108
UNIT ONE
3.1
FROM SCIENCE TO TECHNOLOGY
Tailoring Stem Cells to Treat Disease
Culture
(a)
Donor stem cells
(b)
Own cells,
unaltered
(c)
Own cells,
reprogrammed
Isolate + reprogram
to less differentiated state
Stimulate division
and differentiation
Blood cells
Muscle cells
Nerve cells
FIGURE 3A
Using stem cells to heal. (
a
) Stem cells from donors
(bone marrow or umbilical cord blood) are already in use. (
b
) A person’s
cells may be used, unaltered, to replace damaged tissue, such as bone
marrow. (
c
) It is possible to “reprogram” a person’s cells in culture,
taking them back to a less specialized state and then nurturing them
to diF
erentiate as a needed cell type. This has been done. Implanting
the cells back into donors and stimulating the cells to correct the
disease are remaining challenges currently being investigated for many
applications, such as described in ±rom Science to Technology 15.1
(p. 566).
I
n the human body, lineages of dividing stem
cells and progenitor cells produce the special-
ized (diF
erentiated) cell types that assemble
and interact to form tissues and organs. Stem
and progenitor cells are essential for growth and
healing. Stem cell technology is part of an emerg-
ing ²
eld, called regenerative medicine, that har-
nesses the body’s ability to generate new cells to
treat certain diseases and injuries.
Stem cells to treat disease come from donors
or from the patient. Donor stem cells include
umbilical cord stem cells saved from newborns
and are used to treat a variety of blood disorders
and certain metabolic conditions. Stem cells
derived from a patient have two sources: their
natural sites or cultured from “reprogrammed”
diF
erentiated cells.
An example of using stem cells from their
natural site is an autologous bone marrow trans-
plant, in which a person’s immune system is
essentially destroyed with drugs or radiation after
the valuable stem cells are set aside. The stem
cells are then infused to repopulate the bone
marrow. This is already done.
±uture examples
of using a patient’s cells include directing neural
stem cells in the brain to treat neurodegenera-
tive diseases and spinal cord injury and applying
stem cells to bolster failing heart muscle. Stem
cells from a patient’s body may one day be used
to treat less serious conditions, too. The discovery
that a single stem cell can divide to give rise to
skin, hair, and oil glands suggests that manipulat-
ing them can provide treatments for burns, bald-
ness, and acne.
Reprogramming differentiated cells is a
promising approach to producing therapeutic
stem and progenitor cells. A ²
broblast taken from
a skin sample, for example, can be given genetic
instructions to produce key proteins that return
the cell to a state that resembles a stem cell from
an embryo. Then a cocktail of speci²
c biochemi-
cals is added to guide diF
erentiation. The altered
cell divides in culture, specializing and passing
on its new characteristics to its daughter cells.
The resulting tissue is implanted in the body. The
patient’s immune system presumably will not
reject the implant because it originated from that
person’s skin cell. ±ibroblasts from a boy with mus-
cular dystrophy, for example, might be taken back
to an embryonic-like state and then coaxed to
develop as muscle, along with genetic instructions
to produce normal muscle.
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