce more stem cells
• Differentiation = become specialized cells
• Three main types: Adult, Embryonic, Induced pluripotent
• Adult stem cells = multipotent
• Embryonic stem cells = pluripotent
• iPSCs = made in lab; pluripotent
• Potency: Totipotent > Pluripotent > Multipotent > Oligopotent > Unipotent
• Advantages of iPSCs: No ethical concerns, patient-specific, lower risk of rejection
• Disadvantages of iPSCs: Retroviruses (cancer risk), overgrowth (cancer)
• iPSCs discovered by: Shinya Yamanaka (2006); Nobel Prize 2012
• Market: 2.8 billion (2021) →4.4 billion (2026); CAGR 9.3%
• Warning: Not all stem cells are the same. Adult stem cells are multipotent; embryonic and iPSCs are pluripotent. iPSCs have advantages but also risks (cancer). Shinya Yamanaka discovered iPSCs in 2006.