Stem Cells

intestinal epithelium

1-3 days (in mice)

How many different cells do humans have?

220

Problem with mice studies

90% of Safe and effective in mice, fail -Processes differ between mice and human

What is a progenitor cell...

A cell that is more committed than a stem cell, can produce many cells in that tissue, short lived.

Three stem cell types?

ASC, ESC, iPS

ASC sources

ASCS, Umbilical chord stem cells, Placental stem cells

Pulse chase assay

BrdU into cells for a new hours, labels cells, acts as a pulse, indintify how many cells have the signal after a few generations. Assay differentiated cell fates.

Oligopotency

Can differentiate into a few different cells (e.g. progenitors)

Unipotency

Can only make one cell type (itself)

ESCS can produce ... if...

Can produce many different cell types if grown under the correct conditions.

Potential uses of SC technology

Cell therapy, Drug discovery and Basic research.

Pros of iPS

Cells originate from the donor patient (no immune rejection!) No need to destroy an embryo

Cons of iPS

Cells would still have genetic defects (if not fixed through genetic engineering) Concerns over cancer developments. One of the pluripotency genes is a cancer gene Viruses insert genes randomly in the genome, which might lead to unpredictable defects...

Turnover assay?

Detects cell turnover rate by pulse chase.

What are the three main signals to stem cells?

Direct contact, soluble factors, other cells, matrix etc.

What is cell therapy used for?

Disease and Injuries and accidents to replace damaged cells.

What do SC enable for Drug tests?

Drug screening in human cells, minimalist animal use, safer way for development of new drugs.

Disadvantages of ESCs

Ethical issues Can elicit the formation of a benign tumor

How is FACs used to isolate stem cells?

FACS ( fluorescent activated cell sorting)- SSc l surface proteins with a tag- often antibody tag, use the tags with different colors to: sort individual cells assay for SC properties - Sort labeled stem cells from differentiated cells. Passed through vibrating novel, charged tag, dependent on laser detection of colour.

What state are stem cells kept in?

G0.

ES harvesting

Harvesting living embryos which are generally 5-7 days old. Another kind of stem cell, called an embryonic germ cell, can be obtained from either miscarriages or aborted fetuses.

Pluripotency

Has the potential to differentiate into almost any cell

Examples of adult stem cells (4 types)

Hematopoietic stem cells: blood and immune system Mesenchymal stem cells: bone, cartilage, fat, muscle, tendon/ligament Neural stem cells: neurons, glial cells Epithelial stem cells: skin, linings

ECS where are they found?

ICM, may be cultured in a lab.

Where are stem cells in hairs?

In the sebaceous gland and bulge.

What tends to correlate with increased differentiation?

Increased gene expression, positive feedback loops, expression altered by external inputs from other cells etc.

What is pluripotent?

Inner Cell Mass.

Repopulation assay.

Irradiation destroys bone marrow of a mouse. Inject normal bone marrow, repopulates stem cell niche, isolate more stem cells.

SC Skin grafting.

Keranocytes cultured, culture an epidermal sheet, graft.

haematopoietic stem cell is...

Multipotent

Disadvantages of ASCs

Multipotent - can become many cell types but not any Less Stable- limited self renewal capacity Difficult to isolate in adult tissue

What is the role of progenitors?

Non self renewing, divide rapidly, multipoint transient cells. Transient amplifying cells.

Potency

Number of possible fates that a cell can acquire.

lymphoid progenitor is...

Oligopotent

But what about neural stem cells in the brain?

Only in confined regions of the brain, cannot replace neurones lost in specific regions.

Autologous cell therapies

Own tissue and Ips cells.

Advantages of ESCs

Pluripotent - can become any cell type Stable- can undergo many cell divisions Easy to obtain but embryo is destroyed

Invitro induction assay.

Pure-Isa stem cells, culture in a culture medium, ad inducers, produce different cell types.

How are ASCs isolated?

