Biomedical Engineering Reference
In-Depth Information
cases, could be attracted to the inflammatory areas, and if not properly incorporated
into the damaged tissue they may transform and initiate tumor growth. These cells
are by a deeper analytical approach categorized as very small embryonic like cells
(VSELs) which are probably the cells found by other researchers, earlier in the past
who were not able to reproduce them. Their presence in mouse and humans is
confirmed and their characteristics given in Figs.
15.2
and
15.3
.
Summary and Conclusions
Stem cells maintain tissues in adult life, and are regulated so that they generate
exactly the right number of differentiating cells to balance cell loss from the
tissue. Different stem cells from different organ sources seem to have different
homing ability and capacity, but there is always a small fraction of them circulat-
ing throughout the body and trying to repair damaged tissues. Although stem cell
research has been hailed for the potential to revolutionize the future of medicine
with the ability to regenerate damaged and diseased organs, it has been highly
controversial due to the ethical issues concerned with the culture and use of stem
cells derived from human embryos. So, after all, looking critically at what we
have today, the use of ESCs in therapy of different diseases is more problematic
than the story that precedes their establishment. They are actually allogeneic
transplants which need immunosupression due to in vitro intervention called stem
cell genetic cloning, where embryonal cell is fused into hybrid with the nucleus of
chosen egg cell in order to continue self-renewal and repair of the desired tissue
line or organ (nuclear gene transfer technique). This is a critical issue from both
scientific and clinical point of view, having in mind that the concept of VSEL
(very small embryonic like adult, non-hematopoietic stem cells) has been recently
developed and proved by Dr. Ratjczak's group (
15
). The question is whether ESCs
should be used at all, if VSELs can already replace them, successfully. On the
other hand, the number of VSELs is very low and requires mobilization to reach
efficient level in the bloodstream in order to make efficient homing in targeted
organ or tissue. Furthermore, some individuals are poor mobilizers and some can-
not be mobilized at all. In those cases ESC could be of valuable help. A lot of
further work and methodological advances are required, making the field of stem
cell therapy more intriguing and closer to clarification of ideas and problem solu-
tions in clinical application.
The unique characteristics of stem cells make them very promising potential for
supplying cells and tissues instead of organs in a spectrum of devastating diseases
from diabetes type1 to stroke, spinal cord injuries, and myocardial infarction
(
15,
35-
47
). In the situation when the number of people needing organ and tissue
transplants exceeds the number of donated organs and tissues, this is the promise
and hope, which deserve a deep and serious consideration.
