Challenges to Stem Cell/Cloning Research
Stem cell development or proliferation must be
controlled once placed into patients.
Possibility of rejection of stem cell transplants as
foreign tissues is very high.
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Slide 23 of 63
cells could produce tumors and multiply unchecked within a patient,
causing more problems than providing appropriate therapy. According to a
recent article ion the New England Journal
"There are still many
hurdles to clear before embryonic stem cells can be used
therapeutically. For example, because undifferentiated embryonic
stem cells can form tumors after transplantation in histocompatible
animals, it is important to determine an appropriate state of
differentiation before transplantation. Differentiation protocols for
many cell types have yet to be established. Targeting the differentiated
cells to the appropriate organ and the appropriate part of the organ is
also a challenge.”
scientists reported in the Proceedings of the National Academy of
Sciences that five out of the 19 mice injected with embryonic
stem cells developed tumors and
lines will suffer the same tissue rejection problems as adult
transplants. Once differentiated, these cells will express the HLA
tissue antigens programmed by their parental DNA. These antigens must
match those of the recipient or else tissue rejection will occur. An
admission of the problem of immune rejection can be found from The
"[W]ithin the [embryonic stem cell] research community, realism has
overtaken early euphoria as scientists realize the difficulty of
harnessing ESCs safely and effectively for clinical applications.
After earlier papers in 2000 and 2001 identified some possibilities,
research continued to highlight the tasks that lie ahead in steering
cell differentiation and avoiding side effects, such as immune
rejection and tumorigenesis.”1
E. Phimister and J. Drazen.
2004. Two Fillips for Human Embryonic Stem Cells.” New England Journal
of Medicine 350: 1351-1352.
Bjorklund, L. M., R. Sanchez-Pernaute, et al.
2002 "Embryonic stem
cells develop into functional dopaminergic neurons after
transplantation in a Parkinson rat model." Proceedings of the
National Academy of Sciences 99: 2344-2349.
Hunter, Philip. 2003.
Differentiating Hope from Embryonic Stem Cells.
The Scientist 17: 31.
Last Modified August 2, 2004