Stem cell technology is a rapidly developing field that combines the efforts of cell biologists, geneticists, and clinicians and offers hope of effective treatment for a variety of malignant and non-malignant diseases. So this topic is integrated with Class XII syllabus. Let's have few glimpses of the same......

STEM CELL TECHNOLOGY

Definition of Stem Cells:

•      A cell that has the ability to continuously divide and  differentiate (develop) into various other kind(s) of cells/tissues

•      These are Unspecialized and Undifferentiated cells.

FACTS

•  The body is made up of different kinds of specialised cells such as muscle cells, nerve cells, fat cells and skin cells.

•  All cells in the body come from stem cells.

•  A stem cell  is a cell that is not yet specialised.

•  The process of specialisation is called differentiation.

•  Once the differentiation pathway of a stem cell has been decided, it can no longer become another type of cell on its own.

In mammals, there are two broad types of stem cells: 

1. Embryonic stem cells, which are isolated from the inner cell mass of blastocysts, and 

2.   Adult stem cells, which are found in various tissues.

•      In adult organisms, stem cells and progenitor cells act as a repair system for the body, replenishing adult tissues. In a developing embryo, stem cells can differentiate into all the specialized cells—ectoderm, endoderm and mesoderm but also maintain the normal turnover of regenerative organs, such as blood, skin, or intestinal tissues.

There are three known accessible sources of autologous adult stem cells in humans:

1. Bone marrow, which requires extraction by harvesting, that    is, drilling into bone (typically the femur or iliac crest).

2. Adipose tissue (fat cells), which requires extraction by liposuction.

3. Blood, which requires extraction through apheresis, wherein blood is drawn from the donor (similar to a blood donation), and passed through a machine that extracts the stem cells and returns other portions of the blood to the donor.

·        Stem cells can also be taken from umbilical cord blood just after birth. Of all stem cell types, autologous harvesting involves the least risk.

·        By definition, autologous cells are obtained from one's own body, just as one may bank his or her own blood for elective surgical procedures.

•      Adult stem cells are frequently used in various medical therapies (e.g., bone marrow transplantation). Stem cells can now be artificially grown and transformed (differentiated) into specialized cell types with characteristics consistent with cells of various tissues such as muscles or nerves.

•      Embryonic cell lines and autologous embryonic stem cells generated  through somatic cell nuclear transfer or dedifferentiation have also been proposed as promising candidates for future therapies.

Embryonic stem cells

•      Totipotent: (toti = total ; potent = capacity)

•      The state of the cells after the first few divisions of the fertilised egg.

•      Have the capacity to become all cell types  plus placenta.

•      Pluripotent:  (pluri = many ; potent = capacity)

•      At blastocyst stage cells become   pluripotent.

•      Have the capacity to become all cell types but not placenta.

•      Cells of most interest to research scientists.

Adult stem cells

•  Multipotent.

•  Can develop into cells that are closely related.

•  Limited number of several cell types.

•  Make all cell types from the tissue they come from.

•  Found in many parts of the body.

•  Can self-renew over a lifetime.

Tissue stem cells

•  Often known as adult stem cells

•  Also includes stem cells isolated from foetal and cord blood

•  Reside in most tissues of the body where they are involved  in repair and replacement

•  Generally very difficult to isolate

•  Already used to treat patients (haematological malignancies,  diseases of the immune system)

Embryonic stem cells

•    Derived from  embryos

•    Can be grown indefinitely in the laboratory in an unspecialized state.

•    Retain ability to specialize into many different tissue type known as  Pluripotent.

•  Can restore function in animal models following transplantation.

Induced pluripotent stem cell

•  Derived from adult cells

•  Can be grown indefinitely in culture in an undifferentiated  state

•  Similar properties to  embryonic stem cells as can  differentiate into many  different tissue types –  pluripotent

Pros and Cons to induced pluripotent stem cell technology

Prons

    Cells would be genetically identical to patient or donor of     skin cells (no immune rejection!)

     Do not need to use an embryo

Cons:

          Cells would still have genetic defects

         One of the pluripotency genes is a cancer gene

        Viruses might insert genes in places we don’t want them causing mutations)

Science is discovering the unknown

•      Stem cell field is still in its infancy

•      Human embryonic stem cell research is a decade  old, adult stem cell research has 30-year head start

•       Holds hope for curing or improving treatments for  70+ diseases

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