STEM CELL TECHNOLOGY

Submited to:Dr. Aruna Bhatia

Submited by:Priyanka M.Sc Hon’s BT (II)130181123

CONTENTS

• Introduction • Properties of stem cell• Potency definition of stem cell• Types of stem cells• Sources of stem cells• Stages of early embryonic development• Embryonic stem cells are grown in laboratory• Where is adult stem cells found and what they normally do?• How stem cells therapy work?

What are Stem cells?• Stem cells are “master cells”

• Unique cells of body in that they are unspecialized and have ability to develop into several different type of cells (by differentiation).

• When unspecialized stem cells give rise to specialized cells the process is called differentiation.

• an important part of body’s natural repair system.

• Stem cells give rise to brain cells, nerve cells, heart cells, pancreatic cells etc.

The unique properties of all stem cells

Undifferentiated / unspecialized cells

Undifferentiated cells can differentiate to yield major specialized cell types or organs

Self-renewal property is to maintain and repair the tissue. Thus they have potential to replace cell tissue damaged

Potency definitions of stem cells Categorized by their potential to differentiate into other types of cells

• Totipotent : ability to differentiate into other types e.g. the zygote formed at egg fertilization (fertilized egg) and

the first few cells that result from the division of the zygote.

• Pluripotent : can differentiate into almost all cell types. e.g. embryonic stem cell (cells from the inner mass cells) and

cells that derived from mesoderm, endoderm and ectoderm germ layers that are formed in the beginning stages of embryonic stem cell differentiation.

• Mutipotent : the ability to differentiate into closely related family of cells. e.g. hematopoietic (adult) stem cells that can become red and

white blood cells or platelets.

• Oligopotent: the ability to differentiate into few cells e.g. lymphoid and myeloid stem cells.

• Unipotent: ability to only produce cells of their own type, but have the property of self renewal required to be labelled a stem cell.

e.g. muscle stem cells.

Types of stem cells

• Embryonic stem cells : derived from the inner cell mass of a blastocysts / human embryo.

• Adult stem cells: found in adult tissues. derived from mature organisms that can divide to form more

differentiated cells - are less versatile and more difficult to identify, isolate, and

purify.

Sources of stem cells

Stem cells come from several sources in the body. Embryonic stem cells: these stem cells isolated from 4-5 day old

embryos in the early stage of development.

Fetal stem cells: come from a fetus. At about 9 weeks, a maturing embryo enters into the fetal stage of

development. found in fetal tissues, blood and bone marrow

Umbilical cord blood stem cells: derived from umbilical cord blood.

Similar to those found in mature or adult stem cells. All blood cell types (red blood cells, white blood cells, and platelets)

Placental stem cells: contained within placenta.

Adult stem cells: present in mature body tissues in infants, children and adults.

Found in fetal and umbilical cord. Stem cells have been found in the blood, bone marrow, liver, kidney,

cornea, dental pulp, brain, skin, muscle

What stages of early embryonic development are important for generating embryonic stem cells??

• derived from embryos that develop from eggs that have been fertilized in vitro.

• The embryos from which human embryonic stem cells are derived are typically four or five days old and are a hollow microscopic ball of cells called the blastocyst.

• The blastocyst includes three structures:

the trophoblast, which is the layer of cells that surrounds the blastocyst

the blastocoel, which is the hollow cavity inside the blastocyst

the inner cell mass, which is a group of approximately 30 cells at one end of the blastocoel.

How are embryonic stem cells grown in the laboratory?

• Growing cells in the laboratory is known as cell culture.

• Human embryonic stem cells are isolated by transferring the inner cell mass into a plastic laboratory culture dish that contains a nutrient broth known as culture medium.

• The cells divide and spread over the surface of the dish.

• The inner surface of the culture dish is typically coated with mouse embryonic skin cells that have been treated so they will not divide.

• This coating layer of cells is called a feeder layer.

• The mouse cells in the bottom of the culture dish is provide to give the cells a sticky surface to which they can attach.

• Also, the feeder cells release nutrients into the culture medium

• If the plated cells survive, divide and multiply enough to crowd the culture dish, they are removed gently and plated into several fresh culture dishes.

• The process of re-plating the cells is repeated many times and for many months, and is called subculturing.

• Each cycle of subculturing the cells is referred to as a passage.

• After six months or more, the original 30 cells of the inner cell mass yield millions of embryonic stem cells.

• Embryonic stem cells that have proliferated in cell culture for six or more months without differentiating, are pluripotent, and appear genetically normal are referred to as an embryonic stem cell line.

Where are adult stem cells found and what do they normally do?

• adult stem cells have been identified in many organs and tissues.

• Stem cells are thought to reside in a specific area of each tissue where they may remain non-dividing for many years until they are activated by disease or tissue injury.

