Scaffold to Treat Aneurysms, Optimized to Direct
Tissue Development and Control Blood Flow
Background: Abdominal aortic aneurysms, commonly
referred to as AAA, consist of a 50% enlargement of the abdominal aorta. While
the exact cause of AAA is not well understood, it is believed to be a complex
process involving loss of elasticity and strength, leading to arterial
expansion. Studies show that 3% of all individuals aged 50 and over, have AAA.
Only 25% of patients with ruptured aneurysms reach the hospital and only 10%
make it to the operating room.
Because of such high mortality rates, it is important to treat the
aneurysm before it ruptures.
Current treatment of the AAA
includes either open surgery or endovascular aneurysm repair (EVAR), depending
on the patient physiology and pathology.
EVAR utilizes stent technology to place the graft over the aneurysm and
into the iliofemoral arteries. The
graft serves to block off the aneurismal segment of the aorta without extensive
damage to the arteries. Currently
there are several FDA approved stent-grafts. However, because the graft is meant to
separate the unhealthy portion from the blood flow, inherent problems exist such
as endoleaks after implantation, in which blood seeps between the graft and the
lumen of the aorta, reaching the aneurysm. Additional risks associated with EVAR are
due to the permanent introduction of a material that is not bioactive. For
example, current bioinert materials can result in a fibrous capsule as a result
of the immune system’s rejection response.
Invention: Such risks may be circumvented with
this current invention from the UT Health Science Center at San Antonio, which
introduces a biodegradable scaffold that provides a three dimensional structure
on which the cells can proliferate and organize into a new tissue, allowing
native cells to infiltrate the scaffold and remodel into an aortic wall of
proper diameter. Infiltrating cells will come from both the blood flowing
through the scaffold as well as the surrounding tissue. Initially, the cells will act according
to the wound healing response. Then
the initially adhered cells signal for other more appropriate cells to adhere
and migrate through the scaffold.
As different cells adhere, migrate,
and proliferate, a remodeling process takes place in which extracellular matrix
components and scaffold fibers are broken down in some areas and bolstered in
others. Therefore, as time
progresses the scaffold is slowly replaced by functional tissue organized in
response to physiological conditions.
Eventually the scaffold will be completely degraded leaving tissue in its
place of the correct shape and containing vital structural components. At this point the aneurysm will be
minimized or no longer present. Unlike current EVAR treatments which try to
present an impermeable barrier, this scaffold will initially be permeable to
allow cell infiltration. Once
appropriate cells adhere, put down extracellular matrix components and
proliferate, the scaffold will become substantially impermeable. Furthermore, the scaffold is
biodegradable, so that as new tissue is formed, it will slowly be broken down by
natural metabolic pathways. Unlike current tissue engineered blood vessels, the
scaffold may be positioned within the damaged cardiovascular tissue with minimum
excision or damage to surrounding tissue.
Inventors
Dr. Steven R. Bailey, M.D. Chief of
the Division of Cardiology, UTHSCSA
Dr. C. Mauli Agrawal, Ph.D., P.E., Dean,
College of Engineering, UTSA
Dr. Jordan Massey, Ph.D.