HEMATOPOIETIC STEM CELLS-

CELLULAR AND GENE THERAPY

Introduction to Stem Cells

The two broad types of mammalian stem cells are:

1. Embryonic stem cells: Isolated from four- or five-day-old human embryo

that is in the blastocyst phase of development. The blastocyst consists of an inner cell mass

(embryoblast) and an outer cell mass (trophoblast). The inner cell mass is the source of embryonic

stem cells - totipotent cells .

2.Adult stem cells

These stem cells have been found in tissues such as the brain, bone marrow, blood, blood vessels, skeletal muscles, skin, and the liver.

Adult stem cells are limited in their ability to

differentiate based on their tissue of origin.

Properties

Self-renewal - the ability to go through numerous cycles of cell division while maintaining the undifferentiated state.

Potency - the capacity to differentiate into specialized cell types.

Hematopoietic Stem Cells

HSCs are multipotent stem cells that give rise to all the blood cell types including myeloid and lymphoid lineages.

Hematopoietic tissue contains cells with long-term and short-term regeneration capacities and committed multipotent, oligopotent, and unipotent progenitors.

HSCs constitute 1:10.000 of cells in myeloid tissue.

Sources of Hematopoietic Stem Cells

1.Bone Marrow

The method is referred to as a bone marrow harvest .

2.Peripheral stem cell

The most common source of stem cells for allogeneic HSCT.

Process known as apheresis.

Yield is boosted with daily subcutaneous

injections of Granulocyte-colony stimulating factor.

PBSCs are easier to collect than bone marrow stem cells.

PBSCs are sparse in the bloodstream, so collecting enough to perform a transplant can pose a challenge.

3 Umbilical cord blood

Is obtained when a mother donates her infant's umbilical cord and placenta after birth.

Umbilical cord blood stem cell transplants are less prone to rejection than either bone marrow or peripheral blood stem cells.

Cord blood has a higher concentration of HSC than is normally found in adult blood.

The small quantity of blood obtained from an umbilical cord (typically about 50 mL) makes it more suitable for transplantation into small children than into adults.

4 Placental Blood

Placental blood from sibling donors can reconstitute hematopoiesis.

HLA-mismatched placental blood from unrelated donors is an alternative source of stem cells for hematopoietic reconstitution.

5 Fetal Hematopoietic System

Is the developing blood-producing tissues of fetal animals.

Appear early in the development of all vertebrates.

Activity is indicated by the appearance of blood

islands in the yolk sac.

Growth and isolation of hematopoietic stem cells

Growth medium used

AIM V® Medium

MarrowMAX™ Bone Marrow Medium

KnockOut™ DMEM/F-12

Identification and characterizatin

It is difficult to identify and characterize HSCs because these cells look and behave in culture like ordinary white blood cells

The studies have revealed that there are two kinds of HSCs:-Long term stem cells.

-Short term stem cells.

Differentiation of HSCs and stromal cells

Production of differentiated WBCs and RBCs is the real work of HSCs and progenitor cells.

The original HSCs will undergo between 17 and 19.5 divisions to produce a mature, circulating blood cells.

.

DIFFERENT

TYPES OF

CELLS RELATED

TO BLOOD AND

IMMUNE

SYSTEM

OBTAINED

AFTER THE

DIFFERENTIATI

ON OF

HEMATOPOIETI

C STEM CELLS

Hematopoietic stem cells

Regulation of hematopoietic cell population

The number of blood cells in the bone marrow and blood is regulated by genetic and molecular mechanisms.

The process by which HSCs stop proliferating is called apoptosis.

Excess numbers of stem cells in an HSC transplant actually seem to improve the likelihood and speed of engraftment, though there seems to be no rigorous identification of a mechanism for this empirical observation.

Functional characteristics

1.Multipotency and self-renewal

Replenish all blood cell types

Self-renewal is thought to occur in the stem cell

niche in the bone marrow

2.Functional assays

Cobble stone area-forming Cell (CAFC) assay

3.Stem Cell Heterogeneity

It was originally believed that all HSC were alike in their self-renewal and differentiation abilities

4.Mobility

HSCs have a higher potential than other immature blood cells to pass the bone marrow barrier

5.Physical characteristic Resemble lymphocytes Non-adherent Rounded nucleus and low cytoplasm-to-nucleus ratio.

6.Markers Identified by their small size Lack of lineage markers Low staining with vital dyes Various antigenic markers on their surface

Clinical Uses of Hematopoietic Stem

Cells

1.Leukemia and Lymphoma

The first clinical uses of HSCs

The patient's cancerous hematopoietic cells were destroyed and replaced with a transplant of HSCs collected from the peripheral circulation of a matched donor.

.

.

Leukocytes are made in the bone marrow through a process that begins with multipotent adult stem cells

Mature leukocytes are released into the bloodstream, where they work to fight off infections in our bodies

2.Inherited Blood Disorders

Anemia

Inborn errors of metabolism.

The blood disorders include aplastic anemia, beta-thalassemia, Blackfan-Diamond syndrome, globoid cell leukodystrophy, sickle-cell anemia, severe combined immunodeficiency, X-linked lymphoproliferative syndrome, and Wiskott-Aldrich syndrome.

3.Cancer Chemotherapy

Done by mobilizing HSCs and collecting them from peripheral blood.

Disadvantage: cancer cells are sometimes inadvertently collected and reinfused back into the patient along with the stem cells.

4.Other Applications of Hematopoietic Stem Cells

Autoimmune diseases, such as diabetes, rheumatoid arthritis, and system lupus erythematosis

5.Plasticity of Hematopoietic Stem Cells HSCs can be differentiated into other types of

tissue, such as brain, muscle, and liver cells. Muscular dystrophy, weakness of the skeletal

muscles

6.Type 1 Diabetes in Children.

Disease characterized by destruction of insulin producing cells in the pancreas.

Current efforts to treat these patients with human

islet transplantation

7.Nervous System Diseases

In Parkinson’s disease In Alzheimer’s disease Amyotrophic lateral sclerosis In multiple sclerosis, glia, Create new nerve tissue restoring function from

pluripotent stem cells

8.Primary Immunodeficiency Diseases

AIDS

The transplantation of stem cells reconstituted with the normal gene could result in restoration of immune function and effective normalization of life span and quality of life for these people.

10.Diseases of Bone and Cartilage

Osteogenesis imperfecta and chondrodysplasias

Cells could be cultivated and introduced into

damaged areas of joint cartilage in cases of osteoarthritis or into large gaps in bone from fractures or surgery.

Treatment of murine malignant osteopetrosis

Embryonic Adult stem cell