Biomedical Engineering Reference
In-Depth Information
various time points. No systemic dissemination of virus was seen in any group. It
was concluded that adenovirus- and AAV2-coated stents can be used to deliver
genes to the blood vessel wall for up to 28 days. The results are being used as a
platform to design phase I clinical gene therapy studies in collaboration with part-
ners in the industry. In addition, this mode of gene delivery may also be of relevance
to a wide variety of disorders including cancer, as therapeutic products may be
delivered at high concentrations specifically to the diseased tissue by this means.
Stem Cell-Based Stents
Scientists at Sheffield University (Yorkshire, UK) are developing the world's first
regenerative stent utilizing stem cells. The body reacts to the presence of the stent
as a foreign body. By using the patient's own stem cells to line the stent, one can
prevent the reaction. Supportive evidence comes from another study, which showed
that stent coating with an integrin-binding cyclic Arg-Gly-Asp peptide may be use-
ful for reducing in-stent restenosis by accelerating endothelialization through
recruitment of endothelial progenitor cells (Blindt et al.
2006
).
Axordia, in collaboration with Lombard Medical Technologies PLC, is develop-
ing a new generation of treatment for coronary artery disease - a regenerative stent.
The collaboration between Lombard and Axordia is for a two and a half year
project to develop a regenerative stent that encourages rather than restricts local
vascular repair. Attaching Axordia's proprietary, stem cell-derived endovascular
cells to Lombard Medical's PEP
™
programmable polymer coating on the stent
surface shall allow the human body to promote controlled vascular repair and heal
the damaged coronary artery vessel wall.
The stent shall represent a major step forward into a new format for stent tech-
nology where early healing (endothelialization) is promoted rather than using
cytotoxic drugs on DES which inhibit growth and can cause late stage thrombotic
events. As a result, this stent technology could revolutionize the DES market.
A caveat for the use of stem cells for vascular repair is that these cells may be the
culprits in the development of restenosis. Scientists at the Weill Cornell Medical
College in New York are currently studying how stem cells implant themselves in
the wall of arteries and grow out of control following angioplasty and contribute to
development of restenosis. The researchers observed that transforming growth
factor beta (TGFb), which stimulates tissue growth, is released in high levels inside
the artery following the trauma of angioplasty. This could happen because TGFb
may beckon stem cells to the irritated area to heal the wound, leading to the growth
of dense tissue, which blocks the artery. If this mechanism of restenosis is proven,
one strategy would be to incorporate a TGFb antagonist tin the DES to shut off this
response.
Drug-Eluting Stents Coated with Polymer Surfaces
Local drug delivery can be achieved by DES coated with polymer surfaces used for
controlled drug release. However, several polymer coatings have shown an induction
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