Stem
cells are undifferentiated “mother” cells that have the ability to develop into
any kind of cell in the human body. Dedicated non-stem cells have a specific
function (e.g. liver cells, skin cells, brain cells, etc.) and once dedicated
cells have taken on their function, in a process called differentiation, they
can't be adapted for any other function.
Stem cells, however, have not yet differentiated. Stem cells can, theoretically,
multiply and differentiate an unlimited number of times and, by doing so,
replenish any and all other cells. When a stem cell divides, each new cell has
the potential to either remain a stem cell or differentiate into another, more
dedicated type of cell with a more specialized function, such as a muscle cell,
a red blood cell, a brain cell, etc. Classes of Stem
Cells:
There
are three main classes of stem cells: totipotent, pluripotent, and multipotent
* Totipotent stem cells have the potential to become all other types of cells in
the body. A fertilized egg is totipotent.
* Pluripotent stem cells can produce any type of cell in the body except those
needed to develop a fetus. Embryonic stem cells are produced when a newly
fertilized egg begins to divide and are pluripotent.
* Multipotent stem cells can produce only certain types of cells. Adult stem
cells are multipotent and are found in adults, infants and children. Mesenchymal
stem cells (MSCs) are also multipotent adult stem cells and are found in the
placenta as well as organs that have already developed. MSCs act as a repair and
maintenance cells dividing regularly to provide the body with specialized cells
to take the place of those that die or are otherwise lost.
What Is a
Hematopoietic Stem Cell (HSC)? A
hematopoietic stem cell (HSC) is an adult stem cell isolated from the bone
marrow, umbilical cord or peripheral blood that can renew itself, differentiate
to a variety of specialized blood cells such as red and white blood cells and
platelets. HSCs are exclusively required for bone marrow transplantation (BMT)
and are the only cells that can reconstitute the hematopoietic or blood system
following BMT. HSCs are now routinely used to treat patients with cancers and
other disorders of the blood and immune systems. Examples of the diseases where
BMT may be of value are the following:
How can stem cells be used to
treat disease?
Researchers are exploring two main avenues for using stem cells to treat disease
1) Stem cells as “replacement parts”: A wide range of diseases (heart disease,
Parkinson’s, Alzheimer’s, diabetes, motor neuron disease, etc.) may be amenable
to stem cell therapy if stem cells can be directed to the appropriate place in
the body and become the appropriate cell type. For example, if stem cells could
be made to migrate to an injured spinal cord and become nerve cells, it might be
possible to cure paralysis.
2) Developing drug therapies: It is possible to make stem cells that are
genetically identical to those of a patient with a disease such as amyotrophic
lateral sclerosis. The stem cells can be made to generate the cell type that is
defective in that disease (e.g. nerve cells). By studying these cells,
researchers may be able to gain insight into what goes wrong at the molecular
level in the disease. They can also use these cells to test drugs that might
block the progression of the disease. Umbilical cord
blood (CB) transplantations:
A very
effective source of transplantable and readily available hematopoietic stem
cells (HSCs) comes from umbilical cord blood (CB). Since the collection of CB
from the donor is simple and non-invasive and the extracted stem cells are
highly immunologically tolerant, CB transplantations have received tremendous
attention. However, due to the small volume of blood collected from umbilical
cords, transplantations have been limited to infants and children weighing less
than 80 lbs. Therefore the need to develop an expansion technology that will
increase the effectiveness of the small volume of blood found in the umbilical
cord has become imperative for CB to become a viable option for BMT for all size
individuals.
Pluristem believes their proprietary PluriX™ 3D bioreactor provides the solution
for this needed expansion technology. In preclinical studies to date, the
resultant cells from the PluriX™ 3D bioreactor, termed PLX I,
has significantly improved the engraftment of the HSCs found in CB by up to 500%
over controls. WHEN HI-TECH IS APPLIED TO
STEM CELLS
In the
laboratory, stem cells have historically been cultivated and grown in a limited
two dimensional environment using a cocktail of nutrients and growth factors.
In April 2004 Pluristem revealed its proprietary PluriX™ 3D bioreactor. Unlike
conventional two-dimensional (i.e., flat) culturing, the uniqueness of the
PluriX™ bioreactor is its ability to create a three dimensional microenvironment
that closely resembles the structure and function of the body's bone marrow.
Pluristem’s PluriX™ 3D bioreactor, consisting of a uniquely structured ‘stromal’
cell culture, provides an optimal environment to support and maintain the
expansion of mesenchymal stem cells (MSCs). MSCs are non-blood multipotent adult
stem cells that contribute to the regeneration of supporting tissues including
bone, cartilage, fat and muscle.
Using its PluriX™ 3D bioreactor system, Pluristem has
broken new ground by developing a unique process that allows the growth of MSCs
in an artificial physiological structure which closely replicates the natural
bone marrow environment. In one application, this system enables umbilical cord
blood (CB) derived hematopoietic stem cells (HSCs) to expand, without
differentiating, to proportions large enough for transplantation into adult.
The Company's efforts have been validated by the issuance of U.S. patents that
protect the concept and mechanism of action of the PluriX™ 3D bioreactor
technology.
