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Understand the issues associated with cell therapy
Stem Cell therapy involves
grafting cells to restore the function of a tissue or organ. The goal is to
sustainably treat the patient with a single injection of therapeutic cells.
Graft stem cells for long-term care
These cells are obtained from
Pluripotent stem cells (which can give all types of cells) or multipotent cells
(which can give a limited number of cell types) from the patient himself or
from a donor. Many stem cell therapy approaches are under development. Some of
them are already validated.
The different kinds of stem cells:
Several kinds of stem cells
are used to obtain differentiated and functional cells suitable for cell
therapy. These different types of cells, however, share two properties: that of
self- renewal indefinitely, offering an unlimited stock of material, and that
of being able to give birth to several cell types.
Pluripotent stem cells
Pluripotent stem cells can
give all types of cells in the body. It can be:
Embryonic stem cells are
taken from embryos of 5 to 7 days,
Induced Pluripotent stem
cells (IPS for Induced Pluripotent Stem cells) taken from adults and
reprogrammed into Pluripotent cells by genetic engineering.
Researchers today know how to
differentiate Pluripotent cells into several cell types, such as retinal cells
or skin cells.
Each cell type is obtained
through a cocktail of growth factors and specific differentiation, the recipe
is complex and long to develop. For some cell types, such as skeletal muscle
cells, the necessary cocktail has not yet been discovered.
Multipotent stem cells
Stem cell therapy can also be
performed with multipotent stem cells that can differentiate into a limited
number of cell types.
The most used are the
mesenchymal stem cells, present throughout the body within the adipose tissue,
bone marrow, organ support tissues, but also within the bones, cartilage,
muscles.
These cells Strains are particularly easy to collect in adipose tissue
or bone marrow. They can give rise to cartilage cells (chondrocytes), bone
cells (osteoblasts), fat cells (adipocytes), muscle fibers (myocytes),
cardiomyocytes, etc. They secrete, in addition, growth factors favorable to the
surrounding cells and are sometimes used exclusively for this property.
They
also produce anti-inflammatory factors that cause local immunosuppressant and
promote the function of regulatory cells of immunity. These properties limit
local inflammation and protect, a priori, against transplant rejection.
Other multipotent cells can
be used in stem cell therapy, such as cutaneous stem cells. The latter has been
used since the 1980s to reconstitute the different layers of the epidermis and
graft burn victims.
The stem cells of the eye,
derived from the limbus (on the periphery of the cornea), allow, as for them,
to repair lesions of the cornea. Finally, hematopoietic stem cells derived from
the bone marrow are at the origin of all the blood cells: in case of
hematological cancer, they make it possible to reconstitute a stock of healthy
blood cells in the patient, after having it destroy own diseased cells. This
intervention has been practiced since the 1970s.
Cord blood also rich in stem cells
Umbilical cord blood contains
hematopoietic stem cells that are immune-naive and therefore very well
tolerated in transplantation. Cord blood is used to treat hematological
malignancies such as leukemia’s or lymphomas, or genetic diseases such as
Franconia anemia.
It offers a serious alternative to bone marrow
transplantation in the absence of a compatible donor. However, the number of
therapeutic cells recovered per cord is small.
The preservation of placental
blood is authorized in France only to treat other patients anonymously and free
of charge. The French placental blood network (RFSP) coordinates the collection
and preservation of cord blood, thanks to a network of maternity partners
covering more than a quarter of births in France.
Women, who agree to donate
this blood product on the occasion of the birth of their child, do so
altruistically to help patients they do not know, suffering from deadly
diseases of the blood.
From the fourth month of
pregnancy, if the mother is eligible, she can give her consent. The removal
takes place within minutes of delivery when the umbilical cord has just been
cut and the placenta is still in the uterus. The blood is then frozen and
stored in a bank for later use.
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