Stem cells and cell differentiation

What is the process called through which cells reproduce by dividing into two offspring cells?

Binary division.

What marks the beginning of an individual cell’s existence?

A cell division event

What can mark the end of a cell's existence?

A second division event or cell death (apoptosis).

What do generations of cells linked by reproductive division form?

A lineage.

Why is binary division important for multicellular organisms?

It is essential for growth, development, and tissue repair.

In a lineage of cells, what represents a common ancestor?

The parent cell from which the lineage originated.

Stem cell:

functionally defined as having the capacity to self-renew and the ability to generate differentiated cells

Self-renewal

cell division producing one or more cells similar to the parent

Differentiation:

loss of developmental potential and acquisition of specialized traits of a mature cell type

What are embryonic stem cells (ESCs)?

Stem cells derived from the inner cell mass of a blastocyst that can differentiate into nearly any cell type in the body (pluripotent).

What is the main characteristic of pluripotency in embryonic stem cells?

ESCs can differentiate into almost any cell type, including cells from all three germ layers: ectoderm, mesoderm, and endoderm.

What property allows embryonic stem cells to be produced in large quantities for research?

Their ability to self-renew indefinitely while maintaining their pluripotent state.

What are adult stem cells (ASCs)?

Undifferentiated stem cells found in various tissues after development, which can differentiate into a limited range of cell types related to their tissue of origin (multipotent).

How does multipotency differ from pluripotency?

Multipotent stem cells (like adult stem cells) can differentiate into a limited number of cell types, while pluripotent stem cells (like embryonic stem cells) can differentiate into almost any cell type.

Where are adult stem cells typically found?

In specific tissues such as bone marrow, skin, liver, and muscle.

How does the self-renewal capacity of adult stem cells compare to that of embryonic stem cells?

Adult stem cells have a more limited capacity for self-renewal compared to embryonic stem cells.

What is a common medical application of adult stem cells?

Bone marrow transplants for leukemia and other blood disorders.

Potency

the number of possible fates that a cell can acquire

Totipotency

the ability to produce an entire organism (Zygote)

Pluripotency

the ability to produce all cell types of an adult organism

Multipotency:

the ability to produce some (but not all) cell types of an adult organism

Oligo-potency:

the ability to produce a limited subset of cell types in an organism

Uni-potency:

the ability to produce only one specialized cell type

potency decreases with :

Age

Formation of blood cells from hematopoietic stem cells in the bone marrow

What are teratomas?

Teratomas are tumors that arise from pluripotent stem cells, characterized by the presence of disorganized cell lineages derived from multiple germ layers.

What does "disorganized cell lineages" mean in the context of teratomas?

It refers to the chaotic arrangement of various differentiated cell types within the tumor, which do not form structured normal tissue.

What types of tissues can be found in teratomas?

Teratomas can contain a mixture of different tissues, including hair, muscle, nerve cells, and even fully formed organs or structures.

Where are teratomas commonly located in the body?

Teratomas often occur in the ovaries or testes, but they can also appear in areas such as the sacrococcygeal region or mediastinum.

What is trans-differentiation?

Trans-differentiation is the process by which one type of differentiated cell is converted directly into another differentiated cell type without reverting to a stem cell state.

What differentiates trans-differentiation from other forms of cell differentiation?

Trans-differentiation bypasses the pluripotent or progenitor states and achieves a direct conversion from one mature cell type to another.

What role do transcription regulators play in trans-differentiation?

Transcription regulators are proteins that, when artificially expressed, can trigger the genetic programs necessary for a differentiated cell to change its identity to another cell type.

Can you give an example of trans-differentiation?

An example is converting human fibroblasts into neurons by introducing a specific combination of transcription factors essential for neuronal identity.

the process of generating induced pluripotent stem (iPS) cells from fibroblasts and their potential differentiation into specialized cell types.

Explanation:

1. Starting with Fibroblasts:

   • Fibroblasts are a type of connective tissue cell found in the body.

   • Specific transcription factors—Oct4, Sox2, and Klf4—are introduced into the fibroblast nucleus.

2. Reprogramming into iPS Cells:

   • These transcription factors reprogram the fibroblast into an induced pluripotent stem (iPS) cell.

   • iPS cells have the ability to proliferate indefinitely, similar to embryonic stem cells.

3. Differentiation into Specialized Cells:

   • In culture, iPS cells can be directed to differentiate into various cell types, such as:

     • Muscle cells (important for movement and structure)

     • Neurons (essential for nervous system function)

     • Fat cells (store energy and regulate metabolism)

Importance:

• iPS cells offer a powerful tool for regenerative medicine, disease modeling, and drug discovery.

• Since iPS cells are derived from adult cells, they avoid ethical concerns associated with embryonic stem cells.

• They can be used for personalized medicine, as patient-derived iPS cells can be used to create compatible tissues for transplantation.

Muscle Cells from Fibroblasts

• Key Factor: MyoD

• MyoD was the first transcription factor discovered that could convert fibroblasts into muscle cells

Macrophages from B Cells

• Key Factor: C/EBPα

• C/EBPα was used to convert B cells into macrophages, demonstrating lineage reprogramming.

Induced Pluripotent Stem Cells (iPSC) from Fibroblasts

• Key Factors: Oct4, Sox2, Klf4, Myc

• This groundbreaking discovery by Shinya Yamanaka reprogrammed fibroblasts into iPSCs, which can differentiate into any cell type.

Blood Cells from B Cells

• Key Factor: Pax5 ablation

• Pax5 is essential for maintaining B cell identity, and its deletion allowed B cells to convert into blood progenitor cells.

Beta Cells from Exocrine Cells

• Key Factors: Pdx1, Ngn3, Mafa

• Exocrine cells were reprogrammed into insulin-producing beta cells, crucial for diabetes research.

Neurons from Fibroblasts

• Key Factors: Ascl1, Brn2, Myt1l

• This discovery enabled direct conversion of fibroblasts into neurons, bypassing the iPSC stage.

Cardiomyocytes from Fibroblasts

• Key Factors: Gata4, Mef2c, Tbx5

• Fibroblasts were directly reprogrammed into cardiomyocytes (heart muscle cells), relevant for heart disease treatments.

Blood Cells and Cardiomyocytes from Fibroblasts

• Key Factors: Oct4 (Blood cells), Oct4, Sox2, Klf4 (Cardiomyocytes)

• Demonstrates further advancements in direct cell reprogramming.

Stem cells importance :

• Stem cells are the starting points of lineage processes.

• Stem-cell differentiation is the process by which a more specialized cell is formed from a stem cell.

• Stem-cell differentiation occurs during development of an organism, and also in adults to replenish cells that are lost.

• Stem cell therapy has become a very promising scientific research topic.

• Potential therapies based on iPSC evoke great expectations

where we find ctem cells ?

Stem cells are found in the bone marrow and in the hair follicle

what is a Determined cell?

A determined cell is a cell committed to a differentiation pathway but has not yet acquired visible structural or functional modifications.

what is the niche ?

The niche is a specific site in a tissue where stem cells reside.