• The adult tissues reported to contain stem cells include brain, bone marrow, peripheral blood, blood vessels, skeletal muscle, skin and liver.

• Some examples of potential treatments include replacing the dopamine-producing cells in the brains of Parkinson's patients, developing insulin-producing cells for type I diabetes and repairing damaged heart muscle following a heart attack with cardiac muscle cells.

Normal differentiation pathways of adult stem cells:

Hematopoietic stem cells: give rise to all the types of blood cells: red blood cells, B lymphocytes, T lymphocytes, natural killer cells, neutrophils, basophils, eosinophils, monocytes, macrophages, and platelets.

Bone marrow stromal cells (mesenchymal stem cells): give rise to a variety of cell types: bone cells (osteocytes), cartilage cells(chondrocytes), fat cells (adipocytes), and other kinds of connective tissue cells such as those in tendons.

Neural stem cells in the brain give rise to its three major cell types: nerve cells (neurons) and two categories of non-neuronal cells—astrocytes and oligodendrocytes.

Epithelial stem cells in the lining of the digestive tract occur in deep crypts and give rise to several cell types: absorptive cells, goblet cells, Paneth cells, and enteroendocrine cells.

Skin stem cells occur in the basal layer of the epidermis and at the base of hair follicles. The epidermal stem cells give rise to keratinocytes, which migrate to the surface of the skin and form a protective layer. The follicular stem cells can give rise to both the hair follicle and to the epidermis.

Advantages of Embryonic Stem Cells over Adult Stem Cells

EEmbryonic stem cells Adult stem cells Adult S.C.

Pluripotent(can become any cell types present

in the human body )

Multipotent(can become many but not any) E.g., blood stem cells can develop into several blood cell types, but

cannot develop into brain, kidney, or liver cells

Stable-Can undergo many cell divisions.

Less Stable-Capacity for self-renewal is limited.

Easy to obtain but blastocyst is destroyed.

Difficult to isolate in adult tissue.

How stem cell therapy works?

• When stem cells are transplanted into the body and arrive into the injured part, brain being targeted for tissue regeneration, the stem cells are coming in contact with growth chemical’s (like EGF’s , NGF’s and HGF’s ) in the body.

• These chemicals program the stem cells to differentiate into the tissue surrounding it.

Application of stem cells or

Potential use of stem cells

Stem cells from patient’s plucked hair can be grow into skin

• Hair follicles contain skin stem cells (keratinocyte)

• Pluck the patient’s hair

• Cultured to form epidermal cells equivalents of the patients own skin

• This is autologous graft thus bypassing the problem of rejection

• Used for venous ulcers and burn victims

Diabetes

• Diabetes patients lose the function of their insulin-producing beta cells of the pancreas.

• Human embryonic stem cells may be grown in cell cultures and stimulate to form insulin-producing cells ,that can be transplanted into the patient

• Pancreas is digested with collagenase that frees islets from surrounding cells

• Centrifugation of isolates containing mainly alpha and beta cells

• Then purified beta cells

• and transplanted through a catheter into the liver where they become permanantly established.

Corneal disease / blindness

• Result in poor vision

• Take stem cells from healthy eye

• Grown onto contact lenses in clinical lab

• Lenses are worn by the patient for a period of three weeks

• Then migration of human stem cells from lens to damaged eye and begin to repair process

• Thus heals the damaged cornea and quickly improves the vision

Parkinson’s disease

• Caused when key brain cells that produce message carrying chemical/neurotransmitter (dopamine) die off.

• Symptoms start with the patients trembling and can end up paralyzed.

• Harvesting of stem cells from patients bone marrow, foetus or any other source

• Culturing of harvested stem cells in lab conditions to get high concentrations of stem cells

• Then purified and high concentration of stem cells are surgically injected in the brain of patient

Brain damage

• Stroke and traumatic brain injury lead to cell death, characterized by a loss of neurons and oligodendrocytes within the brain.

• Healthy adult brain contain neural stem cells, these divide and act to maintain general stem cell numbers or become progenitor cells.

Missing teeth

• Take stem cells/dental pulp from the patient. Both adult mesenchymal stem cells and embryonic stem cells can be used

• Culture in lab.- into a tooth bud

• Then implant tooth bud in gum which fuses with jaw bone and release chemicals that encourage nerves & blood vessels to connect with gum

• As a result it will give rise to new tooth/ dentin approximately within 2 months

REFERENCES www.stemcellcentre.edu.au www.stemcellchannel.com.au http://stemcells.nih.gov/info/basics/pages/ba

sics1.aspx http://scitechdaily.com/ www.sciencedaily.com/release/2004/11/04 11

15001504.htm www.stemcellresearchfoundation.org/about/F

AQ.htm