Biomedical Engineering Reference
In-Depth Information
Human skin cells will fusewith empty pig eggs to create embryos that contain 99.9%
human DNA and 0.1% pig DNA. Stem cells extracted from the embryos will then be
treated with chemicals to destroy the pig DNA before they are grown into human heart
cells. The animal DNA is destroyed to make the cells behave more like human cells.
This will represent a landmark in stem cell science and give researchers a way to
make almost unlimited stocks of human ESCs, which in principle can grow into any
tissue in the body. Scientists have so far been unable to create stem cells using human
eggs, which are in short supply.
Although the stem cells will not contain any animal DNA, they will not be suitable
for treating humans directly. Instead, the scientists will use the cells to learn how
genetic mutations cause heart cells to malfunction and ultimately cause life-threat-
ening cardiomyopathy. Ultimately, they will help us understand where some of the
problems associated with these diseases arise, and they could also provide models for
the pharmaceutical industry to test new drugs.
12.6.2 Upcoming Techniques in Guidance to Homing of Stem Cell
Adipose tissue is another rich source of distinct subsets of stem and progenitor cells
that are potentially useful for cardiac repair and neovascularization improvement.
Both mesenchymal stem cells and endothelial progenitor cells have been isolated
after enzymatic digestion of adipose tissue and showed beneficial effects in
experimental studies. Very recently, pluripotent spermatogonial stem cells from
adult mouse testis that possess the capacity to differentiate to fully active cardiac
myocytes in vitro have been identified.
In diffuse disease such as dilated nonischemic cardiomyopathy, focal deposits of
directly injected cells might be poorly matched to the underlying anatomy and
physiology. Thus, it is likely that the nature of the patient's cardiomyopathy will
ultimately influence, if not dictate, the source and route chosen among potential
progenitor cell therapies. Intravenous administration of cells may be hampered by
trapping of the cells in the pulmonary circulation. Indeed, in clinical trials with
labeled bone marrow-derived cells, no homing to the heart in acute myocardial
infarction was observed after intravenous cell administration. However, intravenous
application of allogeneic mesenchymal stem cells was used safely and is currently
being tested in a clinical phase II study.
Randomized controlled trials currently assessing the effects of intracoronary
administration of BMCs in patients with acute myocardial infarction: are the
REGENT (Myocardial Regeneration by Intracoronary Infusion of Selected Popula-
tion of Stem Cells in Acute Myocardial Infarction), FINCELL (Effects of Intra-
coronary Injection of Mononuclear Bone Marrow Cells on LV Function, Arrhythmia
Risk Profile, and Restenosis After Thrombolytic Therapy of Acute Myocardial
Infarction), and ASTAMI (Autologous Stem Cell Transplantation in Acute Myocar-
dial Infarction) studies (Tables 12.6-12.8).
Three of the trials were placebo controlled. The primary end point common to all
these trials was change in LVEF at 4 to 6 months. In four of the trials, recovery of
global LVEF was significantly greater in the BMC-treated patient group compared
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