Biomedical Engineering Reference
In-Depth Information
Chapter 12
Engraftment: Homing
and Use of Genetic Markers
Do, or do not. There is no 'try'.
- Yoda
Homing refers to the stem cells' innate ability to travel to the right place in the
body—the bone marrow—suited for making blood. The term “engraftment” means
that the stem cells have begun their work; they are functioning properly within the
marrow by producing various kinds of blood cells. Not only that bone marrow is
recruited with fresh pool of concentrated stem cells, but it is also being gradually
repopulated by those cells that emerge through differentiation of transplanted stem
cells. Experimental evidence suggests that manipulated stem cells may lose some of
their homing and engraftment abilities. If this evidence is true for humans as well, a
troubling paradox may arise: The very success of an umbilical cord blood transplant
could be undermined by the manipulations performed on stem cells—manipulations
intended to increase their healing properties, not decrease or eliminate them.
Research needs to clarify this. Work of this kind, at the University of Minnesota, is
crucial to the success of stem cell expansion [
1
] .
Genetic Markers
As in gene therapy, stem cells that are being genetically marked are activated to
accept new genes. But instead of receiving genes that change their behavior, they
receive genes that serve as “flags” or markers that are reproduced and expressed in
every generation of subsequent cells. The markers can then be used by researchers
to keep track of stem cell activity in the body after transplantation. For example,
genetically marked stem cells are being used in a new experimental protocol at the
University of Minnesota [
1
]. In this experiment, one-third of the stem cells the