Rare Hematopoietic SCs 0.01% of bone marrow precursors of immune system, red blood cells

ESC challenges

Scientists around the world are trying to understand how and why embryonic stem cells produce skin, blood, nerve or any other particular kind of specialized cell. What controls the process so that the stem cells make the right amount of each cell type, at the right time? The big challenge for scientists is to learn how to control these fascinating cells. If we could force embryonic stem cells to make whatever kind of cell we want, then we would have a powerful tool for developing treatments for disease. For example, perhaps we could grow new insulin-producing cells to transplant into a patient with diabetes. But there is a great deal to learn before such therapies can be developed. Scientists also want to use stem cells to: Understand how diseases develop (disease modelling) Test drugs in the laboratory

Potential uses of stem cells:

Spinal cord injuries, parkinson, stores, blindness, deafness, wound healing etc.

What is asymmetric replication?

Stem cell divisions produce two cells, one that will self renew, a new STEM cell and a differentiated daughter cell. Maintains a small stem cell pool.

What are Stem cells?

Stem cells are undifferentiated biological cells that can differentiate into specialized cells and can divide (through mitosis) to produce more stem cells. They are found in multicellular organisms. Have variable potency and can self renew.Capable of dividing and renewing themselves for long periods Unspecialized/uncommitted can give rise to specialized cell types

TSC

Stem cells exist in tissues, specific Stem cells, produce cells for that tissue.

Therapeutics

Stem cells injected into a damaged organ etc. Adult stem cells are difficult to isolate and rare. Also need SC with correct potency.

Where are ASCs found?

Surface of the eye, brain, skin, breast, intestine, testicles, muscles and bone marrow.

What cells activate stem cells?

Surrounding cells, maintain the niche too.

What is totipotent?

The morula.

What is cell turnover?

The process by which a tissue produces new cells or an entirely new set of cells.

allogenic cell therapies

The transplant is called an allograft, allogeneic transplant, or homograft. Most human tissue and organ transplants are allografts. A xenograft is a graft from a different species, such as when animal tissue is grafted into human tissue, or when human cancer cells are implanted in mice for experimental tumor studies.

Why can't neurones regenerate?

They are terminally differentiated.

What is Unipotent?

Tissue cells etc.

What are the two types of disease where Neurones may be required?

Types were cells are dead and cells are damaged.

When does potency decrease?

Usually Decrease with age (except stem cells) and as cells specialise

iPS cells

adult cell which has been genetically reprogrammed to a pluripotent state. can make so many tissues.

Neural stem cells

are self-renewing, multipotent cells that generate the main phenotype of the nervous system. Stem cells are characterized by their capability to differentiate into multiple cell types via exogenous stimuli from their environment.

Advantages of ASCs

avoid the ethical issues avoid issues of immune rejection

Multipotency

cells that can give rise to multiple cell types. These cells are typically closely related

Neutrophil turn over rate.

few hours

Embryo incorporation assay

for stem cell potency, find what stem cells contribute to.

Totipotency

has the capacity to create a completely viable organism.

Epidermis

month

Haematopoetic stem cells are...

multipotent... only specialized types of blood cell: red blood cells, white blood cells, platelets

Therapeutic stem cells

repair damaged organs by introducing extra stem cells. E.g bone marrow transplants, skin cell transplants

Stem cells divide ...

slowly.

What is the DP in the hair cycle?

the epithelial cells at the base of the follicle undergo apoptosis, but the DP remains intact and is pulled or migrates upwards, until it comes to rest next to the stem cells of the hair follicle bulge. This situation persists during telogen. In anagen, cells at the base of the follicle start to proliferate, which results in downward growth of the follicle and envelopment of the DP. DP cells themselves are thought to not divide. However, the number of cells in the DP increases during anagen, possibly as a result of replenishment from neighbouring cells of the dermal sheath

What is a stem cell niche?

to a microenvironment, within the specific anatomic location where stem cells are found, which interacts with stem cells to regulate cell fate. changes in microenvironment can activate stem cells.

ASCs

undifferentiated (or partially-differentiated) cell found in tissues and organs more specialized since they are assigned to a specific cell family such as blood cells, nerve cells, etc. Self-renew and differentiate to become most or all of the specialized cell types within their specific tissue lineage Recently, it was discovered that an adult stem cell from one tissue may act as a stem cell for another tissue, i.e. blood to neural Adult stem cell functions: Maintain cell populations Repair/heal Renewal of cells- aging

What is used to produce iPS cells

viruses.

RBC

weeks