Biomedical Engineering Reference
In-Depth Information
proved for the first time that the hESC-derived RPEs were functionally
equivalent to those RPE cells found
in vivo
,
providing an initial
proof of principle for the future development of hESC-generated
RPE cells for potential use in clinical applications (Klimanskaya
et al., 2004). A later study, however, reported some difficulties in
generating consistent batches of hESC-derived RPE cells that needed
to be resolved before moving forward (Klimanskaya, 2006).
Nevertheless, animal studies published around the same time
demonstrated that the clinical premise behind the use of
hESC-derived RPEs was sound: animals with retinal defects were
observed to have 100 per cent improved sight after treatment
compared to non-treated controls (Lund et al., 2006).
The derivation method used by Advanced Cell Technology is
significant in the context of US restrictions on funding of human
embryonic stem cell research and continuing global debate about the
ethical provenance of using human embryos in scientific research.
In 2008, Advanced Cell Technology reported that by refining a
technique previously used in cell expansion from blastomeres, they
were able to achieve a much more efficient means of growing stem
cells than had been achieved previously with this method (Chung
et al., 2008). The technique involves extracting a single cell from a
very early-stage embryo, normally up to two days after fertilization,
in a procedure similar to that used for pre-implantation diagnosis.
Significantly, in this study, 80-85 per cent of the biopsied embryos
went on to develop into healthy blastocysts or five-day-old embryos
(Chung et al., 2008). The improved success rate was largely
attributed to the culture conditions adopted for the blastomeres
(Chung et al., 2008). What remains to be seen, however, is whether
this means that viable embryos may be used for both research and
clinical purposes simultaneously and how prospective parents may
feel about the likelihood that a cell might be removed from their
embryo to be used for research purposes.
The first of the ACT trials approved by the FDA, for patients with
Stargardt's macular dystrophy, is currently recruiting patients in two
locations in the US. Stargardt's macular dystrophy is a hereditary
condition that begins in late childhood and ultimately leads to
blindness. The trial is expected to recruit 12 patients over the age of 18
