It was a busy week in the OR with a spectrum of cases,
literally from head to toe, including a craniotomy, double mastectomy and
breast reconstructions, two abdominal wall reconstructions, a lip
reconstruction, and a femoral popitial bypass surgery. The bypass surgery was
particularly interesting, as it shed light on the needs and challenges of
tissue engineered vessel constructs. In this case, the patient needed to
replace nearly 100 cm of the femoral artery, stretching from the hip to the
foot. The vascular surgeon hoped to harvest the replacement tissue from
whatever he could salvage from the bad leg, as well as both arms. For many
reasons, the best sources of tissue substitutes are other parts of your own
body, which are satisfy the top challenges that tissue engineers face: immunological
response, biocompatible and remodelable, inexpensive. Unfortunately, for the diabetic
patient in question, the arteries also exemplified the biggest drawback of
autologous grafts: availability. The sites that the doctor hoped to retrieve healthy
vessels were not sufficient for the graft, especially in the leg where large
numbers of small, corollary vessels had formed to supplement the femoral
artery. Therefore, the doctor was obliged to use a synthetic alternative,
essentially a plastic Gore-Tex tube, to complete the bypass. Noteably, this
material lacked all of the advantages of the autologous graft, providing only a
mechanically stable channel for blood flow with no hope of biological
performance. Consequently, the expected outcome for the bypass dropped to just
around 3 years. From my perspective as a tissue engineer, and I imagine in the
opinions of the doctors and patients, this dramatic gap between human tissue
and current gold-standards in peripheral bypass surgery is alarming. Even if
the patient had a sufficient supply of healthy vessels, the morbidity
associated with removing 100 cm of native vasculature is non-trivial. This
surgery impressed upon me the urgency of developing and implementing tissue
engineered solutions in the surgical toolbox.
This lesson was reinforced in the total mastectomy case,
which used diep flaps from the patient’s abdomen to replace both breasts. The
benefit of fully vascularized, fully biological, and non-immunological tissue
replacements was obvious. In this operation, fat tissue from the waist is
almost identical to the original adipose. Barring the advantage of a
complementary tummy-tuck, engineering of biologically active tissue is clearly
needed in plastic and reconstructive surgery.
Meanwhile, in the lab, we are working to produce exactly these types of alternative tissue replacements by designing flap and graft scaffolds from extracellular matrix proteins. By micropatterning these materials, the lab already showed improved cellularization in mouse models. Now we are attempting to use a new method of fabrication to produce micro-scale features that facilitate angiogenesis and cellular remodeling. Perhaps this project will lead to promising alternatives for the patients we meet in the OR.
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